Per-thread -fstack-protector guards for x86.
Based on a pair of patches from Intel:
https://android-review.googlesource.com/#/c/43909/
https://android-review.googlesource.com/#/c/44903/
For x86, this patch supports _both_ the global that ARM/MIPS use
and the per-thread TLS entry (%gs:20) that GCC uses by default. This
lets us support binaries built with any x86 toolchain (right now,
the NDK is emitting x86 code that uses the global).
I've also extended the original tests to cover ARM/MIPS too, and
be a little more thorough for x86.
Change-Id: I02f279a80c6b626aecad449771dec91df235ad01
diff --git a/libc/private/bionic_ssp.h b/libc/private/bionic_ssp.h
new file mode 100644
index 0000000..697216c
--- /dev/null
+++ b/libc/private/bionic_ssp.h
@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef _PRIVATE_SSP_H
+#define _PRIVATE_SSP_H
+
+#include <errno.h>
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+/** WARNING WARNING WARNING
+ **
+ ** This header file is *NOT* part of the public Bionic ABI/API
+ ** and should not be used/included by user-serviceable parts of
+ ** the system (e.g. applications).
+ **/
+
+/* GCC uses this on ARM and MIPS. */
+extern void* __stack_chk_guard;
+
+/* GCC calls this if a stack guard check fails. */
+extern void __stack_chk_fail();
+
+__inline__ static void* __attribute__((always_inline)) __generate_stack_chk_guard(void) {
+ union {
+ uintptr_t value;
+ char bytes[sizeof(uintptr_t)];
+ } u;
+
+ /* Try pulling random bytes from /dev/urandom. */
+ int fd = TEMP_FAILURE_RETRY(open("/dev/urandom", O_RDONLY));
+ if (fd != -1) {
+ ssize_t byte_count = TEMP_FAILURE_RETRY(read(fd, &u.bytes, sizeof(u)));
+ close(fd);
+ if (byte_count == sizeof(u)) {
+ return (void*) u.value;
+ }
+ }
+
+ /* If that failed, switch to 'terminator canary'. */
+ u.bytes[0] = 0;
+ u.bytes[1] = 0;
+ u.bytes[2] = '\n';
+ u.bytes[3] = 255;
+ return (void*) u.value;
+}
+
+__END_DECLS
+
+#endif
diff --git a/libc/private/bionic_tls.h b/libc/private/bionic_tls.h
index a626d21..f661ccf 100644
--- a/libc/private/bionic_tls.h
+++ b/libc/private/bionic_tls.h
@@ -43,24 +43,19 @@
** pre-allocated slot directly for performance reason).
**/
-/* maximum number of elements in the TLS array */
+/* Maximum number of elements in the TLS array. */
#define BIONIC_TLS_SLOTS 64
-/* note that slot 0, called TLS_SLOT_SELF must point to itself.
- * this is required to implement thread-local storage with the x86
- * Linux kernel, that reads the TLS from fs:[0], where 'fs' is a
- * thread-specific segment descriptor...
- */
-
-/* Well-known TLS slots. */
-#define TLS_SLOT_SELF 0
+/* Well-known TLS slots. What data goes in which slot is arbitrary unless otherwise noted. */
+#define TLS_SLOT_SELF 0 /* The kernel requires this specific slot for x86. */
#define TLS_SLOT_THREAD_ID 1
#define TLS_SLOT_ERRNO 2
#define TLS_SLOT_OPENGL_API 3
#define TLS_SLOT_OPENGL 4
-#define TLS_SLOT_DLERROR 5
+#define TLS_SLOT_STACK_GUARD 5 /* GCC requires this specific slot for x86. */
+#define TLS_SLOT_DLERROR 6
#define TLS_SLOT_MAX_WELL_KNOWN TLS_SLOT_DLERROR