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Handle host accesses for NCE Memory Trapping API
We cannot ignore accesses from the host to a region protected by the NCE Memory Trapping API, there's often access to regions which have overlap with a protected region unintentionally and those accesses need to be handled correctly rather than leading to a crash. This is done by implementing an additional signal handler `NCE::HostSignalHandler` to lookup any potential traps on a `SIGSEGV` and handle them correctly or when there isn't a corresponding trap raise a `SIGTRAP` when debugger is connected or delegate to `signal::ExceptionalSignalHandler` when it isn't.
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b04a0c386a
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cb2614f80e
@ -107,37 +107,46 @@ namespace skyline::nce {
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*tls = nullptr;
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} else { // If TLS wasn't restored then this occurred in host code
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if (signal == SIGSEGV) {
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bool runningUnderDebugger{[]() {
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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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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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for (char character : line)
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if (std::isspace(character))
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continue;
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else
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return character != '0';
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return false;
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}
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}
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return false;
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}()};
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if (runningUnderDebugger)
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raise(SIGTRAP); // Notify the debugger if we've got a SIGSEGV as the debugger doesn't catch them by default as they might be hooked
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}
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signal::ExceptionalSignalHandler(signal, info, ctx); //!< Delegate throwing a host exception to the exceptional signal handler
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HostSignalHandler(signal, info, ctx);
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}
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}
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static NCE* staticNce{nullptr}; //!< A static instance of NCE for use in the signal handler
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void NCE::HostSignalHandler(int signal, siginfo *info, ucontext *ctx) {
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if (signal == SIGSEGV) {
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if (staticNce && staticNce->TrapHandler(reinterpret_cast<u8 *>(info->si_addr), true))
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return;
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bool runningUnderDebugger{[]() {
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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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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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for (char character : line)
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if (std::isspace(character))
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continue;
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else
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return character != '0';
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return false;
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}
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}
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return false;
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}()};
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if (runningUnderDebugger)
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raise(SIGTRAP); // Notify the debugger if we've got a SIGSEGV as the debugger doesn't catch them by default as they might be hooked
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}
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signal::ExceptionalSignalHandler(signal, info, ctx); // Delegate throwing a host exception to the exceptional signal handler
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}
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void *NceTlsRestorer() {
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ThreadContext *threadCtx;
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asm volatile("MRS %x0, TPIDR_EL0":"=r"(threadCtx));
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@ -149,6 +158,7 @@ namespace skyline::nce {
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NCE::NCE(const DeviceState &state) : state(state) {
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signal::SetTlsRestorer(&NceTlsRestorer);
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staticNce = this;
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}
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constexpr u8 MainSvcTrampolineSize{17}; // Size of the main SVC trampoline function in u32 units
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@ -64,6 +64,15 @@ namespace skyline::nce {
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*/
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static void SignalHandler(int signal, siginfo *info, ucontext *ctx, void **tls);
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/**
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* @brief Handles signals for any host threads which may access NCE trapped memory
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* @note Any untrapped SIGSEGVs will emit SIGTRAP when a debugger is attached rather than throwing an exception
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*/
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static void HostSignalHandler(int signal, siginfo *info, ucontext *ctx);
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/**
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* @note There should only be one instance of NCE concurrently
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*/
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NCE(const DeviceState &state);
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struct PatchData {
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@ -330,7 +330,8 @@ namespace skyline::soc::gm20b {
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void ChannelGpfifo::Run() {
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pthread_setname_np(pthread_self(), "GPFIFO");
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try {
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signal::SetSignalHandler({SIGINT, SIGILL, SIGTRAP, SIGBUS, SIGFPE, SIGSEGV}, signal::ExceptionalSignalHandler);
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signal::SetSignalHandler({SIGINT, SIGILL, SIGTRAP, SIGBUS, SIGFPE}, signal::ExceptionalSignalHandler);
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signal::SetSignalHandler({SIGSEGV}, nce::NCE::HostSignalHandler); // We may access NCE trapped memory
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gpEntries.Process([this](GpEntry gpEntry) {
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Logger::Debug("Processing pushbuffer: 0x{:X}, Size: 0x{:X}", gpEntry.Address(), +gpEntry.size);
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@ -2,6 +2,7 @@
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// Copyright © 2021 Skyline Team and Contributors (https://github.com/skyline-emu/)
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#include <common/signal.h>
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#include <nce.h>
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#include <loader/loader.h>
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#include <kernel/types/KProcess.h>
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#include <soc.h>
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@ -115,7 +116,8 @@ namespace skyline::soc::host1x {
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void ChannelCommandFifo::Run() {
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pthread_setname_np(pthread_self(), "ChannelCommandFifo");
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try {
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signal::SetSignalHandler({SIGINT, SIGILL, SIGTRAP, SIGBUS, SIGFPE, SIGSEGV}, signal::ExceptionalSignalHandler);
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signal::SetSignalHandler({SIGINT, SIGILL, SIGTRAP, SIGBUS, SIGFPE}, signal::ExceptionalSignalHandler);
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signal::SetSignalHandler({SIGSEGV}, nce::NCE::HostSignalHandler); // We may access NCE trapped memory
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gatherQueue.Process([this](span<u32> gather) {
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Logger::Debug("Processing pushbuffer: 0x{:X}, size: 0x{:X}", gather.data(), gather.size());
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