Create StackFrame::FRAME_TRUST_PREWALKED trust type.

Create StackFrame::FRAME_TRUST_PREWALKED trust type.

This creates a new frame trust type for prewalked stack frames, as suggested in
the review of https://breakpad.appspot.com/620002/.

Committed: https://code.google.com/p/google-breakpad/source/detail?r=1208

[chrisha]

PTAL

[Mark Mentovai]

LGTM

[Ted Mielczarek]

https://breakpad.appspot.com/621002/diff/1/src/google_breakpad/processor/stac...
File src/google_breakpad/processor/stack_frame.h (right):

https://breakpad.appspot.com/621002/diff/1/src/google_breakpad/processor/stac...
src/google_breakpad/processor/stack_frame.h:54: FRAME_TRUST_PREWALKED //
Explicitly provided by some external stack walker.
nit: put this above CONTEXT? They're in rough order of "trust metric" per the
comment. (Which of CONTEXT or PREWALKED is more trustworthy is somewhat
nebulous, but CONTEXT feels most trustworthy.)

https://breakpad.appspot.com/621002/diff/1/src/google_breakpad/processor/stac...
src/google_breakpad/processor/stack_frame.h:83: return "prewalked";
You can make this more descriptive, these are just for human consumption (like
in the default minidump_stackwalk output). "recovered by external stack walker"
or something like that?

https://breakpad.appspot.com/621002/diff/1/src/processor/stackwalker_address_...
File src/processor/stackwalker_address_list.cc (right):

https://breakpad.appspot.com/621002/diff/1/src/processor/stackwalker_address_...
src/processor/stackwalker_address_list.cc:67: frame->trust =
StackFrame::FRAME_TRUST_PREWALKED;
I would stick with CONTEXT here, the first frame in a stack has to come from
some sort of CONTEXT, so it's trustworthy.

[chrisha]

Another look?

https://breakpad.appspot.com/621002/diff/1/src/google_breakpad/processor/stac...
File src/google_breakpad/processor/stack_frame.h (right):

https://breakpad.appspot.com/621002/diff/1/src/google_breakpad/processor/stac...
src/google_breakpad/processor/stack_frame.h:54: FRAME_TRUST_PREWALKED //
Explicitly provided by some external stack walker.
On 2013/08/23 18:35:56, Ted Mielczarek wrote:
> nit: put this above CONTEXT? They're in rough order of "trust metric" per the
> comment. (Which of CONTEXT or PREWALKED is more trustworthy is somewhat
> nebulous, but CONTEXT feels most trustworthy.)

Done.

https://breakpad.appspot.com/621002/diff/1/src/google_breakpad/processor/stac...
src/google_breakpad/processor/stack_frame.h:83: return "prewalked";
On 2013/08/23 18:35:56, Ted Mielczarek wrote:
> You can make this more descriptive, these are just for human consumption (like
> in the default minidump_stackwalk output). "recovered by external stack
walker"
> or something like that?

Done.

https://breakpad.appspot.com/621002/diff/1/src/processor/stackwalker_address_...
File src/processor/stackwalker_address_list.cc (right):

https://breakpad.appspot.com/621002/diff/1/src/processor/stackwalker_address_...
src/processor/stackwalker_address_list.cc:67: frame->trust =
StackFrame::FRAME_TRUST_PREWALKED;
On 2013/08/23 18:35:56, Ted Mielczarek wrote:
> I would stick with CONTEXT here, the first frame in a stack has to come from
> some sort of CONTEXT, so it's trustworthy.

Good point. Done.

[Ted Mielczarek]

LGTM

[chrisha]

Thanks, committed.

https://code.google.com/p/google-breakpad/source/detail?r=1208

[Mark Mentovai]

https://breakpad.appspot.com/621002/diff/10001/src/processor/stackwalker_addr...
File src/processor/stackwalker_address_list.cc (right):

https://breakpad.appspot.com/621002/diff/10001/src/processor/stackwalker_addr...
src/processor/stackwalker_address_list.cc:67: frame->trust =
StackFrame::FRAME_TRUST_CONTEXT;
I think this one should have stayed PREWALKED.

We have no idea how the prewalker arrived at the “context” frame. Maybe it came
from a real context. Or maybe it walked up a frame or two from its legitimate
context in order to avoid showing a stackwalk whose tail contained useless
frames like ~FatalLogMessage. Point is, we don’t know, all we know is that we
got a totally prewalked stack.

[chrisha]

Addressing this here:

https://breakpad.appspot.com/624002/