Revert^3 "[MTE] remap stacks with PROT_MTE when requested by dlopened library"
This reverts commit a453c2df744f46f87813e3c3dface12d570d3dc6.
Reason for revert: b/324568991
Bug: 324568991
Change-Id: Ia6250ebe51c505bd4b77af2b4ff4e95c8b370acd
diff --git a/libc/bionic/pthread_attr.cpp b/libc/bionic/pthread_attr.cpp
index f6c0401..de4cc9e 100644
--- a/libc/bionic/pthread_attr.cpp
+++ b/libc/bionic/pthread_attr.cpp
@@ -155,6 +155,36 @@
return 0;
}
+static uintptr_t __get_main_stack_startstack() {
+ FILE* fp = fopen("/proc/self/stat", "re");
+ if (fp == nullptr) {
+ async_safe_fatal("couldn't open /proc/self/stat: %m");
+ }
+
+ char line[BUFSIZ];
+ if (fgets(line, sizeof(line), fp) == nullptr) {
+ async_safe_fatal("couldn't read /proc/self/stat: %m");
+ }
+
+ fclose(fp);
+
+ // See man 5 proc. There's no reason comm can't contain ' ' or ')',
+ // so we search backwards for the end of it. We're looking for this field:
+ //
+ // startstack %lu (28) The address of the start (i.e., bottom) of the stack.
+ uintptr_t startstack = 0;
+ const char* end_of_comm = strrchr(line, ')');
+ if (sscanf(end_of_comm + 1, " %*c "
+ "%*d %*d %*d %*d %*d "
+ "%*u %*u %*u %*u %*u %*u %*u "
+ "%*d %*d %*d %*d %*d %*d "
+ "%*u %*u %*d %*u %*u %*u %" SCNuPTR, &startstack) != 1) {
+ async_safe_fatal("couldn't parse /proc/self/stat");
+ }
+
+ return startstack;
+}
+
static int __pthread_attr_getstack_main_thread(void** stack_base, size_t* stack_size) {
ErrnoRestorer errno_restorer;
@@ -168,11 +198,28 @@
if (stack_limit.rlim_cur == RLIM_INFINITY) {
stack_limit.rlim_cur = 8 * 1024 * 1024;
}
- uintptr_t lo, hi;
- __find_main_stack_limits(&lo, &hi);
- *stack_size = stack_limit.rlim_cur;
- *stack_base = reinterpret_cast<void*>(hi - *stack_size);
- return 0;
+
+ // Ask the kernel where our main thread's stack started.
+ uintptr_t startstack = __get_main_stack_startstack();
+
+ // Hunt for the region that contains that address.
+ FILE* fp = fopen("/proc/self/maps", "re");
+ if (fp == nullptr) {
+ async_safe_fatal("couldn't open /proc/self/maps: %m");
+ }
+ char line[BUFSIZ];
+ while (fgets(line, sizeof(line), fp) != nullptr) {
+ uintptr_t lo, hi;
+ if (sscanf(line, "%" SCNxPTR "-%" SCNxPTR, &lo, &hi) == 2) {
+ if (lo <= startstack && startstack <= hi) {
+ *stack_size = stack_limit.rlim_cur;
+ *stack_base = reinterpret_cast<void*>(hi - *stack_size);
+ fclose(fp);
+ return 0;
+ }
+ }
+ }
+ async_safe_fatal("stack not found in /proc/self/maps");
}
__BIONIC_WEAK_FOR_NATIVE_BRIDGE