base: Adding multi-letter command support to GDB stub

The GDB remote protocol defines multi-letter
 command names that start with a "v".
I added vKill and vMustReplyEmpty as an example.

Change-Id: I10177729c7d6a3e7d469ce66a63bfcfd21aa6f83
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/63525
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>

src/base/remote_gdb.cc

@@ -925,6 +925,8 @@ std::map<char, BaseRemoteGDB::GdbCommand> BaseRemoteGDB::commandMap = {
     { 'S', { "KGDB_ASYNC_STEP", &BaseRemoteGDB::cmdAsyncStep } },
     // find out if the thread is alive
     { 'T', { "KGDB_THREAD_ALIVE", &BaseRemoteGDB::cmdUnsupported } },
+    //multi letter command
+    { 'v', { "KGDB_MULTI_LETTER", &BaseRemoteGDB::cmdMultiLetter } },
     // target exited
     { 'W', { "KGDB_TARGET_EXIT", &BaseRemoteGDB::cmdUnsupported } },
     // write memory
@@ -1104,6 +1106,67 @@ BaseRemoteGDB::cmdMemW(GdbCommand::Context &ctx)
     return true;
 }
 
+bool
+BaseRemoteGDB::cmdMultiLetter(GdbCommand::Context &ctx)
+{
+    GdbMultiLetterCommand::Context new_ctx;
+    new_ctx.type = ctx.type;
+    strtok(ctx.data,";?");
+    char* sep = strtok(NULL,";:?");
+
+    int txt_len = (sep != NULL) ? (sep - ctx.data) : strlen(ctx.data);
+    DPRINTF(GDBMisc, "Multi-letter: %s , len=%i\n", ctx.data,txt_len);
+    new_ctx.cmdTxt = std::string(ctx.data,txt_len);
+    new_ctx.data = sep;
+    new_ctx.len = ctx.len - txt_len;
+    try {
+        auto cmd_it = multiLetterMap.find(new_ctx.cmdTxt);
+        if (cmd_it == multiLetterMap.end()) {
+            DPRINTF(GDBMisc, "Unknown command: %s\n", new_ctx.cmdTxt);
+            throw Unsupported();
+        }
+        new_ctx.cmd = &(cmd_it->second);
+
+        return (this->*(new_ctx.cmd->func))(new_ctx);
+    //catching errors: we don't need to catch anything else
+    //as it will be handled by processCommands
+    } catch (CmdError &e) {
+        send(e.error);
+    }
+    return false;
+}
+
+std::map<std::string, BaseRemoteGDB::GdbMultiLetterCommand>
+BaseRemoteGDB::multiLetterMap = {
+    { "MustReplyEmpty", { "KGDB_REPLY_EMPTY", &BaseRemoteGDB::cmdReplyEmpty}},
+    { "Kill", { "KGDB_VKILL", &BaseRemoteGDB::cmdVKill}},
+};
+
+
+bool
+BaseRemoteGDB::cmdReplyEmpty(GdbMultiLetterCommand::Context &ctx)
+{
+    send("");
+    return true;
+}
+
+bool
+BaseRemoteGDB::cmdVKill(GdbMultiLetterCommand::Context &ctx)
+{
+    warn("GDB command for kill received detaching instead");
+    detach();
+    return false;
+}
+
+bool
+BaseRemoteGDB::cmdMultiUnsupported(GdbMultiLetterCommand::Context &ctx)
+{
+    DPRINTF(GDBMisc, "Unsupported Multi name command : %s\n",
+        ctx.cmd->name);
+    DDUMP(GDBMisc, ctx.data, ctx.len);
+    throw Unsupported();
+}
+
 namespace {
 
 std::pair<std::string, std::string>

src/base/remote_gdb.hh

@@ -344,6 +344,30 @@ class BaseRemoteGDB
 
     static std::map<char, GdbCommand> commandMap;
 
+    struct GdbMultiLetterCommand
+    {
+      public:
+        struct Context
+        {
+            const GdbMultiLetterCommand *cmd;
+            std::string cmdTxt;
+            int type;
+            char *data;
+            int len;
+        };
+
+        typedef bool (BaseRemoteGDB::*Func)(Context &ctx);
+
+        const char * const name;
+        const Func func;
+
+        GdbMultiLetterCommand(const char *_name, Func _func) :
+          name(_name), func(_func) {}
+    };
+
+
+    static std::map<std::string, GdbMultiLetterCommand> multiLetterMap;
+
     bool cmdUnsupported(GdbCommand::Context &ctx);
 
     bool cmdSignal(GdbCommand::Context &ctx);
@@ -361,6 +385,13 @@ class BaseRemoteGDB
     bool cmdClrHwBkpt(GdbCommand::Context &ctx);
     bool cmdSetHwBkpt(GdbCommand::Context &ctx);
     bool cmdDumpPageTable(GdbCommand::Context &ctx);
+    bool cmdMultiLetter(GdbCommand::Context &ctx);
+
+    //Multi letter command
+    bool cmdMultiUnsupported(GdbMultiLetterCommand::Context &ctx);
+
+    bool cmdReplyEmpty(GdbMultiLetterCommand::Context &ctx);
+    bool cmdVKill(GdbMultiLetterCommand::Context &ctx);
 
     struct QuerySetCommand
     {