Re: [PATCH 3/3] tracing/kprobes: Use APIs that matches symbols with .llvm. suffix

Masami Hiramatsu
2024-07-30T13:04:24Z

On Mon, 29 Jul 2024 17:54:33 -0700
Song Liu <song@kernel.org> wrote:

> Use the new kallsyms APIs that matches symbols name with .llvm.<hash>
> suffix. This allows userspace tools to get kprobes on the expected
> function name, while the actual symbol has a .llvm.<hash> suffix.
>

_kprobe_addr@kernel/kprobes.c may also fail with this change.

Thanks,

> This only effects kernel compared with CONFIG_LTO_CLANG.
>
> Signed-off-by: Song Liu <song@kernel.org>
> ---
> kernel/trace/trace_kprobe.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 61a6da808203..c319382c1a09 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -202,7 +202,8 @@ unsigned long trace_kprobe_address(struct trace_kprobe *tk)
>
> if (tk->symbol) {
> addr = (unsigned long)
> - kallsyms_lookup_name(trace_kprobe_symbol(tk));
> + kallsyms_lookup_name_or_prefix(trace_kprobe_symbol(tk));
> +
> if (addr)
> addr += tk->rp.kp.offset;
> } else {
> @@ -766,8 +767,13 @@ static unsigned int number_of_same_symbols(const char *mod, const char *func_nam
> {
> struct sym_count_ctx ctx = { .count = 0, .name = func_name };
>
> - if (!mod)
> + if (!mod) {
> kallsyms_on_each_match_symbol(count_symbols, func_name, &ctx.count);
> + if (IS_ENABLED(CONFIG_LTO_CLANG) && !ctx.count) {
> + kallsyms_on_each_match_symbol_or_prefix(
> + count_symbols, func_name, &ctx.count);
> + }
> + }
>
> module_kallsyms_on_each_symbol(mod, count_mod_symbols, &ctx);
>
> --
> 2.43.0
>

--
Masami Hiramatsu (Google) <mhiramat@kernel.org>