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SubjectRe: ptrace_syscall_32 is failing
On Sat, Aug 29, 2020 at 12:52 PM Andy Lutomirski <luto@kernel.org> wrote:
>
> Seems to be a recent regression, maybe related to entry/exit work changes.
>
> # ./tools/testing/selftests/x86/ptrace_syscall_32
> [RUN] Check int80 return regs
> [OK] getpid() preserves regs
> [OK] kill(getpid(), SIGUSR1) preserves regs
> [RUN] Check AT_SYSINFO return regs
> [OK] getpid() preserves regs
> [OK] kill(getpid(), SIGUSR1) preserves regs
> [RUN] ptrace-induced syscall restart
> Child will make one syscall
> [RUN] SYSEMU
> [FAIL] Initial args are wrong (nr=224, args=10 11 12 13 14 4289172732)
> [RUN] Restart the syscall (ip = 0xf7f3b549)
> [OK] Restarted nr and args are correct
> [RUN] Change nr and args and restart the syscall (ip = 0xf7f3b549)
> [OK] Replacement nr and args are correct
> [OK] Child exited cleanly
> [RUN] kernel syscall restart under ptrace
> Child will take a nap until signaled
> [RUN] SYSCALL
> [FAIL] Initial args are wrong (nr=29, args=0 0 0 0 0 4289172732)
> [RUN] SYSCALL
> [OK] Args after SIGUSR1 are correct (ax = -514)
> [OK] Child got SIGUSR1
> [RUN] Step again
> [OK] pause(2) restarted correctly

Bisected to commit 0b085e68f407 ("x86/entry: Consolidate 32/64 bit
syscall entry").
It looks like it is because syscall_enter_from_user_mode() is called
before reading the 6th argument from the user stack.

--
Brian Gerst

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