Locking for the per-process resource limits structure.

- struct plimit includes a mutex to protect a reference count.  The plimit
  structure is treated similarly to struct ucred in that is is always copy
  on write, so having a reference to a structure is sufficient to read from
  it without needing a further lock.
- The proc lock protects the p_limit pointer and must be held while reading
  limits from a process to keep the limit structure from changing out from
  under you while reading from it.
- Various global limits that are ints are not protected by a lock since
  int writes are atomic on all the archs we support and thus a lock
  wouldn't buy us anything.
- All accesses to individual resource limits from a process are abstracted
  behind a simple lim_rlimit(), lim_max(), and lim_cur() API that return
  either an rlimit, or the current or max individual limit of the specified
  resource from a process.
- dosetrlimit() was renamed to kern_setrlimit() to match existing style of
  other similar syscall helper functions.
- The alpha OSF/1 compat layer no longer calls getrlimit() and setrlimit()
  (it didn't used the stackgap when it should have) but uses lim_rlimit()
  and kern_setrlimit() instead.
- The svr4 compat no longer uses the stackgap for resource limits calls,
  but uses lim_rlimit() and kern_setrlimit() instead.
- The ibcs2 compat no longer uses the stackgap for resource limits.  It
  also no longer uses the stackgap for accessing sysctl's for the
  ibcs2_sysconf() syscall but uses kernel_sysctl() instead.  As a result,
  ibcs2_sysconf() no longer needs Giant.
- The p_rlimit macro no longer exists.

Submitted by:	mtm (mostly, I only did a few cleanups and catchups)
Tested on:	i386
Compiled on:	alpha, amd64

1 files changed, 23 insertions, 40 deletions

diff --git a/sys/compat/ia32/ia32_sysvec.c b/sys/compat/ia32/ia32_sysvec.c
index 0b2d777..2210cec 100644
--- a/sys/compat/ia32/ia32_sysvec.c
+++ b/sys/compat/ia32/ia32_sysvec.c
@@ -273,50 +273,33 @@ static void
 ia32_fixlimits(struct image_params *imgp)
 {
 	struct proc *p = imgp->proc;
-
+	struct plimit *oldlim, *newlim;
+
+	if (ia32_maxdsiz == 0 && ia32_maxssiz == 0 && ia32_maxvmem == 0)
+		return;
+	newlim = lim_alloc();
+	PROC_LOCK(p);
+	oldlim = p->p_limit;
+	lim_copy(newlim, oldlim);
 	if (ia32_maxdsiz != 0) {
-		if (p->p_rlimit[RLIMIT_DATA].rlim_cur > ia32_maxdsiz ||
-		    p->p_rlimit[RLIMIT_DATA].rlim_max > ia32_maxdsiz) {
-			if (p->p_limit->p_refcnt > 1) {
-				p->p_limit->p_refcnt--;
-				p->p_limit = limcopy(p->p_limit);
-			}
-			if (p->p_rlimit[RLIMIT_DATA].rlim_cur > ia32_maxdsiz)
-				p->p_rlimit[RLIMIT_DATA].rlim_cur =
-				    ia32_maxdsiz;
-			if (p->p_rlimit[RLIMIT_DATA].rlim_max > ia32_maxdsiz)
-				p->p_rlimit[RLIMIT_DATA].rlim_max =
-				    ia32_maxdsiz;
-		}
+		if (newlim->pl_rlimit[RLIMIT_DATA].rlim_cur > ia32_maxdsiz)
+		    newlim->pl_rlimit[RLIMIT_DATA].rlim_cur = ia32_maxdsiz;
+		if (newlim->pl_rlimit[RLIMIT_DATA].rlim_max > ia32_maxdsiz)
+		    newlim->pl_rlimit[RLIMIT_DATA].rlim_max = ia32_maxdsiz;
 	}
 	if (ia32_maxssiz != 0) {
-		if (p->p_rlimit[RLIMIT_STACK].rlim_cur > ia32_maxssiz ||
-		    p->p_rlimit[RLIMIT_STACK].rlim_max > ia32_maxssiz) {
-			if (p->p_limit->p_refcnt > 1) {
-				p->p_limit->p_refcnt--;
-				p->p_limit = limcopy(p->p_limit);
-			}
-			if (p->p_rlimit[RLIMIT_STACK].rlim_cur > ia32_maxssiz)
-				p->p_rlimit[RLIMIT_STACK].rlim_cur =
-				    ia32_maxssiz;
-			if (p->p_rlimit[RLIMIT_STACK].rlim_max > ia32_maxssiz)
-				p->p_rlimit[RLIMIT_STACK].rlim_max =
-				    ia32_maxssiz;
-		}
+		if (newlim->pl_rlimit[RLIMIT_STACK].rlim_cur > ia32_maxssiz)
+		    newlim->pl_rlimit[RLIMIT_STACK].rlim_cur = ia32_maxssiz;
+		if (newlim->pl_rlimit[RLIMIT_STACK].rlim_max > ia32_maxssiz)
+		    newlim->pl_rlimit[RLIMIT_STACK].rlim_max = ia32_maxssiz;
 	}
 	if (ia32_maxvmem != 0) {
-		if (p->p_rlimit[RLIMIT_VMEM].rlim_cur > ia32_maxvmem ||
-		    p->p_rlimit[RLIMIT_VMEM].rlim_max > ia32_maxvmem) {
-			if (p->p_limit->p_refcnt > 1) {
-				p->p_limit->p_refcnt--;
-				p->p_limit = limcopy(p->p_limit);
-			}
-			if (p->p_rlimit[RLIMIT_VMEM].rlim_cur > ia32_maxvmem)
-				p->p_rlimit[RLIMIT_VMEM].rlim_cur =
-				    ia32_maxvmem;
-			if (p->p_rlimit[RLIMIT_VMEM].rlim_max > ia32_maxvmem)
-				p->p_rlimit[RLIMIT_VMEM].rlim_max =
-				    ia32_maxvmem;
-		}
+		if (newlim->pl_rlimit[RLIMIT_VMEM].rlim_cur > ia32_maxvmem)
+		    newlim->pl_rlimit[RLIMIT_VMEM].rlim_cur = ia32_maxvmem;
+		if (newlim->pl_rlimit[RLIMIT_VMEM].rlim_max > ia32_maxvmem)
+		    newlim->pl_rlimit[RLIMIT_VMEM].rlim_max = ia32_maxvmem;
 	}
+	p->p_limit = newlim;
+	PROC_UNLOCK(p);
+	lim_free(oldlim);
 }