Patch terminal_log to override log labels

When generating configuration with Dhall it is simpler to specify
a policy rather than rewrite a session label.

packages/genodelabs/depot-targets.nix

@@ -216,7 +216,7 @@ in {
   tclsh = { };
   terminal.depotInputs = with self; [ vfs ];
   terminal_crosslink = { };
-  terminal_log = { };
+  terminal_log.patches = [ ./patches/terminal_log.patch ];
   test-block = { };
   test-bomb = { };
   test-clipboard = { };

packages/genodelabs/patches/terminal_log.patch

@@ -0,0 +1,82 @@
+From 5acbeb7a63aa4fe1b7e9817c5ba56786a1703e06 Mon Sep 17 00:00:00 2001
+From: Emery Hemingway <ehmry@posteo.net>
+Date: Fri, 16 Apr 2021 13:54:16 +0200
+Subject: [PATCH] terminal_log: configurable log labels
+
+---
+ repos/os/src/server/terminal_log/main.cc | 24 ++++++++++++++++--------
+ 1 file changed, 16 insertions(+), 8 deletions(-)
+
+diff --git a/repos/os/src/server/terminal_log/main.cc b/repos/os/src/server/terminal_log/main.cc
+index dd3cb1a46b..07f01d8da4 100644
+--- a/repos/os/src/server/terminal_log/main.cc
++++ b/repos/os/src/server/terminal_log/main.cc
+@@ -30,8 +30,8 @@ namespace Genode {
+ 
+ 		private:
+ 
+-			char                  _label[LABEL_LEN];
+-			Terminal::Connection &_terminal;
++			 String<LABEL_LEN> const  _label;
++			Terminal::Connection     &_terminal;
+ 
+ 		public:
+ 
+@@ -39,7 +39,7 @@ namespace Genode {
+ 			 * Constructor
+ 			 */
+ 			Termlog_component(const char *label, Terminal::Connection &terminal)
+-			: _terminal(terminal) { snprintf(_label, LABEL_LEN, "[%s] ", label); }
++			: _label(label), _terminal(terminal) { }
+ 
+ 
+ 			/*****************
+@@ -76,7 +76,7 @@ namespace Genode {
+ 					return;
+ 				}
+ 
+-				_terminal.write(_label, strlen(_label));
++				_terminal.write(_label);
+ 				_terminal.write(string, len);
+ 
+ 				/* if last character of string was not a line break, add one */
+@@ -93,7 +93,8 @@ namespace Genode {
+ 	{
+ 		private:
+ 
+-			Terminal::Connection _terminal;
++			Genode::Env          &_env;
++			Terminal::Connection  _terminal { _env, "log" };
+ 
+ 		protected:
+ 
+@@ -104,8 +105,15 @@ namespace Genode {
+ 			{
+ 				char label_buf[Termlog_component::LABEL_LEN];
+ 
+-				Arg label_arg = Arg_string::find_arg(args, "label");
+-				label_arg.string(label_buf, sizeof(label_buf), "");
++				Session_label const session_label = label_from_args(args);
++				try {
++					Attached_rom_dataspace config_rom(_env, "config");
++					Session_policy policy(session_label, config_rom.xml());
++					policy.attribute_value("label", label_buf, sizeof(label_buf));
++				} (...) {
++					snprintf(label_buf, sizeof(label_buf),
++					         "[%s] ", session_label.string());
++				}
+ 
+ 				return new (md_alloc()) Termlog_component(label_buf, _terminal);
+ 			}
+@@ -120,7 +128,7 @@ namespace Genode {
+ 			 */
+ 			Termlog_root(Genode::Env &env, Allocator &md_alloc)
+ 			: Root_component<Termlog_component>(env.ep(), md_alloc),
+-			  _terminal(env, "log") { }
++			  _env(env) { }
+ 	};
+ }
+ 
+-- 
+2.31.0
+