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

2 files changed, 27 insertions, 19 deletions

diff --git a/sys/alpha/linux/linux_machdep.c b/sys/alpha/linux/linux_machdep.c
index b0cd44b..061928c 100644
--- a/sys/alpha/linux/linux_machdep.c
+++ b/sys/alpha/linux/linux_machdep.c
@@ -382,7 +382,7 @@ linux_setrlimit(td, uap)
 	if ((error =
 	   copyin(uap->rlim, &rlim, sizeof (struct rlimit))))
 		return (error);
-	return dosetrlimit(td,  which, &rlim);
+	return (kern_setrlimit(td,  which, &rlim));
 }
 
 int
@@ -390,7 +390,9 @@ linux_getrlimit(td, uap)
 	struct thread *td;
 	struct linux_getrlimit_args *uap;
 {
+	struct rlimit rlim;
 	u_int which;
+	int error;
 
 #ifdef DEBUG
 	if (ldebug(getrlimit))
@@ -405,6 +407,9 @@ linux_getrlimit(td, uap)
 	if (which == -1)
 		return EINVAL;
 
-	return (copyout(&td->td_proc->p_rlimit[which],
-	    uap->rlim, sizeof (struct rlimit)));
+	PROC_LOCK(td->td_proc);
+	lim_rlimit(td->td_proc, which, &rlim);
+	PROC_UNLOCK(td->td_proc);
+	error = copyout(&rlim, uap->rlim, sizeof (struct rlimit));
+	return (error);
 }
diff --git a/sys/alpha/osf1/osf1_misc.c b/sys/alpha/osf1/osf1_misc.c
index 1641835..8e2557d 100644
--- a/sys/alpha/osf1/osf1_misc.c
+++ b/sys/alpha/osf1/osf1_misc.c
@@ -390,23 +390,25 @@ osf1_getrlimit(td, uap)
 	struct thread *td;
 	struct osf1_getrlimit_args *uap;
 {
-	struct __getrlimit_args /* {
-		syscallarg(u_int) which;
-		syscallarg(struct rlimit *) rlp;
-	} */ a;
+	struct rlimit bsd_rlim;
+	struct proc *p;
+	int which;
 
 	if (uap->which >= OSF1_RLIMIT_NLIMITS)
 		return (EINVAL);
 
 	if (uap->which <= OSF1_RLIMIT_LASTCOMMON)
-		a.which = uap->which;
+		which = uap->which;
 	else if (uap->which == OSF1_RLIMIT_NOFILE)
-		a.which = RLIMIT_NOFILE;
+		which = RLIMIT_NOFILE;
 	else
 		return (0);
-	a.rlp = (struct rlimit *)uap->rlp;
 
-	return getrlimit(td, &a);
+	p = td->td_proc;
+	PROC_LOCK(p);
+	lim_rlimit(p, which, &bsd_rlim);
+	PROC_UNLOCK(p);
+	return (copyout(&bsd_rlim, uap->rlp, sizeof(bsd_rlim)));
 }
 
 
@@ -415,23 +417,24 @@ osf1_setrlimit(td, uap)
 	struct thread *td;
 	struct osf1_setrlimit_args  *uap;
 {
-	struct __setrlimit_args /* {
-		syscallarg(u_int) which;
-		syscallarg(struct rlimit *) rlp;
-	} */ a;
+	struct rlimit bsd_rlim;
+	int error, which;
 
 	if (uap->which >= OSF1_RLIMIT_NLIMITS)
 		return (EINVAL);
 
 	if (uap->which <= OSF1_RLIMIT_LASTCOMMON)
-		a.which = uap->which;
+		which = uap->which;
 	else if (uap->which == OSF1_RLIMIT_NOFILE)
-		a.which = RLIMIT_NOFILE;
+		which = RLIMIT_NOFILE;
 	else
 		return (0);
-	a.rlp = (struct rlimit *)uap->rlp;
 
-	return setrlimit(td, &a);
+	error = copyin(uap->rlp, &bsd_rlim, sizeof(bsd_rlim));
+	if (error)
+		return (error);
+
+	return (kern_setrlimit(td, which, &bsd_rlim));
 }