x86/signals: Propagate RF EFLAGS bit through the signal restore call

While porting Vince's perf overflow tests I found perf event
breakpoint overflow does not work properly.

I found the x86 RF EFLAG bit not being set when returning
from debug exception after triggering signal handler. Which
is exactly what you get when you set perf breakpoint overflow
SIGIO handler.

This patch and the next two patches fix the underlying bugs.

This patch adds the RF EFLAGS bit to be restored on return from
signal from the original register context before the signal was
entered.

This will prevent the RF flag to disappear when returning
from exception due to the signal handler being executed.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Tested-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Originally-Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Stephane Eranian <eranian@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1367421944-19082-2-git-send-email-jolsa@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/ia32/ia32_signal.c

@@ -34,8 +34,6 @@
 #include <asm/sys_ia32.h>
 #include <asm/smap.h>
 
-#define FIX_EFLAGS	__FIX_EFLAGS
-
 int copy_siginfo_to_user32(compat_siginfo_t __user *to, siginfo_t *from)
 {
 	int err = 0;

arch/x86/include/asm/sighandling.h

@@ -7,10 +7,10 @@
 
 #include <asm/processor-flags.h>
 
-#define __FIX_EFLAGS	(X86_EFLAGS_AC | X86_EFLAGS_OF | \
+#define FIX_EFLAGS	(X86_EFLAGS_AC | X86_EFLAGS_OF | \
 			 X86_EFLAGS_DF | X86_EFLAGS_TF | X86_EFLAGS_SF | \
 			 X86_EFLAGS_ZF | X86_EFLAGS_AF | X86_EFLAGS_PF | \
-			 X86_EFLAGS_CF)
+			 X86_EFLAGS_CF | X86_EFLAGS_RF)
 
 void signal_fault(struct pt_regs *regs, void __user *frame, char *where);
 

arch/x86/kernel/signal.c

@@ -43,12 +43,6 @@
 
 #include <asm/sigframe.h>
 
-#ifdef CONFIG_X86_32
-# define FIX_EFLAGS	(__FIX_EFLAGS | X86_EFLAGS_RF)
-#else
-# define FIX_EFLAGS	__FIX_EFLAGS
-#endif
-
 #define COPY(x)			do {			\
 	get_user_ex(regs->x, &sc->x);			\
 } while (0)