From fa57c51ac74a8301db7ab8b2fc9cbd63d69d26b3 Mon Sep 17 00:00:00 2001
From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date: Wed, 31 Aug 2011 02:10:05 +0200
Subject: Disable global page while writing in kernel space

* i386/i386/db_interface.c (db_write_bytes): If CPU has PGE feature, disable
CR4_PGE before enabling kernel page write access, and re-enable the former after
disabling the latter.
---
 i386/i386/db_interface.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/i386/i386/db_interface.c b/i386/i386/db_interface.c
index d149adc5..c07884de 100644
--- a/i386/i386/db_interface.c
+++ b/i386/i386/db_interface.c
@@ -39,6 +39,7 @@
 #include <i386/setjmp.h>
 #include <i386/pmap.h>
 #include <i386/proc_reg.h>
+#include <i386/locore.h>
 #include "gdt.h"
 #include "trap.h"
 
@@ -390,6 +391,8 @@ db_write_bytes(
 		oldmap1 = *ptep1;
 		*ptep1 |= INTEL_PTE_WRITE;
 	    }
+	    if (CPU_HAS_FEATURE(CPU_FEATURE_PGE))
+		set_cr4(get_cr4() & ~CR4_PGE);
 	    flush_tlb();
 	}
 
@@ -404,6 +407,8 @@ db_write_bytes(
 		*ptep1 = oldmap1;
 	    }
 	    flush_tlb();
+	    if (CPU_HAS_FEATURE(CPU_FEATURE_PGE))
+		set_cr4(get_cr4() | CR4_PGE);
 	}
 }
 
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