Implement the __pthread_map_stacks_exec() for libthr.

Stack creation code is changed to call _rtld_get_stack_prot() to get
the stack protection right. There is a race where thread is created
during dlopen() of dso that requires executable stacks. Then,
_rtld_get_stack_prot() may return PROT_READ | PROT_WRITE, but thread
is still not linked into the thread list. In this case, the callback
misses the thread stack, and rechecks the required protection
afterward.

Reviewed by:	davidxu

1 files changed, 34 insertions, 1 deletions

diff --git a/lib/libthr/thread/thr_stack.c b/lib/libthr/thread/thr_stack.c
index 7684953..cb390cc 100644
--- a/lib/libthr/thread/thr_stack.c
+++ b/lib/libthr/thread/thr_stack.c
@@ -32,6 +32,7 @@
 #include <sys/queue.h>
 #include <stdlib.h>
 #include <pthread.h>
+#include <link.h>
 
 #include "thr_private.h"
 
@@ -128,6 +129,38 @@ round_up(size_t size)
 	return size;
 }
 
+void
+_thr_stack_fix_protection(struct pthread *thrd)
+{
+
+	mprotect((char *)thrd->attr.stackaddr_attr +
+	    round_up(thrd->attr.guardsize_attr),
+	    round_up(thrd->attr.stacksize_attr),
+	    _rtld_get_stack_prot());
+}
+
+void __pthread_map_stacks_exec(void);
+void
+__pthread_map_stacks_exec(void)
+{
+	struct pthread *curthread, *thrd;
+	struct stack *st;
+
+	curthread = _get_curthread();
+	THREAD_LIST_RDLOCK(curthread);
+	LIST_FOREACH(st, &mstackq, qe)
+		mprotect((char *)st->stackaddr + st->guardsize, st->stacksize,
+		    _rtld_get_stack_prot());
+	LIST_FOREACH(st, &dstackq, qe)
+		mprotect((char *)st->stackaddr + st->guardsize, st->stacksize,
+		    _rtld_get_stack_prot());
+	TAILQ_FOREACH(thrd, &_thread_gc_list, gcle)
+		_thr_stack_fix_protection(thrd);
+	TAILQ_FOREACH(thrd, &_thread_list, tle)
+		_thr_stack_fix_protection(thrd);
+	THREAD_LIST_UNLOCK(curthread);
+}
+
 int
 _thr_stack_alloc(struct pthread_attr *attr)
 {
@@ -210,7 +243,7 @@ _thr_stack_alloc(struct pthread_attr *attr)
 		/* Map the stack and guard page together, and split guard
 		   page from allocated space: */
 		if ((stackaddr = mmap(stackaddr, stacksize+guardsize,
-		     PROT_READ | PROT_WRITE, MAP_STACK,
+		     _rtld_get_stack_prot(), MAP_STACK,
 		     -1, 0)) != MAP_FAILED &&
 		    (guardsize == 0 ||
 		     mprotect(stackaddr, guardsize, PROT_NONE) == 0)) {