Skip to contentSkip to conversation

x86: add hooks for kmemcheck

PATCH In review Vegard Nossum 1 participant 1 message Jul 16, 2008

Subsystems (2)
x86 x86 MM
lore
Share & tools
lore

Vegard Nossum

author
#0 lore raw

PATCH 8/13 x86: add hooks for kmemcheck

Quoted 1 line

From 6cea44745d8c759e06c3c993e816377f7c270e62 Mon Sep 17 00:00:00 2001

From: Vegard Nossum <[email protected]>
Date: Fri, 4 Apr 2008 00:53:23 +0200
Subject: [PATCH 08/13] x86: add hooks for kmemcheck

The hooks that we modify are:
- Page fault handler (to handle kmemcheck faults)
- Debug exception handler (to hide pages after single-stepping the instruction that caused the page fault)

Also redefine memset() to use the optimized version if kmemcheck is enabled.

(Thanks to Pekka Enberg for minimizing the impact on the page fault
handler.)

Signed-off-by Vegard Nossum <[email protected]>
---
 arch/x86/kernel/traps_32.c  |    9 +++++++++
 arch/x86/mm/fault.c         |   18 +++++++++++++++---
 include/asm-x86/string_32.h |    8 ++++++++
 3 files changed, 32 insertions(+), 3 deletions(-)
arch/x86/kernel/traps_32.c +9 -0
index a4739a8..4ad88dd 100644
@@ -57,6 +57,7 @@
 #include <asm/nmi.h>
 #include <asm/smp.h>
 #include <asm/io.h>
+#include <asm/kmemcheck.h>
 
 #include "mach_traps.h"
 

@@ -906,6 +907,14 @@ void __kprobes do_debug(struct pt_regs *regs, long error_code)
 
 	get_debugreg(condition, 6);
 
+	/* Catch kmemcheck conditions first of all! */
+	if (condition & DR_STEP) {
+		if (kmemcheck_active(regs)) {
+			kmemcheck_hide(regs);
+			return;
+		}
+	}
+
 	/*
 	 * The processor cleared BTF, so don't mark that we need it set.
 	 */
arch/x86/mm/fault.c +15 -3
index 8bcb6f4..3717195 100644
@@ -33,6 +33,7 @@
 #include <asm/smp.h>
 #include <asm/tlbflush.h>
 #include <asm/proto.h>
+#include <asm/kmemcheck.h>
 #include <asm-generic/sections.h>
 
 /*

@@ -604,6 +605,13 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 
 	si_code = SEGV_MAPERR;
 
+	/*
+	 * Detect and handle instructions that would cause a page fault for
+	 * both a tracked kernel page and a userspace page.
+	 */
+	if(kmemcheck_active(regs))
+		kmemcheck_hide(regs);
+
 	if (notify_page_fault(regs))
 		return;
 

@@ -625,9 +633,13 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 #else
 	if (unlikely(address >= TASK_SIZE64)) {
 #endif
-		if (!(error_code & (PF_RSVD|PF_USER|PF_PROT)) &&
-		    vmalloc_fault(address) >= 0)
-			return;
+		if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) {
+			if (vmalloc_fault(address) >= 0)
+				return;
+
+			if (kmemcheck_fault(regs, address, error_code))
+				return;
+		}
 
 		/* Can handle a stale RO->RW TLB */
 		if (spurious_fault(address, error_code))
include/asm-x86/string_32.h +8 -0
index b49369a..fade185 100644
@@ -262,6 +262,14 @@ __asm__  __volatile__( \
  __constant_c_x_memset((s),(0x01010101UL*(unsigned char)(c)),(count)) : \
  __memset((s),(c),(count)))
 
+/* If kmemcheck is enabled, our best bet is a custom memset() that disables
+ * checking in order to save a whole lot of (unnecessary) page faults. */
+#ifdef CONFIG_KMEMCHECK
+void *kmemcheck_memset(void *s, int c, size_t n);
+#undef memset
+#define memset(s, c, n) kmemcheck_memset((s), (c), (n))
+#endif
+
 /*
  * find the first occurrence of byte 'c', or 1 past the area if none
  */
Signature · 1 line
1.5.5.1