powerpc/ptrace: Combine SYSCALL_EMU & SYSCALL_TRACE handling

Combine the SYSCALL_EMU and SYSCALL_TRACE handling so that we only
call tracehook_report_syscall_entry() in one place.

Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
[mpe: Flesh out change log, s/cached_flags/flags/, reflow comments]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index 714c348..cdd5d1d 100644 (file)
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -3263,32 +3263,40 @@ static inline int do_seccomp(struct pt_regs *regs) { return 0; }
  */
 long do_syscall_trace_enter(struct pt_regs *regs)
 {
+       u32 flags;
+
        user_exit();
 
-       if (test_thread_flag(TIF_SYSCALL_EMU)) {
-               /*
-                * A nonzero return code from tracehook_report_syscall_entry()
-                * tells us to prevent the syscall execution, but we are not
-                * going to execute it anyway.
-                *
-                * Returning -1 will skip the syscall execution. We want to
-                * avoid clobbering any register also, thus, not 'gotoing'
-                * skip label.
-                */
-               if (tracehook_report_syscall_entry(regs))
-                       ;
-               return -1;
-       }
+       flags = READ_ONCE(current_thread_info()->flags) &
+               (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE);
 
-       /*
-        * The tracer may decide to abort the syscall, if so tracehook
-        * will return !0. Note that the tracer may also just change
-        * regs->gpr[0] to an invalid syscall number, that is handled
-        * below on the exit path.
-        */
-       if (test_thread_flag(TIF_SYSCALL_TRACE) &&
-           tracehook_report_syscall_entry(regs))
-               goto skip;
+       if (flags) {
+               int rc = tracehook_report_syscall_entry(regs);
+
+               if (unlikely(flags & _TIF_SYSCALL_EMU)) {
+                       /*
+                        * A nonzero return code from
+                        * tracehook_report_syscall_entry() tells us to prevent
+                        * the syscall execution, but we are not going to
+                        * execute it anyway.
+                        *
+                        * Returning -1 will skip the syscall execution. We want
+                        * to avoid clobbering any registers, so we don't goto
+                        * the skip label below.
+                        */
+                       return -1;
+               }
+
+               if (rc) {
+                       /*
+                        * The tracer decided to abort the syscall. Note that
+                        * the tracer may also just change regs->gpr[0] to an
+                        * invalid syscall number, that is handled below on the
+                        * exit path.
+                        */
+                       goto skip;
+               }
+       }
 
        /* Run seccomp after ptrace; allow it to set gpr[3]. */
        if (do_seccomp(regs))