[Linux] Implement exception handler

src/xenia/base/exception_handler_posix.cc

@@ -9,10 +9,135 @@
 
 #include "xenia/base/exception_handler.h"
 
+#include <signal.h>
+#include <ucontext.h>
+
 namespace xe {
 
-// TODO(DrChat): Exception handling on linux.
-void ExceptionHandler::Install(Handler fn, void* data) {}
-void ExceptionHandler::Uninstall(Handler fn, void* data) {}
+bool signal_handlers_installed_ = false;
+struct sigaction original_sigill_handler_;
+struct sigaction original_sigsegv_handler_;
 
-}  // namespace xe
+// This can be as large as needed, but isn't often needed.
+// As we will be sometimes firing many exceptions we want to avoid having to
+// scan the table too much or invoke many custom handlers.
+constexpr size_t kMaxHandlerCount = 8;
+
+// All custom handlers, left-aligned and null terminated.
+// Executed in order.
+std::pair<ExceptionHandler::Handler, void*> handlers_[kMaxHandlerCount];
+
+void ExceptionHandlerCallback(int signum, siginfo_t* siginfo, void* sigctx) {
+  ucontext_t* ctx = static_cast<ucontext_t*>(sigctx);
+
+  X64Context thread_context;
+
+  thread_context.rip = ctx->uc_mcontext.gregs[REG_RIP];
+  thread_context.eflags = ctx->uc_mcontext.gregs[REG_EFL];
+  thread_context.rax = ctx->uc_mcontext.gregs[REG_RAX];
+  thread_context.rcx = ctx->uc_mcontext.gregs[REG_RCX];
+  thread_context.rdx = ctx->uc_mcontext.gregs[REG_RDX];
+  thread_context.rbx = ctx->uc_mcontext.gregs[REG_RBX];
+  thread_context.rsp = ctx->uc_mcontext.gregs[REG_RSP];
+  thread_context.rbp = ctx->uc_mcontext.gregs[REG_RBP];
+  thread_context.rsi = ctx->uc_mcontext.gregs[REG_RSI];
+  thread_context.rdi = ctx->uc_mcontext.gregs[REG_RDI];
+  thread_context.r8 = ctx->uc_mcontext.gregs[REG_R8];
+  thread_context.r9 = ctx->uc_mcontext.gregs[REG_R9];
+  thread_context.r10 = ctx->uc_mcontext.gregs[REG_R10];
+  thread_context.r11 = ctx->uc_mcontext.gregs[REG_R11];
+  thread_context.r12 = ctx->uc_mcontext.gregs[REG_R12];
+  thread_context.r13 = ctx->uc_mcontext.gregs[REG_R13];
+  thread_context.r14 = ctx->uc_mcontext.gregs[REG_R14];
+  thread_context.r15 = ctx->uc_mcontext.gregs[REG_R15];
+  std::memcpy(thread_context.xmm_registers, ctx->uc_mcontext.fpregs->_xmm,
+              sizeof(thread_context.xmm_registers));
+
+  Exception ex;
+  switch (signum) {
+    case SIGILL:
+      ex.InitializeIllegalInstruction(&thread_context);
+      break;
+    case SIGSEGV: {
+      Exception::AccessViolationOperation access_violation_operation =
+          ((ucontext_t*)sigctx)->uc_mcontext.gregs[REG_ERR] & 0x2
+              ? Exception::AccessViolationOperation::kRead
+              : Exception::AccessViolationOperation::kWrite;
+      ex.InitializeAccessViolation(&thread_context,
+                                   reinterpret_cast<uint64_t>(siginfo->si_addr),
+                                   access_violation_operation);
+    } break;
+    default:
+      assert_always("Unhandled signum");
+  }
+
+  for (size_t i = 0; i < xe::countof(handlers_) && handlers_[i].first; ++i) {
+    if (handlers_[i].first(&ex, handlers_[i].second)) {
+      // Exception handled.
+      return;
+    }
+  }
+
+  assert_always("Unhandled exception");
+}
+
+void ExceptionHandler::Install(Handler fn, void* data) {
+  if (!signal_handlers_installed_) {
+    struct sigaction signal_handler;
+
+    std::memset(&signal_handler, 0, sizeof(signal_handler));
+    signal_handler.sa_sigaction = ExceptionHandlerCallback;
+    signal_handler.sa_flags = SA_SIGINFO;
+
+    if (sigaction(SIGILL, &signal_handler, &original_sigill_handler_) != 0) {
+      assert_always("Failed to install new SIGILL handler");
+    }
+    if (sigaction(SIGSEGV, &signal_handler, &original_sigsegv_handler_) != 0) {
+      assert_always("Failed to install new SIGSEGV handler");
+    }
+    signal_handlers_installed_ = true;
+  }
+
+  for (size_t i = 0; i < xe::countof(handlers_); ++i) {
+    if (!handlers_[i].first) {
+      handlers_[i].first = fn;
+      handlers_[i].second = data;
+      return;
+    }
+  }
+  assert_always("Too many exception handlers installed");
+}
+
+void ExceptionHandler::Uninstall(Handler fn, void* data) {
+  for (size_t i = 0; i < xe::countof(handlers_); ++i) {
+    if (handlers_[i].first == fn && handlers_[i].second == data) {
+      for (; i < xe::countof(handlers_) - 1; ++i) {
+        handlers_[i] = handlers_[i + 1];
+      }
+      handlers_[i].first = nullptr;
+      handlers_[i].second = nullptr;
+      break;
+    }
+  }
+
+  bool has_any = false;
+  for (size_t i = 0; i < xe::countof(handlers_); ++i) {
+    if (handlers_[i].first) {
+      has_any = true;
+      break;
+    }
+  }
+  if (!has_any) {
+    if (signal_handlers_installed_) {
+      if (sigaction(SIGILL, &original_sigill_handler_, NULL) != 0) {
+        assert_always("Failed to restore original SIGILL handler");
+      }
+      if (sigaction(SIGSEGV, &original_sigsegv_handler_, NULL) != 0) {
+        assert_always("Failed to restore original SIGSEGV handler");
+      }
+      signal_handlers_installed_ = false;
+    }
+  }
+}
+
+}  // namespace xe