x86/um/stub_64.S

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 #include <as-layout.h>
0003
0004 .section .__syscall_stub, "ax"
0005     .globl batch_syscall_stub
0006 batch_syscall_stub:
0007     /* %rsp has the pointer to first operation */
0008     mov %rsp, %rbx
0009     add $0x10, %rsp
0010 again:
0011     /* load length of additional data */
0012     mov 0x0(%rsp), %rax
0013
0014     /* if(length == 0) : end of list */
0015     /* write possible 0 to header */
0016     mov %rax, 8(%rbx)
0017     cmp $0, %rax
0018     jz  done
0019
0020     /* save current pointer */
0021     mov %rsp, 8(%rbx)
0022
0023     /* skip additional data */
0024     add %rax, %rsp
0025
0026     /* load syscall-# */
0027     pop %rax
0028
0029     /* load syscall params */
0030     pop %rdi
0031     pop %rsi
0032     pop %rdx
0033     pop %r10
0034     pop %r8
0035     pop %r9
0036
0037     /* execute syscall */
0038     syscall
0039
0040     /* check return value */
0041     pop %rcx
0042     cmp %rcx, %rax
0043     je  again
0044
0045 done:
0046     /* save return value */
0047     mov %rax, (%rbx)
0048
0049     /* stop */
0050     int3