From c72c9924d327eea687aea3e3d1293521079c7297 Mon Sep 17 00:00:00 2001
From: Emery Hemingway <emery@vfemail.net>
Date: Thu, 25 Jun 2015 12:50:01 -0500
Subject: [PATCH] init: prios shall not exceed the lowest prio level

Fixes #1570
---
 repos/os/include/init/child.h | 25 ++++++++++++++++++-------
 repos/os/src/init/main.cc     | 10 +++++-----
 2 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/repos/os/include/init/child.h b/repos/os/include/init/child.h
index dc83b3788b..4d7f076ff3 100644
--- a/repos/os/include/init/child.h
+++ b/repos/os/include/init/child.h
@@ -51,7 +51,7 @@ namespace Init {
 		Genode::printf("         Proceeding with a quota of %zu.\n", avail);
 	}
 
-	inline long read_priority(Genode::Xml_node start_node)
+	inline long read_priority(Genode::Xml_node start_node, long prio_levels)
 	{
 		long priority = Genode::Cpu_session::DEFAULT_PRIORITY;
 		try { start_node.attribute("priority").value(&priority); }
@@ -64,7 +64,18 @@ namespace Init {
 		 * calculations, we use inverted values. Lower values
 		 * correspond to higher priorities.
 		 */
-		return -priority;
+		priority = -priority;
+
+		if (priority && (priority >= prio_levels)) {
+			long new_prio = prio_levels-1;
+			char name[Genode::Service::MAX_NAME_LEN];
+			start_node.attribute("name").value(name, sizeof(name));
+			PERR("%s: invalid priority, upgrading from -%ld to -%ld",
+			     name, priority, new_prio);
+			return new_prio;
+		}
+
+		return priority;
 	}
 
 
@@ -450,13 +461,13 @@ class Init::Child : Genode::Child_policy
 			inline void transfer_cpu_quota();
 
 			Resources(Genode::Xml_node start_node, const char *label,
-			          long prio_levels_log2,
+			          long prio_levels,
 			          Genode::Affinity::Space const &affinity_space,
 			          Genode::Native_pd_args const * pd_args)
 			:
 				Read_quota(start_node, ram_quota, cpu_quota_pc, constrain_phys),
-				prio_levels_log2(prio_levels_log2),
-				priority(read_priority(start_node)),
+				prio_levels_log2(Genode::log2(prio_levels)),
+				priority(read_priority(start_node, prio_levels)),
 				affinity(affinity_space,
 				         read_affinity_location(affinity_space, start_node)),
 				pd(label, pd_args),
@@ -526,7 +537,7 @@ class Init::Child : Genode::Child_policy
 		Child(Genode::Xml_node              start_node,
 		      Genode::Xml_node              default_route_node,
 		      Name_registry                *name_registry,
-		      long                          prio_levels_log2,
+		      long                          prio_levels,
 		      Genode::Affinity::Space const &affinity_space,
 		      Genode::Service_registry      *parent_services,
 		      Genode::Service_registry      *child_services,
@@ -538,7 +549,7 @@ class Init::Child : Genode::Child_policy
 			_name_registry(name_registry),
 			_name(start_node, name_registry),
 			_pd_args(start_node),
-			_resources(start_node, _name.unique, prio_levels_log2,
+			_resources(start_node, _name.unique, prio_levels,
 			           affinity_space, &_pd_args),
 			_entrypoint(cap_session, ENTRYPOINT_STACK_SIZE, _name.unique, false, _resources.affinity.location()),
 			_binary_rom(_name.file, _name.file),
diff --git a/repos/os/src/init/main.cc b/repos/os/src/init/main.cc
index b2a229ed77..e0a779a2ec 100644
--- a/repos/os/src/init/main.cc
+++ b/repos/os/src/init/main.cc
@@ -26,7 +26,7 @@ namespace Init { bool config_verbose = false; }
 /**
  * Read priority-levels declaration from config
  */
-inline long read_prio_levels_log2()
+inline long read_prio_levels()
 {
 	using namespace Genode;
 
@@ -35,11 +35,11 @@ inline long read_prio_levels_log2()
 		config()->xml_node().attribute("prio_levels").value(&prio_levels); }
 	catch (...) { }
 
-	if (prio_levels && prio_levels != (1 << log2(prio_levels))) {
+	if (prio_levels && (prio_levels != (1 << log2(prio_levels)))) {
 		printf("Warning: Priolevels is not power of two, priorities are disabled\n");
-		prio_levels = 0;
+		return 0;
 	}
-	return prio_levels ? log2(prio_levels) : 0;
+	return prio_levels;
 }
 
 
@@ -334,7 +334,7 @@ int main(int, char **)
 				try {
 					children.insert(new (env()->heap())
 					                Init::Child(start_node, default_route_node,
-					                            &children, read_prio_levels_log2(),
+					                            &children, read_prio_levels(),
 					                            read_affinity_space(),
 					                            &parent_services, &child_services, &cap));
 				}