2 files changed, 100 insertions, 0 deletions
diff --git a/sysdeps/aarch64/morello/libc-cap.h b/sysdeps/aarch64/morello/libc-cap.h
new file mode 100644
index 0000000000..d772e36dee
--- /dev/null
+++ b/sysdeps/aarch64/morello/libc-cap.h
@@ -0,0 +1,66 @@
+/* Support for allocations with narrow capability bounds.  Morello version.
+   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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _AARCH64_MORELLO_LIBC_CAP_H
+#define _AARCH64_MORELLO_LIBC_CAP_H 1
+
+/* No special alignment is needed for n <= __CAP_ALIGN_THRESHOLD
+   allocations, i.e. __libc_cap_align (n) <= MALLOC_ALIGNMENT.  */
+#define __CAP_ALIGN_THRESHOLD 32759
+
+/* Round up the allocation size so the allocated pointer bounds
+   can be represented.  Note: this may be called before any
+   checks on n, so it should work with all possible n values.  */
+static __always_inline size_t
+__libc_cap_roundup (size_t n)
+{
+  if (__glibc_unlikely (n > PTRDIFF_MAX))
+    return n;
+  return __builtin_cheri_round_representable_length (n);
+}
+
+/* Returns the alignment requirement for an allocation size n such
+   that the allocated pointer bounds can be represented.  Note:
+   same n should be used in __libc_cap_roundup and __libc_cap_align
+   and the results used together for __libc_cap_narrow.  */
+static __always_inline size_t
+__libc_cap_align (size_t n)
+{
+  return -__builtin_cheri_representable_alignment_mask (n);
+}
+
+/* Narrow the bounds of p to be [p, p+n).  Note: the original bounds
+   of p includes the entire mapping where p points to and that bound
+   should be recoverable by __libc_cap_widen.  Called with p aligned
+   and n sized according to __libc_cap_align and __libc_cap_roundup.  */
+static __always_inline void *
+__libc_cap_narrow (void *p, size_t n)
+{
+  return __builtin_cheri_bounds_set_exact (p, n);
+}
+
+/* Given a p with narrowed bound (output of __libc_cap_narrow) return
+   the same pointer with the internal wide bound.  */
+static __always_inline void *
+__libc_cap_widen (void *p)
+{
+  void *cap = __builtin_cheri_global_data_get ();
+  return __builtin_cheri_address_set (cap, p);
+}
+
+#endif
diff --git a/sysdeps/generic/libc-cap.h b/sysdeps/generic/libc-cap.h
new file mode 100644
index 0000000000..85ff2a6b61
--- /dev/null
+++ b/sysdeps/generic/libc-cap.h
@@ -0,0 +1,34 @@
+/* Support for allocations with narrow capability bounds.  Generic version.
+   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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _LIBC_CAP_H
+#define _LIBC_CAP_H 1
+
+/* Larger allocations may need special alignment via cap_align.  */
+#define __CAP_ALIGN_THRESHOLD SIZE_MAX
+
+/* Error if the identifiers bellow are used.  */
+void __libc_cap_link_error (void);
+
+#define __libc_cap_fail(rtype) (__libc_cap_link_error (), (rtype) 0)
+#define __libc_cap_roundup(n) __libc_cap_fail (size_t)
+#define __libc_cap_align(n) __libc_cap_fail (size_t)
+#define __libc_cap_narrow(p, n) __libc_cap_fail (void *)
+#define __libc_cap_widen(p) __libc_cap_fail (void *)
+
+#endif