[PATCH] arm64: fix missing syscall trace exit
jistone at redhat.com
Fri Jun 5 14:28:03 PDT 2015
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.
v2: Re-enable interrupts before branching to __sys_trace_return.
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will.deacon at arm.com>
Cc: Russell King <rmk+kernel at arm.linux.org.uk>
Signed-off-by: Josh Stone <jistone at redhat.com>
arch/arm64/kernel/entry.S | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 959fe8733560..988bea43dc74 100644
@@ -608,11 +608,16 @@ ENDPROC(cpu_switch_to)
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
+ enable_irq // enable interrupts
+ b __sys_trace_return
* Ok, we need to do extra processing, enter the slow path.
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