From 6c30bf2667c88a4079490d100dfded172925520f Mon Sep 17 00:00:00 2001
From: Alexander Boettcher <alexander.boettcher@genode-labs.com>
Date: Wed, 7 Oct 2015 15:16:03 +0200
Subject: [PATCH] nova: interpret write page fault correctly

Fixes #1722
---
 repos/base-nova/src/core/include/ipc_pager.h | 25 +++++++++++---------
 repos/base-nova/src/core/ipc_pager.cc        | 21 +---------------
 repos/base-nova/src/core/platform.cc         |  7 +++---
 3 files changed, 19 insertions(+), 34 deletions(-)

diff --git a/repos/base-nova/src/core/include/ipc_pager.h b/repos/base-nova/src/core/include/ipc_pager.h
index e71b810877..2a71a8cb33 100644
--- a/repos/base-nova/src/core/include/ipc_pager.h
+++ b/repos/base-nova/src/core/include/ipc_pager.h
@@ -77,21 +77,24 @@ namespace Genode {
 	{
 		private:
 
-			/**
-			 * Page-fault type
-			 */
-			enum Pf_type {
-				TYPE_READ  = 0x4,
-				TYPE_WRITE = 0x2,
-				TYPE_EXEC  = 0x1,
-			};
-
 			addr_t  _fault_ip;
 			addr_t  _fault_addr;
-			Pf_type _fault_type;
+			uint8_t _fault_type;
 
 		public:
 
+			/*
+			 * Intel manual: 6.15 EXCEPTION AND INTERRUPT REFERENCE
+			 *                    Interrupt 14—Page-Fault Exception (#PF)
+			 */
+			enum {
+				ERR_I = 1 << 4,
+				ERR_R = 1 << 3,
+				ERR_U = 1 << 2,
+				ERR_W = 1 << 1,
+				ERR_P = 1 << 0,
+			};
+
 			/**
 			 * Wait for page-fault info
 			 *
@@ -123,7 +126,7 @@ namespace Genode {
 			/**
 			 * Return true if fault was a write fault
 			 */
-			bool is_write_fault() const { return _fault_type == TYPE_WRITE; }
+			bool is_write_fault() const { return _fault_type & ERR_W; }
 
 			/**
 			 * Return true if last fault was an exception
diff --git a/repos/base-nova/src/core/ipc_pager.cc b/repos/base-nova/src/core/ipc_pager.cc
index dd49d7454a..31cf213a9c 100644
--- a/repos/base-nova/src/core/ipc_pager.cc
+++ b/repos/base-nova/src/core/ipc_pager.cc
@@ -21,24 +21,8 @@
 #include <nova/syscalls.h>
 
 
-enum { verbose_page_fault = false };
-
 using namespace Genode;
 
-/**
- * Print page-fault information in a human-readable form
- */
-inline void print_page_fault(unsigned type, addr_t addr, addr_t ip)
-{
-	enum { TYPE_READ  = 0x4, TYPE_WRITE = 0x2, TYPE_EXEC  = 0x1, };
-	printf("page (%s%s%s) fault at fault_addr=%lx, fault_ip=%lx\n",
-	       type & TYPE_READ  ? "r" : "-",
-	       type & TYPE_WRITE ? "w" : "-",
-	       type & TYPE_EXEC  ? "x" : "-",
-	       addr, ip);
-}
-
-
 void Ipc_pager::wait_for_fault()
 {
 	/*
@@ -47,12 +31,9 @@ void Ipc_pager::wait_for_fault()
 	 * page-fault information from our UTCB.
 	 */
 	Nova::Utcb *utcb = (Nova::Utcb *)Thread_base::myself()->utcb();
-	_fault_type = (Pf_type)utcb->qual[0];
+	_fault_type = utcb->qual[0];
 	_fault_addr = utcb->qual[1];
 	_fault_ip   = utcb->ip;
-
-	if (verbose_page_fault)
-		print_page_fault(_fault_type, _fault_addr, _fault_ip);
 }
 
 
diff --git a/repos/base-nova/src/core/platform.cc b/repos/base-nova/src/core/platform.cc
index 1c8574c039..f7a11f0888 100644
--- a/repos/base-nova/src/core/platform.cc
+++ b/repos/base-nova/src/core/platform.cc
@@ -17,14 +17,15 @@
 #include <base/printf.h>
 #include <base/sleep.h>
 #include <base/thread.h>
+#include <base/snprintf.h>
+#include <trace/source_registry.h>
 
 /* core includes */
 #include <core_parent.h>
 #include <platform.h>
 #include <nova_util.h>
 #include <util.h>
-#include <trace/source_registry.h>
-#include <base/snprintf.h>
+#include <ipc_pager.h>
 
 /* NOVA includes */
 #include <nova/syscalls.h>
@@ -115,7 +116,7 @@ static void page_fault_handler()
 	addr_t pf_type = utcb->qual[0];
 
 	print_page_fault("\nPAGE-FAULT IN CORE", pf_addr, pf_ip,
-	                 (Genode::Rm_session::Fault_type)pf_type, 0);
+	                 (pf_type & Ipc_pager::ERR_W) ? Rm_session::WRITE_FAULT : Rm_session::READ_FAULT, 0);
 
 	/* dump stack trace */
 	struct Core_img