The caching of the last function sym info in elf_find_function causes a segfault when last_section == section but the pointer to symbols has changed from the last invocation and func is not a valid pointer anymore. The following patch fixes this bug: diff --git a/elf.c b/elf.c --- a/elf.c +++ b/elf.c @@ -7475,6 +7475,7 @@ elf_find_function (bfd *abfd, const char **functionname_ptr) { static asection *last_section; + static asymbol **last_symbols; static asymbol *func; static const char *filename; static bfd_size_type func_size; @@ -7483,6 +7484,7 @@ elf_find_function (bfd *abfd, return FALSE; if (last_section != section + || last_symbols != symbols || func == NULL || offset < func->value || offset >= func->value + func_size) @@ -7531,6 +7533,7 @@ elf_find_function (bfd *abfd, && size > func_size))) { func = sym; + last_symbols = symbols; func_size = size; low_func = code_off;
Hmm, how did you manage to call elf_find_function with a different set of symbols?
CVSROOT: /cvs/src Module name: src Changes by: amodra@sourceware.org 2013-02-07 04:20:32 Modified files: bfd : ChangeLog elf.c Log message: PR binutils/15106 * elf.c (elf_find_function): Don't cache if symbols change. Patches: http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/ChangeLog.diff?cvsroot=src&r1=1.5934&r2=1.5935 http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/elf.c.diff?cvsroot=src&r1=1.582&r2=1.583
CVSROOT: /cvs/src Module name: src Branch: binutils-2_23-branch Changes by: amodra@sourceware.org 2013-02-07 04:21:35 Modified files: bfd : ChangeLog elf.c Log message: PR binutils/15106 * elf.c (elf_find_function): Don't cache if symbols change. Patches: http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/ChangeLog.diff?cvsroot=src&only_with_tag=binutils-2_23-branch&r1=1.5758.2.42&r2=1.5758.2.43 http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/elf.c.diff?cvsroot=src&only_with_tag=binutils-2_23-branch&r1=1.568.2.1&r2=1.568.2.2
Fixed
In my application I open and close continuously DSOs. In rare cases it happens that after closing and opening a DSO, the pointer to a certain section within the new DSO has the same value as the old pointer. Even with my trivial change there is still the remote possibility that you could have the same values for the pointers to section and symbols. One way to fix this cleanly would be to associate the cache to the bfd struct, for example.
Right, I should not have used static vars..
CVSROOT: /cvs/src Module name: src Changes by: amodra@sourceware.org 2013-02-08 07:04:50 Modified files: bfd : ChangeLog elf-bfd.h elf.c Log message: PR binutils/15106 * elf-bfd.h (struct elf_obj_tdata): Add elf_find_function_cache. * elf.c (elf_find_function): Revert last change. Use new tdata field rather than static vars for cache. Patches: http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/ChangeLog.diff?cvsroot=src&r1=1.5936&r2=1.5937 http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/elf-bfd.h.diff?cvsroot=src&r1=1.357&r2=1.358 http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/elf.c.diff?cvsroot=src&r1=1.583&r2=1.584
CVSROOT: /cvs/src Module name: src Branch: binutils-2_23-branch Changes by: amodra@sourceware.org 2013-02-08 07:05:11 Modified files: bfd : ChangeLog elf-bfd.h elf.c Log message: PR binutils/15106 * elf-bfd.h (struct elf_obj_tdata): Add elf_find_function_cache. * elf.c (elf_find_function): Revert last change. Use new tdata field rather than static vars for cache. Patches: http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/ChangeLog.diff?cvsroot=src&only_with_tag=binutils-2_23-branch&r1=1.5758.2.43&r2=1.5758.2.44 http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/elf-bfd.h.diff?cvsroot=src&only_with_tag=binutils-2_23-branch&r1=1.343.2.3&r2=1.343.2.4 http://sourceware.org/cgi-bin/cvsweb.cgi/src/bfd/elf.c.diff?cvsroot=src&only_with_tag=binutils-2_23-branch&r1=1.568.2.2&r2=1.568.2.3