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>

1 files changed, 62 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/alpha/pointer_guard.h b/sysdeps/unix/sysv/linux/alpha/pointer_guard.h
new file mode 100644
index 0000000000..d4d513d816
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/alpha/pointer_guard.h
@@ -0,0 +1,62 @@
+/* Pointer guard implementation.  Alpha version.
+   Copyright (C) 2006-2022 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.  Note that tls access is slow enough that
+   we don't deoptimize things by placing the pointer check value there.  */
+
+#ifdef __ASSEMBLER__
+# if IS_IN (rtld)
+#  define PTR_MANGLE(dst, src, tmp)                             \
+        ldah    tmp, __pointer_chk_guard_local($29) !gprelhigh; \
+        ldq     tmp, __pointer_chk_guard_local(tmp) !gprellow;  \
+        xor     src, tmp, dst
+#  define PTR_MANGLE2(dst, src, tmp)                            \
+        xor     src, tmp, dst
+# elif defined SHARED
+#  define PTR_MANGLE(dst, src, tmp)             \
+        ldq     tmp, __pointer_chk_guard;       \
+        xor     src, tmp, dst
+# else
+#  define PTR_MANGLE(dst, src, tmp)             \
+        ldq     tmp, __pointer_chk_guard_local; \
+        xor     src, tmp, dst
+# endif
+# define PTR_MANGLE2(dst, src, tmp)             \
+        xor     src, tmp, dst
+# define PTR_DEMANGLE(dst, tmp)   PTR_MANGLE(dst, dst, tmp)
+# define PTR_DEMANGLE2(dst, tmp)  PTR_MANGLE2(dst, dst, tmp)
+#else
+# include <stdint.h>
+# if (IS_IN (rtld) \
+      || (!defined SHARED && (IS_IN (libc) \
+                              || IS_IN (libpthread))))
+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)
+# else
+extern uintptr_t __pointer_chk_guard attribute_relro;
+#  define PTR_MANGLE(var) \
+        (var) = (__typeof(var)) ((uintptr_t) (var) ^ __pointer_chk_guard)
+# endif
+# define PTR_DEMANGLE(var)  PTR_MANGLE(var)
+#endif /* ASSEMBLER */
+
+#endif /* POINTER_GUARD_H */