Allocate a small guard region around the shadow call stack.
This lets us do two things:
1) Make setjmp and longjmp compatible with shadow call stack.
To avoid leaking the shadow call stack address into memory, only the
lower log2(SCS_SIZE) bits of x18 are stored to jmp_buf. This requires
allocating an additional guard page so that we're guaranteed to be
able to allocate a sufficiently aligned SCS.
2) SCS overflow detection. Overflows now result in a SIGSEGV instead
of corrupting the allocation that comes after it.
Change-Id: I04d6634f96162bf625684672a87fba8b402b7fd1
Test: bionic-unit-tests
diff --git a/tests/setjmp_test.cpp b/tests/setjmp_test.cpp
index dde0be1..44d8af1 100644
--- a/tests/setjmp_test.cpp
+++ b/tests/setjmp_test.cpp
@@ -264,3 +264,14 @@
fprintf(stderr, "setjmp_cookie_checksum: longjmp succeeded?");
}
}
+
+__attribute__((noinline)) void call_longjmp(jmp_buf buf) {
+ longjmp(buf, 123);
+}
+
+TEST(setjmp, setjmp_stack) {
+ jmp_buf buf;
+ int value = setjmp(buf);
+ if (value == 0) call_longjmp(buf);
+ EXPECT_EQ(123, value);
+}