Patch "MIPS: Negate error syscall return in trace" has been added to the 3.18-stable tree

Patch "MIPS: Negate error syscall return in trace" has been added to the 3.18-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    MIPS: Negate error syscall return in trace

to the 3.18-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mips-negate-error-syscall-return-in-trace.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 4f32a39d49b25eaa66d2420f1f03d371ea4cd906 Mon Sep 17 00:00:00 2001
From: James Hogan <james.hogan@imgtec.com>
Date: Thu, 29 Jun 2017 10:12:34 +0100
Subject: MIPS: Negate error syscall return in trace

From: James Hogan <james.hogan@imgtec.com>

commit 4f32a39d49b25eaa66d2420f1f03d371ea4cd906 upstream.

The sys_exit trace event takes a single return value for the system
call, which MIPS passes the value of the $v0 (result) register, however
MIPS returns positive error codes in $v0 with $a3 specifying that $v0
contains an error code. As a result erroring system calls are traced
returning positive error numbers that can't always be distinguished from
success.

Use regs_return_value() to negate the error code if $a3 is set.

Fixes: 1d7bf993e073 ("MIPS: ftrace: Add support for syscall tracepoints.")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16651/
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/kernel/ptrace.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/mips/kernel/ptrace.c
+++ b/arch/mips/kernel/ptrace.c
@@ -802,7 +802,7 @@ asmlinkage void syscall_trace_leave(stru
 	audit_syscall_exit(regs);
 
 	if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
-		trace_sys_exit(regs, regs->regs[2]);
+		trace_sys_exit(regs, regs_return_value(regs));
 
 	if (test_thread_flag(TIF_SYSCALL_TRACE))
 		tracehook_report_syscall_exit(regs, 0);


Patches currently in stable-queue which might be from james.hogan@imgtec.com are

queue-3.18/mips-actually-decode-jalx-in-__compute_return_epc_for_insn.patch
queue-3.18/mips-fix-mips_atomic_set-retry-condition.patch
queue-3.18/mips-fix-mips_atomic_set-with-eva.patch
queue-3.18/mips-save-static-registers-before-sysmips.patch
queue-3.18/mips-fix-unaligned-pc-interpretation-in-compute_return_epc.patch
queue-3.18/mips-negate-error-syscall-return-in-trace.patch
queue-3.18/mips-math-emu-prevent-wrong-isa-mode-instruction-emulation.patch