From 9e7d0583513142cff5bf65db5b22f89f56030600 Mon Sep 17 00:00:00 2001
From: Mikolaj Golub <trociny@FreeBSD.org>
Date: Thu, 24 Nov 2011 20:43:37 +0000
Subject: [PATCH] Add sysctl to get process resource limits.

Reviewed by:	kib
MFC after:	2 weeks
---
 sys/kern/kern_proc.c | 46 ++++++++++++++++++++++++++++++++++++++++++++
 sys/sys/sysctl.h     |  1 +
 2 files changed, 47 insertions(+)

diff --git a/sys/kern/kern_proc.c b/sys/kern/kern_proc.c
index 6d1430cc041d..35f13b9f6fa6 100644
--- a/sys/kern/kern_proc.c
+++ b/sys/kern/kern_proc.c
@@ -54,6 +54,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/proc.h>
 #include <sys/ptrace.h>
 #include <sys/refcount.h>
+#include <sys/resourcevar.h>
 #include <sys/sbuf.h>
 #include <sys/sysent.h>
 #include <sys/sched.h>
@@ -2389,6 +2390,48 @@ sysctl_kern_proc_groups(SYSCTL_HANDLER_ARGS)
 	return (error);
 }
 
+/*
+ * This sysctl allows a process to retrieve the resource limits for
+ * another process.
+ */
+static int
+sysctl_kern_proc_rlimit(SYSCTL_HANDLER_ARGS)
+{
+	int *name = (int*) arg1;
+	u_int namelen = arg2;
+	struct plimit *limp;
+	struct proc *p;
+	int error = 0;
+
+	if (namelen != 1)
+		return (EINVAL);
+
+	p = pfind((pid_t)name[0]);
+	if (p == NULL)
+		return (ESRCH);
+
+	if ((error = p_cansee(curthread, p)) != 0) {
+		PROC_UNLOCK(p);
+		return (error);
+	}
+
+	/*
+	 * Check the request size.  We alow sizes smaller rlimit array for
+	 * backward binary compatibility: the number of resource limits may
+	 * grow.
+	 */
+	if (sizeof(limp->pl_rlimit) < req->oldlen) {
+		PROC_UNLOCK(p);
+		return (EINVAL);
+	}
+
+	limp = lim_hold(p->p_limit);
+	PROC_UNLOCK(p);
+	error = SYSCTL_OUT(req, limp->pl_rlimit, req->oldlen);
+	lim_free(limp);
+	return (error);
+}
+
 SYSCTL_NODE(_kern, KERN_PROC, proc, CTLFLAG_RD,  0, "Process table");
 
 SYSCTL_PROC(_kern_proc, KERN_PROC_ALL, all, CTLFLAG_RD|CTLTYPE_STRUCT|
@@ -2484,3 +2527,6 @@ static SYSCTL_NODE(_kern_proc, KERN_PROC_KSTACK, kstack, CTLFLAG_RD |
 
 static SYSCTL_NODE(_kern_proc, KERN_PROC_GROUPS, groups, CTLFLAG_RD |
 	CTLFLAG_MPSAFE, sysctl_kern_proc_groups, "Process groups");
+
+static SYSCTL_NODE(_kern_proc, KERN_PROC_RLIMIT, rlimit, CTLFLAG_RD |
+	CTLFLAG_MPSAFE, sysctl_kern_proc_rlimit, "Process resource limits");
diff --git a/sys/sys/sysctl.h b/sys/sys/sysctl.h
index 99ea342b80b5..db08a3a7802d 100644
--- a/sys/sys/sysctl.h
+++ b/sys/sys/sysctl.h
@@ -561,6 +561,7 @@ SYSCTL_ALLOWED_TYPES(UINT64, uint64_t *a; unsigned long long *b; );
 #define	KERN_PROC_GROUPS	34	/* process groups */
 #define	KERN_PROC_ENV		35	/* get environment */
 #define	KERN_PROC_AUXV		36	/* get ELF auxiliary vector */
+#define	KERN_PROC_RLIMIT	37	/* process resource limits */
 
 /*
  * KERN_IPC identifiers