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eeedfc2f74
No functional change here, just a small refactoring to simplify using __alloc_gcs() for allocating shadow stacks. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
108 lines
3.0 KiB
C
108 lines
3.0 KiB
C
/* Create new context.
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Copyright (C) 2002-2025 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 <stdarg.h>
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#include <stdint.h>
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#include <ucontext.h>
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#include <sys/mman.h>
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#include "aarch64-gcs.h"
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#define GCS_MAGIC 0x47435300
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static struct _aarch64_ctx *extension (void *p)
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{
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return p;
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}
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/* Allocate GCS stack for new context. */
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static void *
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alloc_makecontext_gcs (size_t stack_size)
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{
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void *gcsp = __alloc_gcs (stack_size, NULL);
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if (gcsp == NULL)
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/* ENOSYS, bad size or OOM. */
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abort ();
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return gcsp;
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}
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/* makecontext sets up a stack and the registers for the
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user context. The stack looks like this:
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+-----------------------+
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| padding as required |
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+-----------------------+
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sp -> | parameter 7-n |
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+-----------------------+
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The registers are set up like this:
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%x0 .. %x7: parameter 1 to 8
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%x19 : uc_link
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%sp : stack pointer.
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*/
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void
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__makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
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{
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extern void __startcontext (void);
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uint64_t *sp;
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va_list ap;
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int i;
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sp = (uint64_t *)
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((uintptr_t) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
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/* Allocate stack arguments. */
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sp -= argc < 8 ? 0 : argc - 8;
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/* Keep the stack aligned. */
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sp = (uint64_t *) (((uintptr_t) sp) & -16L);
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ucp->uc_mcontext.regs[19] = (uintptr_t) ucp->uc_link;
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ucp->uc_mcontext.regs[20] = (uintptr_t) func;
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ucp->uc_mcontext.sp = (uintptr_t) sp;
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ucp->uc_mcontext.pc = (uintptr_t) __startcontext;
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ucp->uc_mcontext.regs[29] = (uintptr_t) 0;
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ucp->uc_mcontext.regs[30] = (uintptr_t) 0;
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void *p = ucp->uc_mcontext.__reserved;
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if (extension (p)->magic == FPSIMD_MAGIC)
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p = (char *)p + extension (p)->size;
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if (extension (p)->magic == GCS_MAGIC)
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{
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/* Using the kernel struct gcs_context layout. */
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struct { uint64_t x, gcspr, y, z; } *q = p;
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/* TODO: this allocation remains mapped even after thread
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that uses it exits. */
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q->gcspr = (uint64_t) alloc_makecontext_gcs (ucp->uc_stack.ss_size);
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}
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va_start (ap, argc);
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for (i = 0; i < argc; ++i)
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if (i < 8)
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ucp->uc_mcontext.regs[i] = va_arg (ap, uint64_t);
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else
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sp[i - 8] = va_arg (ap, uint64_t);
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va_end (ap);
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}
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weak_alias (__makecontext, makecontext)
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