Merge pull request #6395 from ian-h-chamberlain/feature/gdbstub-hio

Initial port of luma3ds' gdb_hio to Citra

src/core/CMakeLists.txt

@@ -115,6 +115,8 @@ add_library(core STATIC
     frontend/mic.h
     gdbstub/gdbstub.cpp
     gdbstub/gdbstub.h
+    gdbstub/hio.cpp
+    gdbstub/hio.h
     hle/applets/applet.cpp
     hle/applets/applet.h
     hle/applets/erreula.cpp

src/core/gdbstub/gdbstub.cpp

@@ -35,6 +35,7 @@
 #include "core/arm/arm_interface.h"
 #include "core/core.h"
 #include "core/gdbstub/gdbstub.h"
+#include "core/gdbstub/hio.h"
 #include "core/hle/kernel/process.h"
 #include "core/loader/loader.h"
 #include "core/memory.h"
@@ -261,13 +262,7 @@ static u8 NibbleToHex(u8 n) {
     }
 }
 
-/**
+u32 HexToInt(const u8* src, std::size_t len) {
- * Converts input hex string characters into an array of equivalent of u8 bytes.
- *
- * @param src Pointer to array of output hex string characters.
- * @param len Length of src array.
- */
-static u32 HexToInt(const u8* src, std::size_t len) {
     u32 output = 0;
     while (len-- > 0) {
         output = (output << 4) | HexCharToValue(src[0]);
@@ -492,12 +487,7 @@ static void SendPacket(const char packet) {
     }
 }
 
-/**
+void SendReply(const char* reply) {
- * Send reply to gdb client.
- *
- * @param reply Reply to be sent to client.
- */
-static void SendReply(const char* reply) {
     if (!IsConnected()) {
         return;
     }
@@ -653,7 +643,7 @@ static void ReadCommand() {
     memset(command_buffer, 0, sizeof(command_buffer));
 
     u8 c = ReadByte();
-    if (c == '+') {
+    if (c == GDB_STUB_ACK) {
         // ignore ack
         return;
     } else if (c == 0x03) {
@@ -843,7 +833,7 @@ static void ReadMemory() {
     u32 len =
         HexToInt(start_offset, static_cast<u32>((command_buffer + command_length) - start_offset));
 
-    LOG_DEBUG(Debug_GDBStub, "gdb: addr: {:08x} len: {:08x}\n", addr, len);
+    LOG_DEBUG(Debug_GDBStub, "ReadMemory addr: {:08x} len: {:08x}", addr, len);
 
     if (len * 2 > sizeof(reply)) {
         SendReply("E01");
@@ -860,7 +850,11 @@ static void ReadMemory() {
 
     MemToGdbHex(reply, data.data(), len);
     reply[len * 2] = '\0';
-    SendReply(reinterpret_cast<char*>(reply));
+
+    auto reply_str = reinterpret_cast<char*>(reply);
+
+    LOG_DEBUG(Debug_GDBStub, "ReadMemory result: {}", reply_str);
+    SendReply(reply_str);
 }
 
 /// Modify location in memory with data received from the gdb client.
@@ -1050,6 +1044,11 @@ void HandlePacket() {
         return;
     }
 
+    if (HandlePendingHioRequestPacket()) {
+        // Don't do anything else while we wait for the client to respond
+        return;
+    }
+
     if (!IsDataAvailable()) {
         return;
     }
@@ -1059,7 +1058,7 @@ void HandlePacket() {
         return;
     }
 
-    LOG_DEBUG(Debug_GDBStub, "Packet: {}", command_buffer[0]);
+    LOG_DEBUG(Debug_GDBStub, "Packet: {0:d} ('{0:c}')", command_buffer[0]);
 
     switch (command_buffer[0]) {
     case 'q':
@@ -1072,9 +1071,14 @@ void HandlePacket() {
         SendSignal(current_thread, latest_signal);
         break;
     case 'k':
-        Shutdown();
         LOG_INFO(Debug_GDBStub, "killed by gdb");
+        ToggleServer(false);
+        // Continue execution so we don't hang forever after shutting down the server
+        Continue();
         return;
+    case 'F':
+        HandleHioReply(command_buffer, command_length);
+        break;
     case 'g':
         ReadRegisters();
         break;
@@ -1251,6 +1255,10 @@ bool GetCpuHaltFlag() {
     return halt_loop;
 }
 
+void SetCpuHaltFlag(bool halt) {
+    halt_loop = halt;
+}
+
 bool GetCpuStepFlag() {
     return step_loop;
 }
@@ -1265,6 +1273,7 @@ void SendTrap(Kernel::Thread* thread, int trap) {
     }
 
     current_thread = thread;
+
     SendSignal(thread, trap);
 
     halt_loop = true;

src/core/gdbstub/gdbstub.h

@@ -90,6 +90,13 @@ bool CheckBreakpoint(VAddr addr, GDBStub::BreakpointType type);
 // If set to true, the CPU will halt at the beginning of the next CPU loop.
 bool GetCpuHaltFlag();
 
+/**
+ * If set to true, the CPU will halt at the beginning of the next CPU loop.
+ *
+ * @param halt whether to halt on the next loop
+ */
+void SetCpuHaltFlag(bool halt);
+
 // If set to true and the CPU is halted, the CPU will step one instruction.
 bool GetCpuStepFlag();
 
@@ -107,4 +114,19 @@ void SetCpuStepFlag(bool is_step);
  * @param trap Trap no.
  */
 void SendTrap(Kernel::Thread* thread, int trap);
+
+/**
+ * Send reply to gdb client.
+ *
+ * @param reply Reply to be sent to client.
+ */
+void SendReply(const char* reply);
+
+/**
+ * Converts input hex string characters into an array of equivalent of u8 bytes.
+ *
+ * @param src Pointer to array of output hex string characters.
+ * @param len Length of src array.
+ */
+u32 HexToInt(const u8* src, std::size_t len);
 } // namespace GDBStub

src/core/gdbstub/hio.cpp

@@ -0,0 +1,261 @@
+// Copyright 2023 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <fmt/ranges.h>
+#include "common/string_util.h"
+#include "core/core.h"
+#include "core/gdbstub/gdbstub.h"
+#include "core/gdbstub/hio.h"
+
+namespace GDBStub {
+
+namespace {
+
+static VAddr current_hio_request_addr;
+static PackedGdbHioRequest current_hio_request;
+
+enum class Status {
+    NoRequest,
+    NotSent,
+    SentWaitingReply,
+};
+
+static std::atomic<Status> request_status{Status::NoRequest};
+
+static std::atomic<bool> was_halted = false;
+static std::atomic<bool> was_stepping = false;
+
+} // namespace
+
+/**
+ * @return Whether the application has requested I/O, and it has not been sent.
+ */
+static bool HasPendingHioRequest() {
+    return current_hio_request_addr != 0 && request_status == Status::NotSent;
+}
+
+/**
+ * @return Whether the GDB stub is awaiting a reply from the client.
+ */
+static bool IsWaitingForHioReply() {
+    return current_hio_request_addr != 0 && request_status == Status::SentWaitingReply;
+}
+
+/**
+ * Send a response indicating an error back to the application.
+ *
+ * @param error_code The error code to respond back to the app. This typically corresponds to errno.
+ *
+ * @param retval The return value of the syscall the app requested.
+ */
+static void SendErrorReply(int error_code, int retval = -1) {
+    auto packet = fmt::format("F{:x},{:x}", retval, error_code);
+    SendReply(packet.data());
+}
+
+void SetHioRequest(const VAddr addr) {
+    if (!IsServerEnabled()) {
+        LOG_WARNING(Debug_GDBStub, "HIO requested but GDB stub is not running");
+        return;
+    }
+
+    if (IsWaitingForHioReply()) {
+        LOG_WARNING(Debug_GDBStub, "HIO requested while already in progress");
+        return;
+    }
+
+    if (HasPendingHioRequest()) {
+        LOG_INFO(Debug_GDBStub, "overwriting existing HIO request that was not sent yet");
+    }
+
+    auto& memory = Core::System::GetInstance().Memory();
+    const auto process = Core::System::GetInstance().Kernel().GetCurrentProcess();
+
+    if (!memory.IsValidVirtualAddress(*process, addr)) {
+        LOG_WARNING(Debug_GDBStub, "Invalid address for HIO request");
+        return;
+    }
+
+    memory.ReadBlock(*process, addr, &current_hio_request, sizeof(PackedGdbHioRequest));
+
+    if (current_hio_request.magic != std::array{'G', 'D', 'B', '\0'}) {
+        std::string_view bad_magic{
+            current_hio_request.magic.data(),
+            current_hio_request.magic.size(),
+        };
+        LOG_WARNING(Debug_GDBStub, "Invalid HIO request sent by application: bad magic '{}'",
+                    bad_magic);
+
+        current_hio_request_addr = 0;
+        current_hio_request = {};
+        request_status = Status::NoRequest;
+        return;
+    }
+
+    LOG_DEBUG(Debug_GDBStub, "HIO request initiated at 0x{:X}", addr);
+    current_hio_request_addr = addr;
+    request_status = Status::NotSent;
+
+    was_halted = GetCpuHaltFlag();
+    was_stepping = GetCpuStepFlag();
+
+    // Now halt, so that no further instructions are executed until the request
+    // is processed by the client. We will continue after the reply comes back
+    Break();
+    SetCpuHaltFlag(true);
+    SetCpuStepFlag(false);
+    Core::GetRunningCore().ClearInstructionCache();
+}
+
+void HandleHioReply(const u8* const command_buffer, const u32 command_length) {
+    if (!IsWaitingForHioReply()) {
+        LOG_WARNING(Debug_GDBStub, "Got HIO reply but never sent a request");
+        return;
+    }
+
+    // Skip 'F' header
+    auto* command_pos = command_buffer + 1;
+
+    if (*command_pos == 0 || *command_pos == ',') {
+        LOG_WARNING(Debug_GDBStub, "bad HIO packet format position 0: {}", *command_pos);
+        SendErrorReply(EILSEQ);
+        return;
+    }
+
+    // Set the sign of the retval
+    if (*command_pos == '-') {
+        command_pos++;
+        current_hio_request.retval = -1;
+    } else {
+        if (*command_pos == '+') {
+            command_pos++;
+        }
+
+        current_hio_request.retval = 1;
+    }
+
+    const std::string command_str{command_pos, command_buffer + command_length};
+    std::vector<std::string> command_parts;
+    Common::SplitString(command_str, ',', command_parts);
+
+    if (command_parts.empty() || command_parts.size() > 3) {
+        LOG_WARNING(Debug_GDBStub, "Unexpected reply packet size: {}", command_parts);
+        SendErrorReply(EILSEQ);
+        return;
+    }
+
+    u64 unsigned_retval =
+        HexToInt(reinterpret_cast<const u8*>(command_parts[0].data()), command_parts[0].size());
+    current_hio_request.retval *= unsigned_retval;
+
+    if (command_parts.size() > 1) {
+        // Technically the errno could be signed but in practice this doesn't happen
+        current_hio_request.gdb_errno =
+            HexToInt(reinterpret_cast<const u8*>(command_parts[1].data()), command_parts[1].size());
+    } else {
+        current_hio_request.gdb_errno = 0;
+    }
+
+    current_hio_request.ctrl_c = false;
+
+    if (command_parts.size() > 2 && !command_parts[2].empty()) {
+        if (command_parts[2][0] != 'C') {
+            LOG_WARNING(Debug_GDBStub, "expected ctrl-c flag got '{}'", command_parts[2][0]);
+            SendErrorReply(EILSEQ);
+            return;
+        }
+
+        // for now we just ignore any trailing ";..." attachments
+        current_hio_request.ctrl_c = true;
+    }
+
+    std::fill(std::begin(current_hio_request.param_format),
+              std::end(current_hio_request.param_format), 0);
+
+    LOG_TRACE(Debug_GDBStub, "HIO reply: {{retval = {}, errno = {}, ctrl_c = {}}}",
+              current_hio_request.retval, current_hio_request.gdb_errno,
+              current_hio_request.ctrl_c);
+
+    const auto process = Core::System::GetInstance().Kernel().GetCurrentProcess();
+    auto& memory = Core::System::GetInstance().Memory();
+
+    // should have been checked when we first initialized the request,
+    // but just double check again before we write to memory
+    if (!memory.IsValidVirtualAddress(*process, current_hio_request_addr)) {
+        LOG_WARNING(Debug_GDBStub, "Invalid address {:#X} to write HIO reply",
+                    current_hio_request_addr);
+        return;
+    }
+
+    memory.WriteBlock(*process, current_hio_request_addr, &current_hio_request,
+                      sizeof(PackedGdbHioRequest));
+
+    current_hio_request = {};
+    current_hio_request_addr = 0;
+    request_status = Status::NoRequest;
+
+    // Restore state from before the request came in
+    SetCpuStepFlag(was_stepping);
+    SetCpuHaltFlag(was_halted);
+    Core::GetRunningCore().ClearInstructionCache();
+}
+
+bool HandlePendingHioRequestPacket() {
+    if (!HasPendingHioRequest()) {
+        return false;
+    }
+
+    if (IsWaitingForHioReply()) {
+        // We already sent it, continue waiting for a reply
+        return true;
+    }
+
+    // We need a null-terminated string from char* instead of using
+    // the full length of the array (like {.begin(), .end()} constructor would)
+    std::string_view function_name{current_hio_request.function_name.data()};
+
+    std::string packet = fmt::format("F{}", function_name);
+
+    u32 str_length_idx = 0;
+
+    for (u32 i = 0; i < 8 && current_hio_request.param_format[i] != 0; i++) {
+        u64 param = current_hio_request.parameters[i];
+
+        // TODO: should we use the IntToGdbHex funcs instead of fmt::format_to ?
+        switch (current_hio_request.param_format[i]) {
+        case 'i':
+        case 'I':
+        case 'p':
+            // For pointers and 32-bit ints, truncate down to size before sending
+            param = static_cast<u32>(param);
+            [[fallthrough]];
+
+        case 'l':
+        case 'L':
+            fmt::format_to(std::back_inserter(packet), ",{:x}", param);
+            break;
+
+        case 's':
+            // strings are written as {pointer}/{length}
+            fmt::format_to(std::back_inserter(packet), ",{:x}/{:x}",
+                           static_cast<u32>(current_hio_request.parameters[i]),
+                           current_hio_request.string_lengths[str_length_idx++]);
+            break;
+
+        default:
+            LOG_WARNING(Debug_GDBStub, "unexpected hio request param format '{}'",
+                        current_hio_request.param_format[i]);
+            SendErrorReply(EILSEQ);
+            return false;
+        }
+    }
+
+    LOG_TRACE(Debug_GDBStub, "HIO request packet: '{}'", packet);
+
+    SendReply(packet.data());
+    request_status = Status::SentWaitingReply;
+    return true;
+}
+
+} // namespace GDBStub

src/core/gdbstub/hio.h

@@ -0,0 +1,64 @@
+// Copyright 2023 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "common/common_types.h"
+
+namespace GDBStub {
+
+/**
+ * A request from a debugged application to perform some I/O with the GDB client.
+ * This structure is also used to encode the reply back to the application.
+ *
+ * Based on the Rosalina + libctru implementations:
+ * https://github.com/LumaTeam/Luma3DS/blob/master/sysmodules/rosalina/include/gdb.h#L46C27-L62
+ * https://github.com/devkitPro/libctru/blob/master/libctru/source/gdbhio.c#L71-L87
+ */
+struct PackedGdbHioRequest {
+    std::array<char, 4> magic; // "GDB\0"
+    u32 version;
+
+private:
+    static inline constexpr std::size_t MAX_FUNCNAME_LEN = 16;
+    static inline constexpr std::size_t PARAM_COUNT = 8;
+
+public:
+    // Request. Char arrays have +1 entry for null terminator
+    std::array<char, MAX_FUNCNAME_LEN + 1> function_name;
+    std::array<char, PARAM_COUNT + 1> param_format;
+
+    std::array<u64, PARAM_COUNT> parameters;
+    std::array<u32, PARAM_COUNT> string_lengths;
+
+    // Return
+    s64 retval;
+    s32 gdb_errno;
+    bool ctrl_c;
+};
+
+static_assert(sizeof(PackedGdbHioRequest) == 152,
+              "HIO request size must match libctru implementation");
+
+/**
+ * Set the current HIO request to the given address. This is how the debugged
+ * app indicates to the gdbstub that it wishes to perform a request.
+ *
+ *  @param address The memory address of the \ref PackedGdbHioRequest.
+ */
+void SetHioRequest(const VAddr address);
+
+/**
+ * If there is a pending HIO request, send it to the client.
+ *
+ * @returns whethere any request was sent to the client.
+ */
+bool HandlePendingHioRequestPacket();
+
+/**
+ * Process an HIO reply from the client.
+ */
+void HandleHioReply(const u8* const command_buffer, const u32 command_length);
+
+} // namespace GDBStub

src/core/hle/kernel/svc.cpp

@@ -13,6 +13,7 @@
 #include "core/arm/arm_interface.h"
 #include "core/core.h"
 #include "core/core_timing.h"
+#include "core/gdbstub/hio.h"
 #include "core/hle/kernel/address_arbiter.h"
 #include "core/hle/kernel/client_port.h"
 #include "core/hle/kernel/client_session.h"
@@ -1140,9 +1141,21 @@ void SVC::Break(u8 break_reason) {
     system.SetStatus(Core::System::ResultStatus::ErrorUnknown);
 }
 
-/// Used to output a message on a debug hardware unit - does nothing on a retail unit
+/// Used to output a message on a debug hardware unit, or for the GDB file I/O
+/// (HIO) protocol - does nothing on a retail unit.
 void SVC::OutputDebugString(VAddr address, s32 len) {
-    if (len <= 0) {
+    if (!memory.IsValidVirtualAddress(*kernel.GetCurrentProcess(), address)) {
+        LOG_WARNING(Kernel_SVC, "OutputDebugString called with invalid address {:X}", address);
+        return;
+    }
+
+    if (len == 0) {
+        GDBStub::SetHioRequest(address);
+        return;
+    }
+
+    if (len < 0) {
+        LOG_WARNING(Kernel_SVC, "OutputDebugString called with invalid length {}", len);
         return;
     }