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/* Changing the per-thread memory protection key, AArch64 version.
Copyright (C) 2024-2025 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/>. */
#include <arch-pkey.h>
#include <errno.h>
#include <sys/mman.h>
#define MAX_PKEY_RIGHTS (PKEY_DISABLE_ACCESS | \
PKEY_DISABLE_WRITE | PKEY_DISABLE_EXECUTE | PKEY_DISABLE_READ)
int
pkey_set (int key, unsigned int restrictions)
{
if (key < 0 || key > 15 || restrictions > MAX_PKEY_RIGHTS)
{
__set_errno (EINVAL);
return -1;
}
unsigned long mask = S1POE_PERM_MASK << (S1POE_BITS_PER_POI * key);
unsigned long por_el0 = pkey_read ();
unsigned long perm;
/* POR ot PKEY mapping: -WXR
PKEY_UNRESTRICTED => 0111 (read-write-execute)
PKEY_DISABLE_ACCESS => removes R and W access
PKEY_DISABLE_READ => removes R access
PKEY_DISABLE_WRITE => removes W access
PKEY_DISABLE_EXECUTE => removes X access
Either of PKEY_DISABLE_ACCESS or PKEY_DISABLE_READ removes R access.
Either of PKEY_DISABLE_ACCESS or PKEY_DISABLE_WRITE removes W access.
Using PKEY_DISABLE_ACCESS along with only one of PKEY_DISABLE_READ or
PKEY_DISABLE_WRITE is considered to be in error.
Furthermore, for avoidance of doubt:
PKEY flags Permissions
rxwa -WXR
1111 => 0000 S1POE_PERM_NO_ACCESS
1110 => 0000 S1POE_PERM_NO_ACCESS
1101 => EINVAL
1100 => 0100 S1POE_PERM_W
1011 => 0010 S1POE_PERM_X
1010 => 0010 S1POE_PERM_X
1001 => EINVAL
1000 => 0110 S1POE_PERM_WX
0111 => EINVAL
0110 => 0001 S1POE_PERM_R
0101 => 0000 S1POE_PERM_NO_ACCESS
0100 => 0101 S1POE_PERM_RW
0011 => EINVAL
0010 => 0011 S1POE_PERM_RX
0001 => 0010 S1POE_PERM_X
0000 => 0111 S1POE_PERM_RWX */
switch (restrictions)
{
case PKEY_DISABLE_ACCESS | PKEY_DISABLE_READ | PKEY_DISABLE_WRITE
| PKEY_DISABLE_EXECUTE:
case PKEY_DISABLE_ACCESS | PKEY_DISABLE_EXECUTE:
case PKEY_DISABLE_ACCESS | PKEY_DISABLE_READ | PKEY_DISABLE_EXECUTE:
case PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE | PKEY_DISABLE_EXECUTE:
case PKEY_DISABLE_READ | PKEY_DISABLE_WRITE | PKEY_DISABLE_EXECUTE:
perm = S1POE_PERM_NO_ACCESS;
break;
case PKEY_DISABLE_READ | PKEY_DISABLE_EXECUTE:
perm = S1POE_PERM_W;
break;
case PKEY_DISABLE_ACCESS | PKEY_DISABLE_READ:
case PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE:
case PKEY_DISABLE_ACCESS | PKEY_DISABLE_READ | PKEY_DISABLE_WRITE:
case PKEY_DISABLE_READ | PKEY_DISABLE_WRITE:
case PKEY_DISABLE_ACCESS:
perm = S1POE_PERM_X;
break;
case PKEY_DISABLE_READ:
perm = S1POE_PERM_WX;
break;
case PKEY_DISABLE_WRITE | PKEY_DISABLE_EXECUTE:
perm = S1POE_PERM_R;
break;
case PKEY_DISABLE_EXECUTE:
perm = S1POE_PERM_RW;
break;
case PKEY_DISABLE_WRITE:
perm = S1POE_PERM_RX;
break;
case PKEY_UNRESTRICTED:
perm = S1POE_PERM_RWX;
break;
default:
__set_errno (EINVAL);
return -1;
}
por_el0 = (por_el0 & ~mask) | (perm << (S1POE_BITS_PER_POI * key));
pkey_write (por_el0);
return 0;
}
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