Introduce <pointer_guard.h>, extracted from <sysdep.h>

This allows us to define a generic no-op version of PTR_MANGLE and
PTR_DEMANGLE.  In the future, we can use PTR_MANGLE and PTR_DEMANGLE
unconditionally in C sources, avoiding an unintended loss of hardening
due to missing include files or unlucky header inclusion ordering.

In i386 and x86_64, we can avoid a <tls.h> dependency in the C
code by using the computed constant from <tcb-offsets.h>.  <sysdep.h>
no longer includes these definitions, so there is no cyclic dependency
anymore when computing the <tcb-offsets.h> constants.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

5 files changed, 70 insertions, 44 deletions

diff --git a/sysdeps/arm/__longjmp.S b/sysdeps/arm/__longjmp.S
index 5f1cf3643f..411055b9b3 100644
--- a/sysdeps/arm/__longjmp.S
+++ b/sysdeps/arm/__longjmp.S
@@ -17,6 +17,7 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <sysdep.h>
+#include <pointer_guard.h>
 #include <stap-probe.h>
 #include <bits/setjmp.h>
 #include <rtld-global-offsets.h>
diff --git a/sysdeps/arm/jmpbuf-unwind.h b/sysdeps/arm/jmpbuf-unwind.h
index e6b118f4d0..641444eaf3 100644
--- a/sysdeps/arm/jmpbuf-unwind.h
+++ b/sysdeps/arm/jmpbuf-unwind.h
@@ -18,6 +18,7 @@
 #include <setjmp.h>
 #include <stdint.h>
 #include <sysdep.h>
+#include <pointer_guard.h>
 #include <unwind.h>
 
 /* Test if longjmp to JMPBUF would unwind the frame
diff --git a/sysdeps/arm/pointer_guard.h b/sysdeps/arm/pointer_guard.h
new file mode 100644
index 0000000000..6b90cec2f3
--- /dev/null
+++ b/sysdeps/arm/pointer_guard.h
@@ -0,0 +1,67 @@
+/* Pointer guard implementation.  Arm version.
+   Copyright (C) 2013-2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef POINTER_GUARD_H
+#define POINTER_GUARD_H
+
+/* Pointer mangling support.  */
+#if (IS_IN (rtld) \
+     || (!defined SHARED && (IS_IN (libc) || IS_IN (libpthread))))
+# ifdef __ASSEMBLER__
+#  define PTR_MANGLE_LOAD(guard, tmp)                                   \
+  LDR_HIDDEN (guard, tmp, C_SYMBOL_NAME(__pointer_chk_guard_local), 0)
+#  define PTR_MANGLE(dst, src, guard, tmp)                              \
+  PTR_MANGLE_LOAD(guard, tmp);                                          \
+  PTR_MANGLE2(dst, src, guard)
+/* Use PTR_MANGLE2 for efficiency if guard is already loaded.  */
+#  define PTR_MANGLE2(dst, src, guard)          \
+  eor dst, src, guard
+#  define PTR_DEMANGLE(dst, src, guard, tmp)    \
+  PTR_MANGLE (dst, src, guard, tmp)
+#  define PTR_DEMANGLE2(dst, src, guard)        \
+  PTR_MANGLE2 (dst, src, guard)
+# else
+extern uintptr_t __pointer_chk_guard_local attribute_relro attribute_hidden;
+#  define PTR_MANGLE(var) \
+  (var) = (__typeof (var)) ((uintptr_t) (var) ^ __pointer_chk_guard_local)
+#  define PTR_DEMANGLE(var)     PTR_MANGLE (var)
+# endif
+#else
+# ifdef __ASSEMBLER__
+#  define PTR_MANGLE_LOAD(guard, tmp)                                   \
+  LDR_GLOBAL (guard, tmp, C_SYMBOL_NAME(__pointer_chk_guard), 0);
+#  define PTR_MANGLE(dst, src, guard, tmp)                              \
+  PTR_MANGLE_LOAD(guard, tmp);                                          \
+  PTR_MANGLE2(dst, src, guard)
+/* Use PTR_MANGLE2 for efficiency if guard is already loaded.  */
+#  define PTR_MANGLE2(dst, src, guard)          \
+  eor dst, src, guard
+#  define PTR_DEMANGLE(dst, src, guard, tmp)    \
+  PTR_MANGLE (dst, src, guard, tmp)
+#  define PTR_DEMANGLE2(dst, src, guard)        \
+  PTR_MANGLE2 (dst, src, guard)
+# else
+#  include <stdint.h>
+extern uintptr_t __pointer_chk_guard attribute_relro;
+#  define PTR_MANGLE(var) \
+  (var) = (__typeof (var)) ((uintptr_t) (var) ^ __pointer_chk_guard)
+#  define PTR_DEMANGLE(var)     PTR_MANGLE (var)
+# endif
+#endif
+
+#endif /* POINTER_GUARD_H */
diff --git a/sysdeps/arm/setjmp.S b/sysdeps/arm/setjmp.S
index 1c26227437..271454d769 100644
--- a/sysdeps/arm/setjmp.S
+++ b/sysdeps/arm/setjmp.S
@@ -17,6 +17,7 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <sysdep.h>
+#include <pointer_guard.h>
 #include <stap-probe.h>
 #include <bits/setjmp.h>
 #include <rtld-global-offsets.h>
diff --git a/sysdeps/arm/sysdep.h b/sysdeps/arm/sysdep.h
index f19146b85f..ffd848de88 100644
--- a/sysdeps/arm/sysdep.h
+++ b/sysdeps/arm/sysdep.h
@@ -293,47 +293,3 @@
 #else
 # define PC_OFS  8
 #endif
-
-/* Pointer mangling support.  */
-#if (IS_IN (rtld) \
-     || (!defined SHARED && (IS_IN (libc) || IS_IN (libpthread))))
-# ifdef __ASSEMBLER__
-#  define PTR_MANGLE_LOAD(guard, tmp)					\
-  LDR_HIDDEN (guard, tmp, C_SYMBOL_NAME(__pointer_chk_guard_local), 0)
-#  define PTR_MANGLE(dst, src, guard, tmp)				\
-  PTR_MANGLE_LOAD(guard, tmp);						\
-  PTR_MANGLE2(dst, src, guard)
-/* Use PTR_MANGLE2 for efficiency if guard is already loaded.  */
-#  define PTR_MANGLE2(dst, src, guard)		\
-  eor dst, src, guard
-#  define PTR_DEMANGLE(dst, src, guard, tmp)	\
-  PTR_MANGLE (dst, src, guard, tmp)
-#  define PTR_DEMANGLE2(dst, src, guard)	\
-  PTR_MANGLE2 (dst, src, guard)
-# else
-extern uintptr_t __pointer_chk_guard_local attribute_relro attribute_hidden;
-#  define PTR_MANGLE(var) \
-  (var) = (__typeof (var)) ((uintptr_t) (var) ^ __pointer_chk_guard_local)
-#  define PTR_DEMANGLE(var)     PTR_MANGLE (var)
-# endif
-#else
-# ifdef __ASSEMBLER__
-#  define PTR_MANGLE_LOAD(guard, tmp)					\
-  LDR_GLOBAL (guard, tmp, C_SYMBOL_NAME(__pointer_chk_guard), 0);
-#  define PTR_MANGLE(dst, src, guard, tmp)				\
-  PTR_MANGLE_LOAD(guard, tmp);						\
-  PTR_MANGLE2(dst, src, guard)
-/* Use PTR_MANGLE2 for efficiency if guard is already loaded.  */
-#  define PTR_MANGLE2(dst, src, guard)		\
-  eor dst, src, guard
-#  define PTR_DEMANGLE(dst, src, guard, tmp)	\
-  PTR_MANGLE (dst, src, guard, tmp)
-#  define PTR_DEMANGLE2(dst, src, guard)	\
-  PTR_MANGLE2 (dst, src, guard)
-# else
-extern uintptr_t __pointer_chk_guard attribute_relro;
-#  define PTR_MANGLE(var) \
-  (var) = (__typeof (var)) ((uintptr_t) (var) ^ __pointer_chk_guard)
-#  define PTR_DEMANGLE(var)     PTR_MANGLE (var)
-# endif
-#endif