github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/test/syscalls/linux/rseq/critical_arm64.S (about)

     1  // Copyright 2020 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // Restartable sequences critical sections.
    16  
    17  // Loops continuously until aborted.
    18  //
    19  // void rseq_loop(struct rseq* r, struct rseq_cs* cs)
    20  
    21    .text
    22    .globl  rseq_loop
    23    .type   rseq_loop, @function
    24  
    25  rseq_loop:
    26    b begin
    27  
    28    // Abort block before the critical section.
    29    // Abort signature.
    30    .byte 0x90, 0x90, 0x90, 0x90
    31    .globl  rseq_loop_early_abort
    32  rseq_loop_early_abort:
    33    ret
    34  
    35  begin:
    36    // r->rseq_cs = cs
    37    str x1, [x0, #8]
    38  
    39    // N.B. rseq_cs will be cleared by any preempt, even outside the critical
    40    // section. Thus it must be set in or immediately before the critical section
    41    // to ensure it is not cleared before the section begins.
    42    .globl  rseq_loop_start
    43  rseq_loop_start:
    44    b rseq_loop_start
    45  
    46    // "Pre-commit": extra instructions inside the critical section.  These are
    47    // used as the abort point in TestAbortPreCommit, which is not valid.
    48    .globl  rseq_loop_pre_commit
    49  rseq_loop_pre_commit:
    50    // Extra abort signature + nop for TestAbortPostCommit.
    51    .byte 0x90, 0x90, 0x90, 0x90
    52    nop
    53  
    54    // "Post-commit": never reached in this case.
    55    .globl  rseq_loop_post_commit
    56  rseq_loop_post_commit:
    57  
    58    // Abort signature.
    59    .byte 0x90, 0x90, 0x90, 0x90
    60  
    61    .globl  rseq_loop_abort
    62  rseq_loop_abort:
    63    ret
    64  
    65    .size  rseq_loop,.-rseq_loop
    66    .section  .note.GNU-stack,"",@progbits