linux-kernel - [PATCH] riscv: ftrace: Add parentheses in macro definitions of make_call_t0 and make_call

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Message-ID: <tencent_AE90AA59903A628E87E9F80E563DA5BA5508@qq.com>
Date: Thu,  6 Feb 2025 13:28:36 -0600
From: Juhan Jin <juhan.jin@...mail.com>
To: guoren@...nel.org,
	guoren@...ux.alibaba.com,
	rostedt@...dmis.org,
	mhiramat@...nel.org,
	mark.rutland@....com,
	paul.walmsley@...ive.com,
	palmer@...belt.com,
	aou@...s.berkeley.edu
Cc: linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	Juhan Jin <juhan.jin@...mail.com>
Subject: [PATCH] riscv: ftrace: Add parentheses in macro definitions of make_call_t0 and make_call_ra

This patch adds parentheses to parameters caller and callee of macros
make_call_t0 and make_call_ra. Every existing invocation of these two
macros uses a single variable for each argument, so the absence of the
parentheses seems okay. However, future invocations might use more
complex expressions as arguments. For example, a future invocation might
look like this: make_call_t0(a - b, c, call). Without parentheses in the
macro definition, the macro invocation expands to:

...
unsigned int offset = (unsigned long) c - (unsigned long) a - b;
...

which is clearly wrong.

The use of parentheses ensures arguments are correctly evaluated and
potentially saves future users of make_call_t0 and make_call_ra debugging
trouble.

Fixes: 6724a76cff85 ("riscv: ftrace: Reduce the detour code size to half")
Signed-off-by: Juhan Jin <juhan.jin@...mail.com>
---
 arch/riscv/include/asm/ftrace.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index c4721ce44ca4..2636ee00ccf0 100644
--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -92,7 +92,7 @@ struct dyn_arch_ftrace {
 #define make_call_t0(caller, callee, call)				\
 do {									\
 	unsigned int offset =						\
-		(unsigned long) callee - (unsigned long) caller;	\
+		(unsigned long) (callee) - (unsigned long) (caller);	\
 	call[0] = to_auipc_t0(offset);					\
 	call[1] = to_jalr_t0(offset);					\
 } while (0)
@@ -108,7 +108,7 @@ do {									\
 #define make_call_ra(caller, callee, call)				\
 do {									\
 	unsigned int offset =						\
-		(unsigned long) callee - (unsigned long) caller;	\
+		(unsigned long) (callee) - (unsigned long) (caller);	\
 	call[0] = to_auipc_ra(offset);					\
 	call[1] = to_jalr_ra(offset);					\
 } while (0)

base-commit: 2014c95afecee3e76ca4a56956a936e23283f05b
-- 
2.39.5