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90 lines
2.5 KiB
ArmAsm
90 lines
2.5 KiB
ArmAsm
/* The clone3 syscall wrapper. Linux/x86-64 version.
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Copyright (C) 2021-2024 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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/* clone3() 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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/* The userland implementation is:
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int clone3 (struct clone_args *cl_args, size_t size,
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int (*func)(void *arg), void *arg);
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the kernel entry is:
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int clone3 (struct clone_args *cl_args, size_t size);
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The parameters are passed in registers from userland:
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rdi: cl_args
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rsi: size
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rdx: func
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rcx: arg
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The kernel expects:
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rax: system call number
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rdi: cl_args
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rsi: size */
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.text
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ENTRY (__clone3)
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/* Sanity check arguments. */
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movl $-EINVAL, %eax
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test %RDI_LP, %RDI_LP /* No NULL cl_args pointer. */
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jz SYSCALL_ERROR_LABEL
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test %RDX_LP, %RDX_LP /* No NULL function pointer. */
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jz SYSCALL_ERROR_LABEL
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/* Save the cl_args pointer in R8 which is preserved by the
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syscall. */
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mov %RCX_LP, %R8_LP
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/* Do the system call. */
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movl $SYS_ify(clone3), %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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test %RAX_LP, %RAX_LP
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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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mov %R8_LP, %RDI_LP /* Argument. */
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call *%rdx /* Call function. */
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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 (__clone3)
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libc_hidden_def (__clone3)
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weak_alias (__clone3, clone3)
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