On Fri, 2 Aug 2024 14:08:34 -0700
Song Liu <song@xxxxxxxxxx> wrote:
> With CONFIG_LTO_CLANG=y, the compiler may add suffix to function names
> to avoid duplication. This causes confusion with users of kallsyms.
> On one hand, users like livepatch are required to match the symbols
> exactly. On the other hand, users like kprobe would like to match to
> original function names.
>
> Solve this by splitting kallsyms APIs. Specifically, existing APIs now
> should match the symbols exactly. Add two APIs that match only the part
> without .XXXX suffix. Specifically, the following two APIs are added.
>
> 1. kallsyms_lookup_name_without_suffix()
> 2. kallsyms_on_each_match_symbol_without_suffix()
>
> These APIs will be used by kprobe.
>
> Also cleanup some code and update kallsyms_selftests accordingly.
>
> Signed-off-by: Song Liu <song@xxxxxxxxxx>
Looks good to me, but I have a nitpick.
> --- a/kernel/kallsyms.c
> +++ b/kernel/kallsyms.c
> @@ -164,30 +164,27 @@ static void cleanup_symbol_name(char *s)
> {
> char *res;
>
> - if (!IS_ENABLED(CONFIG_LTO_CLANG))
> - return;
> -
> /*
> * LLVM appends various suffixes for local functions and variables that
> * must be promoted to global scope as part of LTO. This can break
> * hooking of static functions with kprobes. '.' is not a valid
> - * character in an identifier in C. Suffixes only in LLVM LTO observed:
> - * - foo.llvm.[0-9a-f]+
> + * character in an identifier in C, so we can just remove the
> + * suffix.
> */
> - res = strstr(s, ".llvm.");
> + res = strstr(s, ".");
nit: "strchr(s, '.')" ?
Anyway,
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Thank you,
--
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
