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Date: Thu, 21 Apr 2022 08:49:13 +0200 From: Jiri Olsa <olsajiri@...il.com> To: Andrii Nakryiko <andrii.nakryiko@...il.com> Cc: Jiri Olsa <jolsa@...nel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Masami Hiramatsu <mhiramat@...nel.org>, Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>, lkml <linux-kernel@...r.kernel.org>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...omium.org> Subject: Re: [PATCHv2 bpf-next 3/4] bpf: Resolve symbols with kallsyms_lookup_names for kprobe multi link 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@...nel.org> 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@...nel.org> > > --- > > LGTM. > > Acked-by: Andrii Nakryiko <andrii@...nel.org> > > > 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; > > [...]
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