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107 lines
2.8 KiB
ArmAsm
107 lines
2.8 KiB
ArmAsm
/* Copyright (C) 2001-2020 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
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License as published by the Free Software Foundation; either
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version 2.1 of the 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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/* clone() is even more special than fork() as it mucks with stacks
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and invokes a function in the right context after its all over. */
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#include <sysdep.h>
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#define _ERRNO_H 1
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#include <bits/errno.h>
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#include <asm-syntax.h>
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/* The userland implementation is:
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int clone (int (*fn)(void *arg), void *child_stack, int flags, void *arg),
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the kernel entry is:
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int clone (long flags, void *child_stack).
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The parameters are passed in register and on the stack from userland:
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rdi: fn
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rsi: child_stack
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rdx: flags
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rcx: arg
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r8d: TID field in parent
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r9d: thread pointer
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%esp+8: TID field in child
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The kernel expects:
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rax: system call number
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rdi: flags
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rsi: child_stack
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rdx: TID field in parent
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r10: TID field in child
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r8: thread pointer */
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.text
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ENTRY (__clone)
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/* Sanity check arguments. */
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movq $-EINVAL,%rax
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testq %rdi,%rdi /* no NULL function pointers */
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jz SYSCALL_ERROR_LABEL
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testq %rsi,%rsi /* no NULL stack pointers */
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jz SYSCALL_ERROR_LABEL
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/* Insert the argument onto the new stack. */
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subq $16,%rsi
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movq %rcx,8(%rsi)
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/* Save the function pointer. It will be popped off in the
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child in the ebx frobbing below. */
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movq %rdi,0(%rsi)
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/* Do the system call. */
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movq %rdx, %rdi
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movq %r8, %rdx
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movq %r9, %r8
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mov 8(%rsp), %R10_LP
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movl $SYS_ify(clone),%eax
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/* End FDE now, because in the child the unwind info will be
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wrong. */
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cfi_endproc;
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syscall
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testq %rax,%rax
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jl SYSCALL_ERROR_LABEL
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jz L(thread_start)
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ret
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L(thread_start):
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cfi_startproc;
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/* Clearing frame pointer is insufficient, use CFI. */
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cfi_undefined (rip);
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/* Clear the frame pointer. The ABI suggests this be done, to mark
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the outermost frame obviously. */
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xorl %ebp, %ebp
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/* Set up arguments for the function call. */
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popq %rax /* Function to call. */
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popq %rdi /* Argument. */
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call *%rax
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/* Call exit with return value from function call. */
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movq %rax, %rdi
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movl $SYS_ify(exit), %eax
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syscall
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cfi_endproc;
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cfi_startproc;
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PSEUDO_END (__clone)
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libc_hidden_def (__clone)
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weak_alias (__clone, clone)
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