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Fix PR 21337: segfault when re-reading symbols.

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Fix issue exposed by commit 3e29f34.

The basic issue is that section data referenced through an objfile
pointer can also be referenced via the program-space data pointer,
although via a separate mapping mechanism, which is set up by
update_section_map.  Thus once section data attached to an objfile
pointer is released, the section map associated with the program-space
data pointer must be marked dirty to ensure that update_section_map is
called to prevent stale data being referenced.  For the matter at hand
this marking is being done via a call to objfiles_changed.

Before commit 3e29f34 objfiles_changed could be called after all of
the objfile pointers were processed in reread_symbols since section
data references via the program-space data pointer would not occur in
the calls of read_symbols performed by reread_symbols.

With commit 3e29f34 MIPS target specific calls to find_pc_section were
added to the code for DWARF information processing, which is called
via read_symbols.  Thus in reread_symbols the call to objfiles_changed
needs to be called before calling read_symbols, otherwise stale
section data can be referenced.

Thanks to Luis Machado for providing text for the main comment
associated with the change.

gdb/
2017-06-28  Doug Gilmore  <Doug.Gilmore@imgtec.com>
    PR gdb/21337
    * symfile.c (reread_symbols): Call objfiles_changed just before
    read_symbols.

gdb/testsuite/
2017-06-28  Doug Gilmore  <Doug.Gilmore@imgtec.com>
    PR gdb/21337
    * gdb.base/reread-readsym.exp: New file.
    * gdb.base/reread-readsym.c: New file.
This commit is contained in:
Doug Gilmore
2017-06-28 02:54:22 +01:00
committed by Maciej W. Rozycki
parent 819e1f8697
commit 41664b45ab
5 changed files with 115 additions and 3 deletions
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23
gdb/symfile.c
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@ -2587,6 +2587,9 @@ reread_symbols (void)
/* Free the obstacks for non-reusable objfiles. */
psymbol_bcache_free (objfile->psymbol_cache);
objfile->psymbol_cache = psymbol_bcache_init ();
/* NB: after this call to obstack_free, objfiles_changed
will need to be called (see discussion below). */
obstack_free (&objfile->objfile_obstack, 0);
objfile->sections = NULL;
objfile->compunit_symtabs = NULL;
@ -2639,6 +2642,23 @@ reread_symbols (void)
clear_complaints (&symfile_complaints, 1, 1);
objfile->flags &= ~OBJF_PSYMTABS_READ;
/* We are about to read new symbols and potentially also
DWARF information. Some targets may want to pass addresses
read from DWARF DIE's through an adjustment function before
saving them, like MIPS, which may call into
"find_pc_section". When called, that function will make
use of per-objfile program space data.
Since we discarded our section information above, we have
dangling pointers in the per-objfile program space data
structure. Force GDB to update the section mapping
information by letting it know the objfile has changed,
making the dangling pointers point to correct data
again. */
objfiles_changed ();
read_symbols (objfile, 0);
if (!objfile_has_symbols (objfile))
@ -2671,9 +2691,6 @@ reread_symbols (void)
if (!new_objfiles.empty ())
{
/* Notify objfiles that we've modified objfile sections. */
objfiles_changed ();
clear_symtab_users (0);
/* clear_objfile_data for each objfile was called before freeing it and