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libbpf: fallback to tracefs mount point if debugfs is not mounted

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Teach libbpf to fallback to tracefs mount point (/sys/kernel/tracing) if
debugfs (/sys/kernel/debug/tracing) isn't mounted.

Acked-by: Yonghong Song <yhs@fb.com>
Suggested-by: Connor O'Brien <connoro@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20220715185736.898848-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2022-07-15 11:57:36 -07:00 committed by Alexei Starovoitov
parent fd18942244
commit a1ac9fd6c6
1 changed files with 40 additions and 21 deletions
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61
tools/lib/bpf/libbpf.c
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@ -9864,6 +9864,34 @@ 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 const char *tracefs_path(void)
{
return use_debugfs() ? DEBUGFS : TRACEFS;
}
static const char *tracefs_kprobe_events(void)
{
return use_debugfs() ? DEBUGFS"/kprobe_events" : TRACEFS"/kprobe_events";
}
static const char *tracefs_uprobe_events(void)
{
return use_debugfs() ? DEBUGFS"/uprobe_events" : TRACEFS"/uprobe_events";
}
static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
const char *kfunc_name, size_t offset)
{
@ -9876,9 +9904,7 @@ 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";
return append_to_file(file, "%c:%s/%s %s+0x%zx",
return append_to_file(tracefs_kprobe_events(), "%c:%s/%s %s+0x%zx",
retprobe ? 'r' : 'p',
retprobe ? "kretprobes" : "kprobes",
probe_name, kfunc_name, offset);
@ -9886,18 +9912,16 @@ 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";
return append_to_file(file, "-:%s/%s", retprobe ? "kretprobes" : "kprobes", probe_name);
return append_to_file(tracefs_kprobe_events(), "-:%s/%s",
retprobe ? "kretprobes" : "kprobes", probe_name);
}
static int determine_kprobe_perf_type_legacy(const char *probe_name, bool retprobe)
{
char file[256];
snprintf(file, sizeof(file),
"/sys/kernel/debug/tracing/events/%s/%s/id",
retprobe ? "kretprobes" : "kprobes", probe_name);
snprintf(file, sizeof(file), "%s/events/%s/%s/id",
tracefs_path(), retprobe ? "kretprobes" : "kprobes", probe_name);
return parse_uint_from_file(file, "%d\n");
}
@ -10347,9 +10371,7 @@ 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";
return append_to_file(file, "%c:%s/%s %s:0x%zx",
return append_to_file(tracefs_uprobe_events(), "%c:%s/%s %s:0x%zx",
retprobe ? 'r' : 'p',
retprobe ? "uretprobes" : "uprobes",
probe_name, binary_path, offset);
@ -10357,18 +10379,16 @@ 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";
return append_to_file(file, "-:%s/%s", retprobe ? "uretprobes" : "uprobes", probe_name);
return append_to_file(tracefs_uprobe_events(), "-:%s/%s",
retprobe ? "uretprobes" : "uprobes", probe_name);
}
static int determine_uprobe_perf_type_legacy(const char *probe_name, bool retprobe)
{
char file[512];
snprintf(file, sizeof(file),
"/sys/kernel/debug/tracing/events/%s/%s/id",
retprobe ? "uretprobes" : "uprobes", probe_name);
snprintf(file, sizeof(file), "%s/events/%s/%s/id",
tracefs_path(), retprobe ? "uretprobes" : "uprobes", probe_name);
return parse_uint_from_file(file, "%d\n");
}
@ -10916,9 +10936,8 @@ 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",
tp_category, tp_name);
ret = snprintf(file, sizeof(file), "%s/events/%s/%s/id",
tracefs_path(), tp_category, tp_name);
if (ret < 0)
return -errno;
if (ret >= sizeof(file)) {