[dynarmic/backend/exception_handler] normalize EH for arches, use LOG_ERROR instead of fmt::print (#4283)

Signed-off-by: lizzie <lizzie@eden-emu.dev>

- [x] I have read and followed the [Contribution Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/CONTRIBUTING.md#code-contributions).
- [x] I have read and followed the [AI Policy](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/docs/policies/AI.md)
- [x] I have read and followed the [Coding Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/docs/policies/Coding.md) to the best of my ability.

-------------------

this should simplify a bit of code logic
akin to NetBSD's UC_CONTEXT_PC...
additionally use LOG_ERROR so the
"unhandled ..."
is logged unto a file
before sigsegv'ing

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4283
Reviewed-by: Maufeat <sahyno1996@gmail.com>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

2 files changed, 28 insertions, 53 deletions

diff --git a/src/dynarmic/src/dynarmic/backend/exception_handler_posix.cpp b/src/dynarmic/src/dynarmic/backend/exception_handler_posix.cpp
index c586cf2fb1..a64423581b 100644
--- a/src/dynarmic/src/dynarmic/backend/exception_handler_posix.cpp
+++ b/src/dynarmic/src/dynarmic/backend/exception_handler_posix.cpp
@@ -22,6 +22,7 @@
 #include <sys/mman.h>
 
 #include "common/assert.h"
+#include "common/logging.h"
 #include "common/common_types.h"
 #include "dynarmic/backend/exception_handler.h"
 #include "dynarmic/common/context.h"
@@ -53,23 +54,21 @@ class SigHandler {
             return e.first <= offset && e.first + e.second.size > offset;
         });
     }
-    static void SigAction(int sig, siginfo_t* info, void* raw_context);
 
-    bool supports_fast_mem = true;
-    void* signal_stack_memory = nullptr;
     ankerl::unordered_dense::map<u64, CodeBlockInfo> code_block_infos;
     std::shared_mutex code_block_infos_mutex;
     struct sigaction old_sa_segv;
     struct sigaction old_sa_bus;
-    std::size_t signal_stack_size;
+    std::unique_ptr<uint8_t[]> signal_stack_memory;
+    bool supports_fast_mem = true;
 public:
     SigHandler() noexcept {
-        signal_stack_size = std::max<size_t>(SIGSTKSZ, 2 * 1024 * 1024);
-        signal_stack_memory = mmap(nullptr, signal_stack_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+        auto const stack_size = std::max<size_t>(SIGSTKSZ, 2 * 1024 * 1024);
+        signal_stack_memory = std::make_unique<uint8_t[]>(stack_size);
 
         stack_t signal_stack{};
-        signal_stack.ss_sp = signal_stack_memory;
-        signal_stack.ss_size = signal_stack_size;
+        signal_stack.ss_sp = signal_stack_memory.get();
+        signal_stack.ss_size = stack_size;
         signal_stack.ss_flags = 0;
         if (sigaltstack(&signal_stack, nullptr) != 0) {
             fmt::print(stderr, "dynarmic: POSIX SigHandler: init failure at sigaltstack\n");
@@ -87,7 +86,7 @@ public:
             supports_fast_mem = false;
             return;
         }
-#ifdef __APPLE__
+#if defined(__APPLE__)
         if (sigaction(SIGBUS, &sa, &old_sa_bus) != 0) {
             fmt::print(stderr, "dynarmic: POSIX SigHandler: could not set SIGBUS handler\n");
             supports_fast_mem = false;
@@ -96,10 +95,6 @@ public:
 #endif
     }
 
-    ~SigHandler() noexcept {
-        munmap(signal_stack_memory, signal_stack_size);
-    }
-
     void AddCodeBlock(u64 offset, CodeBlockInfo cbi) noexcept {
         std::unique_lock guard(code_block_infos_mutex);
         code_block_infos.insert_or_assign(offset, cbi);
@@ -109,14 +104,17 @@ public:
         code_block_infos.erase(offset);
     }
 
-    bool SupportsFastmem() const noexcept { return supports_fast_mem; }
+    [[nodiscard]] inline bool SupportsFastmem() const noexcept {
+        return supports_fast_mem;
+    }
+
+    static void RegisterHandler();
+    static void SigAction(int sig, siginfo_t* info, void* raw_context);
 };
 
-std::mutex handler_lock;
 std::optional<SigHandler> sig_handler;
 
-void RegisterHandler() {
-    std::lock_guard<std::mutex> guard(handler_lock);
+void SigHandler::RegisterHandler() {
     if (!sig_handler) {
         sig_handler.emplace();
     }
@@ -125,51 +123,27 @@ void RegisterHandler() {
 void SigHandler::SigAction(int sig, siginfo_t* info, void* raw_context) {
     DEBUG_ASSERT(sig == SIGSEGV || sig == SIGBUS);
     CTX_DECLARE(raw_context);
-#if defined(ARCHITECTURE_x86_64)
     {
         std::shared_lock guard(sig_handler->code_block_infos_mutex);
         if (auto const iter = sig_handler->FindCodeBlockInfo(CTX_PC); iter != sig_handler->code_block_infos.end()) {
             FakeCall fc = iter->second.cb(CTX_PC);
+#if defined(ARCHITECTURE_x86_64)
             CTX_SP -= sizeof(u64);
             *std::bit_cast<u64*>(CTX_SP) = fc.ret_rip;
             CTX_PC = fc.call_rip;
-            return;
-        }
-    }
-    fmt::print(stderr, "Unhandled {} at rip {:#018x}\n", sig == SIGSEGV ? "SIGSEGV" : "SIGBUS", CTX_PC);
 #elif defined(ARCHITECTURE_arm64)
-    {
-        std::shared_lock guard(sig_handler->code_block_infos_mutex);
-        if (const auto iter = sig_handler->FindCodeBlockInfo(CTX_PC); iter != sig_handler->code_block_infos.end()) {
-            FakeCall fc = iter->second.cb(CTX_PC);
             CTX_PC = fc.call_pc;
-            return;
-        }
-    }
-    fmt::print(stderr, "Unhandled {} at pc {:#018x}\n", sig == SIGSEGV ? "SIGSEGV" : "SIGBUS", CTX_PC);
 #elif defined(ARCHITECTURE_riscv64)
-    {
-        std::shared_lock guard(sig_handler->code_block_infos_mutex);
-        if (const auto iter = sig_handler->FindCodeBlockInfo(CTX_SEPC); iter != sig_handler->code_block_infos.end()) {
-            FakeCall fc = iter->second.cb(CTX_SEPC);
-            CTX_SEPC = fc.call_sepc;
-            return;
-        }
-    }
-    fmt::print(stderr, "Unhandled {} at pc {:#018x}\n", sig == SIGSEGV ? "SIGSEGV" : "SIGBUS", CTX_SEPC);
+            CTX_PC = fc.call_sepc;
 #elif defined(ARCHITECTURE_loongarch64)
-    {
-        std::shared_lock guard(sig_handler->code_block_infos_mutex);
-        if (const auto iter = sig_handler->FindCodeBlockInfo(CTX_PC); iter != sig_handler->code_block_infos.end()) {
-            FakeCall fc = iter->second.cb(CTX_PC);
             CTX_PC = fc.call_pc;
+#else
+            ASSERT(false);
+#endif
             return;
         }
     }
-    fmt::print(stderr, "Unhandled {} at pc {:#018x}\n", sig == SIGSEGV ? "SIGSEGV" : "SIGBUS", CTX_PC);
-#else
-#    error "Invalid architecture"
-#endif
+    LOG_ERROR(Core, "Unhandled {} at {:#018x}\n", sig == SIGSEGV ? "SIGSEGV" : "SIGBUS", CTX_PC);
 
     struct sigaction* retry_sa = sig == SIGSEGV ? &sig_handler->old_sa_segv : &sig_handler->old_sa_bus;
     if (retry_sa->sa_flags & SA_SIGINFO) {
@@ -190,9 +164,10 @@ void SigHandler::SigAction(int sig, siginfo_t* info, void* raw_context) {
 
 struct ExceptionHandler::Impl final {
     Impl(u64 offset_, u64 size_)
-            : offset(offset_)
-            , size(size_) {
-        RegisterHandler();
+        : offset(offset_)
+        , size(size_)
+    {
+        SigHandler::RegisterHandler();
     }
 
     void SetCallback(std::function<FakeCall(u64)> cb) {
diff --git a/src/dynarmic/src/dynarmic/common/context.h b/src/dynarmic/src/dynarmic/common/context.h
index db7af8e0ae..0c18807ce5 100644
--- a/src/dynarmic/src/dynarmic/common/context.h
+++ b/src/dynarmic/src/dynarmic/common/context.h
@@ -136,14 +136,14 @@
 #    endif
 #elif defined(ARCHITECTURE_riscv64)
 #   if defined(__FreeBSD__)
-#       define CTX_SEPC (mctx.mc_gpregs.gp_sepc)
+#       define CTX_PC (mctx.mc_gpregs.gp_sepc)
 #       define CTX_SP (mctx.mc_gpregs.gp_sp)
 #   elif defined(__linux__)
-#       define CTX_SEPC (mctx.__gregs[REG_PC])
+#       define CTX_PC (mctx.__gregs[REG_PC])
 #       define CTX_SP (mctx.__gregs[REG_SP])
 #   elif defined(__OpenBSD__)
 // https://github.com/openbsd/src/blob/master/sys/arch/riscv64/include/signal.h
-#        define CTX_SEPC (ucontext->sc_sepc)
+#        define CTX_PC (ucontext->sc_sepc)
 #        define CTX_SP (ucontext->sc_sp)
 #    else
 #        error "unknown platform"