From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Mon, 8 Jun 2015 11:21:05 +0100 Subject: [PATCH] arm64: fix missing syscall trace exit In-Reply-To: <1433539683-29539-1-git-send-email-jistone@redhat.com> References: <20150605153816.GG7420@arm.com> <1433539683-29539-1-git-send-email-jistone@redhat.com> Message-ID: <20150608102104.GB1654@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Josh, Thanks for the patch. On Fri, Jun 05, 2015 at 10:28:03PM +0100, Josh Stone wrote: > 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. Please don't include the changelog in the commit message. > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Russell King > Signed-off-by: Josh Stone > --- > 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 > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -608,11 +608,16 @@ 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 Looks good to me: Reviewed-by: Will Deacon I assume this can wait until 4.2? Will