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edd9297eba
Your Actually Portable Executables now contains a simple virtual memory that works similarly to the Linux Kernel in the sense that it maps your physical memory to negative addresses. This is needed to support mmap() and malloc(). This functionality has zero code size impact. For example the MODE=tiny LIFE.COM executable is still only 12KB in size. The APE bootloader code has also been simplified to improve readibility and further elevate the elegance by which we're able to support so many platforms thereby enhancing verifiability so that we may engender trust in this bootloading process.
187 lines
7.4 KiB
C
187 lines
7.4 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2021 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/bits/bits.h"
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#include "libc/dce.h"
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#include "libc/macros.h"
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#include "libc/nt/efi.h"
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#include "libc/nt/thunk/msabi.h"
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#include "libc/runtime/e820.internal.h"
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#include "libc/runtime/internal.h"
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#include "libc/runtime/pc.internal.h"
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#include "libc/runtime/runtime.h"
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#include "libc/str/str.h"
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/* TOOD: Why can't we change CR3? Could it really need PML5T? */
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/* TOOD: Why does QEMU in UEFI mode take ten seconds to boot? */
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struct EfiArgs {
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char *Args[0x400 / sizeof(char *)];
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char ArgBlock[0xC00];
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};
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static const EFI_GUID kEfiLoadedImageProtocol = LOADED_IMAGE_PROTOCOL;
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/**
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* EFI Application Entrypoint.
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*
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* This entrypoint is mutually exclusive from WinMain since
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* Windows apps and EFI apps use the same PE binary format.
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* So if you want to trade away Windows so that you can use
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* UEFI instead of the normal BIOS boot process, do this:
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*
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* STATIC_YOINK("EfiMain");
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* int main() { ... }
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*
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* You can use QEMU to test this, but please note that UEFI
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* goes thousands of times slower than the normal BIOS boot
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*
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* qemu-system-x86_64 \
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* -bios OVMF.fd \
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* -nographic \
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* -net none \
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* -drive format=raw,file=fat:rw:o/tool/viz
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* FS0:
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* deathstar.com
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*
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* @see libc/dce.h
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*/
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__msabi noasan EFI_STATUS EfiMain(EFI_HANDLE ImageHandle,
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EFI_SYSTEM_TABLE *SystemTable) {
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bool ispml5t;
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int type, x87cw;
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struct mman *mm;
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uint32_t DescVersion;
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uintptr_t i, j, MapSize;
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struct EfiArgs *ArgBlock;
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EFI_LOADED_IMAGE *ImgInfo;
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EFI_MEMORY_DESCRIPTOR *Map;
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uintptr_t Args, MapKey, DescSize;
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uint64_t p, pe, cr4, *m, *pd, *sp, *pml4t, *pdt1, *pdt2, *pdpt1, *pdpt2;
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extern char __os asm("__hostos");
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__os = METAL;
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/*
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* Allocates and clears PC-compatible memory and copies image.
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*/
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SystemTable->BootServices->AllocatePages(
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EfiConventionalMemory, AllocateAddress,
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MAX(2 * 1024 * 1024, 1024 * 1024 + (_end - _base)) / 4096, 0);
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SystemTable->BootServices->SetMem(0, 0x80000, 0);
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SystemTable->BootServices->CopyMem((void *)(1024 * 1024), _base,
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_end - _base);
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/*
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* Converts UEFI shell arguments to argv.
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*/
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ArgBlock = (struct EfiArgs *)0x7e000;
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SystemTable->BootServices->HandleProtocol(ImageHandle,
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&kEfiLoadedImageProtocol, &ImgInfo);
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Args = GetDosArgv(ImgInfo->LoadOptions, ArgBlock->ArgBlock,
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sizeof(ArgBlock->ArgBlock), ArgBlock->Args,
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ARRAYLEN(ArgBlock->Args));
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/*
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* Asks UEFI which parts of our RAM we're allowed to use.
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*/
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Map = NULL;
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MapSize = 0;
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SystemTable->BootServices->GetMemoryMap(&MapSize, Map, &MapKey, &DescSize,
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&DescVersion);
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SystemTable->BootServices->AllocatePool(EfiLoaderData, MapSize, Map);
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SystemTable->BootServices->GetMemoryMap(&MapSize, Map, &MapKey, &DescSize,
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&DescVersion);
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asm("xor\t%0,%0" : "=r"(mm)); /* gcc assumes null isn't mapped */
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for (j = i = 0; i < MapSize / sizeof(EFI_MEMORY_DESCRIPTOR); ++i) {
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if (Map[i].Type != EfiConventionalMemory) continue;
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mm->e820[j].addr = Map[i].PhysicalStart;
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mm->e820[j].size = Map[i].NumberOfPages * 4096;
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mm->e820[j].type = kMemoryUsable;
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++j;
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}
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SystemTable->BootServices->FreePool(Map);
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/*
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* Sets up page tables.
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*/
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pd = (uint64_t *)0x79000;
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pdt1 = (uint64_t *)0x7b000;
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pdt2 = (uint64_t *)0x7a000;
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pdpt1 = (uint64_t *)0x7d000;
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pdpt2 = (uint64_t *)0x7c000;
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pml4t = (uint64_t *)0x7e000;
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for (i = 0; i < 512; ++i) {
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pd[i] = 0x1000 * i + PAGE_V + PAGE_RW;
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}
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pdt1[0] = (intptr_t)pd + PAGE_V + PAGE_RW;
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pdt2[0] = (intptr_t)pd + PAGE_V + PAGE_RW;
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pdpt1[0] = (intptr_t)pdt1 + PAGE_V + PAGE_RW;
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pdpt2[0] = (intptr_t)pdt2 + PAGE_V + PAGE_RW;
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pml4t[0] = (intptr_t)pdpt1 + PAGE_V + PAGE_RW;
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pml4t[256] = (intptr_t)pdpt2 + PAGE_V + PAGE_RW;
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__map_phdrs(mm, pml4t, 1024 * 1024);
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/*
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* Asks UEFI to handover control?
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*/
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SystemTable->BootServices->ExitBootServices(ImageHandle, MapKey);
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/*
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* Launches program.
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*/
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asm volatile("fldcw\t%3\n\t"
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"mov\t%4,%%cr3\n\t"
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".weak\tape_stack_vaddr\n\t"
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".weak\tape_stack_memsz\n\t"
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"movabs\t$ape_stack_vaddr,%%rsp\n\t"
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"add\t$ape_stack_memsz,%%rsp\n\t"
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"push\t$0\n\t" /* auxv[1][1] */
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"push\t$0\n\t" /* auxv[1][0] */
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"push\t(%1)\n\t" /* auxv[0][1] */
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"push\t$31\n\t" /* auxv[0][0] AT_EXECFN */
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"push\t$0\n\t" /* envp[0] */
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"sub\t%2,%%rsp\n\t"
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"mov\t%%rsp,%%rdi\n\t"
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"rep movsb\n\t" /* argv */
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"push\t%0\n\t" /* argc */
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"xor\t%%edi,%%edi\n\t"
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"xor\t%%eax,%%eax\n\t"
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"xor\t%%ebx,%%ebx\n\t"
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"xor\t%%ecx,%%ecx\n\t"
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"xor\t%%edx,%%edx\n\t"
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"xor\t%%edi,%%edi\n\t"
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"xor\t%%esi,%%esi\n\t"
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"xor\t%%ebp,%%ebp\n\t"
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"xor\t%%r8d,%%r8d\n\t"
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"xor\t%%r9d,%%r9d\n\t"
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"xor\t%%r10d,%%r10d\n\t"
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"xor\t%%r11d,%%r11d\n\t"
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"xor\t%%r12d,%%r12d\n\t"
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"xor\t%%r13d,%%r13d\n\t"
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"xor\t%%r14d,%%r14d\n\t"
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"xor\t%%r15d,%%r15d\n\t"
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".weak\t_start\n\t"
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"jmp\t_start"
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: /* no outputs */
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: "a"(Args), "S"(ArgBlock->Args), "c"((Args + 1) * 8),
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"m"(x87cw), "r"(pml4t)
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: "memory");
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unreachable;
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}
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