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//===-- Implementation of _start for aarch64 ------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "startup/linux/do_start.h"
extern "C" [[noreturn]] void _start() {
// Skip the Frame Pointer and the Link Register
// https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst
// Section 6.2.3. Note that this only works if the current function
// is not using any callee-saved registers (x19 to x28). If the
// function uses such registers, then their value is pushed on to the
// stack before the frame pointer an link register values. That breaks
// the assumption that stepping over the frame pointer and link register
// will take us to the previous stack pointer. That is the reason why the
// actual business logic of the startup code is pushed into a non-inline
// function do_start so that this function is free of any stack usage.
LIBC_NAMESPACE::app.args = reinterpret_cast<LIBC_NAMESPACE::Args *>(
reinterpret_cast<uintptr_t *>(__builtin_frame_address(0)) + 2);
LIBC_NAMESPACE::do_start();
}
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