commit f45d4395e68c9d5bae53da13537f54c6c929bf50
author Arve Hjønnevåg <arve@android.com> Thu Aug 20 15:11:17 2020 -0700
committer Arve Hjønnevåg <arve@android.com> Mon Nov 09 12:07:51 2020 -0800
tree cf2a15cc99d5a1bee66ed05498ab4137841a37b7
parent f80971a1b074ebcebc2e2cdc64d492f18a010225

[kernel][thread] Add guard page around most kernel stacks

Allocate kernel stacks with vmm_alloc instead of malloc to get guard
pages.

The initial thread for each cpu, which later becomes idle threads, are
not affected by this, and will still run without guard pages.

Bug: 165825378
Change-Id: I103bcfdc330d88ac0957e3dad75aa232dc20e084

kernel/thread.c

diff --git a/kernel/thread.c b/kernel/thread.c
index 4d1b05d..6b375e4 100644
--- a/kernel/thread.c
+++ b/kernel/thread.c
@@ -165,6 +165,7 @@
  */
 thread_t *thread_create_etc(thread_t *t, const char *name, thread_start_routine entry, void *arg, int priority, void *stack, size_t stack_size)
 {
+    int ret;
     unsigned int flags = 0;
 
     if (!t) {
@@ -197,8 +198,9 @@
         stack_size += THREAD_STACK_PADDING_SIZE;
         flags |= THREAD_FLAG_DEBUG_STACK_BOUNDS_CHECK;
 #endif
-        t->stack = malloc(stack_size);
-        if (!t->stack) {
+        ret = vmm_alloc(vmm_get_kernel_aspace(), "kernel-stack", stack_size,
+                        &t->stack, 0, 0, ARCH_MMU_FLAG_PERM_NO_EXECUTE);
+        if (ret) {
             if (flags & THREAD_FLAG_FREE_STRUCT)
                 free(t);
             return NULL;
@@ -384,7 +386,7 @@
 {
     /* free its stack and the thread structure itself */
     if (t->flags & THREAD_FLAG_FREE_STACK && t->stack)
-        free(t->stack);
+        vmm_free_region(vmm_get_kernel_aspace(), (vaddr_t)t->stack);
 
     if (t->flags & THREAD_FLAG_FREE_STRUCT)
         free(t);