Have pthread_attr_getstack for the main thread report RLIMIT_STACK...
...rather than just what's already mapped in. This seems somewhat
contrary to POSIX's "All pages within the stack described by stackaddr
and stacksize shall be both readable and writable by the thread", but
it's what glibc does.
Bug: 17111575
(cherry picked from commit 9e4ffa7032eaab308876b8e3da86b05c3c613878)
Change-Id: I73f219a569917b2e4546c09436d7ef5231facc07
diff --git a/libc/bionic/pthread_attr.cpp b/libc/bionic/pthread_attr.cpp
index 8df3bff..c93970a 100644
--- a/libc/bionic/pthread_attr.cpp
+++ b/libc/bionic/pthread_attr.cpp
@@ -116,6 +116,16 @@
static int __pthread_attr_getstack_main_thread(void** stack_base, size_t* stack_size) {
ErrnoRestorer errno_restorer;
+ rlimit stack_limit;
+ if (getrlimit(RLIMIT_STACK, &stack_limit) == -1) {
+ return errno;
+ }
+
+ // If the current RLIMIT_STACK is RLIM_INFINITY, only admit to an 8MiB stack for sanity's sake.
+ if (stack_limit.rlim_cur == RLIM_INFINITY) {
+ stack_limit.rlim_cur = 8 * 1024 * 1024;
+ }
+
// It doesn't matter which thread we are; we're just looking for "[stack]".
FILE* fp = fopen("/proc/self/maps", "re");
if (fp == NULL) {
@@ -126,17 +136,8 @@
if (ends_with(line, " [stack]\n")) {
uintptr_t lo, hi;
if (sscanf(line, "%" SCNxPTR "-%" SCNxPTR, &lo, &hi) == 2) {
- *stack_base = reinterpret_cast<void*>(lo);
- *stack_size = hi - lo;
-
- // Does our current RLIMIT_STACK mean we won't actually get everything /proc/maps promises?
- rlimit stack_limit;
- if (getrlimit(RLIMIT_STACK, &stack_limit) != -1) {
- if (*stack_size > stack_limit.rlim_cur) {
- *stack_size = stack_limit.rlim_cur;
- }
- }
-
+ *stack_size = stack_limit.rlim_cur;
+ *stack_base = reinterpret_cast<void*>(hi - *stack_size);
fclose(fp);
return 0;
}