| Message ID | 20230602085239.91138-6-laoar.shao@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF |
| Headers | show |
| Series | bpf: Support ->fill_link_info for kprobe prog | expand |
On Fri, Jun 2, 2023 at 1:52 AM Yafang Shao <laoar.shao@gmail.com> wrote: > > By adding support for ->fill_link_info to the perf_event link, users will > be able to inspect it using `bpftool link show`. While users can currently > access this information via `bpftool perf show`, consolidating the link > information for all link types in one place would be more convenient. > > Signed-off-by: Yafang Shao <laoar.shao@gmail.com> > --- > include/uapi/linux/bpf.h | 6 ++++++ > kernel/bpf/syscall.c | 45 ++++++++++++++++++++++++++++++++++++++++++ > tools/include/uapi/linux/bpf.h | 6 ++++++ > 3 files changed, 57 insertions(+) > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index 22c8168..87ecf8b 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -6442,6 +6442,12 @@ struct bpf_link_info { > __u64 addrs; > __u32 count; > } kprobe_multi; > + struct { > + __aligned_u64 name; /* in/out: symbol name buffer ptr */ > + __u64 addr; > + __u32 name_len; > + __u32 offset; > + } perf_event; perf_event link could be: a) uprobe b) kprobe c) tracepoint d) generic perf_event (e.g., cpu_cycles) This interface doesn't make it very clear which one it is. And what's "name" for cpu_cycles event? What is the name for uprobe? Let's actually document this, otherwise it's hard to understand how this information can be interpreted... > }; > } __attribute__((aligned(8))); > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index 80c9ec0..da2de8e 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -3303,9 +3303,54 @@ static void bpf_perf_link_dealloc(struct bpf_link *link) > kfree(perf_link); > } > [...]
On Sat, Jun 3, 2023 at 6:20 AM Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote: > > On Fri, Jun 2, 2023 at 1:52 AM Yafang Shao <laoar.shao@gmail.com> wrote: > > > > By adding support for ->fill_link_info to the perf_event link, users will > > be able to inspect it using `bpftool link show`. While users can currently > > access this information via `bpftool perf show`, consolidating the link > > information for all link types in one place would be more convenient. > > > > Signed-off-by: Yafang Shao <laoar.shao@gmail.com> > > --- > > include/uapi/linux/bpf.h | 6 ++++++ > > kernel/bpf/syscall.c | 45 ++++++++++++++++++++++++++++++++++++++++++ > > tools/include/uapi/linux/bpf.h | 6 ++++++ > > 3 files changed, 57 insertions(+) > > > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > > index 22c8168..87ecf8b 100644 > > --- a/include/uapi/linux/bpf.h > > +++ b/include/uapi/linux/bpf.h > > @@ -6442,6 +6442,12 @@ struct bpf_link_info { > > __u64 addrs; > > __u32 count; > > } kprobe_multi; > > + struct { > > + __aligned_u64 name; /* in/out: symbol name buffer ptr */ > > + __u64 addr; > > + __u32 name_len; > > + __u32 offset; > > + } perf_event; > > perf_event link could be: > > a) uprobe > b) kprobe > c) tracepoint > d) generic perf_event (e.g., cpu_cycles) > > This interface doesn't make it very clear which one it is. And what's > "name" for cpu_cycles event? What is the name for uprobe? Let's > actually document this, otherwise it's hard to understand how this > information can be interpreted... Agreed. It would be better to have a document on it. I will do it.
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 22c8168..87ecf8b 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -6442,6 +6442,12 @@ struct bpf_link_info { __u64 addrs; __u32 count; } kprobe_multi; + struct { + __aligned_u64 name; /* in/out: symbol name buffer ptr */ + __u64 addr; + __u32 name_len; + __u32 offset; + } perf_event; }; } __attribute__((aligned(8))); diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 80c9ec0..da2de8e 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3303,9 +3303,54 @@ static void bpf_perf_link_dealloc(struct bpf_link *link) kfree(perf_link); } +static int bpf_perf_link_fill_link_info(const struct bpf_link *link, + struct bpf_link_info *info) +{ + struct bpf_perf_link *perf_link = container_of(link, struct bpf_perf_link, link); + char __user *ubuf = u64_to_user_ptr(info->perf_event.name); + u32 ulen = info->perf_event.name_len; + const struct perf_event *event; + u64 probe_offset, probe_addr; + u32 prog_id, fd_type; + const char *buf; + size_t len; + int err; + + if (!ulen ^ !ubuf) + return -EINVAL; + if (!ubuf) + return 0; + + event = perf_get_event(perf_link->perf_file); + if (IS_ERR(event)) + return PTR_ERR(event); + + err = bpf_get_perf_event_info(event, &prog_id, &fd_type, + &buf, &probe_offset, + &probe_addr); + if (err) + return err; + + len = strlen(buf); + if (buf) { + err = bpf_copy_to_user(ubuf, buf, ulen, len); + if (err) + return err; + } else { + char zero = '\0'; + + if (put_user(zero, ubuf)) + return -EFAULT; + } + info->perf_event.addr = probe_addr; + info->perf_event.offset = probe_offset; + return 0; +} + static const struct bpf_link_ops bpf_perf_link_lops = { .release = bpf_perf_link_release, .dealloc = bpf_perf_link_dealloc, + .fill_link_info = bpf_perf_link_fill_link_info, }; static int bpf_perf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 22c8168..87ecf8b 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -6442,6 +6442,12 @@ struct bpf_link_info { __u64 addrs; __u32 count; } kprobe_multi; + struct { + __aligned_u64 name; /* in/out: symbol name buffer ptr */ + __u64 addr; + __u32 name_len; + __u32 offset; + } perf_event; }; } __attribute__((aligned(8)));
By adding support for ->fill_link_info to the perf_event link, users will be able to inspect it using `bpftool link show`. While users can currently access this information via `bpftool perf show`, consolidating the link information for all link types in one place would be more convenient. Signed-off-by: Yafang Shao <laoar.shao@gmail.com> --- include/uapi/linux/bpf.h | 6 ++++++ kernel/bpf/syscall.c | 45 ++++++++++++++++++++++++++++++++++++++++++ tools/include/uapi/linux/bpf.h | 6 ++++++ 3 files changed, 57 insertions(+)