4 files changed, 29 insertions, 13 deletions

diff --git a/arch/tile/include/asm/signal.h b/arch/tile/include/asm/signal.h
index c1ee1d61d44c..81d92a45cd4b 100644
--- a/arch/tile/include/asm/signal.h
+++ b/arch/tile/include/asm/signal.h
@@ -25,7 +25,7 @@
 
 #if defined(__KERNEL__) && !defined(__ASSEMBLY__)
 struct pt_regs;
-int restore_sigcontext(struct pt_regs *, struct sigcontext __user *, long *);
+int restore_sigcontext(struct pt_regs *, struct sigcontext __user *);
 int setup_sigcontext(struct sigcontext __user *, struct pt_regs *);
 void do_signal(struct pt_regs *regs);
 #endif
diff --git a/arch/tile/kernel/compat_signal.c b/arch/tile/kernel/compat_signal.c
index 543d6a33aa26..dbb0dfc7bece 100644
--- a/arch/tile/kernel/compat_signal.c
+++ b/arch/tile/kernel/compat_signal.c
@@ -290,12 +290,12 @@ long compat_sys_sigaltstack(const struct compat_sigaltstack __user *uss_ptr,
         return ret;
 }
 
+/* The assembly shim for this function arranges to ignore the return value. */
 long compat_sys_rt_sigreturn(struct pt_regs *regs)
 {
         struct compat_rt_sigframe __user *frame =
                 (struct compat_rt_sigframe __user *) compat_ptr(regs->sp);
         sigset_t set;
-        long r0;
 
         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
                 goto badframe;
@@ -308,13 +308,13 @@ long compat_sys_rt_sigreturn(struct pt_regs *regs)
         recalc_sigpending();
         spin_unlock_irq(&current->sighand->siglock);
 
-        if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &r0))
+        if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
                 goto badframe;
 
         if (compat_sys_sigaltstack(&frame->uc.uc_stack, NULL, regs) != 0)
                 goto badframe;
 
-        return r0;
+        return 0;
 
 badframe:
         force_sig(SIGSEGV, current);
diff --git a/arch/tile/kernel/intvec_32.S b/arch/tile/kernel/intvec_32.S
index f5821626247f..5eed4a02bf62 100644
--- a/arch/tile/kernel/intvec_32.S
+++ b/arch/tile/kernel/intvec_32.S
@@ -1342,8 +1342,8 @@ handle_syscall:
         lw      r20, r20
 
         /* Jump to syscall handler. */
-        jalr    r20; .Lhandle_syscall_link:
-        FEEDBACK_REENTER(handle_syscall)
+        jalr    r20
+.Lhandle_syscall_link: /* value of "lr" after "jalr r20" above */
 
         /*
          * Write our r0 onto the stack so it gets restored instead
@@ -1352,6 +1352,9 @@ handle_syscall:
         PTREGS_PTR(r29, PTREGS_OFFSET_REG(0))
         sw      r29, r0
 
+.Lsyscall_sigreturn_skip:
+        FEEDBACK_REENTER(handle_syscall)
+
         /* Do syscall trace again, if requested. */
         lw      r30, r31
         andi    r30, r30, _TIF_SYSCALL_TRACE
@@ -1536,9 +1539,24 @@ STD_ENTRY_LOCAL(bad_intr)
         };                                              \
         STD_ENDPROC(_##x)
 
+/*
+ * Special-case sigreturn to not write r0 to the stack on return.
+ * This is technically more efficient, but it also avoids difficulties
+ * in the 64-bit OS when handling 32-bit compat code, since we must not
+ * sign-extend r0 for the sigreturn return-value case.
+ */
+#define PTREGS_SYSCALL_SIGRETURN(x, reg)                \
+        STD_ENTRY(_##x);                                \
+        addli   lr, lr, .Lsyscall_sigreturn_skip - .Lhandle_syscall_link; \
+        {                                               \
+         PTREGS_PTR(reg, PTREGS_OFFSET_BASE);           \
+         j      x                                       \
+        };                                              \
+        STD_ENDPROC(_##x)
+
 PTREGS_SYSCALL(sys_execve, r3)
 PTREGS_SYSCALL(sys_sigaltstack, r2)
-PTREGS_SYSCALL(sys_rt_sigreturn, r0)
+PTREGS_SYSCALL_SIGRETURN(sys_rt_sigreturn, r0)
 PTREGS_SYSCALL(sys_cmpxchg_badaddr, r1)
 
 /* Save additional callee-saves to pt_regs, put address in r4 and jump. */
diff --git a/arch/tile/kernel/signal.c b/arch/tile/kernel/signal.c
index 757407e36696..1260321155f1 100644
--- a/arch/tile/kernel/signal.c
+++ b/arch/tile/kernel/signal.c
@@ -52,7 +52,7 @@ SYSCALL_DEFINE3(sigaltstack, const stack_t __user *, uss,
  */
 
 int restore_sigcontext(struct pt_regs *regs,
-                       struct sigcontext __user *sc, long *pr0)
+                       struct sigcontext __user *sc)
 {
         int err = 0;
         int i;
@@ -75,17 +75,15 @@ int restore_sigcontext(struct pt_regs *regs,
 
         regs->faultnum = INT_SWINT_1_SIGRETURN;
 
-        err |= __get_user(*pr0, &sc->gregs[0]);
         return err;
 }
 
-/* sigreturn() returns long since it restores r0 in the interrupted code. */
+/* The assembly shim for this function arranges to ignore the return value. */
 SYSCALL_DEFINE1(rt_sigreturn, struct pt_regs *, regs)
 {
         struct rt_sigframe __user *frame =
                 (struct rt_sigframe __user *)(regs->sp);
         sigset_t set;
-        long r0;
 
         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
                 goto badframe;
@@ -98,13 +96,13 @@ SYSCALL_DEFINE1(rt_sigreturn, struct pt_regs *, regs)
         recalc_sigpending();
         spin_unlock_irq(&current->sighand->siglock);
 
-        if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &r0))
+        if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
                 goto badframe;
 
         if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
                 goto badframe;
 
-        return r0;
+        return 0;
 
 badframe:
         force_sig(SIGSEGV, current);