[PATCH] riscv: ftrace: Add parentheses in macro definitions of make_call_t0 and make_call_ra

[PATCH] riscv: ftrace: Add parentheses in macro definitions of make_call_t0 and make_call_ra

[Juhan Jin]

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@foxmail.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

Re: [PATCH] riscv: ftrace: Add parentheses in macro definitions of make_call_t0 and make_call_ra

[Alexandre Ghiti]

Hi Juhan,

On 06/02/2025 20:28, Juhan Jin wrote:
> 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@foxmail.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


Probably not worth going into fixes since the problem is not around for 
now, but that's still a good catch:

Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>

Thanks,

Alex

Re: [PATCH] riscv: ftrace: Add parentheses in macro definitions of make_call_t0 and make_call_ra

[patchwork-bot+linux-riscv]

Hello:

This patch was applied to riscv/linux.git (for-next)
by Alexandre Ghiti <alexghiti@rivosinc.com>:

On Thu,  6 Feb 2025 13:28:36 -0600 you wrote:
> 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:
> 
> [...]

Here is the summary with links:
  - riscv: ftrace: Add parentheses in macro definitions of make_call_t0 and make_call_ra
    https://git.kernel.org/riscv/c/5f1a58ed91a0

You are awesome, thank you!
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