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, 19 insertions, 14 deletions

diff --git a/sys/compat/linux/linux_misc.c b/sys/compat/linux/linux_misc.c
index 9938785..9e38f91 100644
--- a/sys/compat/linux/linux_misc.c
+++ b/sys/compat/linux/linux_misc.c
@@ -378,20 +378,19 @@ linux_uselib(struct thread *td, struct linux_uselib_args *args)
 		goto cleanup;
 	}
 
-	/* To protect td->td_proc->p_rlimit in the if condition. */
-	mtx_assert(&Giant, MA_OWNED);
-
 	/*
 	 * text/data/bss must not exceed limits
 	 * XXX - this is not complete. it should check current usage PLUS
 	 * the resources needed by this library.
 	 */
+	PROC_LOCK(td->td_proc);
 	if (a_out->a_text > maxtsiz ||
-	    a_out->a_data + bss_size >
-	    td->td_proc->p_rlimit[RLIMIT_DATA].rlim_cur) {
+	    a_out->a_data + bss_size > lim_cur(td->td_proc, RLIMIT_DATA)) {
+		PROC_UNLOCK(td->td_proc);
 		error = ENOMEM;
 		goto cleanup;
 	}
+	PROC_UNLOCK(td->td_proc);
 
 	mp_fixme("Unlocked vflags access.");
 	/* prevent more writers */
@@ -1111,7 +1110,7 @@ linux_setrlimit(struct thread *td, struct linux_setrlimit_args *args)
 
 	bsd_rlim.rlim_cur = (rlim_t)rlim.rlim_cur;
 	bsd_rlim.rlim_max = (rlim_t)rlim.rlim_max;
-	return (dosetrlimit(td, which, &bsd_rlim));
+	return (kern_setrlimit(td, which, &bsd_rlim));
 }
 
 int
@@ -1119,7 +1118,7 @@ linux_old_getrlimit(struct thread *td, struct linux_old_getrlimit_args *args)
 {
 	struct l_rlimit rlim;
 	struct proc *p = td->td_proc;
-	struct rlimit *bsd_rlp;
+	struct rlimit bsd_rlim;
 	u_int which;
 
 #ifdef DEBUG
@@ -1134,12 +1133,15 @@ linux_old_getrlimit(struct thread *td, struct linux_old_getrlimit_args *args)
 	which = linux_to_bsd_resource[args->resource];
 	if (which == -1)
 		return (EINVAL);
-	bsd_rlp = &p->p_rlimit[which];
 
-	rlim.rlim_cur = (unsigned long)bsd_rlp->rlim_cur;
+	PROC_LOCK(p);
+	lim_rlimit(p, which, &bsd_rlim);
+	PROC_UNLOCK(p);
+
+	rlim.rlim_cur = (unsigned long)bsd_rlim.rlim_cur;
 	if (rlim.rlim_cur == ULONG_MAX)
 		rlim.rlim_cur = LONG_MAX;
-	rlim.rlim_max = (unsigned long)bsd_rlp->rlim_max;
+	rlim.rlim_max = (unsigned long)bsd_rlim.rlim_max;
 	if (rlim.rlim_max == ULONG_MAX)
 		rlim.rlim_max = LONG_MAX;
 	return (copyout(&rlim, args->rlim, sizeof(rlim)));
@@ -1150,7 +1152,7 @@ linux_getrlimit(struct thread *td, struct linux_getrlimit_args *args)
 {
 	struct l_rlimit rlim;
 	struct proc *p = td->td_proc;
-	struct rlimit *bsd_rlp;
+	struct rlimit bsd_rlim;
 	u_int which;
 
 #ifdef DEBUG
@@ -1165,10 +1167,13 @@ linux_getrlimit(struct thread *td, struct linux_getrlimit_args *args)
 	which = linux_to_bsd_resource[args->resource];
 	if (which == -1)
 		return (EINVAL);
-	bsd_rlp = &p->p_rlimit[which];
 
-	rlim.rlim_cur = (l_ulong)bsd_rlp->rlim_cur;
-	rlim.rlim_max = (l_ulong)bsd_rlp->rlim_max;
+	PROC_LOCK(p);
+	lim_rlimit(p, which, &bsd_rlim);
+	PROC_UNLOCK(p);
+
+	rlim.rlim_cur = (l_ulong)bsd_rlim.rlim_cur;
+	rlim.rlim_max = (l_ulong)bsd_rlim.rlim_max;
 	return (copyout(&rlim, args->rlim, sizeof(rlim)));
 }
 #endif /*!__alpha__*/