perf: Add pipe-specific header read/write and event processing code

This patch makes several changes to allow the perf event stream
to be sent and received over a pipe:

- adds pipe-specific versions of the header read/write code

- adds pipe-specific version of the event processing code

- adds a range of event types to be used for header or other
  pseudo events, above the range used by the kernel

- checks the return value of event handlers, which they can use
  to skip over large events during event processing rather than actually
  reading them into event objects.

- unifies the multiple do_read() functions and updates its
  users.

Note that none of these changes affect the existing perf data
file format or processing - this code only comes into play if
perf output is sent to stdout (or is read from stdin).

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: fweisbec@gmail.com
Cc: rostedt@goodmis.org
Cc: k-keiichi@bx.jp.nec.com
Cc: acme@ghostprotocols.net
LKML-Reference: <1270184365-8281-2-git-send-email-tzanussi@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 60 insertions, 18 deletions

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 6c9aa16ee51f..8d05337d1a59 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -427,6 +427,25 @@ out_free:
         return err;
 }
 
+int perf_header__write_pipe(int fd)
+{
+        struct perf_pipe_file_header f_header;
+        int err;
+
+        f_header = (struct perf_pipe_file_header){
+                .magic     = PERF_MAGIC,
+                .size      = sizeof(f_header),
+        };
+
+        err = do_write(fd, &f_header, sizeof(f_header));
+        if (err < 0) {
+                pr_debug("failed to write perf pipe header\n");
+                return err;
+        }
+
+        return 0;
+}
+
 int perf_header__write(struct perf_header *self, int fd, bool at_exit)
 {
         struct perf_file_header f_header;
@@ -518,25 +537,10 @@ int perf_header__write(struct perf_header *self, int fd, bool at_exit)
         return 0;
 }
 
-static int do_read(int fd, void *buf, size_t size)
-{
-        while (size) {
-                int ret = read(fd, buf, size);
-
-                if (ret <= 0)
-                        return -1;
-
-                size -= ret;
-                buf += ret;
-        }
-
-        return 0;
-}
-
 static int perf_header__getbuffer64(struct perf_header *self,
                                     int fd, void *buf, size_t size)
 {
-        if (do_read(fd, buf, size))
+        if (do_read(fd, buf, size) <= 0)
                 return -1;
 
         if (self->needs_swap)
@@ -592,7 +596,7 @@ int perf_file_header__read(struct perf_file_header *self,
 {
         lseek(fd, 0, SEEK_SET);
 
-        if (do_read(fd, self, sizeof(*self)) ||
+        if (do_read(fd, self, sizeof(*self)) <= 0 ||
             memcmp(&self->magic, __perf_magic, sizeof(self->magic)))
                 return -1;
 
@@ -662,13 +666,51 @@ static int perf_file_section__process(struct perf_file_section *self,
         return 0;
 }
 
-int perf_header__read(struct perf_header *self, int fd)
+static int perf_file_header__read_pipe(struct perf_pipe_file_header *self,
+                                       struct perf_header *ph, int fd)
 {
+        if (do_read(fd, self, sizeof(*self)) <= 0 ||
+            memcmp(&self->magic, __perf_magic, sizeof(self->magic)))
+                return -1;
+
+        if (self->size != sizeof(*self)) {
+                u64 size = bswap_64(self->size);
+
+                if (size != sizeof(*self))
+                        return -1;
+
+                ph->needs_swap = true;
+        }
+
+        return 0;
+}
+
+static int perf_header__read_pipe(struct perf_session *session, int fd)
+{
+        struct perf_header *self = &session->header;
+        struct perf_pipe_file_header f_header;
+
+        if (perf_file_header__read_pipe(&f_header, self, fd) < 0) {
+                pr_debug("incompatible file format\n");
+                return -EINVAL;
+        }
+
+        session->fd = fd;
+
+        return 0;
+}
+
+int perf_header__read(struct perf_session *session, int fd)
+{
+        struct perf_header *self = &session->header;
         struct perf_file_header f_header;
         struct perf_file_attr   f_attr;
         u64                     f_id;
         int nr_attrs, nr_ids, i, j;
 
+        if (session->fd_pipe)
+                return perf_header__read_pipe(session, fd);
+
         if (perf_file_header__read(&f_header, self, fd) < 0) {
                 pr_debug("incompatible file format\n");
                 return -EINVAL;