RE: [PATCH] compiler.h: avoid escaped section names

[David Laight]

From: Nick Desaulniers
> Sent: 29 September 2020 20:43
> 
> The stringification operator, `#`, in the preprocessor escapes strings.
> For example, `# "foo"` becomes `"\"foo\""`.  GCC and Clang differ in how
> they treat section names that contain \".
> 
> The portable solution is to not use a string literal with the
> preprocessor stringification operator.
> 
> In this case, since __section unconditionally uses the stringification
> operator, we actually want the more verbose
> __attribute__((__section__())).
> 
> Link: https://bugs.llvm.org/show_bug.cgi?id=42950
> Fixes: commit e04462fb82f8 ("Compiler Attributes: remove uses of __attribute__ from compiler.h")
> Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> ---
>  include/linux/compiler.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index 92ef163a7479..ac45f6d40d39 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -155,7 +155,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
>  	extern typeof(sym) sym;					\
>  	static const unsigned long __kentry_##sym		\
>  	__used							\
> -	__section("___kentry" "+" #sym )			\
> +	__attribute__((__section__("___kentry+" #sym)))		\
>  	= (unsigned long)&sym;
>  #endif

I guess what this really wants is:
	__section(__kentry+##sym)
but that generates an error because you can only use ## between
variable names.

Perhaps someone shouldn't have tries to be clever and not put
an unusual character in the section name.

	David

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