perf: Robustify proc and debugfs file recording

While attempting to create a timechart of boot up I found perf didn't
tolerate modules being loaded/unloaded.  This patch fixes this by
reading the file once and then writing the size read at the correct
point in the file.  It also simplifies the code somewhat.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: Sonny Rao <sonnyrao@chromium.org>
Signed-off-by: Michael Neuling <mikey@neuling.org>
Link: http://lkml.kernel.org/r/10011.1310614483@neuling.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/tools/perf/util/trace-event-info.c b/tools/perf/util/trace-event-info.c
index 35729f4..3403f81 100644 (file)
--- a/tools/perf/util/trace-event-info.c
+++ b/tools/perf/util/trace-event-info.c
@@ -183,106 +183,59 @@ int bigendian(void)
        return *ptr == 0x01020304;
 }
 
-static unsigned long long copy_file_fd(int fd)
+/* unfortunately, you can not stat debugfs or proc files for size */
+static void record_file(const char *file, size_t hdr_sz)
 {
        unsigned long long size = 0;
-       char buf[BUFSIZ];
-       int r;
-
-       do {
-               r = read(fd, buf, BUFSIZ);
-               if (r > 0) {
-                       size += r;
-                       write_or_die(buf, r);
-               }
-       } while (r > 0);
-
-       return size;
-}
-
-static unsigned long long copy_file(const char *file)
-{
-       unsigned long long size = 0;
-       int fd;
+       char buf[BUFSIZ], *sizep;
+       off_t hdr_pos = lseek(output_fd, 0, SEEK_CUR);
+       int r, fd;
 
        fd = open(file, O_RDONLY);
        if (fd < 0)
                die("Can't read '%s'", file);
-       size = copy_file_fd(fd);
-       close(fd);
 
-       return size;
-}
-
-static unsigned long get_size_fd(int fd)
-{
-       unsigned long long size = 0;
-       char buf[BUFSIZ];
-       int r;
+       /* put in zeros for file size, then fill true size later */
+       write_or_die(&size, hdr_sz);
 
        do {
                r = read(fd, buf, BUFSIZ);
-               if (r > 0)
+               if (r > 0) {
                        size += r;
+                       write_or_die(buf, r);
+               }
        } while (r > 0);
-
-       lseek(fd, 0, SEEK_SET);
-
-       return size;
-}
-
-static unsigned long get_size(const char *file)
-{
-       unsigned long long size = 0;
-       int fd;
-
-       fd = open(file, O_RDONLY);
-       if (fd < 0)
-               die("Can't read '%s'", file);
-       size = get_size_fd(fd);
        close(fd);
 
-       return size;
+       /* ugh, handle big-endian hdr_size == 4 */
+       sizep = (char*)&size;
+       if (bigendian())
+               sizep += sizeof(u64) - hdr_sz;
+
+       if (pwrite(output_fd, sizep, hdr_sz, hdr_pos) < 0)
+               die("writing to %s", output_file);
 }
 
 static void read_header_files(void)
 {
-       unsigned long long size, check_size;
        char *path;
-       int fd;
+       struct stat st;
 
        path = get_tracing_file("events/header_page");
-       fd = open(path, O_RDONLY);
-       if (fd < 0)
+       if (stat(path, &st) < 0)
                die("can't read '%s'", path);
 
-       /* unfortunately, you can not stat debugfs files for size */
-       size = get_size_fd(fd);
-
        write_or_die("header_page", 12);
-       write_or_die(&size, 8);
-       check_size = copy_file_fd(fd);
-       close(fd);
-
-       if (size != check_size)
-               die("wrong size for '%s' size=%lld read=%lld",
-                   path, size, check_size);
+       record_file(path, 8);
        put_tracing_file(path);
 
        path = get_tracing_file("events/header_event");
-       fd = open(path, O_RDONLY);
-       if (fd < 0)
+       if (stat(path, &st) < 0)
                die("can't read '%s'", path);
 
-       size = get_size_fd(fd);
-
        write_or_die("header_event", 13);
-       write_or_die(&size, 8);
-       check_size = copy_file_fd(fd);
-       if (size != check_size)
-               die("wrong size for '%s'", path);
+       record_file(path, 8);
        put_tracing_file(path);
-       close(fd);
 }
 
 static bool name_in_tp_list(char *sys, struct tracepoint_path *tps)
@@ -298,7 +251,6 @@ static bool name_in_tp_list(char *sys, struct tracepoint_path *tps)
 
 static void copy_event_system(const char *sys, struct tracepoint_path *tps)
 {
-       unsigned long long size, check_size;
        struct dirent *dent;
        struct stat st;
        char *format;
@@ -338,14 +290,8 @@ static void copy_event_system(const char *sys, struct tracepoint_path *tps)
                sprintf(format, "%s/%s/format", sys, dent->d_name);
                ret = stat(format, &st);
 
-               if (ret >= 0) {
-                       /* unfortunately, you can not stat debugfs files for size */
-                       size = get_size(format);
-                       write_or_die(&size, 8);
-                       check_size = copy_file(format);
-                       if (size != check_size)
-                               die("error in size of file '%s'", format);
-               }
+               if (ret >= 0)
+                       record_file(format, 8);
 
                free(format);
        }
@@ -426,7 +372,7 @@ static void read_event_files(struct tracepoint_path *tps)
 
 static void read_proc_kallsyms(void)
 {
-       unsigned int size, check_size;
+       unsigned int size;
        const char *path = "/proc/kallsyms";
        struct stat st;
        int ret;
@@ -438,17 +384,12 @@ static void read_proc_kallsyms(void)
                write_or_die(&size, 4);
                return;
        }
-       size = get_size(path);
-       write_or_die(&size, 4);
-       check_size = copy_file(path);
-       if (size != check_size)
-               die("error in size of file '%s'", path);
-
+       record_file(path, 4);
 }
 
 static void read_ftrace_printk(void)
 {
-       unsigned int size, check_size;
+       unsigned int size;
        char *path;
        struct stat st;
        int ret;
@@ -461,11 +402,8 @@ static void read_ftrace_printk(void)
                write_or_die(&size, 4);
                goto out;
        }
-       size = get_size(path);
-       write_or_die(&size, 4);
-       check_size = copy_file(path);
-       if (size != check_size)
-               die("error in size of file '%s'", path);
+       record_file(path, 4);
+
 out:
        put_tracing_file(path);
 }