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https://github.com/skyline-emu/skyline.git
synced 2024-12-23 07:11:52 +01:00
Implement NCE Memory Trapping API
An API for trapping accesses to guest memory and performing callbacks based on those accesses alongside managing protection of the memory. This is a fundamental building block for avoiding redundant synchronization of resources from the guest and host. Note: All accesses are treated as write accesses at the moment, support for picking up read accesses will be implemented later
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PixelyIon
parent
08510d75b0
commit
3e33d49faf
@ -75,6 +75,12 @@ namespace skyline::nce {
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if (*tls) { // If TLS was restored then this occurred in guest code
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auto &mctx{ctx->uc_mcontext};
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const auto &state{*reinterpret_cast<ThreadContext *>(*tls)->state};
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if (signal == SIGSEGV && info->si_code == SEGV_ACCERR)
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// If we get a guest access violation then we want to handle any accesses that may be from a trapped region
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if (state.nce->TrapHandler(reinterpret_cast<u8 *>(info->si_addr), true))
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return;
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if (signal != SIGINT) {
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signal::StackFrame topFrame{.lr = reinterpret_cast<void *>(ctx->uc_mcontext.pc), .next = reinterpret_cast<signal::StackFrame *>(ctx->uc_mcontext.regs[29])};
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std::string trace{state.loader->GetStackTrace(&topFrame)};
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@ -84,7 +90,7 @@ namespace skyline::nce {
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cpuContext += fmt::format("\n Fault Address: 0x{:X}", mctx.fault_address);
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if (mctx.sp)
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cpuContext += fmt::format("\n Stack Pointer: 0x{:X}", mctx.sp);
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for (u8 index{}; index < (sizeof(mcontext_t::regs) / sizeof(u64)); index += 2)
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for (size_t index{}; index < (sizeof(mcontext_t::regs) / sizeof(u64)); index += 2)
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cpuContext += fmt::format("\n X{:<2}: 0x{:<16X} X{:<2}: 0x{:X}", index, mctx.regs[index], index + 1, mctx.regs[index + 1]);
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Logger::Error("Thread #{} has crashed due to signal: {}\nStack Trace:{}\nCPU Context:{}", state.thread->id, strsignal(signal), trace, cpuContext);
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@ -106,7 +112,7 @@ namespace skyline::nce {
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static std::ifstream status("/proc/self/status");
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status.seekg(0);
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constexpr std::string_view TracerPidTag = "TracerPid:";
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constexpr std::string_view TracerPidTag{"TracerPid:"};
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for (std::string line; std::getline(status, line);) {
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if (line.starts_with(TracerPidTag)) {
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line = line.substr(TracerPidTag.size());
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@ -355,4 +361,128 @@ namespace skyline::nce {
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}
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}
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}
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NCE::CallbackEntry::CallbackEntry(TrapProtection protection, NCE::TrapCallback readCallback, NCE::TrapCallback writeCallback) : protection(protection), readCallback(std::move(readCallback)), writeCallback(std::move(writeCallback)) {}
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void NCE::ReprotectIntervals(const std::vector<TrapMap::Interval> &intervals, TrapProtection protection) {
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auto reprotectIntervalsWithFunction = [&intervals](auto getProtection) {
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for (auto region : intervals) {
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region = region.Align(PAGE_SIZE);
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mprotect(region.start, region.Size(), getProtection(region));
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}
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};
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// We need to determine the lowest protection possible for the given interval
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if (protection == TrapProtection::None) {
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reprotectIntervalsWithFunction([&](auto region) {
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auto entries{trapMap.GetRange(region)};
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TrapProtection lowestProtection{TrapProtection::None};
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for (const auto &entry : entries) {
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auto entryProtection{entry.get().protection};
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if (entryProtection > lowestProtection) {
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lowestProtection = entryProtection;
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if (entryProtection == TrapProtection::ReadWrite)
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return PROT_EXEC;
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}
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}
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switch (lowestProtection) {
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case TrapProtection::None:
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return PROT_READ | PROT_WRITE | PROT_EXEC;
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case TrapProtection::WriteOnly:
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return PROT_READ | PROT_EXEC;
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case TrapProtection::ReadWrite:
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return PROT_EXEC;
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}
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});
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} else if (protection == TrapProtection::WriteOnly) {
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reprotectIntervalsWithFunction([&](auto region) {
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auto entries{trapMap.GetRange(region)};
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for (const auto &entry : entries)
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if (entry.get().protection == TrapProtection::ReadWrite)
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return PROT_EXEC;
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return PROT_READ | PROT_EXEC;
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});
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} else {
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reprotectIntervalsWithFunction([&](auto region) {
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return PROT_EXEC; // No checks are needed as this is already the highest level of protection
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});
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}
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}
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bool NCE::TrapHandler(u8 *address, bool write) {
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std::scoped_lock lock(trapMutex);
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// Check if we have a callback for this address
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auto[entries, intervals]{trapMap.GetAlignedRecursiveRange<PAGE_SIZE>(address)};
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if (entries.empty())
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return false;
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// Do callbacks for every entry in the intervals
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if (write) {
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for (auto entryRef : entries) {
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auto &entry{entryRef.get()};
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if (entry.protection == TrapProtection::None)
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// We don't need to do the callback if the entry doesn't require any protection already
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continue;
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entry.writeCallback();
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entry.protection = TrapProtection::None; // We don't need to protect this entry anymore
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}
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} else {
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bool allNone{true}; // If all entries require no protection, we can protect to allow all accesses
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for (auto entryRef : entries) {
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auto &entry{entryRef.get()};
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if (entry.protection < TrapProtection::ReadWrite) {
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// We don't need to do the callback if the entry can already handle read accesses
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allNone = allNone && entry.protection == TrapProtection::None;
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continue;
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}
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entry.readCallback();
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entry.protection = TrapProtection::WriteOnly; // We only need to trap writes to this entry
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}
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write = allNone;
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}
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int permission{PROT_READ | (write ? PROT_WRITE : 0) | PROT_EXEC};
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for (const auto &interval : intervals)
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// Reprotect the interval to the lowest protection level that the callbacks performed allow
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mprotect(interval.start, interval.Size(), permission);
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return true;
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}
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constexpr NCE::TrapHandle::TrapHandle(const TrapMap::GroupHandle &handle) : TrapMap::GroupHandle(handle) {}
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NCE::TrapHandle NCE::TrapRegions(span<span<u8>> regions, bool writeOnly, const TrapCallback &readCallback, const TrapCallback &writeCallback) {
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std::scoped_lock lock(trapMutex);
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auto protection{writeOnly ? TrapProtection::WriteOnly : TrapProtection::ReadWrite};
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TrapHandle handle{trapMap.Insert(regions, CallbackEntry{protection, readCallback, writeCallback})};
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ReprotectIntervals(handle->intervals, protection);
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return handle;
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}
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void NCE::RetrapRegions(TrapHandle handle, bool writeOnly) {
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std::scoped_lock lock(trapMutex);
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auto protection{writeOnly ? TrapProtection::WriteOnly : TrapProtection::ReadWrite};
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handle->value.protection = protection;
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ReprotectIntervals(handle->intervals, protection);
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}
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void NCE::RemoveTrap(TrapHandle handle) {
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std::scoped_lock lock(trapMutex);
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handle->value.protection = TrapProtection::None;
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ReprotectIntervals(handle->intervals, TrapProtection::None);
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}
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void NCE::DeleteTrap(TrapHandle handle) {
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std::scoped_lock lock(trapMutex);
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handle->value.protection = TrapProtection::None;
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ReprotectIntervals(handle->intervals, TrapProtection::None);
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trapMap.Remove(handle);
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}
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}
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@ -3,8 +3,9 @@
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#pragma once
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#include "common.h"
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#include <sys/wait.h>
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#include "common.h"
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#include "common/interval_map.h"
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namespace skyline::nce {
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/**
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@ -14,6 +15,35 @@ namespace skyline::nce {
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private:
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const DeviceState &state;
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/**
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* @brief The level of protection that is required for a callback entry
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*/
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enum class TrapProtection {
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None = 0, //!< No protection is required
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WriteOnly = 1, //!< Only write protection is required
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ReadWrite = 2, //!< Both read and write protection are required
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};
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using TrapCallback = std::function<void()>;
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struct CallbackEntry {
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TrapProtection protection; //!< The least restrictive protection that this callback needs to have
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TrapCallback readCallback, writeCallback;
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CallbackEntry(TrapProtection protection, NCE::TrapCallback readCallback, NCE::TrapCallback writeCallback);
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};
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std::mutex trapMutex; //!< Synchronizes the accesses to the trap map
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using TrapMap = IntervalMap<u8*, CallbackEntry>;
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TrapMap trapMap; //!< A map of all intervals and corresponding callbacks that have been registered
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/**
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* @brief Reprotects the intervals to the least restrictive protection given the supplied protection
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*/
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void ReprotectIntervals(const std::vector<TrapMap::Interval>& intervals, TrapProtection protection);
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bool TrapHandler(u8* address, bool write);
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static void SvcHandler(u16 svcId, ThreadContext *ctx);
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public:
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@ -26,7 +56,7 @@ namespace skyline::nce {
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ExitException(bool killAllThreads = true);
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virtual const char* what() const noexcept;
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virtual const char *what() const noexcept;
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};
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/**
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@ -48,5 +78,38 @@ namespace skyline::nce {
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* @param patch A pointer to the .patch section which should be exactly patchSize in size and located before the .text section
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*/
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static void PatchCode(std::vector<u8> &text, u32 *patch, size_t patchSize, const std::vector<size_t> &offsets);
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/**
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* @brief An opaque handle to a group of trapped region
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*/
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class TrapHandle : private TrapMap::GroupHandle {
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constexpr TrapHandle(const TrapMap::GroupHandle &handle);
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friend NCE;
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};
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/**
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* @brief Traps a region of guest memory with a callback for when an access to it has been made
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* @param writeOnly If the trap is optimally for write-only accesses initially, this is not guarenteed
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* @note The handle **must** be deleted using DeleteTrap before the NCE instance is destroyed
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* @note It is UB to supply a region of host memory rather than guest memory
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*/
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TrapHandle TrapRegions(span<span<u8>> regions, bool writeOnly, const TrapCallback& readCallback, const TrapCallback& writeCallback);
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/**
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* @brief Re-traps a region of memory after protections were removed
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* @param writeOnly If the trap is optimally for write-only accesses, this is not guarenteed
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*/
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void RetrapRegions(TrapHandle handle, bool writeOnly);
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/**
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* @brief Removes protections from a region of memory
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*/
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void RemoveTrap(TrapHandle handle);
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/**
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* @brief Deletes a trap handle and removes the protection from the region
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*/
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void DeleteTrap(TrapHandle handle);
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};
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}
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