[glibc/arm/morello/main] cheri: aarch64: Add header for CHERI permissions

[Szabolcs Nagy <nsz@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=2d0278e6d7ed487d940be0df2b06383db1fcde7a

commit 2d0278e6d7ed487d940be0df2b06383db1fcde7a
Author: Carlos Eduardo Seo <carlos.seo@arm.com>
Date:   Mon Jul 18 14:47:32 2022 -0300

    cheri: aarch64: Add header for CHERI permissions
    
    New file containing the capability permission bits.
    
    The capability permission bits are defined in the Arm Architecture
    Reference Manual Suplement- Morello for A-Profile Architecture:
    
    https://developer.arm.com/documentation/ddi0606/latest

Diff:
---
 sysdeps/aarch64/morello/cheri_perms.h | 66 +++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/sysdeps/aarch64/morello/cheri_perms.h b/sysdeps/aarch64/morello/cheri_perms.h
new file mode 100644
index 0000000000..8c44233016
--- /dev/null
+++ b/sysdeps/aarch64/morello/cheri_perms.h
@@ -0,0 +1,66 @@
+/* Copyright (C) 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 _AARCH64_MORELLO_CHERI_PERMS_H
+#define _AARCH64_MORELLO_CHERI_PERMS_H
+
+/* Capability permission bits.  These are defined in the Arm Architecture
+   Reference Manual Suplement- Morello for A-Profile Architecture:
+   https://developer.arm.com/documentation/ddi0606/latest  */
+#define CAP_PERM_LOAD (1 << 17)
+#define CAP_PERM_STORE (1 << 16)
+#define CAP_PERM_EXECUTE (1 << 15)
+#define CAP_PERM_LOAD_CAP (1 << 14)
+#define CAP_PERM_STORE_CAP (1 << 13)
+#define CAP_PERM_STORE_LOCAL (1 << 12)
+#define CAP_PERM_SEAL (1 << 11)
+#define CAP_PERM_UNSEAL (1 << 10)
+#define CAP_PERM_COMPARTMENT_ID (1 << 7)
+#define CAP_PERM_MUTABLE_LOAD (1 << 6)
+#define CAP_PERM_EXECUTIVE (1 << 1)
+#define CAP_PERM_GLOBAL (1 << 0)
+
+/* Used with __builtin_cheri_perms_and.  */
+#define CAP_PERM_MASK_BASE (-1UL ^ ( \
+  CAP_PERM_LOAD | \
+  CAP_PERM_STORE | \
+  CAP_PERM_EXECUTE | \
+  CAP_PERM_LOAD_CAP | \
+  CAP_PERM_STORE_CAP | \
+  CAP_PERM_SEAL | \
+  CAP_PERM_UNSEAL | \
+  CAP_PERM_COMPARTMENT_ID))
+#define CAP_PERM_MASK_R (CAP_PERM_MASK_BASE | CAP_PERM_LOAD | CAP_PERM_LOAD_CAP)
+#define CAP_PERM_MASK_RW (CAP_PERM_MASK_R | CAP_PERM_STORE | CAP_PERM_STORE_CAP)
+#define CAP_PERM_MASK_RX (CAP_PERM_MASK_R | CAP_PERM_EXECUTE)
+
+#define STACK_CAP_PERM_PCS ( \
+  CAP_PERM_LOAD | \
+  CAP_PERM_STORE | \
+  CAP_PERM_LOAD_CAP | \
+  CAP_PERM_STORE_CAP | \
+  CAP_PERM_MUTABLE_LOAD)
+
+/* Check if stack is valid according to stack PCS rules.  Only permissions
+   are checked, seal and invalid tag cause fault on access.  */
+#define STACK_CAP_CHECK(stack, size) \
+  ({unsigned long __perm = __builtin_cheri_perms_get (stack); \
+    (__perm & (CAP_PERM_GLOBAL|CAP_PERM_STORE_LOCAL)) \
+    && (__perm & STACK_CAP_PERM_PCS) == STACK_CAP_PERM_PCS;})
+
+#endif