set the monitor process title to something useful

Instead of having a parent process that's called whatever the caller of the
library is called, we instead set it to "[lxc monitor] <lxcpath> <container>"

Closes #180

v2: check for null in tok for loop, only truncate environment when necessary

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>

diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
index 4da1627c3da9df1989563dc8e279fb031b420781..e02ee93e9536f14156bdaeca1e9390545b6411e5 100644 (file)
--- a/src/lxc/lxccontainer.c
+++ b/src/lxc/lxccontainer.c
@@ -598,6 +598,7 @@ static bool lxcapi_start(struct lxc_container *c, int useinit, char * const argv
        * while container is running...
        */
        if (daemonize) {
+               char title[2048];
                lxc_monitord_spawn(c->config_path);
 
                pid_t pid = fork();
@@ -612,6 +613,14 @@ static bool lxcapi_start(struct lxc_container *c, int useinit, char * const argv
                        return wait_on_daemonized_start(c, pid);
                }
 
+               /* We don't really care if this doesn't print all the
+                * characters; all that it means is that the proctitle will be
+                * ugly. Similarly, we also don't care if setproctitle()
+                * fails. */
+               snprintf(title, sizeof(title), "[lxc monitor] %s %s", c->config_path, c->name);
+               INFO("Attempting to set proc title to %s", title);
+               setproctitle(title);
+
                /* second fork to be reparented by init */
                pid = fork();
                if (pid < 0) {

diff --git a/src/lxc/utils.c b/src/lxc/utils.c
index 93de1c3503fc6d3cfa93fbb0b84977b2b591845b..9acf7e6722c5a82c142d76bdbfd49b0c375154c3 100644 (file)
--- a/src/lxc/utils.c
+++ b/src/lxc/utils.c
@@ -39,6 +39,7 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <assert.h>
+#include <sys/prctl.h>
 
 #include "utils.h"
 #include "log.h"
@@ -1540,3 +1541,69 @@ char *get_template_path(const char *t)
 
        return tpath;
 }
+
+/*
+ * Sets the process title to the specified title. Note:
+ *   1. this function requires root to succeed
+ *   2. it clears /proc/self/environ
+ *   3. it may not succed (e.g. if title is longer than /proc/self/environ +
+ *      the original title)
+ */
+int setproctitle(char *title)
+{
+       char buf[2048], *tmp;
+       FILE *f;
+       int i, len, ret = 0;
+       unsigned long arg_start, arg_end, env_start, env_end;
+
+       f = fopen_cloexec("/proc/self/stat", "r");
+       if (!f) {
+               return -1;
+       }
+
+       tmp = fgets(buf, sizeof(buf), f);
+       fclose(f);
+       if (!tmp) {
+               return -1;
+       }
+
+       /* Skip the first 47 fields, column 48-51 are ARG_START and
+        * ARG_END. */
+       tmp = strchr(buf, ' ');
+       for (i = 0; i < 46; i++) {
+               if (!tmp)
+                       return -1;
+               tmp = strchr(tmp+1, ' ');
+       }
+
+       i = sscanf(tmp, "%lu %lu %lu %lu", &arg_start, &arg_end, &env_start, &env_end);
+       if (i != 4) {
+               return -1;
+       }
+
+       /* We're truncating the environment, so we should use at most the
+        * length of the argument + environment for the title. */
+       len = strlen(title);
+       if (len > env_end - arg_start) {
+               arg_end = env_end;
+               len = env_end - arg_start;
+       } else {
+               /* Only truncate the environment if we're actually going to
+                * overwrite part of it. */
+               if (len >= arg_end - arg_start) {
+                       env_start = env_end;
+               }
+               arg_end = arg_start + len;
+       }
+
+
+       /* memcpy instead of strcpy since this isn't null terminated */
+       memcpy((void*)arg_start, title, len);
+
+       ret |= prctl(PR_SET_MM, PR_SET_MM_ARG_START,   (long)arg_start, 0, 0);
+       ret |= prctl(PR_SET_MM, PR_SET_MM_ARG_END,     (long)arg_end, 0, 0);
+       ret |= prctl(PR_SET_MM, PR_SET_MM_ENV_START,   (long)env_start, 0, 0);
+       ret |= prctl(PR_SET_MM, PR_SET_MM_ENV_END,     (long)env_end, 0, 0);
+
+       return ret;
+}

diff --git a/src/lxc/utils.h b/src/lxc/utils.h
index b23cd8eeab80af85089e8bd17bdf7bad5ecc15b7..cc189060439f57a94b3055cf744c3785cf3058fb 100644 (file)
--- a/src/lxc/utils.h
+++ b/src/lxc/utils.h
@@ -286,3 +286,4 @@ int print_to_file(const char *file, const char *content);
 bool switch_to_ns(pid_t pid, const char *ns);
 int is_dir(const char *path);
 char *get_template_path(const char *t);
+int setproctitle(char *title);