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https://github.com/FEX-Emu/FEX.git
synced 2026-10-07 18:00:17 +02:00
Ryan Houdek
c5ffc0664d
We are required in our syscall emulation to handle cases where pointers are invalid. This means we need to pessimistically assume a memcpy will fault when reading application memory. This implements a signal handler based approach to catching the SIGSEGV on memcpy and returning an EFAULT if it faults.
73 lines
1.5 KiB
C++
73 lines
1.5 KiB
C++
// SPDX-License-Identifier: MIT
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#include "LinuxSyscalls/Syscalls.h"
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namespace FEX::HLE::FaultSafeMemcpy {
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#ifdef _M_ARM_64
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__attribute__((naked))
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size_t CopyFromUser(void *Dest, const void* Src, size_t Size) {
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__asm volatile(R"(
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// Early exit if a memcpy of size zero.
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cbz x2, 2f;
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1:
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.globl CopyFromUser_FaultInst
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CopyFromUser_FaultInst:
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ldrb w3, [x1], 1; // <- This line can fault.
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strb w3, [x0], 1;
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sub x2, x2, 1;
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cbnz x2, 1b;
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2:
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mov x0, 0;
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ret;
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)"
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::: "memory");
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}
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__attribute__((naked))
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size_t CopyToUser(void *Dest, const void* Src, size_t Size) {
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__asm volatile(R"(
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// Early exit if a memcpy of size zero.
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cbz x2, 2f;
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1:
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ldrb w3, [x1], 1;
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.globl CopyToUser_FaultInst
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CopyToUser_FaultInst:
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strb w3, [x0], 1; // <- This line can fault.
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sub x2, x2, 1;
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cbnz x2, 1b;
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2:
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mov x0, 0;
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ret;
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)"
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::: "memory");
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}
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extern "C" uint64_t CopyFromUser_FaultInst;
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void * const CopyFromUser_FaultLocation = &CopyFromUser_FaultInst;
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extern "C" uint64_t CopyToUser_FaultInst;
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void * const CopyToUser_FaultLocation = &CopyToUser_FaultInst;
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bool IsFaultLocation(uint64_t PC) {
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return reinterpret_cast<void*>(PC) == CopyFromUser_FaultLocation ||
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reinterpret_cast<void*>(PC) == CopyToUser_FaultLocation;
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}
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#else
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size_t CopyFromUser(void *Dest, const void* Src, size_t Size) {
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memcpy(Dest, Src, Size);
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return Size;
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}
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size_t CopyToUser(void *Dest, const void* Src, size_t Size) {
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memcpy(Dest, Src, Size);
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return Size;
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}
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bool IsFaultLocation(uint64_t PC) {
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return false;
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}
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#endif
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}
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