| // Copyright 2023 The Fuchsia Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include <lib/arch/asm.h> |
| |
| // This defines the entry point in assembly, such that it calls: |
| // extern "C" StartLdResult StartLd(...); |
| // The arguments are whatever the arguments to _start were. |
| // The return value is two words: first the argument to pass to the |
| // user entry point, and then the user entry point PC. |
| |
| .function _start, global |
| |
| // This can assume the sp is already aligned to 16 by the kernel. |
| |
| #if defined(__aarch64__) |
| |
| .prologue.fp |
| bl StartLd |
| .epilogue.fp |
| |
| // The argument is already in x0. |
| br x1 |
| |
| #elif defined(__riscv) |
| |
| .prologue.fp |
| call StartLd |
| .epilogue.fp |
| |
| // The argument is already in a0. |
| jr a1 |
| |
| #elif defined(__x86_64__) |
| |
| .prologue.fp |
| call StartLd |
| .epilogue.fp |
| |
| // Move the argument into place. |
| mov %rax, %rdi |
| jmp *%rdx |
| |
| #else |
| #error "unsupported machine" |
| #endif |
| |
| .end_function |
