Write a memory around the instruction pointer from the crashing thread to the minidump on Linux

On Windows, MinidumpWriteDump includes a window of memory around
the instruction pointer from the crashing thread in the minidump,
which can be useful for debugging JIT crashes. This patch implements
the same behavior for the Linux dumper.

[Ted Mielczarek]

I pretty much always forget --send-mail when I use upload.py.

[mochalatte]

LGTM

http://breakpad.appspot.com/194001/diff/1/4
File src/client/linux/handler/exception_handler_unittest.cc (right):

http://breakpad.appspot.com/194001/diff/1/4#newcode234
Line 234: //TODO(ted): verify contents of memory region
if verifying the contents is too complicated for this iteration, is it possible
to at least do some checks on the size?

http://breakpad.appspot.com/194001/diff/1/5
File src/client/linux/minidump_writer/minidump_writer.cc (right):

http://breakpad.appspot.com/194001/diff/1/5#newcode408
Line 408: ++kNumWriters;
wow, thank you for rewriting this.

http://breakpad.appspot.com/194001/diff/1/5#newcode650
Line 650: const size_t ip_memory_size = 256;
precede constant variable names with k

http://breakpad.appspot.com/194001/diff/1/5#newcode666
Line 666: uintptr_t(ip - ip_memory_size / 2));
i know the order of operations is like elementary school algebra but can we have
parens around the ones we want to take place first just for clarity? :-)

[Ted Mielczarek]

On 2010/09/16 20:50:22, mochalatte wrote:
> LGTM
> 
> http://breakpad.appspot.com/194001/diff/1/4
> File src/client/linux/handler/exception_handler_unittest.cc (right):
> 
> http://breakpad.appspot.com/194001/diff/1/4#newcode234
> Line 234: //TODO(ted): verify contents of memory region
> if verifying the contents is too complicated for this iteration, is it
possible
> to at least do some checks on the size?

I just went ahead and implemented the TODO. I should have done it in the first
place, I was just lazy. (Also I wrote the test first, so just getting that much
to pass required a bunch of work anyway.)

I fixed everything else you mentioned. In case you were wondering, I even tested
it on ARM.