GDB backtrace and signal trampolines
hollisb at us.ibm.com
Fri Aug 12 23:58:32 EST 2005
On Aug 12, 2005, at 12:06 AM, Anton Blanchard wrote:
>> Would it make sense to limit the test to within a few hundred bytes of
>> the stack pointer? Or some better way to detect that the PC is in a
>> signal trampoline?
> With recent kernels we should be able to use the dwarf2 unwind
> information in the vdso I think.
I guess compatibility with older kernels will still need to be
I see this note in arch/ppc64/mm/fault.c:
* N.B. The POWER/Open ABI allows programs to access up to
* 288 bytes below the stack pointer.
* The kernel signal delivery code writes up to about 1.5kB
* below the stack pointer (r1) before decrementing it.
* The exec code can write slightly over 640kB to the stack
* before setting the user r1. Thus we allow the stack to
* expand to 1MB without further checks.
So would 2KB be a reasonable limit to the signal frame check, as I
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