Re: [PATCH 2/3] selftests/nolibc: avoid function pointer comparisons

[Helge Deller]

On 4/7/26 18:37, Thomas Weißschuh wrote:
> The upcoming parisc support would require libgcc to implement function
> pointer comparisons. As we try to avoid the libgcc dependency rework
> the logic to work without such comparisons.

Instead of working around at this specific code, I think it makes more sense
to simply add the __canonicalize_funcptr_for_compare() symbol somewhere.
Code is in arch/parisc/kernel/real2.S:
 
ENTRY_CFI(__canonicalize_funcptr_for_compare)
#ifdef CONFIG_64BIT
        bve (%r2)
#else
        bv %r0(%r2)
#endif
        copy %r26,%r28
ENDPROC_CFI(__canonicalize_funcptr_for_compare)

Or am I missing something?

Btw, since you want to avoid libgcc, I think this is quite hard, since
gcc automatically adds lots of parisc specific millicode functions (see the "$$" symbols
in parisc_ksyms.c) and many of the gcc helper functions (e.g. __muldi3).

So, I'm not sure if it makes sense to try to avoid libgcc....

Helge
 
> Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
> ---
>   tools/testing/selftests/nolibc/nolibc-test.c | 13 +++++++++----
>   1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
> index d3c4facb54c0..de4e87586d75 100644
> --- a/tools/testing/selftests/nolibc/nolibc-test.c
> +++ b/tools/testing/selftests/nolibc/nolibc-test.c
> @@ -647,20 +647,25 @@ int expect_str_buf_eq(size_t expr, const char *buf, size_t val, int llen, const
>   	return 0;
>   }
>   
> +enum strtox_func {
> +	strtox_func_strtol,
> +	strtox_func_strtoul,
> +};
> +
>   #define EXPECT_STRTOX(cond, func, input, base, expected, chars, expected_errno)				\
> -	do { if (!(cond)) result(llen, SKIPPED); else ret += expect_strtox(llen, func, input, base, expected, chars, expected_errno); } while (0)
> +	do { if (!(cond)) result(llen, SKIPPED); else ret += expect_strtox(llen, strtox_func_ ## func, input, base, expected, chars, expected_errno); } while (0)
>   
>   static __attribute__((unused))
> -int expect_strtox(int llen, void *func, const char *input, int base, intmax_t expected, int expected_chars, int expected_errno)
> +int expect_strtox(int llen, enum strtox_func func, const char *input, int base, intmax_t expected, int expected_chars, int expected_errno)
>   {
>   	char *endptr;
>   	int actual_errno, actual_chars;
>   	intmax_t r;
>   
>   	errno = 0;
> -	if (func == strtol) {
> +	if (func == strtox_func_strtol) {
>   		r = strtol(input, &endptr, base);
> -	} else if (func == strtoul) {
> +	} else if (func == strtox_func_strtoul) {
>   		r = strtoul(input, &endptr, base);
>   	} else {
>   		result(llen, FAIL);