Re: [PATCH]: proc: export a processes resource limits via proc/<pid>

[Neil Horman <nhorman@tuxdriver.com>]

On Mon, Aug 13, 2007 at 12:47:38PM -0400, Valdis.Kletnieks@vt.edu wrote:
> On Mon, 13 Aug 2007 10:00:44 EDT, Neil Horman said:
> > Hey there-
> > 	Currently, there exists no method for a process to query the resource
> > limits of another process.  They can be inferred via some mechanisms but they
> > cannot be explicitly determined.  Given that this information can be usefull to
> > know during the debugging of an application, I've written this patch which
> > exports all of a processes limits via /proc/<pid>/limits.  Tested successfully
> > by myself on x86 on top of 2.6.23-rc2-mm1.
> 
> >  /************************************************************************/
> >  /*                       Here the fs part begins                        */
> >  /************************************************************************/
> > @@ -2017,6 +2080,7 @@ static const struct pid_entry tgid_base_stuff[] = {
> >  	INF("environ",    S_IRUSR, pid_environ),
> >  	INF("auxv",       S_IRUSR, pid_auxv),
> >  	INF("status",     S_IRUGO, pid_status),
> > +	INF("limits",	  S_IRUGO, pid_limits),
> 
> Any takers for S_IRUSR instead?  Either that, or lay out the use case for
> making it S_IRUGO.  (I'm OK on it being world-visible *if* there's a good
> and sane reason for it)
> 
> >  #ifdef CONFIG_SCHED_DEBUG
> >  	REG("sched",      S_IRUGO|S_IWUSR, pid_sched),
> >  #endif
> > @@ -2310,6 +2374,7 @@ static const struct pid_entry tid_base_stuff[] = {
> >  	INF("environ",   S_IRUSR, pid_environ),
> >  	INF("auxv",      S_IRUSR, pid_auxv),
> >  	INF("status",    S_IRUGO, pid_status),
> > +	INF("limits",	 S_IRUGO, pid_limits),
> 
> Here too.


Given that making it S_IRUSR would still accomplish the goals that I set out
for, I certainly have no objections.  New patch attached with permissions
changed.

Regards
Neil

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>


 base.c |   65 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)


diff --git a/fs/proc/base.c b/fs/proc/base.c
index ed2b224..b3ddf08 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -74,6 +74,7 @@
 #include <linux/nsproxy.h>
 #include <linux/oom.h>
 #include <linux/elf.h>
+#include <asm/resource.h>
 #include "internal.h"
 
 /* NOTE:
@@ -323,6 +324,68 @@ static int proc_oom_score(struct task_struct *task, char *buffer)
 	return sprintf(buffer, "%lu\n", points);
 }
 
+struct limit_names {
+	char *name;
+	char *unit;
+};
+
+static struct limit_names lnames[RLIM_NLIMITS] = {
+	[RLIMIT_CPU] = {"Max cpu time", "ms"},
+	[RLIMIT_FSIZE] = {"Max file size", "bytes"},
+	[RLIMIT_DATA] = {"Max data size", "bytes"},
+	[RLIMIT_STACK] = {"Max stack size", "bytes"},
+	[RLIMIT_CORE] = {"Max core file size", "bytes"},
+	[RLIMIT_RSS] = {"Max resident set", "bytes"},
+	[RLIMIT_NPROC] = {"Max processes", "processes"},
+	[RLIMIT_NOFILE] = {"Max open files", "files"},
+	[RLIMIT_MEMLOCK] = {"Max locked memory", "bytes"},
+	[RLIMIT_AS] = {"Max address space", "bytes"},
+	[RLIMIT_LOCKS] = {"Max file locks", "locks"},
+	[RLIMIT_SIGPENDING] = {"Max pending signals", "signals"},
+	[RLIMIT_MSGQUEUE] = {"Max msgqueue size", "bytes"},
+	[RLIMIT_NICE] = {"Max nice priority", NULL},
+	[RLIMIT_RTPRIO] = {"Max realtime priority", NULL},
+};	
+
+/* Display limits for a process */
+static int proc_pid_limits(struct task_struct *task, char *buffer)
+{
+	unsigned int i;
+	int count = 0;
+	char *bufptr = buffer;
+
+	struct rlimit rlim[RLIM_NLIMITS];
+
+	read_lock(&tasklist_lock);
+	memcpy(rlim, task->signal->rlim, (sizeof(struct rlimit) * RLIM_NLIMITS));
+	read_unlock(&tasklist_lock);
+
+	/*
+	 * print the file header
+	 */
+	count += sprintf(&bufptr[count], "%-25s %-20s %-20s %-10s\n",
+			"Limit","Soft Limit","Hard Limit","Units");
+
+	for (i=0; i < RLIM_NLIMITS; i++) {
+		if (rlim[i].rlim_cur == RLIM_INFINITY)
+			count += sprintf(&bufptr[count], "%-25s %-20s ", lnames[i].name,"unlimited");
+		else
+			count += sprintf(&bufptr[count], "%-25s %-20lu ", lnames[i].name, rlim[i].rlim_cur);
+
+		if (rlim[i].rlim_max == RLIM_INFINITY)
+			count += sprintf(&bufptr[count], "%-20s ","unlimited");
+		else
+			count += sprintf(&bufptr[count], "%-20lu ", rlim[i].rlim_max);
+
+		if (lnames[i].unit)
+			count += sprintf(&bufptr[count],"%-10s\n", lnames[i].unit);
+		else
+			count += sprintf(&bufptr[count],"\n");
+	}
+
+	return count;
+}
+
 /************************************************************************/
 /*                       Here the fs part begins                        */
 /************************************************************************/
@@ -2017,6 +2080,7 @@ static const struct pid_entry tgid_base_stuff[] = {
 	INF("environ",    S_IRUSR, pid_environ),
 	INF("auxv",       S_IRUSR, pid_auxv),
 	INF("status",     S_IRUGO, pid_status),
+	INF("limits",	  S_IRUSR, pid_limits),
 #ifdef CONFIG_SCHED_DEBUG
 	REG("sched",      S_IRUGO|S_IWUSR, pid_sched),
 #endif
@@ -2310,6 +2374,7 @@ static const struct pid_entry tid_base_stuff[] = {
 	INF("environ",   S_IRUSR, pid_environ),
 	INF("auxv",      S_IRUSR, pid_auxv),
 	INF("status",    S_IRUGO, pid_status),
+	INF("limits",	 S_IRUSR, pid_limits),
 #ifdef CONFIG_SCHED_DEBUG
 	REG("sched",     S_IRUGO|S_IWUSR, pid_sched),
 #endif

-- 
/***************************************************
 *Neil Horman
 *Software Engineer
 *Red Hat, Inc.
 *nhorman@tuxdriver.com
 *gpg keyid: 1024D / 0x92A74FA1
 *http://pgp.mit.edu
 ***************************************************/
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