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>

3 files changed, 44 insertions, 19 deletions

diff --git a/sysdeps/unix/sysv/linux/sh/____longjmp_chk.S b/sysdeps/unix/sysv/linux/sh/____longjmp_chk.S
index e821e158c4..cf69926316 100644
--- a/sysdeps/unix/sysv/linux/sh/____longjmp_chk.S
+++ b/sysdeps/unix/sysv/linux/sh/____longjmp_chk.S
@@ -16,6 +16,7 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <sysdep.h>
+#include <pointer_guard.h>
 
 #include <sigaltstack-offsets.h>
 
diff --git a/sysdeps/unix/sysv/linux/sh/pointer_guard.h b/sysdeps/unix/sysv/linux/sh/pointer_guard.h
new file mode 100644
index 0000000000..32a571d496
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/sh/pointer_guard.h
@@ -0,0 +1,43 @@
+/* Pointer obfuscation implenentation.  Generic (no-op) version.
+   Copyright (C) 2005-2022 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
+
+#if IS_IN (rtld)
+/* We cannot use the thread descriptor because in ld.so we use setjmp
+   earlier than the descriptor is initialized.  Using a global variable
+   is too complicated here since we have no PC-relative addressing mode.  */
+# include <sysdeps/generic/pointer_guard.h>
+#else
+# ifdef __ASSEMBLER__
+#  define PTR_MANGLE(reg, tmp) \
+     stc gbr,tmp; mov.l @(POINTER_GUARD,tmp),tmp; xor tmp,reg
+#  define PTR_MANGLE2(reg, tmp) xor tmp,reg
+#  define PTR_DEMANGLE(reg, tmp)        PTR_MANGLE (reg, tmp)
+#  define PTR_DEMANGLE2(reg, tmp)       PTR_MANGLE2 (reg, tmp)
+# else
+#  include <stdint.h>
+#  include <tls.h>
+#  define PTR_MANGLE(var) \
+     (var) = (void *) ((uintptr_t) (var) ^ THREAD_GET_POINTER_GUARD ())
+#  define PTR_DEMANGLE(var)     PTR_MANGLE (var)
+# endif
+#endif
+
+#endif /* POINTER_GUARD_H */
diff --git a/sysdeps/unix/sysv/linux/sh/sysdep.h b/sysdeps/unix/sysv/linux/sh/sysdep.h
index e9e13cd184..a2f43f68c3 100644
--- a/sysdeps/unix/sysv/linux/sh/sysdep.h
+++ b/sysdeps/unix/sysv/linux/sh/sysdep.h
@@ -315,23 +315,4 @@
 
 #endif	/* __ASSEMBLER__ */
 
-/* Pointer mangling support.  */
-#if IS_IN (rtld)
-/* We cannot use the thread descriptor because in ld.so we use setjmp
-   earlier than the descriptor is initialized.  Using a global variable
-   is too complicated here since we have no PC-relative addressing mode.  */
-#else
-# ifdef __ASSEMBLER__
-#  define PTR_MANGLE(reg, tmp) \
-     stc gbr,tmp; mov.l @(POINTER_GUARD,tmp),tmp; xor tmp,reg
-#  define PTR_MANGLE2(reg, tmp)	xor tmp,reg
-#  define PTR_DEMANGLE(reg, tmp)	PTR_MANGLE (reg, tmp)
-#  define PTR_DEMANGLE2(reg, tmp)	PTR_MANGLE2 (reg, tmp)
-# else
-#  define PTR_MANGLE(var) \
-     (var) = (void *) ((uintptr_t) (var) ^ THREAD_GET_POINTER_GUARD ())
-#  define PTR_DEMANGLE(var)	PTR_MANGLE (var)
-# endif
-#endif
-
 #endif /* linux/sh/sysdep.h */