Hi Arnd,
On Thu, Apr 4, 2024 at 4:52 PM Arnd Bergmann <[email protected]> wrote:
> From: Arnd Bergmann <[email protected]>
>
> Building with W=1 in some configurations produces a false positive
> warning for kallsyms:
>
> kernel/kallsyms.c: In function '__sprint_symbol.isra':
> kernel/kallsyms.c:503:17: error: 'strcpy' source argument is the same as
> destination [-Werror=restrict]
> 503 | strcpy(buffer, name);
> | ^~~~~~~~~~~~~~~~~~~~
>
> This originally showed up while building with -O3, but later started
> happening in other configurations as well, depending on inlining
> decisions. The underlying issue is that the local 'name' variable is
> always initialized to the be the same as 'buffer' in the called functions
> that fill the buffer, which gcc notices while inlining, though it could
> see that the address check always skips the copy.
>
> The calling conventions here are rather unusual, as all of the internal
> lookup functions (bpf_address_lookup, ftrace_mod_address_lookup,
> ftrace_func_address_lookup, module_address_lookup and
> kallsyms_lookup_buildid) already use the provided buffer and either return
> the address of that buffer to indicate success, or NULL for failure,
> but the callers are written to also expect an arbitrary other buffer
> to be returned.
>
> Rework the calling conventions to return the length of the filled buffer
> instead of its address, which is simpler and easier to follow as well
> as avoiding the warning. Leave only the kallsyms_lookup() calling conventions
> unchanged, since that is called from 16 different functions and
> adapting this would be a much bigger change.
>
> Link: https://lore.kernel.org/all/[email protected]/
> Link: https://lore.kernel.org/lkml/[email protected]/
> Reviewed-by: Luis Chamberlain <[email protected]>
> Acked-by: Steven Rostedt (Google) <[email protected]>
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> v5: fix ftrace_mod_address_lookup return value,
> rebased on top of 2e114248e086 ("bpf: Replace deprecated strncpy with
> strscpy")
> v4: fix string length
> v3: use strscpy() instead of strlcpy()
> v2: complete rewrite after the first patch was rejected (in 2020). This
> is now one of only two warnings that are in the way of enabling
> -Wextra/-Wrestrict by default.
Aha, commit 06bb7fc0feee32d9 ("kbuild: turn on -Wrestrict by default")
still made v6.10-rc1, without this one...
> Signed-off-by: Arnd Bergmann <[email protected]>
Thanks, this fixes
kernel/kallsyms.c: In function ‘__sprint_symbol.constprop’:
kernel/kallsyms.c:492:17: warning: ‘strcpy’ source argument is the
same as destination [-Werror=restrict]
492 | strcpy(buffer, name);
| ^~~~~~~~~~~~~~~~~~~~
I am seeing with shmobile_defconfig and gcc version 11.4.0 (Ubuntu
11.4.0-1ubuntu1~22.04).
Tested-by: Geert Uytterhoeven <[email protected]>
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
