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Implement displaced stepping.

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gdb/
	* gdbarch.sh (max_insn_length): New 'variable'.
	(displaced_step_copy, displaced_step_fixup)
	(displaced_step_free_closure, displaced_step_location): New
	functions.
	(struct displaced_step_closure): Add forward declaration.
	* gdbarch.c, gdbarch.h: Regenerated.

	* arch-utils.c: #include "objfiles.h".
	(simple_displaced_step_copy_insn)
	(simple_displaced_step_free_closure)
	(displaced_step_at_entry_point): New functions.
	* arch-utils.h (simple_displaced_step_copy_insn)
	(simple_displaced_step_free_closure)
	(displaced_step_at_entry_point): New prototypes.

	* i386-tdep.c (I386_MAX_INSN_LEN): Rename to...
	(I386_MAX_MATCHED_INSN_LEN): ... this.
	(i386_absolute_jmp_p, i386_absolute_call_p)
	(i386_ret_p, i386_call_p, i386_breakpoint_p, i386_syscall_p)
	(i386_displaced_step_fixup): New functions.
	(struct i386_insn, i386_match_insn): Update.
	(i386_gdbarch_init): Set gdbarch_max_insn_length.
	* i386-tdep.h (I386_MAX_INSN_LEN): New.
	(i386_displaced_step_fixup): New prototype.
	* i386-linux-tdep.c (i386_linux_init_abi): Include "arch-utils.h".
	Register gdbarch_displaced_step_copy,
	gdbarch_displaced_step_fixup, gdbarch_displaced_step_free_closure,
	and gdbarch_displaced_step_location functions.

	* infrun.c (debug_displaced): New variable.
	(show_debug_displaced): New function.
	(struct displaced_step_request): New struct.
	(displaced_step_request_queue, displaced_step_ptid)
	(displaced_step_gdbarch, displaced_step_closure)
	(displaced_step_original, displaced_step_copy)
	(displaced_step_saved_copy, can_use_displaced_stepping): New
	variables.
	(show_can_use_displaced_stepping, use_displaced_stepping)
	(displaced_step_clear, cleanup_displaced_step_closure)
	(displaced_step_dump_bytes, displaced_step_prepare)
	(displaced_step_clear_cleanup, write_memory_ptid)
	(displaced_step_fixup): New functions.
	(resume): Call displaced_step_prepare.
	(proceed): Call read_pc once, and remember the value.  If using
	displaced stepping, don't remove breakpoints.
	(handle_inferior_event): Call displaced_step_fixup.  Add some
	debugging output.  When we try to step over a breakpoint, but get
	a signal to deliver to the thread instead, ensure the step-resume
	breakpoint is actually inserted.  If a thread hop is needed, and
	displaced stepping is enabled, don't remove breakpoints.
	(init_wait_for_inferior): Call displaced_step_clear.
	(_initialize_infrun): Add "set debug displaced" command.  Add
	"maint set can-use-displaced-stepping" command.  Clear
	displaced_step_ptid.
	* inferior.h (debug_displaced): Declare variable.
	(displaced_step_dump_bytes): Declare function.

	* Makefile.in (arch-utils.o, i386-linux-tdep.o): Update
	dependencies.

	gdb/testsuite/
	* gdb.asm/asmsrc1.s: Add scratch space.

	gdb/doc/
	* gdb.texinfo (Debugging Output): Document "set/show debug
	displaced".
	(Maintenance Commands): Document "maint set/show
	can-use-displaced-stepping".
This commit is contained in:
Pedro Alves
2008-05-02 16:49:54 +00:00
parent 0428b8f567
commit 237fc4c9cd
16 changed files with 1257 additions and 34 deletions
Download Patch File Download Diff File Expand all files Collapse all files

65
gdb/ChangeLog
View File

@ -1,3 +1,68 @@
2008-05-02 Jim Blandy <jimb@codesourcery.com>
Pedro Alves <pedro@codesourcery.com>
Implement displaced stepping.
* gdbarch.sh (max_insn_length): New 'variable'.
(displaced_step_copy, displaced_step_fixup)
(displaced_step_free_closure, displaced_step_location): New
functions.
(struct displaced_step_closure): Add forward declaration.
* gdbarch.c, gdbarch.h: Regenerated.
* arch-utils.c: #include "objfiles.h".
(simple_displaced_step_copy_insn)
(simple_displaced_step_free_closure)
(displaced_step_at_entry_point): New functions.
* arch-utils.h (simple_displaced_step_copy_insn)
(simple_displaced_step_free_closure)
(displaced_step_at_entry_point): New prototypes.
* i386-tdep.c (I386_MAX_INSN_LEN): Rename to...
(I386_MAX_MATCHED_INSN_LEN): ... this.
(i386_absolute_jmp_p, i386_absolute_call_p)
(i386_ret_p, i386_call_p, i386_breakpoint_p, i386_syscall_p)
(i386_displaced_step_fixup): New functions.
(struct i386_insn, i386_match_insn): Update.
(i386_gdbarch_init): Set gdbarch_max_insn_length.
* i386-tdep.h (I386_MAX_INSN_LEN): New.
(i386_displaced_step_fixup): New prototype.
* i386-linux-tdep.c (i386_linux_init_abi): Include "arch-utils.h".
Register gdbarch_displaced_step_copy,
gdbarch_displaced_step_fixup, gdbarch_displaced_step_free_closure,
and gdbarch_displaced_step_location functions.
* infrun.c (debug_displaced): New variable.
(show_debug_displaced): New function.
(struct displaced_step_request): New struct.
(displaced_step_request_queue, displaced_step_ptid)
(displaced_step_gdbarch, displaced_step_closure)
(displaced_step_original, displaced_step_copy)
(displaced_step_saved_copy, can_use_displaced_stepping): New
variables.
(show_can_use_displaced_stepping, use_displaced_stepping)
(displaced_step_clear, cleanup_displaced_step_closure)
(displaced_step_dump_bytes, displaced_step_prepare)
(displaced_step_clear_cleanup, write_memory_ptid)
(displaced_step_fixup): New functions.
(resume): Call displaced_step_prepare.
(proceed): Call read_pc once, and remember the value. If using
displaced stepping, don't remove breakpoints.
(handle_inferior_event): Call displaced_step_fixup. Add some
debugging output. When we try to step over a breakpoint, but get
a signal to deliver to the thread instead, ensure the step-resume
breakpoint is actually inserted. If a thread hop is needed, and
displaced stepping is enabled, don't remove breakpoints.
(init_wait_for_inferior): Call displaced_step_clear.
(_initialize_infrun): Add "set debug displaced" command. Add
"maint set can-use-displaced-stepping" command. Clear
displaced_step_ptid.
* inferior.h (debug_displaced): Declare variable.
(displaced_step_dump_bytes): Declare function.
* Makefile.in (arch-utils.o, i386-linux-tdep.o): Update
dependencies.
2008-05-02 Daniel Jacobowitz <dan@codesourcery.com> 2008-05-02 Daniel Jacobowitz <dan@codesourcery.com>
* arm-tdep.c (arm_mode_strings, arm_fallback_mode_string) * arm-tdep.c (arm_mode_strings, arm_fallback_mode_string)

5
gdb/Makefile.in
View File

@ -1917,7 +1917,7 @@ annotate.o: annotate.c $(defs_h) $(annotate_h) $(value_h) $(target_h) \
arch-utils.o: arch-utils.c $(defs_h) $(arch_utils_h) $(buildsym_h) \ arch-utils.o: arch-utils.c $(defs_h) $(arch_utils_h) $(buildsym_h) \
$(gdbcmd_h) $(inferior_h) $(gdb_string_h) $(regcache_h) \ $(gdbcmd_h) $(inferior_h) $(gdb_string_h) $(regcache_h) \
$(gdb_assert_h) $(sim_regno_h) $(gdbcore_h) $(osabi_h) $(version_h) \ $(gdb_assert_h) $(sim_regno_h) $(gdbcore_h) $(osabi_h) $(version_h) \
$(floatformat_h) $(target_descriptions_h) $(floatformat_h) $(target_descriptions_h) $(objfiles_h)
arm-linux-nat.o: arm-linux-nat.c $(defs_h) $(inferior_h) $(gdbcore_h) \ arm-linux-nat.o: arm-linux-nat.c $(defs_h) $(inferior_h) $(gdbcore_h) \
$(gdb_string_h) $(regcache_h) $(arm_tdep_h) $(gregset_h) \ $(gdb_string_h) $(regcache_h) $(arm_tdep_h) $(gregset_h) \
$(target_h) $(linux_nat_h) $(gdb_proc_service_h) $(arm_linux_tdep_h) \ $(target_h) $(linux_nat_h) $(gdb_proc_service_h) $(arm_linux_tdep_h) \
@ -2257,7 +2257,8 @@ i386-linux-nat.o: i386-linux-nat.c $(defs_h) $(inferior_h) $(gdbcore_h) \
i386-linux-tdep.o: i386-linux-tdep.c $(defs_h) $(gdbcore_h) $(frame_h) \ i386-linux-tdep.o: i386-linux-tdep.c $(defs_h) $(gdbcore_h) $(frame_h) \
$(value_h) $(regcache_h) $(inferior_h) $(osabi_h) $(reggroups_h) \ $(value_h) $(regcache_h) $(inferior_h) $(osabi_h) $(reggroups_h) \
$(dwarf2_frame_h) $(gdb_string_h) $(i386_tdep_h) \ $(dwarf2_frame_h) $(gdb_string_h) $(i386_tdep_h) \
$(i386_linux_tdep_h) $(glibc_tdep_h) $(solib_svr4_h) $(symtab_h) $(i386_linux_tdep_h) $(glibc_tdep_h) $(solib_svr4_h) $(symtab_h) \
$(arch_utils_h)
i386-nat.o: i386-nat.c $(defs_h) $(breakpoint_h) $(command_h) $(gdbcmd_h) \ i386-nat.o: i386-nat.c $(defs_h) $(breakpoint_h) $(command_h) $(gdbcmd_h) \
$(target_h) $(target_h)
i386nbsd-nat.o: i386nbsd-nat.c $(defs_h) $(gdbcore_h) $(regcache_h) \ i386nbsd-nat.o: i386nbsd-nat.c $(defs_h) $(gdbcore_h) $(regcache_h) \

52
gdb/arch-utils.c
View File

@ -31,12 +31,64 @@
#include "gdbcore.h" #include "gdbcore.h"
#include "osabi.h" #include "osabi.h"
#include "target-descriptions.h" #include "target-descriptions.h"
#include "objfiles.h"
#include "version.h" #include "version.h"
#include "floatformat.h" #include "floatformat.h"
struct displaced_step_closure *
simple_displaced_step_copy_insn (struct gdbarch *gdbarch,
CORE_ADDR from, CORE_ADDR to,
struct regcache *regs)
{
size_t len = gdbarch_max_insn_length (gdbarch);
gdb_byte *buf = xmalloc (len);
read_memory (from, buf, len);
write_memory (to, buf, len);
if (debug_displaced)
{
fprintf_unfiltered (gdb_stdlog, "displaced: copy 0x%s->0x%s: ",
paddr_nz (from), paddr_nz (to));
displaced_step_dump_bytes (gdb_stdlog, buf, len);
}
return (struct displaced_step_closure *) buf;
}
void
simple_displaced_step_free_closure (struct gdbarch *gdbarch,
struct displaced_step_closure *closure)
{
xfree (closure);
}
CORE_ADDR
displaced_step_at_entry_point (struct gdbarch *gdbarch)
{
CORE_ADDR addr;
int bp_len;
addr = entry_point_address ();
/* Make certain that the address points at real code, and not a
function descriptor. */
addr = gdbarch_convert_from_func_ptr_addr (gdbarch, addr, &current_target);
/* Inferior calls also use the entry point as a breakpoint location.
We don't want displaced stepping to interfere with those
breakpoints, so leave space. */
gdbarch_breakpoint_from_pc (gdbarch, &addr, &bp_len);
addr += bp_len * 2;
return addr;
}
int int
legacy_register_sim_regno (struct gdbarch *gdbarch, int regnum) legacy_register_sim_regno (struct gdbarch *gdbarch, int regnum)
{ {

24
gdb/arch-utils.h
View File

@ -30,6 +30,30 @@ struct gdbarch_info;
/* gdbarch trace variable */ /* gdbarch trace variable */
extern int gdbarch_debug; extern int gdbarch_debug;
/* An implementation of gdbarch_displaced_step_copy_insn for
processors that don't need to modify the instruction before
single-stepping the displaced copy.
Simply copy gdbarch_max_insn_length (ARCH) bytes from FROM to TO.
The closure is an array of that many bytes containing the
instruction's bytes, allocated with xmalloc. */
extern struct displaced_step_closure *
simple_displaced_step_copy_insn (struct gdbarch *gdbarch,
CORE_ADDR from, CORE_ADDR to,
struct regcache *regs);
/* Simple implementation of gdbarch_displaced_step_free_closure: Call
xfree.
This is appropriate for use with simple_displaced_step_copy_insn. */
extern void
simple_displaced_step_free_closure (struct gdbarch *gdbarch,
struct displaced_step_closure *closure);
/* Possible value for gdbarch_displaced_step_location:
Place displaced instructions at the program's entry point,
leaving space for inferior function call return breakpoints. */
extern CORE_ADDR displaced_step_at_entry_point (struct gdbarch *gdbarch);
/* The only possible cases for inner_than. */ /* The only possible cases for inner_than. */
extern int core_addr_lessthan (CORE_ADDR lhs, CORE_ADDR rhs); extern int core_addr_lessthan (CORE_ADDR lhs, CORE_ADDR rhs);
extern int core_addr_greaterthan (CORE_ADDR lhs, CORE_ADDR rhs); extern int core_addr_greaterthan (CORE_ADDR lhs, CORE_ADDR rhs);

7
gdb/doc/ChangeLog
View File

@ -1,3 +1,10 @@
2008-05-02 Pedro Alves <pedro@codesourcery.com>
* gdb.texinfo (Debugging Output): Document "set/show debug
displaced".
(Maintenance Commands): Document "maint set/show
can-use-displaced-stepping".
2008-05-02 Daniel Jacobowitz <dan@codesourcery.com> 2008-05-02 Daniel Jacobowitz <dan@codesourcery.com>
* gdb.texinfo (ARM): Document set/show arm fallback-mode * gdb.texinfo (ARM): Document set/show arm fallback-mode

20
gdb/doc/gdb.texinfo
View File

@ -16483,6 +16483,13 @@ Display debugging messages about inner workings of the AIX thread
module. module.
@item show debug aix-thread @item show debug aix-thread
Show the current state of AIX thread debugging info display. Show the current state of AIX thread debugging info display.
@item set debug displaced
@cindex displaced stepping debugging info
Turns on or off display of @value{GDBN} debugging info for the
displaced stepping support. The default is off.
@item show debug displaced
Displays the current state of displaying @value{GDBN} debugging info
related to displaced stepping.
@item set debug event @item set debug event
@cindex event debugging info @cindex event debugging info
Turns on or off display of @value{GDBN} event debugging info. The Turns on or off display of @value{GDBN} event debugging info. The
@ -23159,6 +23166,19 @@ Shared library events.
@end table @end table
@kindex maint set can-use-displaced-stepping
@kindex maint show can-use-displaced-stepping
@cindex displaced stepping support
@cindex out-of-line single-stepping
@item maint set can-use-displaced-stepping
@itemx maint show can-use-displaced-stepping
Control whether or not @value{GDBN} will do @dfn{displaced stepping}
if the target supports it. The default is on. Displaced stepping is
a way to single-step over breakpoints without removing them from the
inferior, by executing an out-of-line copy of the instruction that was
originally at the breakpoint location. It is also known as
out-of-line single-stepping.
@kindex maint check-symtabs @kindex maint check-symtabs
@item maint check-symtabs @item maint check-symtabs
Check the consistency of psymtabs and symtabs. Check the consistency of psymtabs and symtabs.

152
gdb/gdbarch.c
View File

@ -226,6 +226,11 @@ struct gdbarch
int vtable_function_descriptors; int vtable_function_descriptors;
int vbit_in_delta; int vbit_in_delta;
gdbarch_skip_permanent_breakpoint_ftype *skip_permanent_breakpoint; gdbarch_skip_permanent_breakpoint_ftype *skip_permanent_breakpoint;
ULONGEST max_insn_length;
gdbarch_displaced_step_copy_insn_ftype *displaced_step_copy_insn;
gdbarch_displaced_step_fixup_ftype *displaced_step_fixup;
gdbarch_displaced_step_free_closure_ftype *displaced_step_free_closure;
gdbarch_displaced_step_location_ftype *displaced_step_location;
gdbarch_overlay_update_ftype *overlay_update; gdbarch_overlay_update_ftype *overlay_update;
gdbarch_core_read_description_ftype *core_read_description; gdbarch_core_read_description_ftype *core_read_description;
gdbarch_static_transform_name_ftype *static_transform_name; gdbarch_static_transform_name_ftype *static_transform_name;
@ -350,6 +355,11 @@ struct gdbarch startup_gdbarch =
0, /* vtable_function_descriptors */ 0, /* vtable_function_descriptors */
0, /* vbit_in_delta */ 0, /* vbit_in_delta */
0, /* skip_permanent_breakpoint */ 0, /* skip_permanent_breakpoint */
0, /* max_insn_length */
0, /* displaced_step_copy_insn */
0, /* displaced_step_fixup */
NULL, /* displaced_step_free_closure */
NULL, /* displaced_step_location */
0, /* overlay_update */ 0, /* overlay_update */
0, /* core_read_description */ 0, /* core_read_description */
0, /* static_transform_name */ 0, /* static_transform_name */
@ -435,6 +445,9 @@ gdbarch_alloc (const struct gdbarch_info *info,
gdbarch->coff_make_msymbol_special = default_coff_make_msymbol_special; gdbarch->coff_make_msymbol_special = default_coff_make_msymbol_special;
gdbarch->name_of_malloc = "malloc"; gdbarch->name_of_malloc = "malloc";
gdbarch->register_reggroup_p = default_register_reggroup_p; gdbarch->register_reggroup_p = default_register_reggroup_p;
gdbarch->displaced_step_fixup = NULL;
gdbarch->displaced_step_free_closure = NULL;
gdbarch->displaced_step_location = NULL;
gdbarch->target_signal_from_host = default_target_signal_from_host; gdbarch->target_signal_from_host = default_target_signal_from_host;
gdbarch->target_signal_to_host = default_target_signal_to_host; gdbarch->target_signal_to_host = default_target_signal_to_host;
/* gdbarch_alloc() */ /* gdbarch_alloc() */
@ -592,6 +605,13 @@ verify_gdbarch (struct gdbarch *gdbarch)
/* Skip verify of vtable_function_descriptors, invalid_p == 0 */ /* Skip verify of vtable_function_descriptors, invalid_p == 0 */
/* Skip verify of vbit_in_delta, invalid_p == 0 */ /* Skip verify of vbit_in_delta, invalid_p == 0 */
/* Skip verify of skip_permanent_breakpoint, has predicate */ /* Skip verify of skip_permanent_breakpoint, has predicate */
/* Skip verify of max_insn_length, has predicate */
/* Skip verify of displaced_step_copy_insn, has predicate */
/* Skip verify of displaced_step_fixup, has predicate */
if ((! gdbarch->displaced_step_free_closure) != (! gdbarch->displaced_step_copy_insn))
fprintf_unfiltered (log, "\n\tdisplaced_step_free_closure");
if ((! gdbarch->displaced_step_location) != (! gdbarch->displaced_step_copy_insn))
fprintf_unfiltered (log, "\n\tdisplaced_step_location");
/* Skip verify of overlay_update, has predicate */ /* Skip verify of overlay_update, has predicate */
/* Skip verify of core_read_description, has predicate */ /* Skip verify of core_read_description, has predicate */
/* Skip verify of static_transform_name, has predicate */ /* Skip verify of static_transform_name, has predicate */
@ -716,6 +736,24 @@ gdbarch_dump (struct gdbarch *gdbarch, struct ui_file *file)
fprintf_unfiltered (file, fprintf_unfiltered (file,
"gdbarch_dump: deprecated_function_start_offset = 0x%s\n", "gdbarch_dump: deprecated_function_start_offset = 0x%s\n",
paddr_nz (gdbarch->deprecated_function_start_offset)); paddr_nz (gdbarch->deprecated_function_start_offset));
fprintf_unfiltered (file,
"gdbarch_dump: gdbarch_displaced_step_copy_insn_p() = %d\n",
gdbarch_displaced_step_copy_insn_p (gdbarch));
fprintf_unfiltered (file,
"gdbarch_dump: displaced_step_copy_insn = <0x%lx>\n",
(long) gdbarch->displaced_step_copy_insn);
fprintf_unfiltered (file,
"gdbarch_dump: gdbarch_displaced_step_fixup_p() = %d\n",
gdbarch_displaced_step_fixup_p (gdbarch));
fprintf_unfiltered (file,
"gdbarch_dump: displaced_step_fixup = <0x%lx>\n",
(long) gdbarch->displaced_step_fixup);
fprintf_unfiltered (file,
"gdbarch_dump: displaced_step_free_closure = <0x%lx>\n",
(long) gdbarch->displaced_step_free_closure);
fprintf_unfiltered (file,
"gdbarch_dump: displaced_step_location = <0x%lx>\n",
(long) gdbarch->displaced_step_location);
fprintf_unfiltered (file, fprintf_unfiltered (file,
"gdbarch_dump: double_bit = %s\n", "gdbarch_dump: double_bit = %s\n",
paddr_d (gdbarch->double_bit)); paddr_d (gdbarch->double_bit));
@ -818,6 +856,12 @@ gdbarch_dump (struct gdbarch *gdbarch, struct ui_file *file)
fprintf_unfiltered (file, fprintf_unfiltered (file,
"gdbarch_dump: long_long_bit = %s\n", "gdbarch_dump: long_long_bit = %s\n",
paddr_d (gdbarch->long_long_bit)); paddr_d (gdbarch->long_long_bit));
fprintf_unfiltered (file,
"gdbarch_dump: gdbarch_max_insn_length_p() = %d\n",
gdbarch_max_insn_length_p (gdbarch));
fprintf_unfiltered (file,
"gdbarch_dump: max_insn_length = %s\n",
paddr_d (gdbarch->max_insn_length));
fprintf_unfiltered (file, fprintf_unfiltered (file,
"gdbarch_dump: memory_insert_breakpoint = <0x%lx>\n", "gdbarch_dump: memory_insert_breakpoint = <0x%lx>\n",
(long) gdbarch->memory_insert_breakpoint); (long) gdbarch->memory_insert_breakpoint);
@ -2906,6 +2950,114 @@ set_gdbarch_skip_permanent_breakpoint (struct gdbarch *gdbarch,
gdbarch->skip_permanent_breakpoint = skip_permanent_breakpoint; gdbarch->skip_permanent_breakpoint = skip_permanent_breakpoint;
} }
int
gdbarch_max_insn_length_p (struct gdbarch *gdbarch)
{
gdb_assert (gdbarch != NULL);
return gdbarch->max_insn_length != 0;
}
ULONGEST
gdbarch_max_insn_length (struct gdbarch *gdbarch)
{
gdb_assert (gdbarch != NULL);
/* Check variable changed from pre-default. */
gdb_assert (gdbarch->max_insn_length != 0);
if (gdbarch_debug >= 2)
fprintf_unfiltered (gdb_stdlog, "gdbarch_max_insn_length called\n");
return gdbarch->max_insn_length;
}
void
set_gdbarch_max_insn_length (struct gdbarch *gdbarch,
ULONGEST max_insn_length)
{
gdbarch->max_insn_length = max_insn_length;
}
int
gdbarch_displaced_step_copy_insn_p (struct gdbarch *gdbarch)
{
gdb_assert (gdbarch != NULL);
return gdbarch->displaced_step_copy_insn != NULL;
}
struct displaced_step_closure *
gdbarch_displaced_step_copy_insn (struct gdbarch *gdbarch, CORE_ADDR from, CORE_ADDR to, struct regcache *regs)
{
gdb_assert (gdbarch != NULL);
gdb_assert (gdbarch->displaced_step_copy_insn != NULL);
if (gdbarch_debug >= 2)
fprintf_unfiltered (gdb_stdlog, "gdbarch_displaced_step_copy_insn called\n");
return gdbarch->displaced_step_copy_insn (gdbarch, from, to, regs);
}
void
set_gdbarch_displaced_step_copy_insn (struct gdbarch *gdbarch,
gdbarch_displaced_step_copy_insn_ftype displaced_step_copy_insn)
{
gdbarch->displaced_step_copy_insn = displaced_step_copy_insn;
}
int
gdbarch_displaced_step_fixup_p (struct gdbarch *gdbarch)
{
gdb_assert (gdbarch != NULL);
return gdbarch->displaced_step_fixup != NULL;
}
void
gdbarch_displaced_step_fixup (struct gdbarch *gdbarch, struct displaced_step_closure *closure, CORE_ADDR from, CORE_ADDR to, struct regcache *regs)
{
gdb_assert (gdbarch != NULL);
gdb_assert (gdbarch->displaced_step_fixup != NULL);
/* Do not check predicate: gdbarch->displaced_step_fixup != NULL, allow call. */
if (gdbarch_debug >= 2)
fprintf_unfiltered (gdb_stdlog, "gdbarch_displaced_step_fixup called\n");
gdbarch->displaced_step_fixup (gdbarch, closure, from, to, regs);
}
void
set_gdbarch_displaced_step_fixup (struct gdbarch *gdbarch,
gdbarch_displaced_step_fixup_ftype displaced_step_fixup)
{
gdbarch->displaced_step_fixup = displaced_step_fixup;
}
void
gdbarch_displaced_step_free_closure (struct gdbarch *gdbarch, struct displaced_step_closure *closure)
{
gdb_assert (gdbarch != NULL);
gdb_assert (gdbarch->displaced_step_free_closure != NULL);
if (gdbarch_debug >= 2)
fprintf_unfiltered (gdb_stdlog, "gdbarch_displaced_step_free_closure called\n");
gdbarch->displaced_step_free_closure (gdbarch, closure);
}
void
set_gdbarch_displaced_step_free_closure (struct gdbarch *gdbarch,
gdbarch_displaced_step_free_closure_ftype displaced_step_free_closure)
{
gdbarch->displaced_step_free_closure = displaced_step_free_closure;
}
CORE_ADDR
gdbarch_displaced_step_location (struct gdbarch *gdbarch)
{
gdb_assert (gdbarch != NULL);
gdb_assert (gdbarch->displaced_step_location != NULL);
if (gdbarch_debug >= 2)
fprintf_unfiltered (gdb_stdlog, "gdbarch_displaced_step_location called\n");
return gdbarch->displaced_step_location (gdbarch);
}
void
set_gdbarch_displaced_step_location (struct gdbarch *gdbarch,
gdbarch_displaced_step_location_ftype displaced_step_location)
{
gdbarch->displaced_step_location = displaced_step_location;
}
int int
gdbarch_overlay_update_p (struct gdbarch *gdbarch) gdbarch_overlay_update_p (struct gdbarch *gdbarch)
{ {

90
gdb/gdbarch.h
View File

@ -50,6 +50,7 @@ struct target_ops;
struct obstack; struct obstack;
struct bp_target_info; struct bp_target_info;
struct target_desc; struct target_desc;
struct displaced_step_closure;
extern struct gdbarch *current_gdbarch; extern struct gdbarch *current_gdbarch;
@ -663,6 +664,95 @@ typedef void (gdbarch_skip_permanent_breakpoint_ftype) (struct regcache *regcach
extern void gdbarch_skip_permanent_breakpoint (struct gdbarch *gdbarch, struct regcache *regcache); extern void gdbarch_skip_permanent_breakpoint (struct gdbarch *gdbarch, struct regcache *regcache);
extern void set_gdbarch_skip_permanent_breakpoint (struct gdbarch *gdbarch, gdbarch_skip_permanent_breakpoint_ftype *skip_permanent_breakpoint); extern void set_gdbarch_skip_permanent_breakpoint (struct gdbarch *gdbarch, gdbarch_skip_permanent_breakpoint_ftype *skip_permanent_breakpoint);
/* The maximum length of an instruction on this architecture. */
extern int gdbarch_max_insn_length_p (struct gdbarch *gdbarch);
extern ULONGEST gdbarch_max_insn_length (struct gdbarch *gdbarch);
extern void set_gdbarch_max_insn_length (struct gdbarch *gdbarch, ULONGEST max_insn_length);
/* Copy the instruction at FROM to TO, and make any adjustments
necessary to single-step it at that address.
REGS holds the state the thread's registers will have before
executing the copied instruction; the PC in REGS will refer to FROM,
not the copy at TO. The caller should update it to point at TO later.
Return a pointer to data of the architecture's choice to be passed
to gdbarch_displaced_step_fixup. Or, return NULL to indicate that
the instruction's effects have been completely simulated, with the
resulting state written back to REGS.
For a general explanation of displaced stepping and how GDB uses it,
see the comments in infrun.c.
The TO area is only guaranteed to have space for
gdbarch_max_insn_length (arch) bytes, so this function must not
write more bytes than that to that area.
If you do not provide this function, GDB assumes that the
architecture does not support displaced stepping.
If your architecture doesn't need to adjust instructions before
single-stepping them, consider using simple_displaced_step_copy_insn
here. */
extern int gdbarch_displaced_step_copy_insn_p (struct gdbarch *gdbarch);
typedef struct displaced_step_closure * (gdbarch_displaced_step_copy_insn_ftype) (struct gdbarch *gdbarch, CORE_ADDR from, CORE_ADDR to, struct regcache *regs);
extern struct displaced_step_closure * gdbarch_displaced_step_copy_insn (struct gdbarch *gdbarch, CORE_ADDR from, CORE_ADDR to, struct regcache *regs);
extern void set_gdbarch_displaced_step_copy_insn (struct gdbarch *gdbarch, gdbarch_displaced_step_copy_insn_ftype *displaced_step_copy_insn);
/* Fix up the state resulting from successfully single-stepping a
displaced instruction, to give the result we would have gotten from
stepping the instruction in its original location.
REGS is the register state resulting from single-stepping the
displaced instruction.
CLOSURE is the result from the matching call to
gdbarch_displaced_step_copy_insn.
If you provide gdbarch_displaced_step_copy_insn.but not this
function, then GDB assumes that no fixup is needed after
single-stepping the instruction.
For a general explanation of displaced stepping and how GDB uses it,
see the comments in infrun.c. */
extern int gdbarch_displaced_step_fixup_p (struct gdbarch *gdbarch);
typedef void (gdbarch_displaced_step_fixup_ftype) (struct gdbarch *gdbarch, struct displaced_step_closure *closure, CORE_ADDR from, CORE_ADDR to, struct regcache *regs);
extern void gdbarch_displaced_step_fixup (struct gdbarch *gdbarch, struct displaced_step_closure *closure, CORE_ADDR from, CORE_ADDR to, struct regcache *regs);
extern void set_gdbarch_displaced_step_fixup (struct gdbarch *gdbarch, gdbarch_displaced_step_fixup_ftype *displaced_step_fixup);
/* Free a closure returned by gdbarch_displaced_step_copy_insn.
If you provide gdbarch_displaced_step_copy_insn, you must provide
this function as well.
If your architecture uses closures that don't need to be freed, then
you can use simple_displaced_step_free_closure here.
For a general explanation of displaced stepping and how GDB uses it,
see the comments in infrun.c. */
typedef void (gdbarch_displaced_step_free_closure_ftype) (struct gdbarch *gdbarch, struct displaced_step_closure *closure);
extern void gdbarch_displaced_step_free_closure (struct gdbarch *gdbarch, struct displaced_step_closure *closure);
extern void set_gdbarch_displaced_step_free_closure (struct gdbarch *gdbarch, gdbarch_displaced_step_free_closure_ftype *displaced_step_free_closure);
/* Return the address of an appropriate place to put displaced
instructions while we step over them. There need only be one such
place, since we're only stepping one thread over a breakpoint at a
time.
For a general explanation of displaced stepping and how GDB uses it,
see the comments in infrun.c. */
typedef CORE_ADDR (gdbarch_displaced_step_location_ftype) (struct gdbarch *gdbarch);
extern CORE_ADDR gdbarch_displaced_step_location (struct gdbarch *gdbarch);
extern void set_gdbarch_displaced_step_location (struct gdbarch *gdbarch, gdbarch_displaced_step_location_ftype *displaced_step_location);
/* Refresh overlay mapped state for section OSECT. */ /* Refresh overlay mapped state for section OSECT. */
extern int gdbarch_overlay_update_p (struct gdbarch *gdbarch); extern int gdbarch_overlay_update_p (struct gdbarch *gdbarch);

70
gdb/gdbarch.sh
View File

@ -616,6 +616,75 @@ v:int:vbit_in_delta:::0:0::0
# Advance PC to next instruction in order to skip a permanent breakpoint. # Advance PC to next instruction in order to skip a permanent breakpoint.
F:void:skip_permanent_breakpoint:struct regcache *regcache:regcache F:void:skip_permanent_breakpoint:struct regcache *regcache:regcache
# The maximum length of an instruction on this architecture.
V:ULONGEST:max_insn_length:::0:0
# Copy the instruction at FROM to TO, and make any adjustments
# necessary to single-step it at that address.
#
# REGS holds the state the thread's registers will have before
# executing the copied instruction; the PC in REGS will refer to FROM,
# not the copy at TO. The caller should update it to point at TO later.
#
# Return a pointer to data of the architecture's choice to be passed
# to gdbarch_displaced_step_fixup. Or, return NULL to indicate that
# the instruction's effects have been completely simulated, with the
# resulting state written back to REGS.
#
# For a general explanation of displaced stepping and how GDB uses it,
# see the comments in infrun.c.
#
# The TO area is only guaranteed to have space for
# gdbarch_max_insn_length (arch) bytes, so this function must not
# write more bytes than that to that area.
#
# If you do not provide this function, GDB assumes that the
# architecture does not support displaced stepping.
#
# If your architecture doesn't need to adjust instructions before
# single-stepping them, consider using simple_displaced_step_copy_insn
# here.
M:struct displaced_step_closure *:displaced_step_copy_insn:CORE_ADDR from, CORE_ADDR to, struct regcache *regs:from, to, regs
# Fix up the state resulting from successfully single-stepping a
# displaced instruction, to give the result we would have gotten from
# stepping the instruction in its original location.
#
# REGS is the register state resulting from single-stepping the
# displaced instruction.
#
# CLOSURE is the result from the matching call to
# gdbarch_displaced_step_copy_insn.
#
# If you provide gdbarch_displaced_step_copy_insn.but not this
# function, then GDB assumes that no fixup is needed after
# single-stepping the instruction.
#
# For a general explanation of displaced stepping and how GDB uses it,
# see the comments in infrun.c.
M:void:displaced_step_fixup:struct displaced_step_closure *closure, CORE_ADDR from, CORE_ADDR to, struct regcache *regs:closure, from, to, regs::NULL
# Free a closure returned by gdbarch_displaced_step_copy_insn.
#
# If you provide gdbarch_displaced_step_copy_insn, you must provide
# this function as well.
#
# If your architecture uses closures that don't need to be freed, then
# you can use simple_displaced_step_free_closure here.
#
# For a general explanation of displaced stepping and how GDB uses it,
# see the comments in infrun.c.
m:void:displaced_step_free_closure:struct displaced_step_closure *closure:closure::NULL::(! gdbarch->displaced_step_free_closure) != (! gdbarch->displaced_step_copy_insn)
# Return the address of an appropriate place to put displaced
# instructions while we step over them. There need only be one such
# place, since we're only stepping one thread over a breakpoint at a
# time.
#
# For a general explanation of displaced stepping and how GDB uses it,
# see the comments in infrun.c.
m:CORE_ADDR:displaced_step_location:void:::NULL::(! gdbarch->displaced_step_location) != (! gdbarch->displaced_step_copy_insn)
# Refresh overlay mapped state for section OSECT. # Refresh overlay mapped state for section OSECT.
F:void:overlay_update:struct obj_section *osect:osect F:void:overlay_update:struct obj_section *osect:osect
@ -742,6 +811,7 @@ struct target_ops;
struct obstack; struct obstack;
struct bp_target_info; struct bp_target_info;
struct target_desc; struct target_desc;
struct displaced_step_closure;
extern struct gdbarch *current_gdbarch; extern struct gdbarch *current_gdbarch;
EOF EOF

10
gdb/i386-linux-tdep.c
View File

@ -34,6 +34,7 @@
#include "glibc-tdep.h" #include "glibc-tdep.h"
#include "solib-svr4.h" #include "solib-svr4.h"
#include "symtab.h" #include "symtab.h"
#include "arch-utils.h"
/* Return the name of register REG. */ /* Return the name of register REG. */
@ -446,6 +447,15 @@ i386_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
/* Enable TLS support. */ /* Enable TLS support. */
set_gdbarch_fetch_tls_load_module_address (gdbarch, set_gdbarch_fetch_tls_load_module_address (gdbarch,
svr4_fetch_objfile_link_map); svr4_fetch_objfile_link_map);
/* Displaced stepping. */
set_gdbarch_displaced_step_copy_insn (gdbarch,
simple_displaced_step_copy_insn);
set_gdbarch_displaced_step_fixup (gdbarch, i386_displaced_step_fixup);
set_gdbarch_displaced_step_free_closure (gdbarch,
simple_displaced_step_free_closure);
set_gdbarch_displaced_step_location (gdbarch,
displaced_step_at_entry_point);
} }
/* Provide a prototype to silence -Wmissing-prototypes. */ /* Provide a prototype to silence -Wmissing-prototypes. */

230
gdb/i386-tdep.c
View File

@ -275,6 +275,225 @@ i386_breakpoint_from_pc (struct gdbarch *gdbarch, CORE_ADDR *pc, int *len)
*len = sizeof (break_insn); *len = sizeof (break_insn);
return break_insn; return break_insn;
} }
/* Displaced instruction handling. */
static int
i386_absolute_jmp_p (gdb_byte *insn)
{
/* jmp far (absolute address in operand) */
if (insn[0] == 0xea)
return 1;
if (insn[0] == 0xff)
{
/* jump near, absolute indirect (/4) */
if ((insn[1] & 0x38) == 0x20)
return 1;
/* jump far, absolute indirect (/5) */
if ((insn[1] & 0x38) == 0x28)
return 1;
}
return 0;
}
static int
i386_absolute_call_p (gdb_byte *insn)
{
/* call far, absolute */
if (insn[0] == 0x9a)
return 1;
if (insn[0] == 0xff)
{
/* Call near, absolute indirect (/2) */
if ((insn[1] & 0x38) == 0x10)
return 1;
/* Call far, absolute indirect (/3) */
if ((insn[1] & 0x38) == 0x18)
return 1;
}
return 0;
}
static int
i386_ret_p (gdb_byte *insn)
{
switch (insn[0])
{
case 0xc2: /* ret near, pop N bytes */
case 0xc3: /* ret near */
case 0xca: /* ret far, pop N bytes */
case 0xcb: /* ret far */
case 0xcf: /* iret */
return 1;
default:
return 0;
}
}
static int
i386_call_p (gdb_byte *insn)
{
if (i386_absolute_call_p (insn))
return 1;
/* call near, relative */
if (insn[0] == 0xe8)
return 1;
return 0;
}
static int
i386_breakpoint_p (gdb_byte *insn)
{
return insn[0] == 0xcc; /* int 3 */
}
/* Return non-zero if INSN is a system call, and set *LENGTHP to its
length in bytes. Otherwise, return zero. */
static int
i386_syscall_p (gdb_byte *insn, ULONGEST *lengthp)
{
if (insn[0] == 0xcd)
{
*lengthp = 2;
return 1;
}
return 0;
}
/* Fix up the state of registers and memory after having single-stepped
a displaced instruction. */
void
i386_displaced_step_fixup (struct gdbarch *gdbarch,
struct displaced_step_closure *closure,
CORE_ADDR from, CORE_ADDR to,
struct regcache *regs)
{
/* The offset we applied to the instruction's address.
This could well be negative (when viewed as a signed 32-bit
value), but ULONGEST won't reflect that, so take care when
applying it. */
ULONGEST insn_offset = to - from;
/* Since we use simple_displaced_step_copy_insn, our closure is a
copy of the instruction. */
gdb_byte *insn = (gdb_byte *) closure;
if (debug_displaced)
fprintf_unfiltered (gdb_stdlog,
"displaced: fixup (0x%s, 0x%s), "
"insn = 0x%02x 0x%02x ...\n",
paddr_nz (from), paddr_nz (to), insn[0], insn[1]);
/* The list of issues to contend with here is taken from
resume_execution in arch/i386/kernel/kprobes.c, Linux 2.6.20.
Yay for Free Software! */
/* Relocate the %eip, if necessary. */
/* Except in the case of absolute or indirect jump or call
instructions, or a return instruction, the new eip is relative to
the displaced instruction; make it relative. Well, signal
handler returns don't need relocation either, but we use the
value of %eip to recognize those; see below. */
if (! i386_absolute_jmp_p (insn)
&& ! i386_absolute_call_p (insn)
&& ! i386_ret_p (insn))
{
ULONGEST orig_eip;
ULONGEST insn_len;
regcache_cooked_read_unsigned (regs, I386_EIP_REGNUM, &orig_eip);
/* A signal trampoline system call changes the %eip, resuming
execution of the main program after the signal handler has
returned. That makes them like 'return' instructions; we
shouldn't relocate %eip.
But most system calls don't, and we do need to relocate %eip.
Our heuristic for distinguishing these cases: if stepping
over the system call instruction left control directly after
the instruction, the we relocate --- control almost certainly
doesn't belong in the displaced copy. Otherwise, we assume
the instruction has put control where it belongs, and leave
it unrelocated. Goodness help us if there are PC-relative
system calls. */
if (i386_syscall_p (insn, &insn_len)
&& orig_eip != to + insn_len)
{
if (debug_displaced)
fprintf_unfiltered (gdb_stdlog,
"displaced: syscall changed %%eip; "
"not relocating\n");
}
else
{
ULONGEST eip = (orig_eip - insn_offset) & 0xffffffffUL;
/* If we have stepped over a breakpoint, set the %eip to
point at the breakpoint instruction itself.
(gdbarch_decr_pc_after_break was never something the core
of GDB should have been concerned with; arch-specific
code should be making PC values consistent before
presenting them to GDB.) */
if (i386_breakpoint_p (insn))
{
fprintf_unfiltered (gdb_stdlog,
"displaced: stepped breakpoint\n");
eip--;
}
regcache_cooked_write_unsigned (regs, I386_EIP_REGNUM, eip);
if (debug_displaced)
fprintf_unfiltered (gdb_stdlog,
"displaced: "
"relocated %%eip from 0x%s to 0x%s\n",
paddr_nz (orig_eip), paddr_nz (eip));
}
}
/* If the instruction was PUSHFL, then the TF bit will be set in the
pushed value, and should be cleared. We'll leave this for later,
since GDB already messes up the TF flag when stepping over a
pushfl. */
/* If the instruction was a call, the return address now atop the
stack is the address following the copied instruction. We need
to make it the address following the original instruction. */
if (i386_call_p (insn))
{
ULONGEST esp;
ULONGEST retaddr;
const ULONGEST retaddr_len = 4;
regcache_cooked_read_unsigned (regs, I386_ESP_REGNUM, &esp);
retaddr = read_memory_unsigned_integer (esp, retaddr_len);
retaddr = (retaddr - insn_offset) & 0xffffffffUL;
write_memory_unsigned_integer (esp, retaddr_len, retaddr);
if (debug_displaced)
fprintf_unfiltered (gdb_stdlog,
"displaced: relocated return addr at 0x%s "
"to 0x%s\n",
paddr_nz (esp),
paddr_nz (retaddr));
}
}
#ifdef I386_REGNO_TO_SYMMETRY #ifdef I386_REGNO_TO_SYMMETRY
#error "The Sequent Symmetry is no longer supported." #error "The Sequent Symmetry is no longer supported."
@ -521,14 +740,14 @@ i386_analyze_stack_align (CORE_ADDR pc, CORE_ADDR current_pc,
} }
/* Maximum instruction length we need to handle. */ /* Maximum instruction length we need to handle. */
#define I386_MAX_INSN_LEN 6 #define I386_MAX_MATCHED_INSN_LEN 6
/* Instruction description. */ /* Instruction description. */
struct i386_insn struct i386_insn
{ {
size_t len; size_t len;
gdb_byte insn[I386_MAX_INSN_LEN]; gdb_byte insn[I386_MAX_MATCHED_INSN_LEN];
gdb_byte mask[I386_MAX_INSN_LEN]; gdb_byte mask[I386_MAX_MATCHED_INSN_LEN];
}; };
/* Search for the instruction at PC in the list SKIP_INSNS. Return /* Search for the instruction at PC in the list SKIP_INSNS. Return
@ -547,12 +766,12 @@ i386_match_insn (CORE_ADDR pc, struct i386_insn *skip_insns)
{ {
if ((op & insn->mask[0]) == insn->insn[0]) if ((op & insn->mask[0]) == insn->insn[0])
{ {
gdb_byte buf[I386_MAX_INSN_LEN - 1]; gdb_byte buf[I386_MAX_MATCHED_INSN_LEN - 1];
int insn_matched = 1; int insn_matched = 1;
size_t i; size_t i;
gdb_assert (insn->len > 1); gdb_assert (insn->len > 1);
gdb_assert (insn->len <= I386_MAX_INSN_LEN); gdb_assert (insn->len <= I386_MAX_MATCHED_INSN_LEN);
target_read_memory (pc + 1, buf, insn->len - 1); target_read_memory (pc + 1, buf, insn->len - 1);
for (i = 1; i < insn->len; i++) for (i = 1; i < insn->len; i++)
@ -2375,6 +2594,7 @@ i386_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
set_gdbarch_breakpoint_from_pc (gdbarch, i386_breakpoint_from_pc); set_gdbarch_breakpoint_from_pc (gdbarch, i386_breakpoint_from_pc);
set_gdbarch_decr_pc_after_break (gdbarch, 1); set_gdbarch_decr_pc_after_break (gdbarch, 1);
set_gdbarch_max_insn_length (gdbarch, I386_MAX_INSN_LEN);
set_gdbarch_frame_args_skip (gdbarch, 8); set_gdbarch_frame_args_skip (gdbarch, 8);

10
gdb/i386-tdep.h
View File

@ -164,6 +164,10 @@ extern struct type *i386_sse_type (struct gdbarch *gdbarch);
#define I386_SEL_UPL 0x0003 /* User Privilige Level. */ #define I386_SEL_UPL 0x0003 /* User Privilige Level. */
#define I386_SEL_KPL 0x0000 /* Kernel Privilige Level. */ #define I386_SEL_KPL 0x0000 /* Kernel Privilige Level. */
/* The length of the longest i386 instruction (according to
include/asm-i386/kprobes.h in Linux 2.6. */
#define I386_MAX_INSN_LEN (16)
/* Functions exported from i386-tdep.c. */ /* Functions exported from i386-tdep.c. */
extern CORE_ADDR i386_pe_skip_trampoline_code (CORE_ADDR pc, char *name); extern CORE_ADDR i386_pe_skip_trampoline_code (CORE_ADDR pc, char *name);
@ -195,6 +199,12 @@ extern const struct regset *
i386_regset_from_core_section (struct gdbarch *gdbarch, i386_regset_from_core_section (struct gdbarch *gdbarch,
const char *sect_name, size_t sect_size); const char *sect_name, size_t sect_size);
extern void i386_displaced_step_fixup (struct gdbarch *gdbarch,
struct displaced_step_closure *closure,
CORE_ADDR from, CORE_ADDR to,
struct regcache *regs);
/* Initialize a basic ELF architecture variant. */ /* Initialize a basic ELF architecture variant. */
extern void i386_elf_init_abi (struct gdbarch_info, struct gdbarch *); extern void i386_elf_init_abi (struct gdbarch_info, struct gdbarch *);

8
gdb/inferior.h
View File

@ -387,6 +387,14 @@ extern struct regcache *stop_registers;
than forked. */ than forked. */
extern int attach_flag; extern int attach_flag;
/* True if we are debugging displaced stepping. */
extern int debug_displaced;
/* Dump LEN bytes at BUF in hex to FILE, followed by a newline. */
void displaced_step_dump_bytes (struct ui_file *file,
const gdb_byte *buf, size_t len);
/* Possible values for gdbarch_call_dummy_location. */ /* Possible values for gdbarch_call_dummy_location. */
#define ON_STACK 1 #define ON_STACK 1

526
gdb/infrun.c
View File

@ -103,6 +103,14 @@ int sync_execution = 0;
static ptid_t previous_inferior_ptid; static ptid_t previous_inferior_ptid;
int debug_displaced = 0;
static void
show_debug_displaced (struct ui_file *file, int from_tty,
struct cmd_list_element *c, const char *value)
{
fprintf_filtered (file, _("Displace stepping debugging is %s.\n"), value);
}
static int debug_infrun = 0; static int debug_infrun = 0;
static void static void
show_debug_infrun (struct ui_file *file, int from_tty, show_debug_infrun (struct ui_file *file, int from_tty,
@ -459,6 +467,377 @@ static int stepping_past_singlestep_breakpoint;
stepping the thread user has selected. */ stepping the thread user has selected. */
static ptid_t deferred_step_ptid; static ptid_t deferred_step_ptid;
/* Displaced stepping. */
/* In non-stop debugging mode, we must take special care to manage
breakpoints properly; in particular, the traditional strategy for
stepping a thread past a breakpoint it has hit is unsuitable.
'Displaced stepping' is a tactic for stepping one thread past a
breakpoint it has hit while ensuring that other threads running
concurrently will hit the breakpoint as they should.
The traditional way to step a thread T off a breakpoint in a
multi-threaded program in all-stop mode is as follows:
a0) Initially, all threads are stopped, and breakpoints are not
inserted.
a1) We single-step T, leaving breakpoints uninserted.
a2) We insert breakpoints, and resume all threads.
In non-stop debugging, however, this strategy is unsuitable: we
don't want to have to stop all threads in the system in order to
continue or step T past a breakpoint. Instead, we use displaced
stepping:
n0) Initially, T is stopped, other threads are running, and
breakpoints are inserted.
n1) We copy the instruction "under" the breakpoint to a separate
location, outside the main code stream, making any adjustments
to the instruction, register, and memory state as directed by
T's architecture.
n2) We single-step T over the instruction at its new location.
n3) We adjust the resulting register and memory state as directed
by T's architecture. This includes resetting T's PC to point
back into the main instruction stream.
n4) We resume T.
This approach depends on the following gdbarch methods:
- gdbarch_max_insn_length and gdbarch_displaced_step_location
indicate where to copy the instruction, and how much space must
be reserved there. We use these in step n1.
- gdbarch_displaced_step_copy_insn copies a instruction to a new
address, and makes any necessary adjustments to the instruction,
register contents, and memory. We use this in step n1.
- gdbarch_displaced_step_fixup adjusts registers and memory after
we have successfuly single-stepped the instruction, to yield the
same effect the instruction would have had if we had executed it
at its original address. We use this in step n3.
- gdbarch_displaced_step_free_closure provides cleanup.
The gdbarch_displaced_step_copy_insn and
gdbarch_displaced_step_fixup functions must be written so that
copying an instruction with gdbarch_displaced_step_copy_insn,
single-stepping across the copied instruction, and then applying
gdbarch_displaced_insn_fixup should have the same effects on the
thread's memory and registers as stepping the instruction in place
would have. Exactly which responsibilities fall to the copy and
which fall to the fixup is up to the author of those functions.
See the comments in gdbarch.sh for details.
Note that displaced stepping and software single-step cannot
currently be used in combination, although with some care I think
they could be made to. Software single-step works by placing
breakpoints on all possible subsequent instructions; if the
displaced instruction is a PC-relative jump, those breakpoints
could fall in very strange places --- on pages that aren't
executable, or at addresses that are not proper instruction
boundaries. (We do generally let other threads run while we wait
to hit the software single-step breakpoint, and they might
encounter such a corrupted instruction.) One way to work around
this would be to have gdbarch_displaced_step_copy_insn fully
simulate the effect of PC-relative instructions (and return NULL)
on architectures that use software single-stepping.
In non-stop mode, we can have independent and simultaneous step
requests, so more than one thread may need to simultaneously step
over a breakpoint. The current implementation assumes there is
only one scratch space per process. In this case, we have to
serialize access to the scratch space. If thread A wants to step
over a breakpoint, but we are currently waiting for some other
thread to complete a displaced step, we leave thread A stopped and
place it in the displaced_step_request_queue. Whenever a displaced
step finishes, we pick the next thread in the queue and start a new
displaced step operation on it. See displaced_step_prepare and
displaced_step_fixup for details. */
/* If this is not null_ptid, this is the thread carrying out a
displaced single-step. This thread's state will require fixing up
once it has completed its step. */
static ptid_t displaced_step_ptid;
struct displaced_step_request
{
ptid_t ptid;
struct displaced_step_request *next;
};
/* A queue of pending displaced stepping requests. */
struct displaced_step_request *displaced_step_request_queue;
/* The architecture the thread had when we stepped it. */
static struct gdbarch *displaced_step_gdbarch;
/* The closure provided gdbarch_displaced_step_copy_insn, to be used
for post-step cleanup. */
static struct displaced_step_closure *displaced_step_closure;
/* The address of the original instruction, and the copy we made. */
static CORE_ADDR displaced_step_original, displaced_step_copy;
/* Saved contents of copy area. */
static gdb_byte *displaced_step_saved_copy;
/* When this is non-zero, we are allowed to use displaced stepping, if
the architecture supports it. When this is zero, we use
traditional the hold-and-step approach. */
int can_use_displaced_stepping = 1;
static void
show_can_use_displaced_stepping (struct ui_file *file, int from_tty,
struct cmd_list_element *c,
const char *value)
{
fprintf_filtered (file, _("\
Debugger's willingness to use displaced stepping to step over "
"breakpoints is %s.\n"), value);
}
/* Return non-zero if displaced stepping is enabled, and can be used
with GDBARCH. */
static int
use_displaced_stepping (struct gdbarch *gdbarch)
{
return (can_use_displaced_stepping
&& gdbarch_displaced_step_copy_insn_p (gdbarch));
}
/* Clean out any stray displaced stepping state. */
static void
displaced_step_clear (void)
{
/* Indicate that there is no cleanup pending. */
displaced_step_ptid = null_ptid;
if (displaced_step_closure)
{
gdbarch_displaced_step_free_closure (displaced_step_gdbarch,
displaced_step_closure);
displaced_step_closure = NULL;
}
}
static void
cleanup_displaced_step_closure (void *ptr)
{
struct displaced_step_closure *closure = ptr;
gdbarch_displaced_step_free_closure (current_gdbarch, closure);
}
/* Dump LEN bytes at BUF in hex to FILE, followed by a newline. */
void
displaced_step_dump_bytes (struct ui_file *file,
const gdb_byte *buf,
size_t len)
{
int i;
for (i = 0; i < len; i++)
fprintf_unfiltered (file, "%02x ", buf[i]);
fputs_unfiltered ("\n", file);
}
/* Prepare to single-step, using displaced stepping.
Note that we cannot use displaced stepping when we have a signal to
deliver. If we have a signal to deliver and an instruction to step
over, then after the step, there will be no indication from the
target whether the thread entered a signal handler or ignored the
signal and stepped over the instruction successfully --- both cases
result in a simple SIGTRAP. In the first case we mustn't do a
fixup, and in the second case we must --- but we can't tell which.
Comments in the code for 'random signals' in handle_inferior_event
explain how we handle this case instead.
Returns 1 if preparing was successful -- this thread is going to be
stepped now; or 0 if displaced stepping this thread got queued. */
static int
displaced_step_prepare (ptid_t ptid)
{
struct cleanup *old_cleanups;
struct regcache *regcache = get_thread_regcache (ptid);
struct gdbarch *gdbarch = get_regcache_arch (regcache);
CORE_ADDR original, copy;
ULONGEST len;
struct displaced_step_closure *closure;
/* We should never reach this function if the architecture does not
support displaced stepping. */
gdb_assert (gdbarch_displaced_step_copy_insn_p (gdbarch));
/* For the first cut, we're displaced stepping one thread at a
time. */
if (!ptid_equal (displaced_step_ptid, null_ptid))
{
/* Already waiting for a displaced step to finish. Defer this
request and place in queue. */
struct displaced_step_request *req, *new_req;
if (debug_displaced)
fprintf_unfiltered (gdb_stdlog,
"displaced: defering step of %s\n",
target_pid_to_str (ptid));
new_req = xmalloc (sizeof (*new_req));
new_req->ptid = ptid;
new_req->next = NULL;
if (displaced_step_request_queue)
{
for (req = displaced_step_request_queue;
req && req->next;
req = req->next)
;
req->next = new_req;
}
else
displaced_step_request_queue = new_req;
return 0;
}
else
{
if (debug_displaced)
fprintf_unfiltered (gdb_stdlog,
"displaced: stepping %s now\n",
target_pid_to_str (ptid));
}
displaced_step_clear ();
original = read_pc_pid (ptid);
copy = gdbarch_displaced_step_location (gdbarch);
len = gdbarch_max_insn_length (gdbarch);
/* Save the original contents of the copy area. */
displaced_step_saved_copy = xmalloc (len);
old_cleanups = make_cleanup (free_current_contents,
&displaced_step_saved_copy);
read_memory (copy, displaced_step_saved_copy, len);
if (debug_displaced)
{
fprintf_unfiltered (gdb_stdlog, "displaced: saved 0x%s: ",
paddr_nz (copy));
displaced_step_dump_bytes (gdb_stdlog, displaced_step_saved_copy, len);
};
closure = gdbarch_displaced_step_copy_insn (gdbarch,
original, copy, regcache);
/* We don't support the fully-simulated case at present. */
gdb_assert (closure);
make_cleanup (cleanup_displaced_step_closure, closure);
/* Resume execution at the copy. */
write_pc_pid (copy, ptid);
discard_cleanups (old_cleanups);
if (debug_displaced)
fprintf_unfiltered (gdb_stdlog, "displaced: displaced pc to 0x%s\n",
paddr_nz (copy));
/* Save the information we need to fix things up if the step
succeeds. */
displaced_step_ptid = ptid;
displaced_step_gdbarch = gdbarch;
displaced_step_closure = closure;
displaced_step_original = original;
displaced_step_copy = copy;
return 1;
}
static void
displaced_step_clear_cleanup (void *ignore)
{
displaced_step_clear ();
}
static void
write_memory_ptid (ptid_t ptid, CORE_ADDR memaddr, const gdb_byte *myaddr, int len)
{
struct cleanup *ptid_cleanup = save_inferior_ptid ();
inferior_ptid = ptid;
write_memory (memaddr, myaddr, len);
do_cleanups (ptid_cleanup);
}
static void
displaced_step_fixup (ptid_t event_ptid, enum target_signal signal)
{
struct cleanup *old_cleanups;
/* Was this event for the pid we displaced? */
if (ptid_equal (displaced_step_ptid, null_ptid)
|| ! ptid_equal (displaced_step_ptid, event_ptid))
return;
old_cleanups = make_cleanup (displaced_step_clear_cleanup, 0);
/* Restore the contents of the copy area. */
{
ULONGEST len = gdbarch_max_insn_length (displaced_step_gdbarch);
write_memory_ptid (displaced_step_ptid, displaced_step_copy,
displaced_step_saved_copy, len);
if (debug_displaced)
fprintf_unfiltered (gdb_stdlog, "displaced: restored 0x%s\n",
paddr_nz (displaced_step_copy));
}
/* Did the instruction complete successfully? */
if (signal == TARGET_SIGNAL_TRAP)
{
/* Fix up the resulting state. */
gdbarch_displaced_step_fixup (displaced_step_gdbarch,
displaced_step_closure,
displaced_step_original,
displaced_step_copy,
get_thread_regcache (displaced_step_ptid));
}
else
{
/* Since the instruction didn't complete, all we can do is
relocate the PC. */
CORE_ADDR pc = read_pc_pid (event_ptid);
pc = displaced_step_original + (pc - displaced_step_copy);
write_pc_pid (pc, event_ptid);
}
do_cleanups (old_cleanups);
/* Are there any pending displaced stepping requests? If so, run
one now. */
if (displaced_step_request_queue)
{
struct displaced_step_request *head;
ptid_t ptid;
head = displaced_step_request_queue;
ptid = head->ptid;
displaced_step_request_queue = head->next;
xfree (head);
if (debug_displaced)
fprintf_unfiltered (gdb_stdlog,
"displaced: stepping queued %s now\n",
target_pid_to_str (ptid));
displaced_step_ptid = null_ptid;
displaced_step_prepare (ptid);
target_resume (ptid, 1, TARGET_SIGNAL_0);
}
}
/* Resuming. */
/* Things to clean up if we QUIT out of resume (). */ /* Things to clean up if we QUIT out of resume (). */
static void static void
@ -510,14 +889,14 @@ resume (int step, enum target_signal sig)
{ {
int should_resume = 1; int should_resume = 1;
struct cleanup *old_cleanups = make_cleanup (resume_cleanups, 0); struct cleanup *old_cleanups = make_cleanup (resume_cleanups, 0);
CORE_ADDR pc = read_pc ();
QUIT; QUIT;
if (debug_infrun) if (debug_infrun)
fprintf_unfiltered (gdb_stdlog, "infrun: resume (step=%d, signal=%d)\n", fprintf_unfiltered (gdb_stdlog,
step, sig); "infrun: resume (step=%d, signal=%d), "
"stepping_over_breakpoint=%d\n",
/* FIXME: calling breakpoint_here_p (read_pc ()) three times! */ step, sig, stepping_over_breakpoint);
/* Some targets (e.g. Solaris x86) have a kernel bug when stepping /* Some targets (e.g. Solaris x86) have a kernel bug when stepping
over an instruction that causes a page fault without triggering over an instruction that causes a page fault without triggering
@ -535,7 +914,7 @@ resume (int step, enum target_signal sig)
removed or inserted, as appropriate. The exception is if we're sitting removed or inserted, as appropriate. The exception is if we're sitting
at a permanent breakpoint; we need to step over it, but permanent at a permanent breakpoint; we need to step over it, but permanent
breakpoints can't be removed. So we have to test for it here. */ breakpoints can't be removed. So we have to test for it here. */
if (breakpoint_here_p (read_pc ()) == permanent_breakpoint_here) if (breakpoint_here_p (pc) == permanent_breakpoint_here)
{ {
if (gdbarch_skip_permanent_breakpoint_p (current_gdbarch)) if (gdbarch_skip_permanent_breakpoint_p (current_gdbarch))
gdbarch_skip_permanent_breakpoint (current_gdbarch, gdbarch_skip_permanent_breakpoint (current_gdbarch,
@ -547,6 +926,24 @@ how to step past a permanent breakpoint on this architecture. Try using\n\
a command like `return' or `jump' to continue execution.")); a command like `return' or `jump' to continue execution."));
} }
/* If enabled, step over breakpoints by executing a copy of the
instruction at a different address.
We can't use displaced stepping when we have a signal to deliver;
the comments for displaced_step_prepare explain why. The
comments in the handle_inferior event for dealing with 'random
signals' explain what we do instead. */
if (use_displaced_stepping (current_gdbarch)
&& stepping_over_breakpoint
&& sig == TARGET_SIGNAL_0)
{
if (!displaced_step_prepare (inferior_ptid))
/* Got placed in displaced stepping queue. Will be resumed
later when all the currently queued displaced stepping
requests finish. */
return;
}
if (step && gdbarch_software_single_step_p (current_gdbarch)) if (step && gdbarch_software_single_step_p (current_gdbarch))
{ {
/* Do it the hard way, w/temp breakpoints */ /* Do it the hard way, w/temp breakpoints */
@ -558,7 +955,7 @@ a command like `return' or `jump' to continue execution."));
`wait_for_inferior' */ `wait_for_inferior' */
singlestep_breakpoints_inserted_p = 1; singlestep_breakpoints_inserted_p = 1;
singlestep_ptid = inferior_ptid; singlestep_ptid = inferior_ptid;
singlestep_pc = read_pc (); singlestep_pc = pc;
} }
} }
@ -642,15 +1039,30 @@ a command like `return' or `jump' to continue execution."));
/* Most targets can step a breakpoint instruction, thus /* Most targets can step a breakpoint instruction, thus
executing it normally. But if this one cannot, just executing it normally. But if this one cannot, just
continue and we will hit it anyway. */ continue and we will hit it anyway. */
if (step && breakpoint_inserted_here_p (read_pc ())) if (step && breakpoint_inserted_here_p (pc))
step = 0; step = 0;
} }
if (debug_displaced
&& use_displaced_stepping (current_gdbarch)
&& stepping_over_breakpoint)
{
CORE_ADDR actual_pc = read_pc_pid (resume_ptid);
gdb_byte buf[4];
fprintf_unfiltered (gdb_stdlog, "displaced: run 0x%s: ",
paddr_nz (actual_pc));
read_memory (actual_pc, buf, sizeof (buf));
displaced_step_dump_bytes (gdb_stdlog, buf, sizeof (buf));
}
target_resume (resume_ptid, step, sig); target_resume (resume_ptid, step, sig);
} }
discard_cleanups (old_cleanups); discard_cleanups (old_cleanups);
} }
/* Proceeding. */
/* Clear out all variables saying what to do when inferior is continued. /* Clear out all variables saying what to do when inferior is continued.
First do this, then set the ones you want, then call `proceed'. */ First do this, then set the ones you want, then call `proceed'. */
@ -787,17 +1199,20 @@ proceed (CORE_ADDR addr, enum target_signal siggnal, int step)
if (oneproc) if (oneproc)
{ {
/* We will get a trace trap after one instruction.
Continue it automatically and insert breakpoints then. */
stepping_over_breakpoint = 1; stepping_over_breakpoint = 1;
/* FIXME: if breakpoints are always inserted, we'll trap /* If displaced stepping is enabled, we can step over the
if trying to single-step over breakpoint. Disable breakpoint without hitting it, so leave all breakpoints
all breakpoints. In future, we'd need to invent some inserted. Otherwise we need to disable all breakpoints, step
smart way of stepping over breakpoint instruction without one instruction, and then re-add them when that step is
hitting breakpoint. */ finished. */
if (!use_displaced_stepping (current_gdbarch))
remove_breakpoints (); remove_breakpoints ();
} }
else
/* We can insert breakpoints if we're not trying to step over one,
or if we are stepping over one but we're using displaced stepping
to do so. */
if (! stepping_over_breakpoint || use_displaced_stepping (current_gdbarch))
insert_breakpoints (); insert_breakpoints ();
if (siggnal != TARGET_SIGNAL_DEFAULT) if (siggnal != TARGET_SIGNAL_DEFAULT)
@ -908,7 +1323,10 @@ init_wait_for_inferior (void)
deferred_step_ptid = null_ptid; deferred_step_ptid = null_ptid;
target_last_wait_ptid = minus_one_ptid; target_last_wait_ptid = minus_one_ptid;
displaced_step_clear ();
} }
/* This enum encodes possible reasons for doing a target_wait, so that /* This enum encodes possible reasons for doing a target_wait, so that
wfi can call target_wait in one place. (Ultimately the call will be wfi can call target_wait in one place. (Ultimately the call will be
@ -1580,10 +1998,31 @@ handle_inferior_event (struct execution_control_state *ecs)
return; return;
} }
/* Do we need to clean up the state of a thread that has completed a
displaced single-step? (Doing so usually affects the PC, so do
it here, before we set stop_pc.) */
displaced_step_fixup (ecs->ptid, stop_signal);
stop_pc = read_pc_pid (ecs->ptid); stop_pc = read_pc_pid (ecs->ptid);
if (debug_infrun) if (debug_infrun)
fprintf_unfiltered (gdb_stdlog, "infrun: stop_pc = 0x%s\n", paddr_nz (stop_pc)); {
fprintf_unfiltered (gdb_stdlog, "infrun: stop_pc = 0x%s\n",
paddr_nz (stop_pc));
if (STOPPED_BY_WATCHPOINT (&ecs->ws))
{
CORE_ADDR addr;
fprintf_unfiltered (gdb_stdlog, "infrun: stopped by watchpoint\n");
if (target_stopped_data_address (&current_target, &addr))
fprintf_unfiltered (gdb_stdlog,
"infrun: stopped data address = 0x%s\n",
paddr_nz (addr));
else
fprintf_unfiltered (gdb_stdlog,
"infrun: (no data address available)\n");
}
}
if (stepping_past_singlestep_breakpoint) if (stepping_past_singlestep_breakpoint)
{ {
@ -1731,7 +2170,7 @@ handle_inferior_event (struct execution_control_state *ecs)
if (thread_hop_needed) if (thread_hop_needed)
{ {
int remove_status; int remove_status = 0;
if (debug_infrun) if (debug_infrun)
fprintf_unfiltered (gdb_stdlog, "infrun: thread_hop_needed\n"); fprintf_unfiltered (gdb_stdlog, "infrun: thread_hop_needed\n");
@ -1746,7 +2185,11 @@ handle_inferior_event (struct execution_control_state *ecs)
singlestep_breakpoints_inserted_p = 0; singlestep_breakpoints_inserted_p = 0;
} }
/* If the arch can displace step, don't remove the
breakpoints. */
if (!use_displaced_stepping (current_gdbarch))
remove_status = remove_breakpoints (); remove_status = remove_breakpoints ();
/* Did we fail to remove breakpoints? If so, try /* Did we fail to remove breakpoints? If so, try
to set the PC past the bp. (There's at least to set the PC past the bp. (There's at least
one situation in which we can fail to remove one situation in which we can fail to remove
@ -1810,9 +2253,6 @@ handle_inferior_event (struct execution_control_state *ecs)
&& (HAVE_STEPPABLE_WATCHPOINT && (HAVE_STEPPABLE_WATCHPOINT
|| gdbarch_have_nonsteppable_watchpoint (current_gdbarch))) || gdbarch_have_nonsteppable_watchpoint (current_gdbarch)))
{ {
if (debug_infrun)
fprintf_unfiltered (gdb_stdlog, "infrun: STOPPED_BY_WATCHPOINT\n");
/* At this point, we are stopped at an instruction which has /* At this point, we are stopped at an instruction which has
attempted to write to a piece of memory under control of attempted to write to a piece of memory under control of
a watchpoint. The instruction hasn't actually executed a watchpoint. The instruction hasn't actually executed
@ -1915,10 +2355,14 @@ handle_inferior_event (struct execution_control_state *ecs)
when we're trying to execute a breakpoint instruction on a when we're trying to execute a breakpoint instruction on a
non-executable stack. This happens for call dummy breakpoints non-executable stack. This happens for call dummy breakpoints
for architectures like SPARC that place call dummies on the for architectures like SPARC that place call dummies on the
stack. */ stack.
If we're doing a displaced step past a breakpoint, then the
breakpoint is always inserted at the original instruction;
non-standard signals can't be explained by the breakpoint. */
if (stop_signal == TARGET_SIGNAL_TRAP if (stop_signal == TARGET_SIGNAL_TRAP
|| (breakpoint_inserted_here_p (stop_pc) || (! stepping_over_breakpoint
&& breakpoint_inserted_here_p (stop_pc)
&& (stop_signal == TARGET_SIGNAL_ILL && (stop_signal == TARGET_SIGNAL_ILL
|| stop_signal == TARGET_SIGNAL_SEGV || stop_signal == TARGET_SIGNAL_SEGV
|| stop_signal == TARGET_SIGNAL_EMT)) || stop_signal == TARGET_SIGNAL_EMT))
@ -2045,7 +2489,7 @@ process_event_stop_test:
{ {
/* We were just starting a new sequence, attempting to /* We were just starting a new sequence, attempting to
single-step off of a breakpoint and expecting a SIGTRAP. single-step off of a breakpoint and expecting a SIGTRAP.
Intead this signal arrives. This signal will take us out Instead this signal arrives. This signal will take us out
of the stepping range so GDB needs to remember to, when of the stepping range so GDB needs to remember to, when
the signal handler returns, resume stepping off that the signal handler returns, resume stepping off that
breakpoint. */ breakpoint. */
@ -2053,6 +2497,10 @@ process_event_stop_test:
code paths as single-step - set a breakpoint at the code paths as single-step - set a breakpoint at the
signal return address and then, once hit, step off that signal return address and then, once hit, step off that
breakpoint. */ breakpoint. */
if (debug_infrun)
fprintf_unfiltered (gdb_stdlog,
"infrun: signal arrived while stepping over "
"breakpoint\n");
insert_step_resume_breakpoint_at_frame (get_current_frame ()); insert_step_resume_breakpoint_at_frame (get_current_frame ());
ecs->step_after_step_resume_breakpoint = 1; ecs->step_after_step_resume_breakpoint = 1;
@ -2076,6 +2524,11 @@ process_event_stop_test:
Note that this is only needed for a signal delivered Note that this is only needed for a signal delivered
while in the single-step range. Nested signals aren't a while in the single-step range. Nested signals aren't a
problem as they eventually all return. */ problem as they eventually all return. */
if (debug_infrun)
fprintf_unfiltered (gdb_stdlog,
"infrun: signal may take us out of "
"single-step range\n");
insert_step_resume_breakpoint_at_frame (get_current_frame ()); insert_step_resume_breakpoint_at_frame (get_current_frame ());
keep_going (ecs); keep_going (ecs);
return; return;
@ -2905,6 +3358,10 @@ keep_going (struct execution_control_state *ecs)
if (ecs->stepping_over_breakpoint) if (ecs->stepping_over_breakpoint)
{ {
if (! use_displaced_stepping (current_gdbarch))
/* Since we can't do a displaced step, we have to remove
the breakpoint while we step it. To keep things
simple, we remove them all. */
remove_breakpoints (); remove_breakpoints ();
} }
else else
@ -4011,6 +4468,14 @@ When non-zero, inferior specific debugging is enabled."),
show_debug_infrun, show_debug_infrun,
&setdebuglist, &showdebuglist); &setdebuglist, &showdebuglist);
add_setshow_boolean_cmd ("displaced", class_maintenance, &debug_displaced, _("\
Set displaced stepping debugging."), _("\
Show displaced stepping debugging."), _("\
When non-zero, displaced stepping specific debugging is enabled."),
NULL,
show_debug_displaced,
&setdebuglist, &showdebuglist);
numsigs = (int) TARGET_SIGNAL_LAST; numsigs = (int) TARGET_SIGNAL_LAST;
signal_stop = (unsigned char *) xmalloc (sizeof (signal_stop[0]) * numsigs); signal_stop = (unsigned char *) xmalloc (sizeof (signal_stop[0]) * numsigs);
signal_print = (unsigned char *) signal_print = (unsigned char *)
@ -4106,9 +4571,22 @@ function is skipped and the step command stops at a different source line."),
show_step_stop_if_no_debug, show_step_stop_if_no_debug,
&setlist, &showlist); &setlist, &showlist);
add_setshow_boolean_cmd ("can-use-displaced-stepping", class_maintenance,
&can_use_displaced_stepping, _("\
Set debugger's willingness to use displaced stepping."), _("\
Show debugger's willingness to use displaced stepping."), _("\
If zero, gdb will not use to use displaced stepping to step over\n\
breakpoints, even if such is supported by the target."),
NULL,
show_can_use_displaced_stepping,
&maintenance_set_cmdlist,
&maintenance_show_cmdlist);
/* ptid initializations */ /* ptid initializations */
null_ptid = ptid_build (0, 0, 0); null_ptid = ptid_build (0, 0, 0);
minus_one_ptid = ptid_build (-1, 0, 0); minus_one_ptid = ptid_build (-1, 0, 0);
inferior_ptid = null_ptid; inferior_ptid = null_ptid;
target_last_wait_ptid = minus_one_ptid; target_last_wait_ptid = minus_one_ptid;
displaced_step_ptid = null_ptid;
} }

4
gdb/testsuite/ChangeLog
View File

@ -1,3 +1,7 @@
2008-05-02 Jim Blandy <jimb@codesourcery.com>
* gdb.asm/asmsrc1.s: Add scratch space.
2007-05-01 Daniel Jacobowitz <dan@codesourcery.com> 2007-05-01 Daniel Jacobowitz <dan@codesourcery.com>
* gdb.arch/thumb-prologue.exp: Do not expect a saved PC. * gdb.arch/thumb-prologue.exp: Do not expect a saved PC.

12
gdb/testsuite/gdb.asm/asmsrc1.s
View File

@ -16,6 +16,18 @@
gdbasm_exit0 gdbasm_exit0
gdbasm_end _start gdbasm_end _start
comment "Displaced stepping requires scratch space at _start"
comment "at least as large as the largest instruction. No"
comment "breakpoints should be set within the scratch space."
gdbasm_several_nops
gdbasm_several_nops
gdbasm_several_nops
gdbasm_several_nops
gdbasm_several_nops
gdbasm_several_nops
gdbasm_several_nops
gdbasm_several_nops
comment "main routine for assembly source debugging test" comment "main routine for assembly source debugging test"
comment "This particular testcase uses macros in <arch>.inc to achieve" comment "This particular testcase uses macros in <arch>.inc to achieve"
comment "machine independence." comment "machine independence."