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From:   Tiezhu Yang <yangtiezhu@loongson.cn>
To:     Huacai Chen <chenhuacai@kernel.org>,
        WANG Xuerui <kernel@xen0n.name>,
        Masami Hiramatsu <mhiramat@kernel.org>
Cc:     loongarch@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: [PATCH v12 4/5] LoongArch: Mark some assembler symbols as non-kprobe-able
Date:   Wed, 18 Jan 2023 10:01:00 +0800
Message-Id: <1674007261-9198-5-git-send-email-yangtiezhu@loongson.cn>
In-Reply-To: <1674007261-9198-1-git-send-email-yangtiezhu@loongson.cn>
References: <1674007261-9198-1-git-send-email-yangtiezhu@loongson.cn>
Precedence: bulk

Some assembler symbols are not kprobe safe, such as handle_syscall
(used as syscall exception handler), *memcpy* (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/

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 arch/loongarch/include/asm/asm.h | 10 ++++++++++
 arch/loongarch/kernel/entry.S    |  1 +
 arch/loongarch/lib/memcpy.S      |  3 +++
 3 files changed, 14 insertions(+)

diff --git a/arch/loongarch/include/asm/asm.h b/arch/loongarch/include/asm/asm.h
index 40eea6a..f591b32 100644
--- a/arch/loongarch/include/asm/asm.h
+++ b/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 */
diff --git a/arch/loongarch/kernel/entry.S b/arch/loongarch/kernel/entry.S
index d53b631..55e23b1 100644
--- a/arch/loongarch/kernel/entry.S
+++ b/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
diff --git a/arch/loongarch/lib/memcpy.S b/arch/loongarch/lib/memcpy.S
index 7c07d59..3b7e1de 100644
--- a/arch/loongarch/lib/memcpy.S
+++ b/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)
-- 
2.1.0