Messages in this thread | | | Subject | Re: [PATCH bpf-next] libbpf: also check /sys/kernel/tracing for tracefs files | From | Daniel Borkmann <> | Date | Fri, 22 Apr 2022 18:32:32 +0200 |
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On 4/21/22 10:11 PM, Connor O'Brien wrote: > libbpf looks for tracefs files only under debugfs, but tracefs may be > mounted even if debugfs is not. When /sys/kernel/debug/tracing is > absent, try looking under /sys/kernel/tracing instead. > > Signed-off-by: Connor O'Brien <connoro@google.com> > --- > tools/lib/bpf/libbpf.c | 26 +++++++++++++++++++------- > 1 file changed, 19 insertions(+), 7 deletions(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 68cc134d070d..6ef587329eb2 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -10140,10 +10140,16 @@ static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz, > __sync_fetch_and_add(&index, 1)); > } > > +static bool debugfs_available(void) > +{ > + return !access("/sys/kernel/debug/tracing", F_OK);
Should this be a one-time probe, so on subsequent debugfs_available() calls we return the initially cached result?
> +} > + > 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 = debugfs_available() ? "/sys/kernel/debug/tracing/kprobe_events" : > + "/sys/kernel/tracing/kprobe_events"; > > return append_to_file(file, "%c:%s/%s %s+0x%zx", > retprobe ? 'r' : 'p', > @@ -10153,7 +10159,8 @@ 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 = debugfs_available() ? "/sys/kernel/debug/tracing/kprobe_events" : > + "/sys/kernel/tracing/kprobe_events"; > > return append_to_file(file, "-:%s/%s", retprobe ? "kretprobes" : "kprobes", probe_name); > } > @@ -10163,7 +10170,8 @@ 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", > + debugfs_available() ? "/sys/kernel/debug/tracing/events/%s/%s/id" : > + "/sys/kernel/tracing/events/%s/%s/id", > retprobe ? "kretprobes" : "kprobes", probe_name); > > return parse_uint_from_file(file, "%d\n"); > @@ -10493,7 +10501,8 @@ 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 = debugfs_available() ? "/sys/kernel/debug/tracing/uprobe_events" : > + "/sys/kernel/tracing/uprobe_events"; > > return append_to_file(file, "%c:%s/%s %s:0x%zx", > retprobe ? 'r' : 'p', > @@ -10503,7 +10512,8 @@ 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 = debugfs_available() ? "/sys/kernel/debug/tracing/uprobe_events" : > + "/sys/kernel/tracing/uprobe_events"; > > return append_to_file(file, "-:%s/%s", retprobe ? "uretprobes" : "uprobes", probe_name); > } > @@ -10513,7 +10523,8 @@ 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", > + debugfs_available() ? "/sys/kernel/debug/tracing/events/%s/%s/id" : > + "/sys/kernel/tracing/events/%s/%s/id", > retprobe ? "uretprobes" : "uprobes", probe_name); > > return parse_uint_from_file(file, "%d\n"); > @@ -11071,7 +11082,8 @@ static int determine_tracepoint_id(const char *tp_category, > int ret; > > ret = snprintf(file, sizeof(file), > - "/sys/kernel/debug/tracing/events/%s/%s/id", > + debugfs_available() ? "/sys/kernel/debug/tracing/events/%s/%s/id" : > + "/sys/kernel/tracing/events/%s/%s/id", > tp_category, tp_name); > if (ret < 0) > return -errno; >
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