[lxc-devel] [PATCH] set the monitor process title to something useful
Tycho Andersen
tycho.andersen at canonical.com
Fri Jan 30 13:59:13 UTC 2015
On Fri, Jan 30, 2015 at 01:38:59PM +0000, Serge Hallyn wrote:
> Quoting Tycho Andersen (tycho.andersen at canonical.com):
> > 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>"
> >
> > Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
> > ---
> > src/lxc/lxccontainer.c | 10 +++++++++
> > src/lxc/utils.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++
> > src/lxc/utils.h | 1 +
> > 3 files changed, 72 insertions(+)
> >
> > diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
> > index 4da1627..1176a6f 100644
> > --- 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 +613,15 @@ 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 93de1c3..f517ee6 100644
> > --- 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 +1541,63 @@ 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++)
> > + tmp = strchr(tmp+1, ' ');
>
> Could you add a check here at each step for tmp != NULL? Or just
>
> for (i = 0; i < 46 && tmp; i++)
> tmp = strchr(tmp+1, ' ');
> if (!tmp)
> return -1;
Yep, here's a few other changes as well.
Tycho
>From 6af924ded6e4ca9f0826a50c73cfcc8715159b18 Mon Sep 17 00:00:00 2001
From: Tycho Andersen <tycho.andersen at canonical.com>
Date: Fri, 30 Jan 2015 14:14:51 +0100
Subject: [PATCH] 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 at canonical.com>
---
src/lxc/lxccontainer.c | 9 +++++++
src/lxc/utils.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++
src/lxc/utils.h | 1 +
3 files changed, 77 insertions(+)
diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
index 4da1627..e02ee93 100644
--- 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 93de1c3..9acf7e6 100644
--- 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 b23cd8e..cc18906 100644
--- 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);
--
2.1.0
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