From: Florian Weimer <fweimer@redhat.com>
To: Nathan Sidwell <nathan@acm.org>, GCC <gcc@gcc.gnu.org>,
GNU C Library <libc-alpha@sourceware.org>,
Binutils <binutils@sourceware.org>,
gnu-gabi@sourceware.org
Subject: Re: Invalid program counters and unwinding
Date: Mon, 01 Jan 2018 00:00:00 -0000 [thread overview]
Message-ID: <0c58f1bb-220c-d03d-7375-6066fb7d53e6@redhat.com> (raw)
In-Reply-To: <7ada5491-f3f4-e048-dfec-6e51cd937163@acm.org>
On 06/26/2018 12:56 PM, Nathan Sidwell wrote:
> On 06/26/2018 05:26 AM, Florian Weimer wrote:
>
>> So it looks to me that the caller of _Unwind_Find_FDE needs to ensure
>> that the PC is a valid element of the call stack. Is this a correct
>> assumption?
>
> I thought this was an (implicit?) requirement. You're unwinding a stack
> to deliver an exception up it. Are there use cases where that is not
> the case?
We have something approaching this scenario.
pthread_cancel in glibc unwinds the stack using DWARF information until
encounters a frame without unwind information, when it switches to
longjmp to get past that obstacle.
However, at the point of transition from a valid DWARF frame into the
wilderness (without unwind data), we should still have accurate
information on the caller's PC, so _Unwind_Find_FDE will reliably fail
to find any unwind data for it. It's not a random pointer somewhere
else, so I think even the pthread_cancel case is fully supported.
Thanks,
Florian
next prev parent reply other threads:[~2018-06-26 11:01 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-01 0:00 Florian Weimer
2018-01-01 0:00 ` Nathan Sidwell
2018-01-01 0:00 ` Florian Weimer [this message]
2018-01-01 0:00 ` Nathan Sidwell
2018-01-01 0:00 ` Florian Weimer
2018-01-01 0:00 ` Nathan Sidwell
2018-01-01 0:00 ` Florian Weimer
2018-01-01 0:00 ` Nathan Sidwell
2018-01-01 0:00 ` Jakub Jelinek
2018-01-01 0:00 ` Jakub Jelinek
2018-01-01 0:00 ` Florian Weimer
2018-01-01 0:00 ` Jeff Law
2018-01-01 0:00 ` Florian Weimer
2018-01-01 0:00 ` Jeff Law
2018-01-01 0:00 ` Michael Matz
2018-01-01 0:00 ` Jakub Jelinek
2018-01-01 0:00 ` Michael Matz
2018-01-01 0:00 ` Florian Weimer
2018-01-01 0:00 ` Florian Weimer
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