x86/srso: Fix unret validation dependencies

CONFIG_CPU_SRSO isn't dependent on CONFIG_CPU_UNRET_ENTRY (AMD
Retbleed), so the two features are independently configurable.  Fix
several issues for the (presumably rare) case where CONFIG_CPU_SRSO is
enabled but CONFIG_CPU_UNRET_ENTRY isn't.

Fixes: fb3bd91 ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/299fb7740174d0f2335e91c58af0e9c242b4bac1.1693889988.git.jpoimboe@kernel.org

Author: jpoimboe

arch/x86/include/asm/nospec-branch.h

@@ -271,7 +271,7 @@
 .Lskip_rsb_\@:
 .endm
 
-#ifdef CONFIG_CPU_UNRET_ENTRY
+#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO)
 #define CALL_UNTRAIN_RET	"call entry_untrain_ret"
 #else
 #define CALL_UNTRAIN_RET	""
@@ -312,7 +312,7 @@
 
 .macro UNTRAIN_RET_FROM_CALL
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING)
+	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\

include/linux/objtool.h

@@ -130,7 +130,8 @@
  * it will be ignored.
  */
 .macro VALIDATE_UNRET_BEGIN
-#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
+#if defined(CONFIG_NOINSTR_VALIDATION) && \
+	(defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO))
 .Lhere_\@:
 	.pushsection .discard.validate_unret
 	.long	.Lhere_\@ - .

scripts/Makefile.vmlinux_o

@@ -37,7 +37,8 @@ objtool-enabled := $(or $(delay-objtool),$(CONFIG_NOINSTR_VALIDATION))
 
 vmlinux-objtool-args-$(delay-objtool)			+= $(objtool-args-y)
 vmlinux-objtool-args-$(CONFIG_GCOV_KERNEL)		+= --no-unreachable
-vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr $(if $(CONFIG_CPU_UNRET_ENTRY), --unret)
+vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr \
+							   $(if $(or $(CONFIG_CPU_UNRET_ENTRY),$(CONFIG_CPU_SRSO)), --unret)
 
 objtool-args = $(vmlinux-objtool-args-y) --link