pie: fix clobber registers for int 0x80

I managed to forgot that kernel erases R8...R11 regitster
prior returning to userspace from `int 0x80`:
https://lkml.org/lkml/2009/10/1/164

That was the reason for hang on gcc v6.1 on Jenkins/elsewhere:
https://ci.openvz.org/job/CRIU/job/CRIU-x86_64/branch/criu-dev/

Tested on gcc v6.1 locally, on Travis-CI:
https://travis-ci.org/0x7f454c46/criu/builds/183976899

travis-ci: success for pie: fix clobber registers for int 0x80 (rev2)
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Tested-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

compel/arch/x86/src/lib/include/uapi/asm/sigframe.h

@@ -185,7 +185,7 @@ struct rt_sigframe {
 		".code64					\n"	\
 		:							\
 		: "rdi"(new_sp)						\
-		: "eax","esp","memory")
+		: "eax","esp", "r8", "r9", "r10", "r11", "memory")
 
 #define ARCH_RT_SIGRETURN(new_sp, rt_sigframe)				\
 do {									\

criu/arch/x86/include/asm/parasite.h

@@ -38,12 +38,8 @@ static int arch_get_user_desc(user_desc_t *desc)
 	"	mov %%eax,%0			\n"
 	: "+m"(ret)
 	: "m"(desc)
-	: "eax", "rbx", "memory");
+	: "rax", "rbx", "r8", "r9", "r10", "r11", "memory");
 
-	/*
-	 * Fixup for Travis: on missing GDT entry get_thread_area()
-	 * retruns -EINTR then descriptor with seg_not_preset = 1
-	 */
 	if (ret)
 		pr_err("Failed to dump TLS descriptor #%d: %d\n",
 				desc->entry_number, ret);

criu/arch/x86/restorer.c

@@ -79,7 +79,7 @@ void restore_tls(tls_t *ptls)
 		"	mov %%eax,%0			\n"
 		: "=g"(ret)
 		: "r"(__NR32_set_thread_area), "r"((uint32_t)(uintptr_t)stack32)
-		: "eax", "ebx", "memory");
+		: "eax", "ebx", "r8", "r9", "r10", "r11", "memory");
 
 		if (ret)
 			pr_err("Failed to restore TLS descriptor %u in GDT: %d\n",