On Mon, Apr 18, 2022 at 5:49 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> Using kallsyms_lookup_names function to speed up symbols lookup in
> kprobe multi link attachment and replacing with it the current
> kprobe_multi_resolve_syms function.
>
> This speeds up bpftrace kprobe attachment:
>
> # perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* { } i:ms:1 { exit(); }'
> ...
> 6.5681 +- 0.0225 seconds time elapsed ( +- 0.34% )
>
> After:
>
> # perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* { } i:ms:1 { exit(); }'
> ...
> 0.5661 +- 0.0275 seconds time elapsed ( +- 4.85% )
>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
LGTM.
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> kernel/trace/bpf_trace.c | 113 +++++++++++++++++++++++----------------
> 1 file changed, 67 insertions(+), 46 deletions(-)
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index b26f3da943de..f49cdc46a21f 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -2226,6 +2226,60 @@ struct bpf_kprobe_multi_run_ctx {
> unsigned long entry_ip;
> };
>
> +struct user_syms {
> + const char **syms;
> + char *buf;
> +};
> +
> +static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32 cnt)
> +{
> + unsigned long __user usymbol;
> + const char **syms = NULL;
> + char *buf = NULL, *p;
> + int err = -EFAULT;
> + unsigned int i;
> +
> + err = -ENOMEM;
> + syms = kvmalloc(cnt * sizeof(*syms), GFP_KERNEL);
> + if (!syms)
> + goto error;
> +
> + buf = kvmalloc(cnt * KSYM_NAME_LEN, GFP_KERNEL);
> + if (!buf)
> + goto error;
> +
> + for (p = buf, i = 0; i < cnt; i++) {
> + if (__get_user(usymbol, usyms + i)) {
> + err = -EFAULT;
> + goto error;
> + }
> + err = strncpy_from_user(p, (const char __user *) usymbol, KSYM_NAME_LEN);
> + if (err == KSYM_NAME_LEN)
> + err = -E2BIG;
> + if (err < 0)
> + goto error;
> + syms[i] = p;
> + p += err + 1;
> + }
> +
> + err = 0;
> + us->syms = syms;
> + us->buf = buf;
return 0 here instead of falling through into error: block?
> +
> +error:
> + if (err) {
> + kvfree(syms);
> + kvfree(buf);
> + }
> + return err;
> +}
> +
> +static void free_user_syms(struct user_syms *us)
> +{
> + kvfree(us->syms);
> + kvfree(us->buf);
> +}
> +
> static void bpf_kprobe_multi_link_release(struct bpf_link *link)
> {
> struct bpf_kprobe_multi_link *kmulti_link;
[...]
