riscv64 SCS support.
Bug: https://github.com/google/android-riscv64/issues/55
Test: treehugger
Change-Id: I05d48a07a302305126942d38529ffa280640c7b7
diff --git a/libc/private/bionic_constants.h b/libc/private/bionic_constants.h
index 09294b6..d7f4474 100644
--- a/libc/private/bionic_constants.h
+++ b/libc/private/bionic_constants.h
@@ -14,18 +14,18 @@
* limitations under the License.
*/
-#ifndef _BIONIC_CONSTANTS_H_
-#define _BIONIC_CONSTANTS_H_
+#pragma once
#define NS_PER_S 1000000000
-// Size of the shadow call stack. This must be a power of 2.
+// Size of the shadow call stack. This can be small because these stacks only
+// contain return addresses. This must be a power of 2 so the mask trick works.
+// See the SCS commentary in pthread_internal.h for more detail.
#define SCS_SIZE (8 * 1024)
+#define SCS_MASK (SCS_SIZE - 1)
// The shadow call stack is allocated at an aligned address within a guard region of this size. The
// guard region must be large enough that we can allocate an SCS_SIZE-aligned SCS while ensuring
// that there is at least one guard page after the SCS so that a stack overflow results in a SIGSEGV
// instead of corrupting the allocation that comes after it.
#define SCS_GUARD_REGION_SIZE (16 * 1024 * 1024)
-
-#endif // _BIONIC_CONSTANTS_H_