x86: Add types to indirectly called assembly functions

With CONFIG_CFI_CLANG, assembly functions indirectly called
from C code must be annotated with type identifiers to pass CFI
checking. Define the __CFI_TYPE helper macro to match the compiler
generated function preamble, and ensure SYM_TYPED_FUNC_START also
emits ENDBR with IBT.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220908215504.3686827-21-samitolvanen@google.com

arch/x86/crypto/blowfish-x86_64-asm_64.S

@@ -6,6 +6,7 @@
  */
 
 #include <linux/linkage.h>
+#include <linux/cfi_types.h>
 
 .file "blowfish-x86_64-asm.S"
 .text
@@ -141,7 +142,7 @@ SYM_FUNC_START(__blowfish_enc_blk)
 	RET;
 SYM_FUNC_END(__blowfish_enc_blk)
 
-SYM_FUNC_START(blowfish_dec_blk)
+SYM_TYPED_FUNC_START(blowfish_dec_blk)
 	/* input:
 	 *	%rdi: ctx
 	 *	%rsi: dst
@@ -332,7 +333,7 @@ SYM_FUNC_START(__blowfish_enc_blk_4way)
 	RET;
 SYM_FUNC_END(__blowfish_enc_blk_4way)
 
-SYM_FUNC_START(blowfish_dec_blk_4way)
+SYM_TYPED_FUNC_START(blowfish_dec_blk_4way)
 	/* input:
 	 *	%rdi: ctx
 	 *	%rsi: dst

arch/x86/include/asm/linkage.h

@@ -43,6 +43,18 @@
 
 #endif /* __ASSEMBLY__ */
 
+#define __CFI_TYPE(name)					\
+	SYM_START(__cfi_##name, SYM_L_LOCAL, SYM_A_NONE)	\
+	.fill 11, 1, 0x90 ASM_NL				\
+	.byte 0xb8 ASM_NL					\
+	.long __kcfi_typeid_##name ASM_NL			\
+	SYM_FUNC_END(__cfi_##name)
+
+/* SYM_TYPED_FUNC_START -- use for indirectly called globals, w/ CFI type */
+#define SYM_TYPED_FUNC_START(name)				\
+	SYM_TYPED_START(name, SYM_L_GLOBAL, SYM_A_ALIGN)	\
+	ENDBR
+
 /* SYM_FUNC_START -- use for global functions */
 #define SYM_FUNC_START(name)				\
 	SYM_START(name, SYM_L_GLOBAL, SYM_A_ALIGN)	\

arch/x86/lib/memcpy_64.S

@@ -2,6 +2,7 @@
 /* Copyright 2002 Andi Kleen */
 
 #include <linux/linkage.h>
+#include <linux/cfi_types.h>
 #include <asm/errno.h>
 #include <asm/cpufeatures.h>
 #include <asm/alternative.h>
@@ -27,7 +28,7 @@
  * Output:
  * rax original destination
  */
-SYM_FUNC_START(__memcpy)
+SYM_TYPED_FUNC_START(__memcpy)
 	ALTERNATIVE_2 "jmp memcpy_orig", "", X86_FEATURE_REP_GOOD, \
 		      "jmp memcpy_erms", X86_FEATURE_ERMS