powerpc64: Add memory protection key support [BZ #23202]

The 32-bit protection key behavior is somewhat unclear on 32-bit powerpc,
so this change is restricted to the 64-bit variants.

Flag translation is needed because of hardware differences between the
POWER implementation (read and write flags) and the Intel implementation
(write and read+write flags).

1 files changed, 42 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/pkey_get.c b/sysdeps/unix/sysv/linux/powerpc/powerpc64/pkey_get.c
new file mode 100644
index 0000000000..856ba061b9
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/pkey_get.c
@@ -0,0 +1,42 @@
+/* Reading the per-thread memory protection key, powerpc64 version.
+   Copyright (C) 2017-2020 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/>.  */
+
+#include <arch-pkey.h>
+#include <errno.h>
+#include <sys/mman.h>
+
+int
+pkey_get (int key)
+{
+  if (key < 0 || key > PKEY_MAX)
+    {
+      __set_errno (EINVAL);
+      return -1;
+    }
+  unsigned int index = pkey_index (key);
+  unsigned long int amr = pkey_read ();
+  unsigned int bits = (amr >> index) & 3;
+
+  /* Translate from AMR values.  PKEY_AMR_READ standing alone is not
+     currently representable.  */
+  if (bits & PKEY_AMR_READ)
+    return PKEY_DISABLE_ACCESS;
+  else if (bits == PKEY_AMR_WRITE)
+    return PKEY_DISABLE_WRITE;
+  return 0;
+}