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Commit f8561296 authored by Vegard Nossum's avatar Vegard Nossum
Browse files

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.)

As kmemcheck doesn't handle MMX/SSE instructions (yet), we also disable
the optimized xor code, and rely instead on the generic C implementation
in order to avoid false-positive warnings.

Signed-off-by: default avatarVegard Nossum <vegardno@ifi.uio.no>

[whitespace fixlet]
Signed-off-by: default avatarPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>

[rebased for mainline inclusion]
Signed-off-by: default avatarVegard Nossum <vegardno@ifi.uio.no>
parent f8b4ece2

arch/x86/include/asm/string_32.h

+8 −0
Original line number Diff line number Diff line
@@ -177,10 +177,18 @@ static inline void *__memcpy3d(void *to, const void *from, size_t len) 
 *	No 3D Now!

 */



#ifndef CONFIG_KMEMCHECK

#define memcpy(t, f, n)				\

	(__builtin_constant_p((n))		\

	 ? __constant_memcpy((t), (f), (n))	\

	 : __memcpy((t), (f), (n)))

#else

/*

 * kmemcheck becomes very happy if we use the REP instructions unconditionally,

 * because it means that we know both memory operands in advance.

 */

#define memcpy(t, f, n) __memcpy((t), (f), (n))

#endif



#endif

arch/x86/include/asm/string_64.h

+8 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ static __always_inline void *__inline_memcpy(void *to, const void *from, size_t 
   function. */



#define __HAVE_ARCH_MEMCPY 1

#ifndef CONFIG_KMEMCHECK

#if (__GNUC__ == 4 && __GNUC_MINOR__ >= 3) || __GNUC__ > 4

extern void *memcpy(void *to, const void *from, size_t len);

#else
@@ -42,6 +43,13 @@ extern void *__memcpy(void *to, const void *from, size_t len); 
	__ret;							\

})

#endif

#else

/*

 * kmemcheck becomes very happy if we use the REP instructions unconditionally,

 * because it means that we know both memory operands in advance.

 */

#define memcpy(dst, src, len) __inline_memcpy((dst), (src), (len))

#endif



#define __HAVE_ARCH_MEMSET

void *memset(void *s, int c, size_t n);

arch/x86/include/asm/xor.h

+5 −0
Original line number Diff line number Diff line 
#ifdef CONFIG_KMEMCHECK

/* kmemcheck doesn't handle MMX/SSE/SSE2 instructions */

# include <asm-generic/xor.h>

#else

#ifdef CONFIG_X86_32

# include "xor_32.h"

#else

# include "xor_64.h"

#endif

#endif

arch/x86/kernel/cpu/intel.c

+23 −0
Original line number Diff line number Diff line
@@ -86,6 +86,29 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c) 
	 */

	if (c->x86 == 6 && c->x86_model < 15)

		clear_cpu_cap(c, X86_FEATURE_PAT);



#ifdef CONFIG_KMEMCHECK

	/*

	 * P4s have a "fast strings" feature which causes single-

	 * stepping REP instructions to only generate a #DB on

	 * cache-line boundaries.

	 *

	 * Ingo Molnar reported a Pentium D (model 6) and a Xeon

	 * (model 2) with the same problem.

	 */

	if (c->x86 == 15) {

		u64 misc_enable;



		rdmsrl(MSR_IA32_MISC_ENABLE, misc_enable);



		if (misc_enable & MSR_IA32_MISC_ENABLE_FAST_STRING) {

			printk(KERN_INFO "kmemcheck: Disabling fast string operations\n");



			misc_enable &= ~MSR_IA32_MISC_ENABLE_FAST_STRING;

			wrmsrl(MSR_IA32_MISC_ENABLE, misc_enable);

		}

	}

#endif

}



#ifdef CONFIG_X86_32

arch/x86/kernel/traps.c

+5 −0
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ 
#include <linux/edac.h>

#endif



#include <asm/kmemcheck.h>

#include <asm/stacktrace.h>

#include <asm/processor.h>

#include <asm/debugreg.h>
@@ -534,6 +535,10 @@ dotraplinkage 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 && kmemcheck_trap(regs))

		return;



	/*

	 * The processor cleared BTF, so don't mark that we need it set.

	 */