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>

1 files changed, 29 insertions, 91 deletions

diff --git a/tools/perf/util/trace-event-info.c b/tools/perf/util/trace-event-info.c
index 35729f4c40cb..3403f814ad72 100644
--- 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);
 }