From mboxrd@z Thu Jan 1 00:00:00 1970 From: jistone@redhat.com (Josh Stone) Date: Tue, 2 Jun 2015 18:01:44 -0700 Subject: [PATCH] arm64: fix missing syscall trace exit In-Reply-To: <20150601102448.GG1641@arm.com> References: <20150601102448.GG1641@arm.com> Message-ID: <1433293304-26539-1-git-send-email-jistone@redhat.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. Cc: Catalin Marinas Cc: Will Deacon Cc: Russell King Signed-off-by: Josh Stone --- arch/arm64/kernel/entry.S | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 959fe8733560..a547a3e8a198 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -608,7 +608,9 @@ 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, __sys_trace_return and x2, x1, #_TIF_WORK_MASK cbnz x2, fast_work_pending enable_step_tsk x1, x2 -- 2.4.1