Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux...

[firefly-linux-kernel-4.4.55.git] / arch / tile / kernel / ptrace.c

diff --git a/arch/tile/kernel/ptrace.c b/arch/tile/kernel/ptrace.c
index bac187498d61a04791af17398890908f71521e19..de98c6ddf136dbeebee00b7d8b1c553cc8bf56c1 100644 (file)
--- a/arch/tile/kernel/ptrace.c
+++ b/arch/tile/kernel/ptrace.c
@@ -265,6 +265,21 @@ int do_syscall_trace_enter(struct pt_regs *regs)
 
 void do_syscall_trace_exit(struct pt_regs *regs)
 {
+       long errno;
+
+       /*
+        * The standard tile calling convention returns the value (or negative
+        * errno) in r0, and zero (or positive errno) in r1.
+        * It saves a couple of cycles on the hot path to do this work in
+        * registers only as we return, rather than updating the in-memory
+        * struct ptregs.
+        */
+       errno = (long) regs->regs[0];
+       if (errno < 0 && errno > -4096)
+               regs->regs[1] = -errno;
+       else
+               regs->regs[1] = 0;
+
        if (test_thread_flag(TIF_SYSCALL_TRACE))
                tracehook_report_syscall_exit(regs, 0);