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SubjectRe: [PATCH -tip 1/2] x86/alternatives: Fix build warning

* Masami Hiramatsu <mhiramat@redhat.com> wrote:

> Fixes below warnings.
>
> ====
> FYI, there's this new build warning on x86 defconfig:
>
> arch/x86/kernel/alternative.c: In function 'alternatives_text_reserved':
> arch/x86/kernel/alternative.c:402: warning: comparison of distinct pointer types lacks a cast
> arch/x86/kernel/alternative.c:402: warning: comparison of distinct pointer types lacks a cast
> arch/x86/kernel/alternative.c:405: warning: comparison of distinct pointer types lacks a cast
> arch/x86/kernel/alternative.c:405: warning: comparison of distinct pointer types lacks a cast
>
> Caused by:
>
> 2cfa197: ftrace/alternatives: Introducing *_text_reserved functions
> ====
>
> Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
> Reported-by: Ingo Molnar <mingo@elte.hu>
> ---
>
> arch/x86/kernel/alternative.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
> index 3832fdc..99d9920 100644
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -399,10 +399,10 @@ int alternatives_text_reserved(void *start, void *end)
> u8 **ptr;
>
> list_for_each_entry(mod, &smp_alt_modules, next) {
> - if (mod->text > end || mod->text_end < start)
> + if (mod->text > (u8 *)end || mod->text_end < (u8 *)start)
> continue;
> for (ptr = mod->locks; ptr < mod->locks_end; ptr++)
> - if (start <= *ptr && end >= *ptr)
> + if ((u8 *)start <= *ptr && (u8 *)end >= *ptr)
> return 1;
> }

Such casts are a bit ugly and in general type casts are somewhat dangerous.

One possible solution would be to add intermediary local variables
(text_start/text_end) with u8 * type and assign start/end to them - which can
be done without a cast.

Thanks,

Ingo


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