x86/uaccess, signal: Fix AC=1 bloat

Occasionally GCC is less agressive with inlining and the following is
observed:

  arch/x86/kernel/signal.o: warning: objtool: restore_sigcontext()+0x3cc: call to force_valid_ss.isra.5() with UACCESS enabled
  arch/x86/kernel/signal.o: warning: objtool: do_signal()+0x384: call to frame_uc_flags.isra.0() with UACCESS enabled

Cure this by moving this code out of the AC=1 region, since it really
isn't needed for the user access.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 08dfd4c..c8aa58a 100644 (file)
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -132,16 +132,6 @@ static int restore_sigcontext(struct pt_regs *regs,
                COPY_SEG_CPL3(cs);
                COPY_SEG_CPL3(ss);
 
-#ifdef CONFIG_X86_64
-               /*
-                * Fix up SS if needed for the benefit of old DOSEMU and
-                * CRIU.
-                */
-               if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) &&
-                            user_64bit_mode(regs)))
-                       force_valid_ss(regs);
-#endif
-
                get_user_ex(tmpflags, &sc->flags);
                regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
                regs->orig_ax = -1;             /* disable syscall checks */
@@ -150,6 +140,15 @@ static int restore_sigcontext(struct pt_regs *regs,
                buf = (void __user *)buf_val;
        } get_user_catch(err);
 
+#ifdef CONFIG_X86_64
+       /*
+        * Fix up SS if needed for the benefit of old DOSEMU and
+        * CRIU.
+        */
+       if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs)))
+               force_valid_ss(regs);
+#endif
+
        err |= fpu__restore_sig(buf, IS_ENABLED(CONFIG_X86_32));
 
        force_iret();
@@ -461,6 +460,7 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig,
 {
        struct rt_sigframe __user *frame;
        void __user *fp = NULL;
+       unsigned long uc_flags;
        int err = 0;
 
        frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
@@ -473,9 +473,11 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig,
                        return -EFAULT;
        }
 
+       uc_flags = frame_uc_flags(regs);
+
        put_user_try {
                /* Create the ucontext.  */
-               put_user_ex(frame_uc_flags(regs), &frame->uc.uc_flags);
+               put_user_ex(uc_flags, &frame->uc.uc_flags);
                put_user_ex(0, &frame->uc.uc_link);
                save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 
@@ -541,6 +543,7 @@ static int x32_setup_rt_frame(struct ksignal *ksig,
 {
 #ifdef CONFIG_X86_X32_ABI
        struct rt_sigframe_x32 __user *frame;
+       unsigned long uc_flags;
        void __user *restorer;
        int err = 0;
        void __user *fpstate = NULL;
@@ -555,9 +558,11 @@ static int x32_setup_rt_frame(struct ksignal *ksig,
                        return -EFAULT;
        }
 
+       uc_flags = frame_uc_flags(regs);
+
        put_user_try {
                /* Create the ucontext.  */
-               put_user_ex(frame_uc_flags(regs), &frame->uc.uc_flags);
+               put_user_ex(uc_flags, &frame->uc.uc_flags);
                put_user_ex(0, &frame->uc.uc_link);
                compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
                put_user_ex(0, &frame->uc.uc__pad0);