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1f756fb386
This is generally more straightforward in cases where bounds checking isn't necessary.
88 lines
2.2 KiB
C++
88 lines
2.2 KiB
C++
// SPDX-License-Identifier: MIT
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/*
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$info$
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tags: glue|x86-guest-code
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desc: Guest-side assembly helpers used by the backends
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$end_info$
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*/
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#include "Interface/Core/X86HelperGen.h"
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#include "FEXCore/Utils/AllocatorHooks.h"
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#include <FEXCore/Config/Config.h>
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#include <FEXCore/Utils/Allocator.h>
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#include <FEXHeaderUtils/Syscalls.h>
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#include <cstdint>
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#include <cstring>
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namespace FEXCore {
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constexpr size_t CODE_SIZE = 0x1000;
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X86GeneratedCode::X86GeneratedCode() {
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#ifdef _WIN32
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// No need to allocate anything in this config.
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#else
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// Allocate a page for our emulated guest
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CodePtr = AllocateGuestCodeSpace(CODE_SIZE);
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constexpr std::array<uint8_t, 2> SignalReturnCode = {
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0x0F, 0x37, // CALLBACKRET FEX Instruction
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};
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CallbackReturn = reinterpret_cast<uint64_t>(CodePtr);
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memcpy(reinterpret_cast<void*>(CallbackReturn), SignalReturnCode.data(), SignalReturnCode.size());
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mprotect(CodePtr, CODE_SIZE, PROT_READ);
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#endif
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}
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X86GeneratedCode::~X86GeneratedCode() {
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#ifndef _WIN32
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FEXCore::Allocator::VirtualFree(CodePtr, CODE_SIZE);
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#endif
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}
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void* X86GeneratedCode::AllocateGuestCodeSpace(size_t Size) {
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#ifndef _WIN32
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FEX_CONFIG_OPT(Is64BitMode, IS64BIT_MODE);
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if (Is64BitMode()) {
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// 64bit mode can have its sigret handler anywhere
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return FEXCore::Allocator::VirtualAlloc(Size);
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}
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// First 64bit page
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constexpr uintptr_t LOCATION_MAX = 0x1'0000'0000;
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// 32bit mode
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// We need to have the sigret handler in the lower 32bits of memory space
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// Scan top down and try to allocate a location
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for (size_t Location = 0xFFFF'E000; Location != 0x0; Location -= 0x1000) {
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void* Ptr = ::mmap(reinterpret_cast<void*>(Location), Size, PROT_READ | PROT_WRITE, MAP_FIXED_NOREPLACE | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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if (Ptr != MAP_FAILED && reinterpret_cast<uintptr_t>(Ptr) >= LOCATION_MAX) {
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// Failed to map in the lower 32bits
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// Try again
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// Can happen in the case that host kernel ignores MAP_FIXED_NOREPLACE
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::munmap(Ptr, Size);
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continue;
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}
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if (Ptr != MAP_FAILED) {
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return Ptr;
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}
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}
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// Can't do anything about this
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// Here's hoping the application doesn't use signals
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return MAP_FAILED;
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#else
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return nullptr;
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#endif
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}
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} // namespace FEXCore
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