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56 lines
1.9 KiB
C
56 lines
1.9 KiB
C
/* Helper function to allocate shadow stack.
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Copyright (C) 2023-2025 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 <sysdep.h>
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#include <stdint.h>
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#include <errno.h>
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#include <sys/mman.h>
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#include <libc-pointer-arith.h>
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#include <allocate-shadow-stack.h>
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/* NB: This can be treated as a syscall by caller. */
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long int
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__allocate_shadow_stack (size_t stack_size,
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shadow_stack_size_t *child_stack)
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{
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#ifdef __NR_map_shadow_stack
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size_t shadow_stack_size
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= stack_size >> STACK_SIZE_TO_SHADOW_STACK_SIZE_SHIFT;
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/* Align shadow stack to 8 bytes. */
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shadow_stack_size = ALIGN_UP (shadow_stack_size, 8);
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/* Since sigaltstack shares shadow stack with the current context in
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the thread, add extra 20 stack frames in shadow stack for signal
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handlers. */
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shadow_stack_size += 20 * 8;
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void *shadow_stack = (void *)INLINE_SYSCALL_CALL
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(map_shadow_stack, NULL, shadow_stack_size, SHADOW_STACK_SET_TOKEN);
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/* Report the map_shadow_stack error. */
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if (shadow_stack == MAP_FAILED)
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return -errno;
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/* Save the shadow stack base and size on child stack. */
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child_stack[0] = (uintptr_t) shadow_stack;
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child_stack[1] = shadow_stack_size;
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return 0;
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#else
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return -ENOSYS;
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#endif
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}
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