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arm64: fix missing syscall trace exit

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If a syscall is entered without TIF_SYSCALL_TRACE set, then it goes on
the fast path.  It's then possible to have TIF_SYSCALL_TRACE added in
the middle of the syscall, but ret_fast_syscall doesn't check this flag
again.  This causes a ptrace syscall-exit-stop to be missed.

For instance, from a PTRACE_EVENT_FORK reported during do_fork, the
tracer might resume with PTRACE_SYSCALL, setting TIF_SYSCALL_TRACE.
Now the completion of the fork should have a syscall-exit-stop.

Russell King fixed this on arm by re-checking _TIF_SYSCALL_WORK in the
fast exit path.  Do the same on arm64.

Reviewed-by: Will Deacon <will.deacon@arm.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Josh Stone <jistone@redhat.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Josh Stone 2015-06-05 14:28:03 -07:00 committed by Catalin Marinas
parent addc8120a7
commit 04d7e098f5
1 changed files with 6 additions and 1 deletions
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7
arch/arm64/kernel/entry.S
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@ -611,11 +611,16 @@ ENDPROC(cpu_switch_to)
*/
ret_fast_syscall:
disable_irq // disable interrupts
ldr x1, [tsk, #TI_FLAGS]
ldr x1, [tsk, #TI_FLAGS] // re-check for syscall tracing
and x2, x1, #_TIF_SYSCALL_WORK
cbnz x2, ret_fast_syscall_trace
and x2, x1, #_TIF_WORK_MASK
cbnz x2, fast_work_pending
enable_step_tsk x1, x2
kernel_exit 0, ret = 1
ret_fast_syscall_trace:
enable_irq // enable interrupts
b __sys_trace_return
/*
* Ok, we need to do extra processing, enter the slow path.