[PATCH trace-cmd V6 7/7] trace-cmd: Use pid instead of libvirt virt domain name

[Masami Hiramatsu]

From: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@xxxxxxxxxxx>

Use pid instead of domain name if libvirt is not found.
This also fix the trace fifo lookup routine to find it
from /proc/<PID>/fd.
With this change, we can use trace-cmd virt-server for
directly running qemu virtual machines.

Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@xxxxxxxxxxx>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
---
 trace-listen.c |   47 ++++++++++++++++++++++++++++++++++-------------
 1 file changed, 34 insertions(+), 13 deletions(-)

diff --git a/trace-listen.c b/trace-listen.c
index f6d53d2..f40b3a5 100644
--- a/trace-listen.c
+++ b/trace-listen.c
@@ -35,6 +35,7 @@
 #include <fcntl.h>
 #include <signal.h>
 #include <errno.h>
+#include <fnmatch.h>
 
 #include "trace-local.h"
 #include "trace-msg.h"
@@ -396,20 +397,41 @@ static int open_udp(const char *node, const char *port, int *pid,
 #define TRACE_PATH_DOMAIN_CPU_O	VIRT_DOMAIN_DIR "trace-path-cpu%d.out"
 #define TRACE_PATH_DOMAIN_CPU_I	VIRT_DOMAIN_DIR "trace-path-cpu%d.in"
 
+#define TRACE_PATH_PATTERN	VIRT_DIR "*/trace-path-cpu%d.out"
+
 static int open_virtio_serial_pipe(int *pid, int cpu, int pagesize,
 				   const char *domain, int virtpid)
 {
+	char path[PATH_MAX];
 	char buf[PATH_MAX];
-	int fd;
-
-	snprintf(buf, PATH_MAX, TRACE_PATH_DOMAIN_CPU_O, domain, cpu);
-	fd = open(buf, O_RDONLY | O_NONBLOCK);
-	if (fd < 0) {
-		warning("open %s", buf);
-		return fd;
+	int fd = -ENOENT;
+	DIR *dir;
+	struct dirent *ent;
+	struct stat st;
+
+	snprintf(path, PATH_MAX, "/proc/%d/fd", virtpid);
+	dir = opendir(path);
+	if (!dir)
+		return -errno;
+	while ((ent = readdir(dir)) != NULL) {
+		snprintf(path, PATH_MAX, "/proc/%d/fd/%s",
+			 virtpid, ent->d_name);
+		if (readlink(path, buf, PATH_MAX) < 0)
+			continue;
+		snprintf(path, PATH_MAX, TRACE_PATH_PATTERN, cpu);
+		/* Find the pipe which matchs pattern */
+		if ((fnmatch(path, buf, FNM_PATHNAME) == 0) &&
+		    (stat(buf, &st) == 0) && (S_ISFIFO(st.st_mode))) {
+			fd = open(buf, O_RDONLY | O_NONBLOCK);
+			break;
+		}
 	}
+	closedir(dir);
 
-	fork_virt_reader(fd, pid, cpu, pagesize, domain, virtpid);
+	if (fd < 0)
+		warning("open %s: %d", buf, fd);
+	else
+		fork_virt_reader(fd, pid, cpu, pagesize, domain, virtpid);
 
 	return fd;
 }
@@ -762,6 +784,7 @@ static int do_fork(int cfd)
 	return 0;
 }
 
+/* Get client (VM) pid from unix domain socket */
 static int get_virtpid(int cfd)
 {
 	struct ucred cr;
@@ -790,11 +813,8 @@ static char *get_guest_domain_from_pid(int pid)
 	int fd;
 
 	dir = opendir(LIBVIRT_DOMAIN_PATH);
-	if (!dir) {
-		if (errno == ENOENT)
-			warning("Only support for using libvirt");
+	if (!dir)
 		return NULL;
-	}
 
 	for (dirent = readdir(dir); dirent != NULL; dirent = readdir(dir)) {
 		snprintf(file_name, NAME_MAX, LIBVIRT_DOMAIN_PATH"%s",
@@ -837,7 +857,8 @@ static int do_connection(int cfd, struct sockaddr *peer_addr,
 
 		domain = get_guest_domain_from_pid(virtpid);
 		if (!domain)
-			return -1;
+			if (asprintf(&domain, "%d", virtpid) < 0)
+				return -ENOMEM;
 	}
 
 	ret = do_fork(cfd);

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