This is the mail archive of the
gdb-patches@sourceware.org
mailing list for the GDB project.
Re: [testsuite patch] for: [PATCH] [PR corefiles/17808] i386: Fix internal error when prstatus in core file is too big
- From: Mark Kettenis <mark dot kettenis at xs4all dot nl>
- To: palves at redhat dot com
- Cc: mark dot kettenis at xs4all dot nl, arnez at linux dot vnet dot ibm dot com, jan dot kratochvil at redhat dot com, gdb-patches at sourceware dot org
- Date: Fri, 9 Jan 2015 20:35:10 +0100 (CET)
- Subject: Re: [testsuite patch] for: [PATCH] [PR corefiles/17808] i386: Fix internal error when prstatus in core file is too big
- Authentication-results: sourceware.org; auth=none
- References: <874ms18cyz dot fsf at br87z6lw dot de dot ibm dot com> <20150108164327 dot GA29029 at host2 dot jankratochvil dot net> <87zj9s70bh dot fsf at br87z6lw dot de dot ibm dot com> <54B00160 dot 5000309 at redhat dot com> <201501091659 dot t09GxO1q016197 at glazunov dot sibelius dot xs4all dot nl> <54B00D92 dot 4050409 at redhat dot com>
> Date: Fri, 09 Jan 2015 17:19:14 +0000
> From: Pedro Alves <palves@redhat.com>
>
> On 01/09/2015 04:59 PM, Mark Kettenis wrote:
> >> Date: Fri, 09 Jan 2015 16:27:12 +0000
> >> From: Pedro Alves <palves@redhat.com>
> >>
> >>> Any other comments?
> >>
> >> Do we need to do the same in other places? This grep seems to suggest yes:
> >>
> >> $ grep assert * | grep sizeof | grep regset
> >> amd64obsd-tdep.c: gdb_assert (len >= tdep->sizeof_gregset + I387_SIZEOF_FXSAVE);
> >> amd64-tdep.c: gdb_assert (len == tdep->sizeof_fpregset);
> >> amd64-tdep.c: gdb_assert (len == tdep->sizeof_fpregset);
> >> i386obsd-tdep.c: gdb_assert (len >= tdep->sizeof_gregset + I387_SIZEOF_FSAVE);
> >> i386-tdep.c: gdb_assert (len == tdep->sizeof_gregset);
> >> i386-tdep.c: gdb_assert (len == tdep->sizeof_gregset);
> >> i386-tdep.c: gdb_assert (len == tdep->sizeof_fpregset);
> >> i386-tdep.c: gdb_assert (len == tdep->sizeof_fpregset);
> >> mips-linux-tdep.c: gdb_assert (len == sizeof (mips_elf_gregset_t));
> >> mips-linux-tdep.c: gdb_assert (len == sizeof (mips_elf_gregset_t));
> >> mips-linux-tdep.c: gdb_assert (len == sizeof (mips_elf_fpregset_t));
> >> mips-linux-tdep.c: gdb_assert (len == sizeof (mips_elf_fpregset_t));
> >> mips-linux-tdep.c: gdb_assert (len == sizeof (mips64_elf_gregset_t));
> >> mips-linux-tdep.c: gdb_assert (len == sizeof (mips64_elf_gregset_t));
> >> mips-linux-tdep.c: gdb_assert (len == sizeof (mips64_elf_fpregset_t));
> >> mips-linux-tdep.c: gdb_assert (len == sizeof (mips64_elf_fpregset_t));
> >> mn10300-linux-tdep.c: gdb_assert (len == sizeof (mn10300_elf_gregset_t));
> >> mn10300-linux-tdep.c: gdb_assert (len == sizeof (mn10300_elf_fpregset_t));
> >> mn10300-linux-tdep.c: gdb_assert (len == sizeof (mn10300_elf_gregset_t));
> >>
> >> On 01/08/2015 04:16 PM, Andreas Arnez wrote:
> >>> Note that this behavior deviates from the default policy: In general, if
> >>> some future kernel adds new registers to a register set, then a GDB
> >>> unaware of this extension would read the known subset and just ignore
> >>> the unknown bytes.
> >>
> >> That's a good point.
> >>
> >> get_core_register_section checks the section size already:
> >>
> >> get_core_register_section (struct regcache *regcache,
> >> const struct regset *regset,
> >> const char *name,
> >> int min_size,
> >> int which,
> >> const char *human_name,
> >> int required)
> >> {
> >> ...
> >> size = bfd_section_size (core_bfd, section);
> >> if (size < min_size)
> >> {
> >> warning (_("Section `%s' in core file too small."), section_name);
> >> return;
> >> }
> >> ...
> >>
> >> Should we remove all those asserts, and make it the
> >> job of get_core_register_section to warn if the section
> >> size is bigger than expected? We may need to pass
> >> the "expected" section size to the callback, in addition
> >> to the "minimum" size though.
> >
> > The code is designed to allow these sections to grow such that the OS
> > kernel can add more registers without breaking GDB.
>
> Not sure what you're disagreeing with. My comment is in that direction
> too (And Andreas' comment I'm quoting). That is, get_core_register_section
> would warn, but still continue processing the section.
>
> The current code clearly does not work that way, given the assertions.
It shouldn't warn if the sections is bigger that "expected", because
in some cases the "expected" size is really the minimum supported
size, where later versions of the OS added extra information. At
least not unconditionally.
I can imagine extending the interface to also specify a maximum size
and interpreting a maximum size of 0 as "no maximum". Continiung
after printing a warning if the section is larger than the maximum
size probably makes sense.
The asserts should probably be changed into >= whatever happens.