perf list: Add scandirat compatibility function

scandirat is used during the printing of tracepoint events but may be
missing from certain libcs. Add a compatibility implementation that
uses the symlink of an fd in /proc as a path for the reliably present
scandir.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: James Clark <james.clark@arm.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Bill Wendling <morbo@google.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Yang Jihong <yangjihong1@huawei.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: llvm@lists.linux.dev
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240221034155.1500118-3-irogers@google.com

diff --git a/tools/perf/util/print-events.c b/tools/perf/util/print-events.c
index 9e47712..0dc70b8 100644 (file)
--- a/tools/perf/util/print-events.c
+++ b/tools/perf/util/print-events.c
@@ -28,6 +28,7 @@
 #include "tracepoint.h"
 #include "pfm.h"
 #include "thread_map.h"
+#include "util.h"
 
 #define MAX_NAME_LEN 100
 
@@ -63,6 +64,8 @@ void print_tracepoint_events(const struct print_callbacks *print_cb __maybe_unus
 {
        char *events_path = get_tracing_file("events");
        int events_fd = open(events_path, O_PATH);
+       struct dirent **sys_namelist = NULL;
+       int sys_items;
 
        put_tracing_file(events_path);
        if (events_fd < 0) {
@@ -70,10 +73,7 @@ void print_tracepoint_events(const struct print_callbacks *print_cb __maybe_unus
                return;
        }
 
-#ifdef HAVE_SCANDIRAT_SUPPORT
-{
-       struct dirent **sys_namelist = NULL;
-       int sys_items = tracing_events__scandir_alphasort(&sys_namelist);
+       sys_items = tracing_events__scandir_alphasort(&sys_namelist);
 
        for (int i = 0; i < sys_items; i++) {
                struct dirent *sys_dirent = sys_namelist[i];
@@ -130,11 +130,6 @@ next_sys:
        }
 
        free(sys_namelist);
-}
-#else
-       printf("\nWARNING: Your libc doesn't have the scandirat function, please ask its maintainers to implement it.\n"
-              "         As a rough fallback, please do 'ls %s' to see the available tracepoint events.\n", events_path);
-#endif
        close(events_fd);
 }
 

diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index c1fd9ba..4f561e5 100644 (file)
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -552,3 +552,22 @@ int sched_getcpu(void)
        return -1;
 }
 #endif
+
+#ifndef HAVE_SCANDIRAT_SUPPORT
+int scandirat(int dirfd, const char *dirp,
+             struct dirent ***namelist,
+             int (*filter)(const struct dirent *),
+             int (*compar)(const struct dirent **, const struct dirent **))
+{
+       char path[PATH_MAX];
+       int err, fd = openat(dirfd, dirp, O_PATH);
+
+       if (fd < 0)
+               return fd;
+
+       snprintf(path, sizeof(path), "/proc/%d/fd/%d", getpid(), fd);
+       err = scandir(path, namelist, filter, compar);
+       close(fd);
+       return err;
+}
+#endif

diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
index 7c8915d..9966c21 100644 (file)
--- a/tools/perf/util/util.h
+++ b/tools/perf/util/util.h
@@ -6,6 +6,7 @@
 /* glibc 2.20 deprecates _BSD_SOURCE in favour of _DEFAULT_SOURCE */
 #define _DEFAULT_SOURCE 1
 
+#include <dirent.h>
 #include <fcntl.h>
 #include <stdbool.h>
 #include <stddef.h>
@@ -56,6 +57,13 @@ int perf_tip(char **strp, const char *dirpath);
 int sched_getcpu(void);
 #endif
 
+#ifndef HAVE_SCANDIRAT_SUPPORT
+int scandirat(int dirfd, const char *dirp,
+             struct dirent ***namelist,
+             int (*filter)(const struct dirent *),
+             int (*compar)(const struct dirent **, const struct dirent **));
+#endif
+
 extern bool perf_singlethreaded;
 
 void perf_set_singlethreaded(void);