am df7f24f3: am 7b68e3f7: Merge "Per-thread -fstack-protector guards for x86."

* commit 'df7f24f310ee3ceb1dc9413d59d5a8816eb584ef':
  Per-thread -fstack-protector guards for x86.

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

libc/private/bionic_tls.h

@@ -43,24 +43,19 @@ __BEGIN_DECLS
  ** 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