From f7fd7b0b11c63f4990bb2bd39c45e0ed255222cf Mon Sep 17 00:00:00 2001
From: Martin Stein <martin.stein@genode-labs.com>
Date: Fri, 30 Aug 2013 16:02:31 +0200
Subject: [PATCH] hw: no assertions in pagers

ref #528
---
 base-hw/include/base/ipc_pager.h       |  5 ++-
 base-hw/src/base/pager.cc              | 31 +++++++++------
 base-hw/src/core/rm_session_support.cc | 54 ++++++++++++++++++--------
 3 files changed, 62 insertions(+), 28 deletions(-)

diff --git a/base-hw/include/base/ipc_pager.h b/base-hw/include/base/ipc_pager.h
index 9444ad528..b3a08cab5 100644
--- a/base-hw/include/base/ipc_pager.h
+++ b/base-hw/include/base/ipc_pager.h
@@ -106,8 +106,11 @@ namespace Genode
 
 			/**
 			 * Resolve current pagefault and wait for a new one
+			 *
+			 * \retval   0  succeeded
+			 * \retval !=0  failed
 			 */
-			void resolve_and_wait_for_fault();
+			int resolve_and_wait_for_fault();
 
 			/**
 			 * Request instruction pointer of current page fault
diff --git a/base-hw/src/base/pager.cc b/base-hw/src/base/pager.cc
index d7e161bb5..687a9f3c9 100644
--- a/base-hw/src/base/pager.cc
+++ b/base-hw/src/base/pager.cc
@@ -29,23 +29,28 @@ void Pager_activation_base::entry()
 	_cap = pager;
 	_cap_valid.unlock();
 
-	/* wait for the first pagefault */
-	bool reply = false;
+	/* receive and handle faults */
+	bool mapping_pending = 0;
 	while (1)
 	{
-		if (reply)
-			pager.resolve_and_wait_for_fault();
-		else
+		if (mapping_pending) {
+			/* apply mapping and await next fault */
+			if (pager.resolve_and_wait_for_fault()) {
+				PERR("failed to resolve page fault");
+				pager.wait_for_fault();
+			}
+		} else {
 			pager.wait_for_fault();
-
-		/* lookup pager object for the current faulter */
+		}
+		/* lookup pager object for current faulter */
 		Object_pool<Pager_object>::Guard o(_ep ? _ep->lookup_and_lock(pager.badge()) : 0);
 		if (!o) {
-			PERR("%s:%d: Invalid pager object", __FILE__, __LINE__);
-			while (1) ;
+			PERR("invalid pager object");
+			mapping_pending = 0;
+		} else {
+			/* try to find an appropriate mapping */
+			mapping_pending = !o->pager(pager);
 		}
-		/* let pager handle the pagefault, apply mapping, await pagefault */
-		reply = !o->pager(pager);
 	}
 }
 
@@ -90,6 +95,10 @@ void Ipc_pager::wait_for_fault()
 	/* receive first message */
 	size_t s = Kernel::wait_for_request();
 	while (1) {
+
+		/*
+		 * FIXME: the message size is a weak indicator for the message type
+		 */
 		switch (s) {
 
 		case sizeof(Pagefault): {
diff --git a/base-hw/src/core/rm_session_support.cc b/base-hw/src/core/rm_session_support.cc
index 3f02169af..3634d7b2f 100644
--- a/base-hw/src/core/rm_session_support.cc
+++ b/base-hw/src/core/rm_session_support.cc
@@ -18,12 +18,24 @@
 #include <rm_session_component.h>
 #include <platform.h>
 #include <platform_thread.h>
-#include <assert.h>
 #include <tlb.h>
 
 using namespace Genode;
 
 
+/**
+ * Try to regain administrative memory that isn't used anymore from 'tlb'
+ */
+static void regain_ram_from_tlb(Tlb * tlb)
+{
+	size_t s;
+	void * base;
+	while (tlb->regain_memory(base, s)) {
+		platform()->ram_alloc()->free(base, s);
+	}
+}
+
+
 /***************
  ** Rm_client **
  ***************/
@@ -33,18 +45,19 @@ void Rm_client::unmap(addr_t core_local_base, addr_t virt_base, size_t size)
 {
 	/* get software TLB of the thread that we serve */
 	Platform_thread * const pt = Kernel::get_thread(badge());
-	assert(pt);
+	if (!pt) {
+		PERR("failed to get RM client-thread");
+		return;
+	}
 	Tlb * const tlb = pt->tlb();
-	assert(tlb);
-
+	if (!tlb) {
+		PERR("failed to get PD of RM client-thread");
+		return;
+	}
 	/* update all translation caches */
 	tlb->remove_region(virt_base, size);
 	Kernel::update_pd(pt->pd_id());
-
-	/* try to regain administrative memory that has been freed by unmap */
-	size_t s;
-	void * base;
-	while (tlb->regain_memory(base, s)) platform()->ram_alloc()->free(base, s);
+	regain_ram_from_tlb(tlb);
 }
 
 
@@ -52,11 +65,13 @@ void Rm_client::unmap(addr_t core_local_base, addr_t virt_base, size_t size)
  ** Ipc_pager **
  ***************/
 
-void Ipc_pager::resolve_and_wait_for_fault()
+int Ipc_pager::resolve_and_wait_for_fault()
 {
-	/* valid mapping? */
-	assert(_mapping.valid());
-
+	/* check mapping */
+	if (!_mapping.valid()) {
+		PERR("invalid mapping");
+		return -1;
+	}
 	/* prepare mapping */
 	Tlb * const tlb = _pagefault.tlb;
 	Page_flags::access_t const flags =
@@ -74,18 +89,25 @@ void Ipc_pager::resolve_and_wait_for_fault()
 		void * ram;
 		bool ram_ok = platform()->ram_alloc()->alloc_aligned(1<<sl2, &ram,
 		                                                     sl2).is_ok();
-		assert(ram_ok);
-
+		if (!ram_ok) {
+			PERR("failed to allocate additional RAM for TLB");
+			return -1;
+		}
 		/* try to translate again with extra RAM */
 		sl2 = tlb->insert_translation(_mapping.virt_address,
 		                              _mapping.phys_address,
 		                              _mapping.size_log2, flags, ram);
-		assert(!sl2);
+		if (sl2) {
+			PERR("TLB needs to much RAM");
+			regain_ram_from_tlb(tlb);
+			return -1;
+		}
 	}
 	/* wake up faulter */
 	Kernel::resume_faulter(_pagefault.thread_id);
 
 	/* wait for next page fault */
 	wait_for_fault();
+	return 0;
 }