backend/x64: Add POSIX exception handler with fastmem support

src/CMakeLists.txt

@@ -286,6 +286,11 @@ if (ARCHITECTURE_x86_64)
                 backend/x64/mig/mach_exc_server.h
             )
         endif()
+    elseif (UNIX)
+        if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+            target_link_libraries(dynarmic PUBLIC rt)
+        endif()
+        target_sources(dynarmic PRIVATE backend/x64/exception_handler_posix.cpp)
     else()
         target_sources(dynarmic PRIVATE backend/x64/exception_handler_generic.cpp)
     endif()

src/backend/x64/exception_handler_posix.cpp

@@ -0,0 +1,194 @@
+/* This file is part of the dynarmic project.
+ * Copyright (c) 2019 MerryMage
+ * This software may be used and distributed according to the terms of the GNU
+ * General Public License version 2 or any later version.
+ */
+
+// Copyright 2008 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#include "backend/x64/exception_handler.h"
+
+#include <cstring>
+#include <functional>
+#include <memory>
+#include <mutex>
+#include <vector>
+
+#include <signal.h>
+#ifdef __APPLE__
+#include <sys/ucontext.h>
+#else
+#include <ucontext.h>
+#endif
+
+#include "backend/x64/block_of_code.h"
+#include "common/assert.h"
+#include "common/cast_util.h"
+#include "common/common_types.h"
+
+namespace Dynarmic::Backend::X64 {
+
+namespace {
+
+struct CodeBlockInfo {
+    u64 code_begin, code_end;
+    std::function<FakeCall(u64)> cb;
+};
+
+class SigHandler {
+public:
+    SigHandler();
+    ~SigHandler();
+
+    void AddCodeBlock(CodeBlockInfo info);
+    void RemoveCodeBlock(u64 rip);
+
+private:
+    auto FindCodeBlockInfo(u64 rip) {
+        return std::find_if(code_block_infos.begin(), code_block_infos.end(), [&](const auto& x) { return x.code_begin <= rip && x.code_end > rip; });
+    }
+
+    std::vector<CodeBlockInfo> code_block_infos;
+    std::mutex code_block_infos_mutex;
+
+    struct sigaction old_sa_segv;
+    struct sigaction old_sa_bus;
+
+    static void SigAction(int sig, siginfo_t* info, void* raw_context);
+};
+
+SigHandler sig_handler;
+
+SigHandler::SigHandler() {
+    // Method below from dolphin.
+
+    constexpr size_t signal_stack_size = std::max(SIGSTKSZ, 2 * 1024 * 1024);
+
+    stack_t signal_stack;
+    signal_stack.ss_sp = malloc(signal_stack_size);
+    signal_stack.ss_size = signal_stack_size;
+    signal_stack.ss_flags = 0;
+    ASSERT_MSG(sigaltstack(&signal_stack, nullptr) == 0, "dynarmic: POSIX SigHandler: init failure at sigaltstack");
+
+    struct sigaction sa;
+    sa.sa_handler = nullptr;
+    sa.sa_sigaction = &SigHandler::SigAction;
+    sa.sa_flags = SA_SIGINFO | SA_ONSTACK | SA_RESTART;
+    sigemptyset(&sa.sa_mask);
+    sigaction(SIGSEGV, &sa, &old_sa_segv);
+#ifdef __APPLE__
+    sigaction(SIGBUS, &sa, &old_sa_bus);
+#endif
+}
+
+SigHandler::~SigHandler() {
+    // No cleanup required.
+}
+
+void SigHandler::AddCodeBlock(CodeBlockInfo cbi) {
+    std::lock_guard<std::mutex> guard(code_block_infos_mutex);
+    if (auto iter = FindCodeBlockInfo(cbi.code_begin); iter != code_block_infos.end()) {
+        code_block_infos.erase(iter);
+    }
+    code_block_infos.push_back(cbi);
+}
+
+void SigHandler::RemoveCodeBlock(u64 rip) {
+    std::lock_guard<std::mutex> guard(code_block_infos_mutex);
+    const auto iter = FindCodeBlockInfo(rip);
+    if (iter == code_block_infos.end()) {
+        return;
+    }
+    code_block_infos.erase(iter);
+}
+
+void SigHandler::SigAction(int sig, siginfo_t* info, void* raw_context) {
+    ASSERT(sig == SIGSEGV || sig == SIGBUS);
+
+#if defined(__APPLE__)
+    #define CTX_RIP (((ucontext_t*)raw_context)->uc_mcontext->__ss.__rip)
+    #define CTX_RSP (((ucontext_t*)raw_context)->uc_mcontext->__ss.__rsp)
+#elif defined(__linux__)
+    #define CTX_RIP (((ucontext_t*)raw_context)->uc_mcontext.gregs[REG_RIP])
+    #define CTX_RSP (((ucontext_t*)raw_context)->uc_mcontext.gregs[REG_RSP])
+#elif defined(__FreeBSD__)
+    #define CTX_RIP (((ucontext_t*)raw_context)->uc_mcontext.mc_rip)
+    #define CTX_RSP (((ucontext_t*)raw_context)->uc_mcontext.mc_rsp)
+#else
+    #error "Unknown platform"
+#endif
+
+    {
+        std::lock_guard<std::mutex> guard(sig_handler.code_block_infos_mutex);
+
+        const auto iter = sig_handler.FindCodeBlockInfo(CTX_RIP);
+        if (iter != sig_handler.code_block_infos.end()) {
+            FakeCall fc = iter->cb(CTX_RIP);
+
+            CTX_RSP -= sizeof(u64);
+            *Common::BitCast<u64*>(CTX_RSP) = fc.ret_rip;
+            CTX_RIP = fc.call_rip;
+
+            return;
+        }
+    }
+
+    fmt::print(stderr, "dynarmic: POSIX SigHandler: Exception was not in registered code blocks (rip {:#016x})\n", CTX_RIP);
+
+    struct sigaction* retry_sa = sig == SIGSEGV ? &sig_handler.old_sa_segv : &sig_handler.old_sa_bus;
+    if (retry_sa->sa_flags & SA_SIGINFO) {
+      retry_sa->sa_sigaction(sig, info, raw_context);
+      return;
+    }
+    if (retry_sa->sa_handler == SIG_DFL) {
+      signal(sig, SIG_DFL);
+      return;
+    }
+    if (retry_sa->sa_handler == SIG_IGN) {
+      return;
+    }
+    retry_sa->sa_handler(sig);
+}
+
+} // anonymous namespace
+
+struct ExceptionHandler::Impl final {
+    Impl(BlockOfCode& code)
+        : code_begin(Common::BitCast<u64>(code.getCode()))
+        , code_end(code_begin + code.GetTotalCodeSize())
+    {}
+
+    void SetCallback(std::function<FakeCall(u64)> cb) {
+        CodeBlockInfo cbi;
+        cbi.code_begin = code_begin;
+        cbi.code_end = code_end;
+        cbi.cb = cb;
+        sig_handler.AddCodeBlock(cbi);
+    }
+
+    ~Impl() {
+        sig_handler.RemoveCodeBlock(code_begin);
+    }
+
+private:
+    u64 code_begin, code_end;
+};
+
+ExceptionHandler::ExceptionHandler() = default;
+ExceptionHandler::~ExceptionHandler() = default;
+
+void ExceptionHandler::Register(BlockOfCode& code) {
+    impl = std::make_unique<Impl>(code);
+}
+
+bool ExceptionHandler::SupportsFastmem() const noexcept {
+    return static_cast<bool>(impl);
+}
+
+void ExceptionHandler::SetFastmemCallback(std::function<FakeCall(u64)> cb) {
+    impl->SetCallback(cb);
+}
+
+} // namespace Dynarmic::Backend::X64