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Date: Fri, 18 Oct 2019 07:54:26 -0700
From: John Fastabend <john.fastabend@...il.com>
To: andriin@...com, ast@...nel.org, daniel@...earbox.net
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org,
john.fastabend@...il.com
Subject: [bpf-next PATCH] bpf: libbpf, support older style kprobe load
Following ./Documentation/trace/kprobetrace.rst add support for loading
kprobes programs on older kernels.
Signed-off-by: John Fastabend <john.fastabend@...il.com>
---
tools/lib/bpf/libbpf.c | 81 +++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 73 insertions(+), 8 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index fcea6988f962..12b3105d112c 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -5005,20 +5005,89 @@ static int determine_uprobe_retprobe_bit(void)
return parse_uint_from_file(file, "config:%d\n");
}
+static int use_kprobe_debugfs(const char *name,
+ uint64_t offset, int pid, bool retprobe)
+{
+ const char *file = "/sys/kernel/debug/tracing/kprobe_events";
+ int fd = open(file, O_WRONLY | O_APPEND, 0);
+ char buf[PATH_MAX];
+ int err;
+
+ if (fd < 0) {
+ pr_warning("failed open kprobe_events: %s\n",
+ strerror(errno));
+ return -errno;
+ }
+
+ snprintf(buf, sizeof(buf), "%c:kprobes/%s %s",
+ retprobe ? 'r' : 'p', name, name);
+
+ err = write(fd, buf, strlen(buf));
+ close(fd);
+ if (err < 0)
+ return -errno;
+ return 0;
+}
+
static int perf_event_open_probe(bool uprobe, bool retprobe, const char *name,
uint64_t offset, int pid)
{
struct perf_event_attr attr = {};
char errmsg[STRERR_BUFSIZE];
+ uint64_t config1 = 0;
int type, pfd, err;
type = uprobe ? determine_uprobe_perf_type()
: determine_kprobe_perf_type();
if (type < 0) {
- pr_warning("failed to determine %s perf type: %s\n",
- uprobe ? "uprobe" : "kprobe",
- libbpf_strerror_r(type, errmsg, sizeof(errmsg)));
- return type;
+ if (uprobe) {
+ pr_warning("failed to determine uprobe perf type %s: %s\n",
+ name,
+ libbpf_strerror_r(type,
+ errmsg, sizeof(errmsg)));
+ } else {
+ /* If we do not have an event_source/../kprobes then we
+ * can try to use kprobe-base event tracing, for details
+ * see ./Documentation/trace/kprobetrace.rst
+ */
+ const char *file = "/sys/kernel/debug/tracing/events/kprobes/";
+ char c[PATH_MAX];
+ int fd, n;
+
+ snprintf(c, sizeof(c), "%s/%s/id", file, name);
+
+ err = use_kprobe_debugfs(name, offset, pid, retprobe);
+ if (err)
+ return err;
+
+ type = PERF_TYPE_TRACEPOINT;
+ fd = open(c, O_RDONLY, 0);
+ if (fd < 0) {
+ pr_warning("failed to open tracepoint %s: %s\n",
+ c, strerror(errno));
+ return -errno;
+ }
+ n = read(fd, c, sizeof(c));
+ close(fd);
+ if (n < 0) {
+ pr_warning("failed to read %s: %s\n",
+ c, strerror(errno));
+ return -errno;
+ }
+ c[n] = '\0';
+ config1 = strtol(c, NULL, 0);
+ attr.size = sizeof(attr);
+ attr.type = type;
+ attr.config = config1;
+ attr.sample_period = 1;
+ attr.wakeup_events = 1;
+ }
+ } else {
+ config1 = ptr_to_u64(name);
+ attr.size = sizeof(attr);
+ attr.type = type;
+ attr.config1 = config1; /* kprobe_func or uprobe_path */
+ attr.config2 = offset; /* kprobe_addr or probe_offset */
}
if (retprobe) {
int bit = uprobe ? determine_uprobe_retprobe_bit()
@@ -5033,10 +5102,6 @@ static int perf_event_open_probe(bool uprobe, bool retprobe, const char *name,
}
attr.config |= 1 << bit;
}
- attr.size = sizeof(attr);
- attr.type = type;
- attr.config1 = ptr_to_u64(name); /* kprobe_func or uprobe_path */
- attr.config2 = offset; /* kprobe_addr or probe_offset */
/* pid filter is meaningful only for uprobes */
pfd = syscall(__NR_perf_event_open, &attr,
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