From:   Chen Guokai <chenguokai17@mails.ucas.ac.cn>
To:     paul.walmsley@sifive.com, palmer@dabbelt.com,
        aou@eecs.berkeley.edu, rostedt@goodmis.org, mingo@redhat.com,
        sfr@canb.auug.org.au
Cc:     linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        liaochang1@huawei.com
Subject: [PATCH v6 12/13] riscv/kprobe: Move exception related symbols to .kprobe_blacklist
Date:   Fri, 27 Jan 2023 21:05:40 +0800
Message-Id: <20230127130541.1250865-13-chenguokai17@mails.ucas.ac.cn>
In-Reply-To: <20230127130541.1250865-1-chenguokai17@mails.ucas.ac.cn>
References: <20230127130541.1250865-1-chenguokai17@mails.ucas.ac.cn>
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From: Liao Chang <liaochang1@huawei.com>

Due to the generic exception entry and exit code is part of the critical
path for kprobe breakpoint and uprobe syscall entry, set a kprobe on the
assembly symbols in entry.S result in kernel stack overflow crash, hence
it has to explicitly blacklist it, requiring a new _ASM_NOKPROBE() asm
helper.

Signed-off-by: Liao Chang <liaochang1@huawei.com>
---
 arch/riscv/include/asm/asm.h | 10 ++++++++++
 arch/riscv/kernel/entry.S    | 12 ++++++++++++
 arch/riscv/kernel/mcount.S   |  1 +
 3 files changed, 23 insertions(+)

diff --git a/arch/riscv/include/asm/asm.h b/arch/riscv/include/asm/asm.h
index 816e753de636..5d9f13d8b809 100644
--- a/arch/riscv/include/asm/asm.h
+++ b/arch/riscv/include/asm/asm.h
@@ -81,6 +81,16 @@
 	.endr
 .endm
 
+#ifdef CONFIG_KPROBES
+#define _ASM_NOKPROBE(entry)				\
+	.pushsection "_kprobe_blacklist", "aw" ;	\
+	.balign SZREG ;					\
+	REG_ASM entry ;					\
+	.popsection
+#else
+#define _ASM_NOKPROBE(entry)
+#endif
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_RISCV_ASM_H */
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index 99d38fdf8b18..9e8882a78523 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -606,3 +606,15 @@ ENTRY(__user_rt_sigreturn)
 	scall
 END(__user_rt_sigreturn)
 #endif
+
+_ASM_NOKPROBE(handle_exception)
+_ASM_NOKPROBE(_restore_kernel_tpsp)
+_ASM_NOKPROBE(_save_context)
+_ASM_NOKPROBE(ret_from_exception)
+_ASM_NOKPROBE(ret_from_syscall)
+_ASM_NOKPROBE(__switch_to)
+_ASM_NOKPROBE(ret_from_syscall_rejected)
+_ASM_NOKPROBE(restore_all)
+_ASM_NOKPROBE(resume_kernel)
+_ASM_NOKPROBE(resume_userspace)
+_ASM_NOKPROBE(check_syscall_nr)
diff --git a/arch/riscv/kernel/mcount.S b/arch/riscv/kernel/mcount.S
index 30102aadc4d7..7393b8895ef3 100644
--- a/arch/riscv/kernel/mcount.S
+++ b/arch/riscv/kernel/mcount.S
@@ -54,6 +54,7 @@ ENTRY(ftrace_stub)
 #endif
 	ret
 ENDPROC(ftrace_stub)
+_ASM_NOKPROBE(MCOUNT_NAME)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 ENTRY(return_to_handler)
-- 
2.34.1