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Re: [PATCH] Fix crash when loading a core with unexpected register section size
- From: Antoine Tremblay <antoine dot tremblay at ericsson dot com>
- To: Pedro Alves <palves at redhat dot com>
- Cc: Antoine Tremblay <antoine dot tremblay at ericsson dot com>, <gdb-patches at sourceware dot org>
- Date: Thu, 26 Jan 2017 08:54:50 -0500
- Subject: Re: [PATCH] Fix crash when loading a core with unexpected register section size
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Pedro Alves writes:
> On 01/26/2017 01:17 PM, Antoine Tremblay wrote:
>> When loading a core without an executable like so:
>> gdb --core core for example often the gdbarch won't contain the
>> iterate_over_regset_sections method.
> Can you give an example? That'd help a lot understand the issue
I can't share the core that I have that reproduced this :(
> Also, please add a line break, ""s and/or punctuation to make
> the command stand out more from the rest of the sentence.
> For example:
> When loading a core without an executable like so:
> $ gdb --core core
> for example, often the gdbarch won't contain the
> iterate_over_regset_sections method. For example arch-foo.
>> This will generate a call to get_core_register_section with a NULL regset
>> like at corelow.c:628
>> get_core_register_section (regcache, NULL, ".reg", 0, 0, "general-purpose", 1);
>> However a check for REGSET_VARIABLE_SIZE in get_core_register_section
>> assumes that regset is != NULL thus leading to a crash with this backtrace:
>> (gdb) bt
>> #0 0x000000000065907b in get_core_register_section
>> (regcache=regcache@entry=0x2c26260, regset=regset@entry=0x0,
>> name=name@entry=0xdbf7b2 ".reg", min_size=min_size@entry=0,
>> which=which@entry=0, human_name=human_name@entry=0xdbac28
>> "general-purpose", required=1)
>> at ../../gdb/corelow.c:542
>> #1 0x0000000000659b70 in get_core_registers (ops=<optimized out>,
>> regcache=0x2c26260, regno=<optimized out>) at ../../gdb/corelow.c:628
>> #2 0x000000000076e5fb in target_fetch_registers
>> (regcache=regcache@entry=0x2c26260, regno=regno@entry=15) at ../../gdb/target.c:3590
>> Note that commit: f962539ad23759af4ba8f7eece1946fdc2f5087
> Please always paste the commit's subject as well, to make
> it easier for us poor humans to quickly tell what the commit
> was about without having to go to a terminal. The Linux guideline
> is to put it in parens:
> Note that commit f962539ad23759 ("Warn if core file register
> section is larger than expected") introduced [...]
> I personally like that style.
> introcuded this
>> issue. Thus releases > 7.8.2 are affected.
>> This patch fixes this crash by adding a check for regset existence before
>> running the condition.
>> * corelow.c (get_core_register_section): Check for regset
>> existance before checking for REGSET_VARIABLE_SIZE.
> Indentation. "existence".
>> gdb/corelow.c | 7 ++++++-
>> 1 file changed, 6 insertions(+), 1 deletion(-)
>> diff --git a/gdb/corelow.c b/gdb/corelow.c
>> index a075d9e..f43f730 100644
>> --- a/gdb/corelow.c
>> +++ b/gdb/corelow.c
>> @@ -515,6 +515,7 @@ get_core_register_section (struct regcache *regcache,
>> struct bfd_section *section;
>> bfd_size_type size;
>> char *contents;
>> + bool variable_size_section = false;
> No need to initialize by default when you're always going to
> initialize it again below. Or declare on first use and avoid
> the issue entirely.
V2 coming in next mail.