Re: [PATCH 2/3] perf riscv: Fix discarded const qualifier error in _get_field()

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] Deterministic NULL pointer dereference in `get_cpuid()` when `/proc/cpuinfo` parsing fails.
- [Low] The patch resolves a const-qualifier warning by forcefully casting to `(char *)` instead of using const-correct variable types.
--

commit 5d7d955a53ac900eccabdb8ae292dcf199883310
Author: Li Guan <guanli.oerv@isrc.iscas.ac.cn>

perf riscv: Fix discarded const qualifier error in _get_field()

This commit addresses a build failure on GCC 14 caused by strict type checking
on pointer assignments. It resolves the discarded-qualifiers warning by
explicitly casting the return values of strrchr() to a (char *).

> diff --git a/tools/perf/arch/riscv/util/header.c b/tools/perf/arch/riscv/util/header.c
> index 4b839203d4a54..d01ba64aecfd5 100644
> --- a/tools/perf/arch/riscv/util/header.c
> +++ b/tools/perf/arch/riscv/util/header.c
> @@ -21,12 +21,12 @@ static char *_get_field(const char *line)
>  {
>  	char *line2, *nl;
>  
> -	line2 = strrchr(line, ' ');
> +	line2 = (char *)strrchr(line, ' ');

Would it be better to declare line2 and nl as const char * rather than
forcefully casting away the const qualifier?

Since these variables are only used for pointer arithmetic and passed to
strndup() (which accepts a const char *), propagating the const qualifier
would prevent bypassing the compiler safety checks.

>  	if (!line2)
>  		return NULL;
>  
>  	line2++;
> -	nl = strrchr(line, '\n');
> +	nl = (char *)strrchr(line, '\n');
>  	if (!nl)
>  		return NULL;

While reviewing this file, I also noticed a pre-existing issue in the
get_cpuid() function:

tools/perf/arch/riscv/util/header.c:get_cpuid() {
	char *cpuid = _get_cpuid();
	int ret = 0;

	if (sz < strlen(cpuid)) {
		ret = -EINVAL;
		goto free;
	}
...
}

Can this unconditional call to strlen() cause a segmentation fault if
_get_cpuid() returns NULL?

If _get_cpuid() fails to open /proc/cpuinfo or cannot find the expected
fields (mvendorid, marchid, mimpid), it will return NULL. Passing that NULL
pointer to strlen() would cause the tool to crash in environments without
/proc mounted or on older RISC-V kernels.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260513154851.1085334-1-guanli.oerv@isrc.iscas.ac.cn?part=2