Usermode exec-stack fix
When loading a shared library that requires an executable stack,
glibc uses the mprotext PROT_GROWSDOWN flag to achieve this.
We don't support PROT_GROWSDOWN.
Add a special case to handle changing the stack permissions in this way.
Signed-off-by: Paul Brook <paul@codesourcery.com>
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index e94f1ee..0ebe7e1 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -5400,6 +5400,17 @@
ret = get_errno(target_munmap(arg1, arg2));
break;
case TARGET_NR_mprotect:
+ {
+ TaskState *ts = ((CPUState *)cpu_env)->opaque;
+ /* Special hack to detect libc making the stack executable. */
+ if ((arg3 & PROT_GROWSDOWN)
+ && arg1 >= ts->info->stack_limit
+ && arg1 <= ts->info->start_stack) {
+ arg3 &= ~PROT_GROWSDOWN;
+ arg2 = arg2 + arg1 - ts->info->stack_limit;
+ arg1 = ts->info->stack_limit;
+ }
+ }
ret = get_errno(target_mprotect(arg1, arg2, arg3));
break;
#ifdef TARGET_NR_mremap
