On Thu, 29 Jun 2017 10:12:34 +0100
James Hogan <james.hogan@xxxxxxxxxx> wrote:
> 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@xxxxxxxxxx>
> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: linux-mips@xxxxxxxxxxxxxx
> Cc: <stable@xxxxxxxxxxxxxxx> # 3.13+
> ---
> arch/mips/kernel/ptrace.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c
> index ba3b1f771256..8e2ea86dc23e 100644
> --- a/arch/mips/kernel/ptrace.c
> +++ b/arch/mips/kernel/ptrace.c
> @@ -913,7 +913,7 @@ asmlinkage void syscall_trace_leave(struct pt_regs *regs)
> 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));
Looks reasonable to me.
Acked-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
-- Steve
>
> if (test_thread_flag(TIF_SYSCALL_TRACE))
> tracehook_report_syscall_exit(regs, 0);