[CRIU] CRIU gcc9 errors

[Adrian Reber]

I just got an email that CRIU will fail building with the upcoming
release of gcc. Fortunately the email also included a patch. I attached
the patch and can submit it properly. Just wanted to hear if anyone has
any feedback/comments to this patch.

I got the following description for the patch



Attached you'll find the fix for criu.  You'll see it's just a matter of
dropping the sp/esp clobber from the relevant asm statements.  THe details:

criu has a macro which defines an asm which appears to want to set a new
stack pointer, then directly issue a sigreturn call to the kernel.  Some
variants clobber sp (aarch64, arm, x86), others do not (ppc, s390)


While the asm does indeed set a new stack pointer, we never return from
a sigreturn syscall -- at least not in the normal way.  We actually
return back to the point where the process was interrupted by the
signal.  So describing the affect of the asm on the stack pointer is
pedantically correct, it actually has no real effect and can just be
dropped to avoid the hard error from gcc-9.



diff --git a/compel/arch/aarch64/src/lib/include/uapi/asm/sigframe.h b/compel/arch/aarch64/src/lib/include/uapi/asm/sigframe.h
index 6b511ce..6b9317b 100644
--- a/compel/arch/aarch64/src/lib/include/uapi/asm/sigframe.h
+++ b/compel/arch/aarch64/src/lib/include/uapi/asm/sigframe.h
@@ -39,7 +39,7 @@ struct rt_sigframe {
 			"svc #0						\n"	\
 			:							\
 			: "r"(new_sp)						\
-			: "sp", "x8", "memory")
+			: "x8", "memory")
 
 /* cr_sigcontext is copied from arch/arm64/include/uapi/asm/sigcontext.h */
 struct cr_sigcontext {
diff --git a/compel/arch/arm/src/lib/include/uapi/asm/sigframe.h b/compel/arch/arm/src/lib/include/uapi/asm/sigframe.h
index 3e7bc01..b90c0f6 100644
--- a/compel/arch/arm/src/lib/include/uapi/asm/sigframe.h
+++ b/compel/arch/arm/src/lib/include/uapi/asm/sigframe.h
@@ -73,7 +73,7 @@ struct rt_sigframe {
 		     "svc #0					    \n"	\
 		     :							\
 		     : "r"(new_sp)					\
-		     : "sp","memory")
+		     : "memory")
 
 #define RT_SIGFRAME_UC(rt_sigframe)		(&rt_sigframe->sig.uc)
 #define RT_SIGFRAME_REGIP(rt_sigframe)		(rt_sigframe)->sig.uc.uc_mcontext.arm_ip
diff --git a/compel/arch/x86/src/lib/include/uapi/asm/sigframe.h b/compel/arch/x86/src/lib/include/uapi/asm/sigframe.h
index 0ad45a5..c29de3b 100644
--- a/compel/arch/x86/src/lib/include/uapi/asm/sigframe.h
+++ b/compel/arch/x86/src/lib/include/uapi/asm/sigframe.h
@@ -162,7 +162,7 @@ struct rt_sigframe {
 		     "syscall					    \n"	\
 		     :							\
 		     : "r"(new_sp)					\
-		     : "rax","rsp","memory")
+		     : "rax","memory")
 #define ARCH_RT_SIGRETURN_COMPAT(new_sp)				\
 	asm volatile(							\
 		"pushq $"__stringify(USER32_CS)"		\n"	\
@@ -176,7 +176,7 @@ struct rt_sigframe {
 		".code64					\n"	\
 		:							\
 		: "rdi"(new_sp)						\
-		: "eax","esp", "r8", "r9", "r10", "r11", "memory")
+		: "eax", "r8", "r9", "r10", "r11", "memory")
 
 #define ARCH_RT_SIGRETURN(new_sp, rt_sigframe)				\
 do {									\