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From: Andy Chiu <andy.chiu@sifive.com>
Date: Thu, 13 Jun 2024 15:11:06 +0800
Subject: [PATCH 1/8] riscv: stacktrace: convert arch_stack_walk() to
 noinstr
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Message-Id: <20240613-dev-andyc-dyn-ftrace-v4-v1-1-1a538e12c01e@sifive.com>
References: <20240613-dev-andyc-dyn-ftrace-v4-v1-0-1a538e12c01e@sifive.com>
In-Reply-To: <20240613-dev-andyc-dyn-ftrace-v4-v1-0-1a538e12c01e@sifive.com>
To: Paul Walmsley <paul.walmsley@sifive.com>, 
 Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, 
 Alexandre Ghiti <alexghiti@rivosinc.com>, Zong Li <zong.li@sifive.com>, 
 Steven Rostedt <rostedt@goodmis.org>, 
 Masami Hiramatsu <mhiramat@kernel.org>, Mark Rutland <mark.rutland@arm.com>, 
 Nathan Chancellor <nathan@kernel.org>, 
 Nick Desaulniers <ndesaulniers@google.com>, 
 Bill Wendling <morbo@google.com>, Justin Stitt <justinstitt@google.com>, 
 Puranjay Mohan <puranjay@kernel.org>
Cc: Palmer Dabbelt <palmer@rivosinc.com>, linux-riscv@lists.infradead.org, 
 linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, 
 llvm@lists.linux.dev, Andy Chiu <andy.chiu@sifive.com>

arch_stack_walk() is called intensively in function_graph when the
kernel is compiled with CONFIG_TRACE_IRQFLAGS. As a result, the kernel
logs a lot of arch_stack_walk and its sub-functions into the ftrace
buffer. However, these functions should not appear on the trace log
because they are part of the ftrace itself. This patch references what
arm64 does for the smae function. So it further prevent the re-enter
kprobe issue, which is also possible on riscv.

Related-to: commit 0fbcd8abf337 ("arm64: Prohibit instrumentation on arch_stack_walk()")
Fixes: 680341382da5 ("riscv: add CALLER_ADDRx support")
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
---
 arch/riscv/kernel/stacktrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
index 528ec7cc9a62..0d3f00eb0bae 100644
--- a/arch/riscv/kernel/stacktrace.c
+++ b/arch/riscv/kernel/stacktrace.c
@@ -156,7 +156,7 @@ unsigned long __get_wchan(struct task_struct *task)
 	return pc;
 }
 
-noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
+noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
 		     struct task_struct *task, struct pt_regs *regs)
 {
 	walk_stackframe(task, regs, consume_entry, cookie);

-- 
2.43.0