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/* Modify saved context.
Copyright (C) 2009-2025 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 <sysdep.h>
#include "ucontext_i.h"
#include "ucontext-internal.h"
/* int swapcontext (ucontext_t *oucp, const ucontext_t *ucp) */
.text
ENTRY(__swapcontext)
PTR_ARG (0)
/* Set the value returned when swapcontext() returns in this context.
And set up x1 to become the return address of the caller, so we
can return there with a normal RET instead of an indirect jump. */
stp xzr, x30, [x0, oX0 + 0 * SZREG]
/* With GCS, swapcontext calls are followed by BTI J, otherwise
we have to be compatible with old BTI enabled binaries. */
mov x16, 1 /* _CHKFEAT_GCS */
CHKFEAT_X16
tbz x16, 0, L(skip_x30_redirect)
/* Arrange the oucp context to return to 2f. */
adr x30, 2f
L(skip_x30_redirect):
stp x18, x19, [x0, oX0 + 18 * SZREG]
stp x20, x21, [x0, oX0 + 20 * SZREG]
stp x22, x23, [x0, oX0 + 22 * SZREG]
stp x24, x25, [x0, oX0 + 24 * SZREG]
stp x26, x27, [x0, oX0 + 26 * SZREG]
stp x28, x29, [x0, oX0 + 28 * SZREG]
str x30, [x0, oX0 + 30 * SZREG]
str x30, [x0, oPC]
mov x2, sp
str x2, [x0, oSP]
/* Figure out where to place the first context extension
block. */
add x2, x0, #oEXTENSION
/* Write the context extension fpsimd header. */
mov w3, #(FPSIMD_MAGIC & 0xffff)
movk w3, #(FPSIMD_MAGIC >> 16), lsl #16
str w3, [x2, #oHEAD + oMAGIC]
mov w3, #FPSIMD_CONTEXT_SIZE
str w3, [x2, #oHEAD + oSIZE]
/* Fill in the FP SIMD context. */
add x3, x2, #oV0 + 8 * SZVREG
stp q8, q9, [x3], #2 * SZVREG
stp q10, q11, [x3], #2 * SZVREG
stp q12, q13, [x3], #2 * SZVREG
stp q14, q15, [x3], #2 * SZVREG
add x3, x2, #oFPSR
mrs x4, fpsr
str w4, [x3, #oFPSR - oFPSR]
mrs x4, fpcr
str w4, [x3, #oFPCR - oFPSR]
add x2, x2, #FPSIMD_CONTEXT_SIZE
/* Save the GCSPR. */
tbnz x16, 0, L(gcs_done)
mov w3, #(GCS_MAGIC & 0xffff)
movk w3, #(GCS_MAGIC >> 16), lsl #16
str w3, [x2, #oHEAD + oMAGIC]
mov w3, #GCS_CONTEXT_SIZE
str w3, [x2, #oHEAD + oSIZE]
MRS_GCSPR (x4)
add x4, x4, 8 /* GCSPR of the caller. */
str x4, [x2, #oGCSPR]
add x2, x2, #GCS_CONTEXT_SIZE
L(gcs_done):
/* Write the termination context extension header. */
str wzr, [x2, #oHEAD + oMAGIC]
str wzr, [x2, #oHEAD + oSIZE]
/* Preserve ucp. */
mov x9, x1
/* rt_sigprocmask (SIG_SETMASK, &ucp->uc_sigmask, &oucp->uc_sigmask,
_NSIG8) */
/* Grab the signal mask */
/* rt_sigprocmask (SIG_BLOCK, NULL, &ucp->uc_sigmask, _NSIG8) */
add x2, x0, #UCONTEXT_SIGMASK
mov x0, SIG_BLOCK
mov x1, 0
mov x3, _NSIG8
mov x8, SYS_ify (rt_sigprocmask)
svc 0
cbnz x0, 1f
mov x0, x9
b JUMPTARGET (__setcontext)
1:
b C_SYMBOL_NAME(__syscall_error)
2:
/* The oucp context is restored here via an indirect branch,
x1 must be restored too which has the real return address. */
BTI_J
mov x30, x1
RET
PSEUDO_END (__swapcontext)
weak_alias (__swapcontext, swapcontext)
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