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Message #21296
[Bug 1239109] Re: aarch64 clock_gettime with CLOCK_REALTIME_COARSE or CLOCK_MONOTONIC_COARSE fails with SIGBUS or SIGSEGV
This bug doesn't need logs, it has all one should need in the
description (except maybe a simple reproducer, but that's literally a
1-liner).
** Changed in: linux (Ubuntu)
Status: Incomplete => Confirmed
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https://bugs.launchpad.net/bugs/1239109
Title:
aarch64 clock_gettime with CLOCK_REALTIME_COARSE or
CLOCK_MONOTONIC_COARSE fails with SIGBUS or SIGSEGV
Status in “linux” package in Ubuntu:
Confirmed
Bug description:
The aarch64 vDSO __kernel_clock_gettime implementation crashes when
clock_gettime is called with CLOCK_MONOTONIC_COARSE or
CLOCK_REALTIME_COARSE, with a SIGSEGV or SIGBUS respectively.
In the implementation
(http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/kernel/vdso/gettimeofday.S#n89)
a value other than CLOCK_REALTIME or CLOCK_MONOTONIC branches past the
usual "mov x2, x30" which preserves lr for return later. Anything
other than CLOCK_REALTIME_COARSE and CLOCK_MONOTONIC_COARSE then
branches directly to the svc call, which correctly returns to the
caller. But CLOCK_REALTIME_COARSE and CLOCK_MONOTONIC_COARSE execute
the special coarse path then fall through to the normal
CLOCK_REALTIME/CLOCK_MONOTONIC path, which does a 'ret x2' at the end,
despite not having saved x30 to x2 in the _COARSE case. So it ends up
setting pc to clk_id, which is either 4 or 5, giving a translation or
alignment fault.
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References