LoongArch: Mark some assembler symbols as non-kprobe-able

Some assembler symbols are not kprobe safe, such as handle_syscall (used
as syscall exception handler), *memset*/*memcpy*/*memmove* (may cause
recursive exceptions), they can not be instrumented, just blacklist them
for kprobing.

Here is a related problem and discussion:
Link: https://lore.kernel.org/lkml/20230114143859.7ccc45c1c5d9ce302113ab0a@kernel.org/

Tested-by: Jeff Xie <xiehuan09@gmail.com>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/include/asm/asm.h

@@ -188,4 +188,14 @@
 #define PTRLOG		3
 #endif
 
+/* Annotate a function as being unsuitable for kprobes. */
+#ifdef CONFIG_KPROBES
+#define _ASM_NOKPROBE(name)				\
+	.pushsection "_kprobe_blacklist", "aw";		\
+	.quad	name;					\
+	.popsection
+#else
+#define _ASM_NOKPROBE(name)
+#endif
+
 #endif /* __ASM_ASM_H */

arch/loongarch/kernel/entry.S

@@ -67,6 +67,7 @@ SYM_FUNC_START(handle_syscall)
 
 	RESTORE_ALL_AND_RET
 SYM_FUNC_END(handle_syscall)
+_ASM_NOKPROBE(handle_syscall)
 
 SYM_CODE_START(ret_from_fork)
 	bl		schedule_tail		# a0 = struct task_struct *prev

arch/loongarch/lib/memcpy.S

@@ -17,6 +17,7 @@ SYM_FUNC_START(memcpy)
 	ALTERNATIVE	"b __memcpy_generic", \
 			"b __memcpy_fast", CPU_FEATURE_UAL
 SYM_FUNC_END(memcpy)
+_ASM_NOKPROBE(memcpy)
 
 EXPORT_SYMBOL(memcpy)
 
@@ -41,6 +42,7 @@ SYM_FUNC_START(__memcpy_generic)
 2:	move	a0, a3
 	jr	ra
 SYM_FUNC_END(__memcpy_generic)
+_ASM_NOKPROBE(__memcpy_generic)
 
 /*
  * void *__memcpy_fast(void *dst, const void *src, size_t n)
@@ -93,3 +95,4 @@ SYM_FUNC_START(__memcpy_fast)
 3:	move	a0, a3
 	jr	ra
 SYM_FUNC_END(__memcpy_fast)
+_ASM_NOKPROBE(__memcpy_fast)

arch/loongarch/lib/memmove.S

@@ -29,6 +29,7 @@ SYM_FUNC_START(memmove)
 	b	rmemcpy
 4:	b	__rmemcpy_generic
 SYM_FUNC_END(memmove)
+_ASM_NOKPROBE(memmove)
 
 EXPORT_SYMBOL(memmove)
 
@@ -39,6 +40,7 @@ SYM_FUNC_START(rmemcpy)
 	ALTERNATIVE	"b __rmemcpy_generic", \
 			"b __rmemcpy_fast", CPU_FEATURE_UAL
 SYM_FUNC_END(rmemcpy)
+_ASM_NOKPROBE(rmemcpy)
 
 /*
  * void *__rmemcpy_generic(void *dst, const void *src, size_t n)
@@ -64,6 +66,7 @@ SYM_FUNC_START(__rmemcpy_generic)
 2:	move	a0, a3
 	jr	ra
 SYM_FUNC_END(__rmemcpy_generic)
+_ASM_NOKPROBE(__rmemcpy_generic)
 
 /*
  * void *__rmemcpy_fast(void *dst, const void *src, size_t n)
@@ -119,3 +122,4 @@ SYM_FUNC_START(__rmemcpy_fast)
 3:	move	a0, a3
 	jr	ra
 SYM_FUNC_END(__rmemcpy_fast)
+_ASM_NOKPROBE(__rmemcpy_fast)

arch/loongarch/lib/memset.S

@@ -23,6 +23,7 @@ SYM_FUNC_START(memset)
 	ALTERNATIVE	"b __memset_generic", \
 			"b __memset_fast", CPU_FEATURE_UAL
 SYM_FUNC_END(memset)
+_ASM_NOKPROBE(memset)
 
 EXPORT_SYMBOL(memset)
 
@@ -45,6 +46,7 @@ SYM_FUNC_START(__memset_generic)
 2:	move	a0, a3
 	jr	ra
 SYM_FUNC_END(__memset_generic)
+_ASM_NOKPROBE(__memset_generic)
 
 /*
  * void *__memset_fast(void *s, int c, size_t n)
@@ -89,3 +91,4 @@ SYM_FUNC_START(__memset_fast)
 3:	move	a0, a3
 	jr	ra
 SYM_FUNC_END(__memset_fast)
+_ASM_NOKPROBE(__memset_fast)