[PATCH 2/4] kmemcheck v4

From: Vegard Nossum
Date: Thu Feb 14 2008 - 15:01:34 EST

From 5cbf7d1cb81b4f8bb4d80c027b74cdf0f08aaaff Mon Sep 17 00:00:00 2001
From: Vegard Nossum <vegard.nossum@xxxxxxxxx>
Date: Thu, 14 Feb 2008 19:20:51 +0100
Subject: [PATCH] kmemcheck: add the x86 hooks

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.

Signed-off-by: Vegard Nossum <vegardno@xxxxxxxxxx>
---
arch/x86/kernel/cpu/common.c | 7 +++++++
arch/x86/kernel/entry_32.S | 8 ++++----
arch/x86/kernel/traps_32.c | 22 +++++++++++++++++++++-
arch/x86/mm/fault.c | 21 +++++++++++++++++----
include/asm-x86/string_32.h | 8 ++++++++
5 files changed, 57 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index f86a3c4..83cd359 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -634,6 +634,13 @@ void __init early_cpu_init(void)
nexgen_init_cpu();
umc_init_cpu();
early_cpu_detect();
+
+#ifdef CONFIG_KMEMCHECK
+ /*
+ * We need 4K granular PTEs for kmemcheck:
+ */
+ setup_clear_cpu_cap(X86_FEATURE_PSE);
+#endif
}

/* Make sure %fs is initialized properly in idle threads */
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 824e21b..30b94e7 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -289,7 +289,7 @@ ENTRY(ia32_sysenter_target)
CFI_DEF_CFA esp, 0
CFI_REGISTER esp, ebp
movl TSS_sysenter_sp0(%esp),%esp
-sysenter_past_esp:
+ENTRY(sysenter_past_esp)
/*
* No need to follow this irqs on/off section: the syscall
* disabled irqs and here we enable it straight after entry:
@@ -767,7 +767,7 @@ label: \
CFI_ADJUST_CFA_OFFSET 4; \
CFI_REL_OFFSET eip, 0

-KPROBE_ENTRY(debug)
+KPROBE_ENTRY(x86_debug)
RING0_INT_FRAME
cmpl $ia32_sysenter_target,(%esp)
jne debug_stack_correct
@@ -781,7 +781,7 @@ debug_stack_correct:
call do_debug
jmp ret_from_exception
CFI_ENDPROC
-KPROBE_END(debug)
+KPROBE_END(x86_debug)

/*
* NMI is doubly nasty. It can happen _while_ we're handling
@@ -835,7 +835,7 @@ nmi_debug_stack_check:
/* We have a RING0_INT_FRAME here */
cmpw $__KERNEL_CS,16(%esp)
jne nmi_stack_correct
- cmpl $debug,(%esp)
+ cmpl $x86_debug,(%esp)
jb nmi_stack_correct
cmpl $debug_esp_fix_insn,(%esp)
ja nmi_stack_correct
diff --git a/arch/x86/kernel/traps_32.c b/arch/x86/kernel/traps_32.c
index b22c01e..1299d38 100644
--- a/arch/x86/kernel/traps_32.c
+++ b/arch/x86/kernel/traps_32.c
@@ -56,6 +56,7 @@
#include <asm/arch_hooks.h>
#include <linux/kdebug.h>
#include <asm/stacktrace.h>
+#include <asm/kmemcheck.h>

#include <linux/module.h>

@@ -841,6 +842,10 @@ void __kprobes do_int3(struct pt_regs *regs, long error_code)
}
#endif

+extern void ia32_sysenter_target(void);
+extern void sysenter_past_esp(void);
+extern void x86_debug(void);
+
/*
* Our handling of the processor debug registers is non-trivial.
* We do not clear them on entry and exit from the kernel. Therefore
@@ -872,6 +877,20 @@ void __kprobes do_debug(struct pt_regs * regs, long error_code)

get_debugreg(condition, 6);

+#ifdef CONFIG_KMEMCHECK
+ /* Catch kmemcheck conditions first of all! */
+ if (condition & DR_STEP) {
+ if (!(regs->flags & VM_MASK) && !user_mode(regs) &&
+ ((void *)regs->ip != system_call) &&
+ ((void *)regs->ip != x86_debug) &&
+ ((void *)regs->ip != ia32_sysenter_target) &&
+ ((void *)regs->ip != sysenter_past_esp)) {
+ kmemcheck_hide(regs);
+ return;
+ }
+ }
+#endif
+
/*
* The processor cleared BTF, so don't mark that we need it set.
*/
@@ -881,6 +900,7 @@ void __kprobes do_debug(struct pt_regs * regs, long error_code)
if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code,
SIGTRAP) == NOTIFY_STOP)
return;
+
/* It's safe to allow irq's after DR6 has been saved */
if (regs->flags & X86_EFLAGS_IF)
local_irq_enable();
@@ -1154,7 +1174,7 @@ void __init trap_init(void)
#endif

set_trap_gate(0,&divide_error);
- set_intr_gate(1,&debug);
+ set_intr_gate(1,&x86_debug);
set_intr_gate(2,&nmi);
set_system_intr_gate(3, &int3); /* int3/4 can be called from all */
set_system_gate(4,&overflow);
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 621afb6..2886cf9 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -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>

/*
@@ -493,7 +494,8 @@ static int spurious_fault(unsigned long address,
*
* This assumes no large pages in there.
*/
-static int vmalloc_fault(unsigned long address)
+static int vmalloc_fault(struct pt_regs *regs, unsigned long address,
+ unsigned long error_code)
{
#ifdef CONFIG_X86_32
unsigned long pgd_paddr;
@@ -511,8 +513,19 @@ static int vmalloc_fault(unsigned long address)
if (!pmd_k)
return -1;
pte_k = pte_offset_kernel(pmd_k, address);
- if (!pte_present(*pte_k))
- return -1;
+ if (!pte_present(*pte_k)) {
+ if (!pte_hidden(*pte_k))
+ return -1;
+
+#ifdef CONFIG_KMEMCHECK
+ kmemcheck_prepare(regs);
+ if (error_code & 2)
+ kmemcheck_access(regs, address, KMEMCHECK_WRITE);
+ else
+ kmemcheck_access(regs, address, KMEMCHECK_READ);
+ kmemcheck_show(regs);
+#endif
+ }
return 0;
#else
pgd_t *pgd, *pgd_ref;
@@ -623,7 +636,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
if (unlikely(address >= TASK_SIZE64)) {
#endif
if (!(error_code & (PF_RSVD|PF_USER|PF_PROT)) &&
- vmalloc_fault(address) >= 0)
+ vmalloc_fault(regs, address, error_code) >= 0)
return;

/* Can handle a stale RO->RW TLB */
diff --git a/include/asm-x86/string_32.h b/include/asm-x86/string_32.h
index c5d13a8..546cea0 100644
--- a/include/asm-x86/string_32.h
+++ b/include/asm-x86/string_32.h
@@ -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(unsigned long s, int c, size_t n);
+#undef memset
+#define memset(s, c, n) kmemcheck_memset((unsigned long) (s), (c), (n))
+#endif
+
/*
* find the first occurrence of byte 'c', or 1 past the area if none
*/
--
1.5.3.8


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