Crash when recording clock_gettime

Robert O'Callahan robert at ocallahan.org
Tue Aug 29 09:38:04 UTC 2017


On Tue, Aug 29, 2017 at 9:28 PM, Benjamin King <benjaminking at web.de> wrote:

> On Tue, Aug 29, 2017 at 08:33:14PM +1200, Robert O'Callahan wrote:
>
>> My best guess right now is that the addr_to_offset call is failing for
>> __vdso_clock_gettime. If so, the logging should show it; then you could
>> run rr
>> under gdb and get a better idea of what happens in addr_to_offset.
>>
>
> Ok, with the added logging, a problem is reported for 0x8c0:
> ----
> rr: Saving execution to trace directory `/home/bki/.local/share/rr/a.o
> ut-35'.
> [Monkeypatcher] Can't convert address 0x8c0 to offset
> [Monkeypatcher] monkeypatched __vdso_gettimeofday to syscall 96 at
> 0x7ffff79b0c30 (0xc30)
> [Monkeypatcher] monkeypatched __vdso_time to syscall 201 at 0x7ffff79b0e10
> (0xe10)
> [Monkeypatcher] monkeypatched __vdso_getcpu to syscall 309 at
> 0x7ffff79b0e30 (0xe30)
> [Monkeypatcher] Patched syscall at 0x7ffff79b0c37 syscall gettimeofday tid
> 4481 bytes 0x90 0x90 0x90 0xc3 0 0
> Segmentation fault
> ----
>
> I'll try to find out what's going on there.
>

If you capture the VDSO bytes to a file and dump its ELF headers then the
problem may become obvious.

Rob
-- 
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