By introducing support for ->fill_link_info to the perf_event link, users
gain the ability to inspect it using `bpftool link show`. While the current
approach involves accessing this information via `bpftool perf show`,
consolidating link information for all link types in one place offers
greater convenience. Additionally, this patch extends support to the
generic perf event, which is not currently accommodated by
`bpftool perf show`. While only the perf type and config are exposed to
userspace, other attributes such as sample_period and sample_freq are
ignored. It's important to note that if kptr_restrict is set to 2, the
probed address will not be exposed, maintaining security measures.
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
---
include/uapi/linux/bpf.h | 22 ++++++++++
kernel/bpf/syscall.c | 98 ++++++++++++++++++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 22 ++++++++++
3 files changed, 142 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index d99cc16..c3b821d 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -6443,6 +6443,28 @@ struct bpf_link_info {
__u32 count;
__u8 retprobe;
} kprobe_multi;
+ union {
+ struct {
+ /* The name is:
+ * a) uprobe: file name
+ * b) kprobe: kernel function
+ */
+ __aligned_u64 name; /* in/out: name buffer ptr */
+ __u32 name_len;
+ __u32 offset; /* offset from the name */
+ __u64 addr;
+ __u8 retprobe;
+ } probe; /* uprobe, kprobe */
+ struct {
+ /* in/out: tracepoint name buffer ptr */
+ __aligned_u64 tp_name;
+ __u32 name_len;
+ } tp; /* tracepoint */
+ struct {
+ __u64 config;
+ __u32 type;
+ } event; /* generic perf event */
+ } perf_event;
};
} __attribute__((aligned(8)));
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 80c9ec0..e349bdb 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3303,9 +3303,107 @@ static void bpf_perf_link_dealloc(struct bpf_link *link)
kfree(perf_link);
}
+static int bpf_perf_link_fill_name(const struct perf_event *event,
+ char __user *uname, u32 ulen,
+ u64 *probe_offset, u64 *probe_addr,
+ u32 *fd_type)
+{
+ const char *buf;
+ u32 prog_id;
+ size_t len;
+ int err;
+
+ if (!ulen ^ !uname)
+ return -EINVAL;
+ if (!uname)
+ return 0;
+
+ 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(uname, buf, ulen, len);
+ if (err)
+ return err;
+ } else {
+ char zero = '\0';
+
+ if (put_user(zero, uname))
+ return -EFAULT;
+ }
+ return 0;
+}
+
+static int bpf_perf_link_fill_probe(const struct perf_event *event,
+ struct bpf_link_info *info)
+{
+ char __user *uname = u64_to_user_ptr(info->perf_event.probe.name);
+ u32 ulen = info->perf_event.probe.name_len;
+ u64 addr, off;
+ u32 type;
+ int err;
+
+ err = bpf_perf_link_fill_name(event, uname, ulen, &off, &addr, &type);
+ if (err)
+ return err;
+ info->perf_event.probe.offset = off;
+ if (type == BPF_FD_TYPE_KRETPROBE || type == BPF_FD_TYPE_URETPROBE)
+ info->perf_event.probe.retprobe = 1;
+ else
+ info->perf_event.probe.retprobe = 0;
+
+ if (kptr_restrict == 2)
+ return 0;
+ info->perf_event.probe.addr = addr;
+ return 0;
+}
+
+static int bpf_perf_link_fill_tp(const struct perf_event *event,
+ struct bpf_link_info *info)
+{
+ char __user *uname = u64_to_user_ptr(info->perf_event.tp.tp_name);
+ u32 ulen = info->perf_event.tp.name_len;
+ u64 addr, off;
+ u32 type;
+
+ return bpf_perf_link_fill_name(event, uname, ulen, &off, &addr, &type);
+}
+
+static int bpf_perf_link_fill_event(const struct perf_event *event,
+ struct bpf_link_info *info)
+{
+ info->perf_event.event.type = event->attr.type;
+ info->perf_event.event.config = event->attr.config;
+ return 0;
+}
+
+static int bpf_perf_link_fill_link_info(const struct bpf_link *link,
+ struct bpf_link_info *info)
+{
+ struct bpf_perf_link *perf_link;
+ const struct perf_event *event;
+
+ perf_link = container_of(link, struct bpf_perf_link, link);
+ event = perf_get_event(perf_link->perf_file);
+ if (IS_ERR(event))
+ return PTR_ERR(event);
+
+ if (!event->prog)
+ return -EINVAL;
+ if (event->prog->type == BPF_PROG_TYPE_PERF_EVENT)
+ return bpf_perf_link_fill_event(event, info);
+ if (event->prog->type == BPF_PROG_TYPE_TRACEPOINT)
+ return bpf_perf_link_fill_tp(event, info);
+ return bpf_perf_link_fill_probe(event, info);
+}
+
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 d99cc16..c3b821d 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -6443,6 +6443,28 @@ struct bpf_link_info {
__u32 count;
__u8 retprobe;
} kprobe_multi;
+ union {
+ struct {
+ /* The name is:
+ * a) uprobe: file name
+ * b) kprobe: kernel function
+ */
+ __aligned_u64 name; /* in/out: name buffer ptr */
+ __u32 name_len;
+ __u32 offset; /* offset from the name */
+ __u64 addr;
+ __u8 retprobe;
+ } probe; /* uprobe, kprobe */
+ struct {
+ /* in/out: tracepoint name buffer ptr */
+ __aligned_u64 tp_name;
+ __u32 name_len;
+ } tp; /* tracepoint */
+ struct {
+ __u64 config;
+ __u32 type;
+ } event; /* generic perf event */
+ } perf_event;
};
} __attribute__((aligned(8)));
--
1.8.3.1
