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114 lines
3.9 KiB
C
114 lines
3.9 KiB
C
/* Changing the per-thread memory protection key, AArch64 version.
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Copyright (C) 2024-2025 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <arch-pkey.h>
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#include <errno.h>
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#include <sys/mman.h>
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#define MAX_PKEY_RIGHTS (PKEY_DISABLE_ACCESS | \
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PKEY_DISABLE_WRITE | PKEY_DISABLE_EXECUTE | PKEY_DISABLE_READ)
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int
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pkey_set (int key, unsigned int restrictions)
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{
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if (key < 0 || key > 15 || restrictions > MAX_PKEY_RIGHTS)
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{
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__set_errno (EINVAL);
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return -1;
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}
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unsigned long mask = S1POE_PERM_MASK << (S1POE_BITS_PER_POI * key);
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unsigned long por_el0 = pkey_read ();
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unsigned long perm;
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/* POR ot PKEY mapping: -WXR
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PKEY_UNRESTRICTED => 0111 (read-write-execute)
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PKEY_DISABLE_ACCESS => removes R and W access
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PKEY_DISABLE_READ => removes R access
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PKEY_DISABLE_WRITE => removes W access
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PKEY_DISABLE_EXECUTE => removes X access
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Either of PKEY_DISABLE_ACCESS or PKEY_DISABLE_READ removes R access.
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Either of PKEY_DISABLE_ACCESS or PKEY_DISABLE_WRITE removes W access.
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Using PKEY_DISABLE_ACCESS along with only one of PKEY_DISABLE_READ or
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PKEY_DISABLE_WRITE is considered to be in error.
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Furthermore, for avoidance of doubt:
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PKEY flags Permissions
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rxwa -WXR
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1111 => 0000 S1POE_PERM_NO_ACCESS
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1110 => 0000 S1POE_PERM_NO_ACCESS
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1101 => EINVAL
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1100 => 0100 S1POE_PERM_W
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1011 => 0010 S1POE_PERM_X
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1010 => 0010 S1POE_PERM_X
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1001 => EINVAL
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1000 => 0110 S1POE_PERM_WX
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0111 => EINVAL
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0110 => 0001 S1POE_PERM_R
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0101 => 0000 S1POE_PERM_NO_ACCESS
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0100 => 0101 S1POE_PERM_RW
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0011 => EINVAL
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0010 => 0011 S1POE_PERM_RX
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0001 => 0010 S1POE_PERM_X
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0000 => 0111 S1POE_PERM_RWX */
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switch (restrictions)
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{
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case PKEY_DISABLE_ACCESS | PKEY_DISABLE_READ | PKEY_DISABLE_WRITE
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| PKEY_DISABLE_EXECUTE:
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case PKEY_DISABLE_ACCESS | PKEY_DISABLE_EXECUTE:
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case PKEY_DISABLE_ACCESS | PKEY_DISABLE_READ | PKEY_DISABLE_EXECUTE:
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case PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE | PKEY_DISABLE_EXECUTE:
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case PKEY_DISABLE_READ | PKEY_DISABLE_WRITE | PKEY_DISABLE_EXECUTE:
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perm = S1POE_PERM_NO_ACCESS;
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break;
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case PKEY_DISABLE_READ | PKEY_DISABLE_EXECUTE:
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perm = S1POE_PERM_W;
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break;
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case PKEY_DISABLE_ACCESS | PKEY_DISABLE_READ:
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case PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE:
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case PKEY_DISABLE_ACCESS | PKEY_DISABLE_READ | PKEY_DISABLE_WRITE:
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case PKEY_DISABLE_READ | PKEY_DISABLE_WRITE:
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case PKEY_DISABLE_ACCESS:
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perm = S1POE_PERM_X;
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break;
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case PKEY_DISABLE_READ:
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perm = S1POE_PERM_WX;
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break;
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case PKEY_DISABLE_WRITE | PKEY_DISABLE_EXECUTE:
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perm = S1POE_PERM_R;
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break;
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case PKEY_DISABLE_EXECUTE:
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perm = S1POE_PERM_RW;
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break;
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case PKEY_DISABLE_WRITE:
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perm = S1POE_PERM_RX;
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break;
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case PKEY_UNRESTRICTED:
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perm = S1POE_PERM_RWX;
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break;
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default:
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__set_errno (EINVAL);
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return -1;
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}
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por_el0 = (por_el0 & ~mask) | (perm << (S1POE_BITS_PER_POI * key));
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pkey_write (por_el0);
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return 0;
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}
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