x86 signals: lift set_fs

This lifts the set_fs(USER_DS) call for signal handler setup out of the
three places copying the same code into the one place that calls them
all.  There is no change in what it does.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/ia32/ia32_signal.c

@@ -499,8 +499,6 @@ int ia32_setup_frame(int sig, struct k_sigaction *ka,
 	regs->cs = __USER32_CS;
 	regs->ss = __USER32_DS;
 
-	set_fs(USER_DS);
-
 #if DEBUG_SIG
 	printk(KERN_DEBUG "SIG deliver (%s:%d): sp=%p pc=%lx ra=%u\n",
 	       current->comm, current->pid, frame, regs->ip, frame->pretcode);
@@ -596,8 +594,6 @@ int ia32_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 	regs->cs = __USER32_CS;
 	regs->ss = __USER32_DS;
 
-	set_fs(USER_DS);
-
 #if DEBUG_SIG
 	printk(KERN_DEBUG "SIG deliver (%s:%d): sp=%p pc=%lx ra=%u\n",
 	       current->comm, current->pid, frame, regs->ip, frame->pretcode);

arch/x86/kernel/signal_64.c

@@ -285,10 +285,6 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 	   even if the handler happens to be interrupting 32-bit code. */
 	regs->cs = __USER_CS;
 
-	/* This, by contrast, has nothing to do with segment registers -
-	   see include/asm-x86_64/uaccess.h for details. */
-	set_fs(USER_DS);
-
 	return 0;
 
 give_sigsegv:
@@ -376,6 +372,13 @@ handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
 	ret = setup_rt_frame(sig, ka, info, oldset, regs);
 
 	if (ret == 0) {
+		/*
+		 * This has nothing to do with segment registers,
+		 * despite the name.  This magic affects uaccess.h
+		 * macros' behavior.  Reset it to the normal setting.
+		 */
+		set_fs(USER_DS);
+
 		/*
 		 * Clear the direction flag as per the ABI for function entry.
 		 */