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PR 20569, segv in follow_exec

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The following testcases make GDB crash whenever an invalid sysroot is
provided, when GDB is unable to find a valid path to the symbol file:

 gdb.base/catch-syscall.exp
 gdb.base/execl-update-breakpoints.exp
 gdb.base/foll-exec-mode.exp
 gdb.base/foll-exec.exp
 gdb.base/foll-vfork.exp
 gdb.base/pie-execl.exp
 gdb.multi/bkpt-multi-exec.exp
 gdb.python/py-finish-breakpoint.exp
 gdb.threads/execl.exp
 gdb.threads/non-ldr-exc-1.exp
 gdb.threads/non-ldr-exc-2.exp
 gdb.threads/non-ldr-exc-3.exp
 gdb.threads/non-ldr-exc-4.exp
 gdb.threads/thread-execl.exp

The immediate cause of the segv is that follow_exec is passing a NULL
argument (the result of exec_file_find) to strlen.

However, the problem is deeper than that: follow_exec simply isn't
prepared for the case where sysroot translation fails to locate the
new executable.  Actually all callers of exec_file_find have bugs due
to confusion between host and target pathnames.  This commit attempts
to fix all that.

In terms of the testcases that were formerly segv'ing, GDB now prints
a warning but continues execution of the new program, so that the
tests now mostly FAIL instead.  You could argue the FAILs are due to a
legitimate problem with the test environment setting up the sysroot
translation incorrectly.

A new representative test is added which exercises the ne wwarning
code path even with native testing.

Tested on x86_64 Fedora 23, native and gdbserver.

gdb/ChangeLog:
2016-10-25  Sandra Loosemore  <sandra@codesourcery.com>
	    Luis Machado  <lgustavo@codesourcery.com>
	    Pedro Alves  <palves@redhat.com>

	PR gdb/20569
	* exceptions.c (exception_print_same): Moved here from exec.c.
	* exceptions.h (exception_print_same): Declare.
	* exec.h: Include "symfile-add-flags.h".
	(try_open_exec_file): New declaration.
	* exec.c (exception_print_same): Moved to exceptions.c.
	(try_open_exec_file): New function.
	(exec_file_locate_attach): Rename exec_file and full_exec_path
	variables to avoid confusion between target and host pathnames.
	Move pathname processing logic to exec_file_find.  Do not return
	early if pathname lookup fails; Call try_open_exec_file.
	* infrun.c (follow_exec): Split and rename execd_pathname variable
	to avoid confusion between target and host pathnames.  Warn if
	pathname lookup fails.  Pass target pathname to
	target_follow_exec, not hostpathname.  Call try_open_exec_file.
	* main.c (symbol_file_add_main_adapter): New function.
	(captured_main_1): Use it.
	* solib-svr4.c (open_symbol_file_object): Adjust to pass
	symfile_add_flags to symbol_file_add_main.
	* solib.c (exec_file_find): Incorporate fallback logic for relative
	pathnames formerly in exec_file_locate_attach.
	* symfile.c (symbol_file_add_main, symbol_file_add_main_1):
	Replace 'from_tty' parameter with a symfile_add_file.
	(symbol_file_command): Adjust to pass symfile_add_flags to
	symbol_file_add_main.
	* symfile.h (symbol_file_add_main): Replace 'from_tty' parameter
	with a symfile_add_file.

gdb/testsuite/ChangeLog:
2016-10-25  Luis Machado  <lgustavo@codesourcery.com>

	* gdb.base/exec-invalid-sysroot.exp: New file.
This commit is contained in:
Sandra Loosemore
2016-10-26 12:12:01 -05:00
committed by Pedro Alves
parent b15cc25cbe
commit ecf45d2cc7
14 changed files with 277 additions and 121 deletions
Download Patch File Download Diff File Expand all files Collapse all files

129
gdb/exec.c
View File

@ -136,73 +136,16 @@ exec_file_clear (int from_tty)
printf_unfiltered (_("No executable file now.\n"));
}
/* Returns non-zero if exceptions E1 and E2 are equal. Returns zero
otherwise. */
static int
exception_print_same (struct gdb_exception e1, struct gdb_exception e2)
{
const char *msg1 = e1.message;
const char *msg2 = e2.message;
if (msg1 == NULL)
msg1 = "";
if (msg2 == NULL)
msg2 = "";
return (e1.reason == e2.reason
&& e1.error == e2.error
&& strcmp (msg1, msg2) == 0);
}
/* See gdbcore.h. */
/* See exec.h. */
void
exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
try_open_exec_file (const char *exec_file_host, struct inferior *inf,
symfile_add_flags add_flags)
{
char *exec_file, *full_exec_path = NULL;
struct cleanup *old_chain;
struct gdb_exception prev_err = exception_none;
/* Do nothing if we already have an executable filename. */
exec_file = (char *) get_exec_file (0);
if (exec_file != NULL)
return;
/* Try to determine a filename from the process itself. */
exec_file = target_pid_to_exec_file (pid);
if (exec_file == NULL)
{
warning (_("No executable has been specified and target does not "
"support\n"
"determining executable automatically. "
"Try using the \"file\" command."));
return;
}
/* If gdb_sysroot is not empty and the discovered filename
is absolute then prefix the filename with gdb_sysroot. */
if (*gdb_sysroot != '\0' && IS_ABSOLUTE_PATH (exec_file))
{
full_exec_path = exec_file_find (exec_file, NULL);
if (full_exec_path == NULL)
return;
}
else
{
/* It's possible we don't have a full path, but rather just a
filename. Some targets, such as HP-UX, don't provide the
full path, sigh.
Attempt to qualify the filename against the source path.
(If that fails, we'll just fall back on the original
filename. Not much more we can do...) */
if (!source_full_path_of (exec_file, &full_exec_path))
full_exec_path = xstrdup (exec_file);
}
old_chain = make_cleanup (xfree, full_exec_path);
make_cleanup (free_current_contents, &prev_err.message);
old_chain = make_cleanup (free_current_contents, &prev_err.message);
/* exec_file_attach and symbol_file_add_main may throw an error if the file
cannot be opened either locally or remotely.
@ -217,7 +160,9 @@ exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
errors/exceptions in the following code. */
TRY
{
exec_file_attach (full_exec_path, from_tty);
/* We must do this step even if exec_file_host is NULL, so that
exec_file_attach will clear state. */
exec_file_attach (exec_file_host, add_flags & SYMFILE_VERBOSE);
}
CATCH (err, RETURN_MASK_ERROR)
{
@ -232,23 +177,61 @@ exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
}
END_CATCH
TRY
if (exec_file_host != NULL)
{
if (defer_bp_reset)
current_inferior ()->symfile_flags |= SYMFILE_DEFER_BP_RESET;
symbol_file_add_main (full_exec_path, from_tty);
TRY
{
symbol_file_add_main (exec_file_host, add_flags);
}
CATCH (err, RETURN_MASK_ERROR)
{
if (!exception_print_same (prev_err, err))
warning ("%s", err.message);
}
END_CATCH
}
CATCH (err, RETURN_MASK_ERROR)
{
if (!exception_print_same (prev_err, err))
warning ("%s", err.message);
}
END_CATCH
current_inferior ()->symfile_flags &= ~SYMFILE_DEFER_BP_RESET;
do_cleanups (old_chain);
}
/* See gdbcore.h. */
void
exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
{
char *exec_file_target, *exec_file_host;
struct cleanup *old_chain;
symfile_add_flags add_flags = 0;
/* Do nothing if we already have an executable filename. */
if (get_exec_file (0) != NULL)
return;
/* Try to determine a filename from the process itself. */
exec_file_target = target_pid_to_exec_file (pid);
if (exec_file_target == NULL)
{
warning (_("No executable has been specified and target does not "
"support\n"
"determining executable automatically. "
"Try using the \"file\" command."));
return;
}
exec_file_host = exec_file_find (exec_file_target, NULL);
old_chain = make_cleanup (xfree, exec_file_host);
if (defer_bp_reset)
add_flags |= SYMFILE_DEFER_BP_RESET;
if (from_tty)
add_flags |= SYMFILE_VERBOSE;
/* Attempt to open the exec file. */
try_open_exec_file (exec_file_host, current_inferior (), add_flags);
do_cleanups (old_chain);
}
/* Set FILENAME as the new exec file.
This function is intended to be behave essentially the same