On Wed, Apr 20, 2022 at 02:49:59PM -0700, Andrii Nakryiko wrote:
> 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?
ok, will change
jirka
>
> > +
> > +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;
>
> [...]
