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/*
* Copyright (c) 2022, Netflix, Inc.
*
* SPDX-Licnse-Identifier: BSD-2-Clause
*/
/*
* Provides a _start routine that calls a _start_c routine that takes a pointer
* to the stack as documented in crt1.c. We skip the pointer to _DYNAMIC since
* we don't support dynamic libraries, at all. And while _start_c is our own
* thing, we comport to the calling conventions that glibc and musl have and
* make sure the second argument (%esi) is 0 for _DYNAMIC placeholder. We
* likely could call main directly with only a few more lines of code, but this
* is simple enough and concentrates all the expressable in C stuff there. We
* also generate eh_frames should we need to debug things (it doesn't change the
* genreated code, but leaves enough breadcrumbs to keep gdb happy).
*/
__asm__(
".text\n" /* ENTRY(_start) */
".p2align 4,0x90\n"
".global _start\n"
".type _start, @function\n"
"_start:\n"
".cfi_startproc\n"
" xor %rbp, %rbp\n" /* Clear out the stack frame pointer */
" mov %rsp, %rdi\n" /* Pass pointer to current stack with argc, argv and envp on it */
" xor %rsi, %rsi\n" /* No dynamic pointer for us, to keep it simple */
" andq $-16, %rsp\n" /* Align stack to 16-byte boundary */
" call _start_c\n" /* Our MI code takes it from here and won't return */
/* NORETURN */
".size _start, . - _start\n" /* END(_start) */
".cfi_endproc"
);
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