196 lines
4.9 KiB
ArmAsm
196 lines
4.9 KiB
ArmAsm
define(`CC', `
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dnl')
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CC Copyright (C) 2023-2024 Free Software Foundation, Inc.
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CC
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CC This file is part of GNU Emacs.
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CC
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CC GNU Emacs is free software: you can redistribute it and/or modify
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CC it under the terms of the GNU General Public License as published
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CC by the Free Software Foundation, either version 3 of the License,
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CC or (at your option) any later version.
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CC
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CC GNU Emacs is distributed in the hope that it will be useful, but
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CC WITHOUT ANY WARRANTY; without even the implied warranty of
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CC MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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CC General Public License for more details.
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CC
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CC You should have received a copy of the GNU General Public License
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CC along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
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.section .text
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.global _start
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_start:
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dnl movq $35, %rax CC SYS_nanosleep
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dnl leaq timespec(%rip), %rdi
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dnl xorq %rsi, %rsi
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dnl syscall
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popq %r13 CC original SP
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popq %r15 CC size of load area.
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movq $-1, %r12 CC r12 is the interpreter fd
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.next_action:
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movq (%rsp), %r14 CC action number
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movq %r14, %r15 CC original action number
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andq $-17, %r14
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cmpq $0, %r14 CC open file?
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je .open_file
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cmpq $3, %r14 CC jump?
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je .rest_of_exec
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cmpq $4, %r14 CC anonymous mmap?
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je .do_mmap_anon
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.do_mmap:
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movq $9, %rax CC SYS_mmap
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movq 8(%rsp), %rdi CC address
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movq 16(%rsp), %r9 CC offset
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movq 24(%rsp), %rdx CC protection
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movq 32(%rsp), %rsi CC length
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movq 40(%rsp), %r10 CC flags
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CC set r8 to the primary fd unless r15 & 16
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testq $16, %r15
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movq %r12, %r8
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cmovzq %rbx, %r8
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.do_mmap_1:
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syscall
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cmpq $-1, %rax CC mmap failed
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je .perror
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movq 48(%rsp), %r9 CC clear
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testq %r9, %r9
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jz .continue
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movq 8(%rsp), %r10 CC start of mapping
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addq 32(%rsp), %r10 CC end of mapping
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subq %r9, %r10 CC start of clear area
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.again:
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testq %r9, %r9
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jz .continue
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subq $1, %r9
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movb $0, (%r10, %r9, 1)
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jmp .again
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.continue:
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leaq 56(%rsp), %rsp
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jmp .next_action
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.do_mmap_anon:
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movq $9, %rax CC SYS_mmap
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movq 8(%rsp), %rdi CC address
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movq 16(%rsp), %r9 CC offset
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movq 24(%rsp), %rdx CC protection
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movq 32(%rsp), %rsi CC length
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movq 40(%rsp), %r10 CC flags
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movq $-1, %r8 CC -1
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jmp .do_mmap_1
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.open_file:
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movq $2, %rax CC SYS_open
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leaq 8(%rsp), %rdi CC rdi = %rsp + 8
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xorq %rsi, %rsi CC flags = O_RDONLY
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xorq %rdx, %rdx CC mode = 0
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syscall
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cmpq $-1, %rax CC open failed
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jle .perror
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movq %rdi, %rsp CC rsp = start of string
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subq $1, %rsp
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movq %rsp, %r14 CC r14 = start of string
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.nextc:
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addq $1, %rsp
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movb (%rsp), %dil CC rdi = *rsp
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cmpb $47, %dil CC *rsp == '/'?
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jne .nextc1
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movq %rsp, %r14 CC r14 = rsp
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addq $1, %r14 CC r14 = char past separator
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.nextc1:
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cmpb $0, %dil CC *rsp == 0?
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jne .nextc
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addq $8, %rsp CC adjust past rsp prior to rounding
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andq $-8, %rsp CC round rsp up to the next quad
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testq $16, %r15 CC r15 & 16?
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jz .primary
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movq %rax, %r12 CC otherwise, move fd to r12
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jmp .next_action
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.primary:
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movq %rax, %rbx CC if not, move fd to rbx
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movq $157, %rax CC SYS_prctl
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movq $15, %rdi CC PR_SET_NAME
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movq %r14, %rsi CC arg1
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xorq %rdx, %rdx CC arg2
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xorq %r10, %r10 CC arg3
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xorq %r8, %r8 CC arg4
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xorq %r9, %r9 CC arg5
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syscall
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jmp .next_action
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.perror:
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movq %rax, %r12 CC error code
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negq %r12
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movq $1, %rax CC SYS_write
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movq $1, %rdi CC stdout
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leaq error(%rip), %rsi CC buffer
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movq $23, %rdx CC count
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syscall
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movq $60, %rax CC SYS_exit
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movq %r12, %rdi CC code
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syscall
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.rest_of_exec: CC rsp now points to six quads:
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movq %rsp, %r8 CC now, they are r8
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movq %r13, %rsp CC restore SP
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popq %r10 CC argc
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leaq 8(%rsp,%r10,8), %rsp CC now at start of environ
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.skip_environ:
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popq %r10 CC envp[N]
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testq %r10, %r10 CC envp[n]?
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jnz .skip_environ CC otherwise, rsp is now at the start of auxv
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.one_auxv:
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popq %rcx CC auxv type
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addq $8, %rsp CC skip value
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testq %rcx, %rcx CC is 0?
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jz .cleanup
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cmpq $3, %rcx CC is AT_PHDR?
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je .replace_phdr
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cmpq $4, %rcx CC is AT_PHENT?
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je .replace_phent
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cmpq $5, %rcx CC is AT_PHNUM?
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je .replace_phnum
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cmpq $9, %rcx CC is AT_ENTRY?
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je .replace_entry
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cmpq $7, %rcx CC is AT_BASE?
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je .replace_base
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jmp .one_auxv
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.replace_phdr:
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movq 40(%r8), %r9
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movq %r9, -8(%rsp) CC set at_phdr
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jmp .one_auxv
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.replace_phent:
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movq 24(%r8), %r9
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movq %r9, -8(%rsp) CC set at_phent
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jmp .one_auxv
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.replace_phnum:
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movq 32(%r8), %r9
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movq %r9, -8(%rsp) CC set at_phnum
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jmp .one_auxv
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.replace_entry:
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movq 16(%r8), %r9
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movq %r9, -8(%rsp) CC set at_entry
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jmp .one_auxv
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.replace_base:
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movq 48(%r8), %r9
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movq %r9, -8(%rsp) CC set at_base
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jmp .one_auxv
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.cleanup:
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movq $3, %rax CC SYS_close
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cmpq $-1, %r12 CC see if interpreter fd is set
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je .cleanup_1
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movq %r12, %rdi
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syscall
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movq $3, %rax CC SYS_close
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.cleanup_1:
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movq %rbx, %rdi
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syscall
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.enter:
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pushq $0
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popfq CC clear FP state
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movq %r13, %rsp CC restore SP
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xorq %rdx, %rdx CC clear rtld_fini
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jmpq *8(%r8) CC entry
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error:
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.ascii "_start: internal error."
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timespec:
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.quad 10
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.quad 10
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