From: Andrii Nakryiko <andrii@kernel.org>
To: <bpf@vger.kernel.org>, <ast@kernel.org>, <daniel@iogearbox.net>
Cc: <andrii@kernel.org>, <kernel-team@fb.com>,
Connor O'Brien <connoro@google.com>
Subject: [PATCH bpf-next] libbpf: fallback to tracefs mount point if debugfs is not mounted
Date: Thu, 14 Jul 2022 16:21:43 -0700 [thread overview]
Message-ID: <20220714232143.3728834-1-andrii@kernel.org> (raw)
Teach libbpf to fallback to tracefs mount point (/sys/kernel/tracing) if
debugfs (/sys/kernel/debug/tracing) isn't mounted.
Suggested-by: Connor O'Brien <connoro@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
tools/lib/bpf/libbpf.c | 33 +++++++++++++++++++++++----------
1 file changed, 23 insertions(+), 10 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 68da1aca406c..4acdc174cc73 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9828,6 +9828,19 @@ static int append_to_file(const char *file, const char *fmt, ...)
return err;
}
+#define DEBUGFS "/sys/kernel/debug/tracing"
+#define TRACEFS "/sys/kernel/tracing"
+
+static bool use_debugfs(void)
+{
+ static int has_debugfs = -1;
+
+ if (has_debugfs < 0)
+ has_debugfs = access(DEBUGFS, F_OK) == 0;
+
+ return has_debugfs == 1;
+}
+
static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
const char *kfunc_name, size_t offset)
{
@@ -9840,7 +9853,7 @@ static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
static int add_kprobe_event_legacy(const char *probe_name, bool retprobe,
const char *kfunc_name, size_t offset)
{
- const char *file = "/sys/kernel/debug/tracing/kprobe_events";
+ const char *file = use_debugfs() ? DEBUGFS"/kprobe_events" : TRACEFS"/kprobe_events";
return append_to_file(file, "%c:%s/%s %s+0x%zx",
retprobe ? 'r' : 'p',
@@ -9850,7 +9863,7 @@ static int add_kprobe_event_legacy(const char *probe_name, bool retprobe,
static int remove_kprobe_event_legacy(const char *probe_name, bool retprobe)
{
- const char *file = "/sys/kernel/debug/tracing/kprobe_events";
+ const char *file = use_debugfs() ? DEBUGFS"/kprobe_events" : TRACEFS"/kprobe_events";
return append_to_file(file, "-:%s/%s", retprobe ? "kretprobes" : "kprobes", probe_name);
}
@@ -9859,8 +9872,8 @@ static int determine_kprobe_perf_type_legacy(const char *probe_name, bool retpro
{
char file[256];
- snprintf(file, sizeof(file),
- "/sys/kernel/debug/tracing/events/%s/%s/id",
+ snprintf(file, sizeof(file), "%s/events/%s/%s/id",
+ use_debugfs() ? DEBUGFS : TRACEFS,
retprobe ? "kretprobes" : "kprobes", probe_name);
return parse_uint_from_file(file, "%d\n");
@@ -10213,7 +10226,7 @@ static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
static inline int add_uprobe_event_legacy(const char *probe_name, bool retprobe,
const char *binary_path, size_t offset)
{
- const char *file = "/sys/kernel/debug/tracing/uprobe_events";
+ const char *file = use_debugfs() ? DEBUGFS"/uprobe_events" : TRACEFS"/uprobe_events";
return append_to_file(file, "%c:%s/%s %s:0x%zx",
retprobe ? 'r' : 'p',
@@ -10223,7 +10236,7 @@ static inline int add_uprobe_event_legacy(const char *probe_name, bool retprobe,
static inline int remove_uprobe_event_legacy(const char *probe_name, bool retprobe)
{
- const char *file = "/sys/kernel/debug/tracing/uprobe_events";
+ const char *file = use_debugfs() ? DEBUGFS"/uprobe_events" : TRACEFS"/uprobe_events";
return append_to_file(file, "-:%s/%s", retprobe ? "uretprobes" : "uprobes", probe_name);
}
@@ -10232,8 +10245,8 @@ static int determine_uprobe_perf_type_legacy(const char *probe_name, bool retpro
{
char file[512];
- snprintf(file, sizeof(file),
- "/sys/kernel/debug/tracing/events/%s/%s/id",
+ snprintf(file, sizeof(file), "%s/events/%s/%s/id",
+ use_debugfs() ? DEBUGFS : TRACEFS,
retprobe ? "uretprobes" : "uprobes", probe_name);
return parse_uint_from_file(file, "%d\n");
@@ -10782,8 +10795,8 @@ static int determine_tracepoint_id(const char *tp_category,
char file[PATH_MAX];
int ret;
- ret = snprintf(file, sizeof(file),
- "/sys/kernel/debug/tracing/events/%s/%s/id",
+ ret = snprintf(file, sizeof(file), "%s/events/%s/%s/id",
+ use_debugfs() ? DEBUGFS : TRACEFS,
tp_category, tp_name);
if (ret < 0)
return -errno;
--
2.30.2
next reply other threads:[~2022-07-14 23:21 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-14 23:21 Andrii Nakryiko [this message]
2022-07-15 0:29 ` [PATCH bpf-next] libbpf: fallback to tracefs mount point if debugfs is not mounted Yonghong Song
2022-07-15 5:25 ` Andrii Nakryiko
2022-07-15 6:12 ` Yonghong Song
2022-07-15 18:46 ` Andrii Nakryiko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220714232143.3728834-1-andrii@kernel.org \
--to=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=connoro@google.com \
--cc=daniel@iogearbox.net \
--cc=kernel-team@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox