x86/asm/entry: Zero EXTRA_REGS for stub32_execve() too

The change which affected how execve clears EXTRA_REGS missed
32-bit execve syscalls.

Fix this by using 64-bit execve stub epilogue for them too.

Run-tested.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1428439424-7258-3-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/ia32/ia32entry.S

@@ -571,8 +571,6 @@ GLOBAL(\label)
 
 	PTREGSCALL stub32_rt_sigreturn, sys32_rt_sigreturn
 	PTREGSCALL stub32_sigreturn, sys32_sigreturn
-	PTREGSCALL stub32_execve, compat_sys_execve
-	PTREGSCALL stub32_execveat, compat_sys_execveat
 	PTREGSCALL stub32_fork, sys_fork
 	PTREGSCALL stub32_vfork, sys_vfork
 

arch/x86/kernel/entry_64.S

@@ -538,6 +538,21 @@ ENTRY(stub_x32_execveat)
 END(stub_x32_execveat)
 #endif
 
+#ifdef CONFIG_IA32_EMULATION
+ENTRY(stub32_execve)
+	CFI_STARTPROC
+	call	compat_sys_execve
+	jmp	return_from_execve
+	CFI_ENDPROC
+END(stub32_execve)
+ENTRY(stub32_execveat)
+	CFI_STARTPROC
+	call	compat_sys_execveat
+	jmp	return_from_execve
+	CFI_ENDPROC
+END(stub32_execveat)
+#endif
+
 /*
  * sigreturn is special because it needs to restore all registers on return.
  * This cannot be done with SYSRET, so use the IRET return path instead.