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9885d13b66
Userspace ucontext needs to store GCSPR, it does not have to be compatible with the kernel ucontext. For now we use the linux struct gcs_context layout but only use the gcspr field from it. Similar implementation to the longjmp code, supports switching GCS if the target GCS is capped, and unwinding a continuous GCS to a previous state. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com> Reviewed-by: Carlos O'Donell <carlos@redhat.com>
187 lines
4.8 KiB
ArmAsm
187 lines
4.8 KiB
ArmAsm
/* Set current context.
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Copyright (C) 2009-2025 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 License as
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published by the Free Software Foundation; either version 2.1 of the
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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 "ucontext_i.h"
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#include "ucontext-internal.h"
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/* int __setcontext (const ucontext_t *ucp)
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Restores the machine context in UCP and thereby resumes execution
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in that context.
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This implementation is intended to be used for *synchronous* context
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switches only. Therefore, it does not have to restore anything
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other than the PRESERVED state. */
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.text
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ENTRY (__setcontext)
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PTR_ARG (0)
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/* Save a copy of UCP. */
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mov x9, x0
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/* Set the signal mask with
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rt_sigprocmask (SIG_SETMASK, mask, NULL, _NSIG/8). */
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mov x0, #SIG_SETMASK
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add x1, x9, #UCONTEXT_SIGMASK
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mov x2, #0
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mov x3, #_NSIG8
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mov x8, SYS_ify (rt_sigprocmask)
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svc 0
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cbz x0, 1f
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b C_SYMBOL_NAME (__syscall_error)
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1:
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/* Disable ZA of SME. */
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#if HAVE_AARCH64_PAC_RET
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PACIASP
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cfi_window_save
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#endif
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stp x29, x30, [sp, -16]!
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cfi_adjust_cfa_offset (16)
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cfi_rel_offset (x29, 0)
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cfi_rel_offset (x30, 8)
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mov x29, sp
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bl __libc_arm_za_disable
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ldp x29, x30, [sp], 16
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cfi_adjust_cfa_offset (-16)
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cfi_restore (x29)
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cfi_restore (x30)
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#if HAVE_AARCH64_PAC_RET
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AUTIASP
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cfi_window_save
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#endif
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/* Restore the general purpose registers. */
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mov x0, x9
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cfi_def_cfa (x0, 0)
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cfi_offset (x18, oX0 + 18 * SZREG)
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cfi_offset (x19, oX0 + 19 * SZREG)
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cfi_offset (x20, oX0 + 20 * SZREG)
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cfi_offset (x21, oX0 + 21 * SZREG)
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cfi_offset (x22, oX0 + 22 * SZREG)
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cfi_offset (x23, oX0 + 23 * SZREG)
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cfi_offset (x24, oX0 + 24 * SZREG)
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cfi_offset (x25, oX0 + 25 * SZREG)
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cfi_offset (x26, oX0 + 26 * SZREG)
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cfi_offset (x27, oX0 + 27 * SZREG)
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cfi_offset (x28, oX0 + 28 * SZREG)
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cfi_offset (x29, oX0 + 29 * SZREG)
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cfi_offset (x30, oX0 + 30 * SZREG)
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cfi_offset ( d8, oV0 + 8 * SZVREG)
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cfi_offset ( d9, oV0 + 9 * SZVREG)
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cfi_offset (d10, oV0 + 10 * SZVREG)
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cfi_offset (d11, oV0 + 11 * SZVREG)
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cfi_offset (d12, oV0 + 12 * SZVREG)
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cfi_offset (d13, oV0 + 13 * SZVREG)
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cfi_offset (d14, oV0 + 14 * SZVREG)
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cfi_offset (d15, oV0 + 15 * SZVREG)
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ldp x18, x19, [x0, oX0 + 18 * SZREG]
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ldp x20, x21, [x0, oX0 + 20 * SZREG]
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ldp x22, x23, [x0, oX0 + 22 * SZREG]
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ldp x24, x25, [x0, oX0 + 24 * SZREG]
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ldp x26, x27, [x0, oX0 + 26 * SZREG]
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ldp x28, x29, [x0, oX0 + 28 * SZREG]
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ldr x30, [x0, oX0 + 30 * SZREG]
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ldr x2, [x0, oSP]
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mov sp, x2
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/* Check for FP SIMD context. We don't support restoring
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contexts created by the kernel, so this context must have
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been created by getcontext. Hence we can rely on the
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first extension block being the FP SIMD context. */
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add x2, x0, #oEXTENSION
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mov w3, #(FPSIMD_MAGIC & 0xffff)
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movk w3, #(FPSIMD_MAGIC >> 16), lsl #16
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ldr w1, [x2, #oHEAD + oMAGIC]
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cmp w1, w3
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b.ne 2f
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/* Restore the FP SIMD context. */
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add x3, x2, #oV0 + 8 * SZVREG
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ldp q8, q9, [x3], #2 * SZVREG
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ldp q10, q11, [x3], #2 * SZVREG
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ldp q12, q13, [x3], #2 * SZVREG
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ldp q14, q15, [x3], #2 * SZVREG
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add x3, x2, oFPSR
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ldr w4, [x3]
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msr fpsr, x4
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ldr w4, [x3, oFPCR - oFPSR]
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msr fpcr, x4
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/* Restore the GCS. */
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mov x16, 1 /* _CHKFEAT_GCS */
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CHKFEAT_X16
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tbnz x16, 0, L(gcs_done)
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/* Get target GCS from GCS context. */
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ldr w1, [x2, #oHEAD + oSIZE]
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add x2, x2, x1
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mov w3, #(GCS_MAGIC & 0xffff)
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movk w3, #(GCS_MAGIC >> 16), lsl #16
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ldr w1, [x2, #oHEAD + oMAGIC]
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cmp w1, w3
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b.ne L(gcs_done)
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ldr x3, [x2, #oGCSPR]
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MRS_GCSPR (x2)
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mov x4, x3
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/* x2: GCSPR now. x3, x4: target GCSPR. x5, x6: tmp regs. */
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L(gcs_scan):
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cmp x2, x4
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b.eq L(gcs_pop)
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sub x4, x4, 8
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/* Check for a cap token. */
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ldr x5, [x4]
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and x6, x4, 0xfffffffffffff000
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orr x6, x6, 1
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cmp x5, x6
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b.ne L(gcs_scan)
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L(gcs_switch):
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add x2, x4, 8
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GCSSS1 (x4)
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GCSSS2 (xzr)
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L(gcs_pop):
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cmp x2, x3
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b.eq L(gcs_done)
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GCSPOPM (xzr)
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add x2, x2, 8
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b L(gcs_pop)
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L(gcs_done):
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2:
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ldr x16, [x0, oPC]
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/* Restore arg registers. */
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ldp x2, x3, [x0, oX0 + 2 * SZREG]
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ldp x4, x5, [x0, oX0 + 4 * SZREG]
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ldp x6, x7, [x0, oX0 + 6 * SZREG]
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ldp x0, x1, [x0, oX0 + 0 * SZREG]
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/* Jump to the new pc value. */
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br x16
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PSEUDO_END (__setcontext)
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weak_alias (__setcontext, setcontext)
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ENTRY (__startcontext)
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mov x0, x19
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cbnz x0, __setcontext
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1: b HIDDEN_JUMPTARGET (exit)
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END (__startcontext)
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