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kmemcheck: add the kmemcheck core

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General description: kmemcheck is a patch to the linux kernel that
detects use of uninitialized memory. It does this by trapping every
read and write to memory that was allocated dynamically (e.g. using
kmalloc()). If a memory address is read that has not previously been
written to, a message is printed to the kernel log.

Thanks to Andi Kleen for the set_memory_4k() solution.

Andrew Morton suggested documenting the shadow member of struct page.

Signed-off-by: Vegard Nossum <vegardno@ifi.uio.no>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

[export kmemcheck_mark_initialized]
[build fix for setup_max_cpus]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

[rebased for mainline inclusion]
Signed-off-by: Vegard Nossum <vegardno@ifi.uio.no>
This commit is contained in:
Vegard Nossum 2008-04-04 00:51:41 +02:00
parent e594c8de3b
commit dfec072ecd
19 changed files with 1304 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
arch/x86/Makefile
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@ -81,6 +81,11 @@ ifdef CONFIG_CC_STACKPROTECTOR
endif
endif
# Don't unroll struct assignments with kmemcheck enabled
ifeq ($(CONFIG_KMEMCHECK),y)
KBUILD_CFLAGS += $(call cc-option,-fno-builtin-memcpy)
endif
# Stackpointer is addressed different for 32 bit and 64 bit x86
sp-$(CONFIG_X86_32) := esp
sp-$(CONFIG_X86_64) := rsp

42
arch/x86/include/asm/kmemcheck.h Normal file
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@ -0,0 +1,42 @@
#ifndef ASM_X86_KMEMCHECK_H
#define ASM_X86_KMEMCHECK_H
#include <linux/types.h>
#include <asm/ptrace.h>
#ifdef CONFIG_KMEMCHECK
bool kmemcheck_active(struct pt_regs *regs);
void kmemcheck_show(struct pt_regs *regs);
void kmemcheck_hide(struct pt_regs *regs);
bool kmemcheck_fault(struct pt_regs *regs,
unsigned long address, unsigned long error_code);
bool kmemcheck_trap(struct pt_regs *regs);
#else
static inline bool kmemcheck_active(struct pt_regs *regs)
{
return false;
}
static inline void kmemcheck_show(struct pt_regs *regs)
{
}
static inline void kmemcheck_hide(struct pt_regs *regs)
{
}
static inline bool kmemcheck_fault(struct pt_regs *regs,
unsigned long address, unsigned long error_code)
{
return false;
}
static inline bool kmemcheck_trap(struct pt_regs *regs)
{
return false;
}
#endif /* CONFIG_KMEMCHECK */
#endif

9
arch/x86/include/asm/pgtable.h
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@ -317,6 +317,15 @@ static inline int pte_present(pte_t a)
return pte_flags(a) & (_PAGE_PRESENT | _PAGE_PROTNONE);
}
static inline int pte_hidden(pte_t x)
{
#ifdef CONFIG_KMEMCHECK
return pte_flags(x) & _PAGE_HIDDEN;
#else
return 0;
#endif
}
static inline int pmd_present(pmd_t pmd)
{
return pmd_flags(pmd) & _PAGE_PRESENT;

4
arch/x86/include/asm/pgtable_types.h
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@ -18,7 +18,7 @@
#define _PAGE_BIT_GLOBAL 8 /* Global TLB entry PPro+ */
#define _PAGE_BIT_UNUSED1 9 /* available for programmer */
#define _PAGE_BIT_IOMAP 10 /* flag used to indicate IO mapping */
#define _PAGE_BIT_UNUSED3 11
#define _PAGE_BIT_HIDDEN 11 /* hidden by kmemcheck */
#define _PAGE_BIT_PAT_LARGE 12 /* On 2MB or 1GB pages */
#define _PAGE_BIT_SPECIAL _PAGE_BIT_UNUSED1
#define _PAGE_BIT_CPA_TEST _PAGE_BIT_UNUSED1
@ -41,7 +41,7 @@
#define _PAGE_GLOBAL (_AT(pteval_t, 1) << _PAGE_BIT_GLOBAL)
#define _PAGE_UNUSED1 (_AT(pteval_t, 1) << _PAGE_BIT_UNUSED1)
#define _PAGE_IOMAP (_AT(pteval_t, 1) << _PAGE_BIT_IOMAP)
#define _PAGE_UNUSED3 (_AT(pteval_t, 1) << _PAGE_BIT_UNUSED3)
#define _PAGE_HIDDEN (_AT(pteval_t, 1) << _PAGE_BIT_HIDDEN)
#define _PAGE_PAT (_AT(pteval_t, 1) << _PAGE_BIT_PAT)
#define _PAGE_PAT_LARGE (_AT(pteval_t, 1) << _PAGE_BIT_PAT_LARGE)
#define _PAGE_SPECIAL (_AT(pteval_t, 1) << _PAGE_BIT_SPECIAL)

2
arch/x86/mm/Makefile
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@ -10,6 +10,8 @@ obj-$(CONFIG_X86_PTDUMP) += dump_pagetables.o
obj-$(CONFIG_HIGHMEM) += highmem_32.o
obj-$(CONFIG_KMEMCHECK) += kmemcheck/
obj-$(CONFIG_MMIOTRACE) += mmiotrace.o
mmiotrace-y := kmmio.o pf_in.o mmio-mod.o
obj-$(CONFIG_MMIOTRACE_TEST) += testmmiotrace.o

1
arch/x86/mm/kmemcheck/Makefile Normal file
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@ -0,0 +1 @@
obj-y := error.o kmemcheck.o opcode.o pte.o shadow.o

229
arch/x86/mm/kmemcheck/error.c Normal file
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@ -0,0 +1,229 @@
#include <linux/interrupt.h>
#include <linux/kdebug.h>
#include <linux/kmemcheck.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/ptrace.h>
#include <linux/stacktrace.h>
#include <linux/string.h>
#include "error.h"
#include "shadow.h"
enum kmemcheck_error_type {
KMEMCHECK_ERROR_INVALID_ACCESS,
KMEMCHECK_ERROR_BUG,
};
#define SHADOW_COPY_SIZE (1 << CONFIG_KMEMCHECK_SHADOW_COPY_SHIFT)
struct kmemcheck_error {
enum kmemcheck_error_type type;
union {
/* KMEMCHECK_ERROR_INVALID_ACCESS */
struct {
/* Kind of access that caused the error */
enum kmemcheck_shadow state;
/* Address and size of the erroneous read */
unsigned long address;
unsigned int size;
};
};
struct pt_regs regs;
struct stack_trace trace;
unsigned long trace_entries[32];
/* We compress it to a char. */
unsigned char shadow_copy[SHADOW_COPY_SIZE];
unsigned char memory_copy[SHADOW_COPY_SIZE];
};
/*
* Create a ring queue of errors to output. We can't call printk() directly
* from the kmemcheck traps, since this may call the console drivers and
* result in a recursive fault.
*/
static struct kmemcheck_error error_fifo[CONFIG_KMEMCHECK_QUEUE_SIZE];
static unsigned int error_count;
static unsigned int error_rd;
static unsigned int error_wr;
static unsigned int error_missed_count;
static struct kmemcheck_error *error_next_wr(void)
{
struct kmemcheck_error *e;
if (error_count == ARRAY_SIZE(error_fifo)) {
++error_missed_count;
return NULL;
}
e = &error_fifo[error_wr];
if (++error_wr == ARRAY_SIZE(error_fifo))
error_wr = 0;
++error_count;
return e;
}
static struct kmemcheck_error *error_next_rd(void)
{
struct kmemcheck_error *e;
if (error_count == 0)
return NULL;
e = &error_fifo[error_rd];
if (++error_rd == ARRAY_SIZE(error_fifo))
error_rd = 0;
--error_count;
return e;
}
static void do_wakeup(unsigned long);
static DECLARE_TASKLET(kmemcheck_tasklet, &do_wakeup, 0);
/*
* Save the context of an error report.
*/
void kmemcheck_error_save(enum kmemcheck_shadow state,
unsigned long address, unsigned int size, struct pt_regs *regs)
{
static unsigned long prev_ip;
struct kmemcheck_error *e;
void *shadow_copy;
void *memory_copy;
/* Don't report several adjacent errors from the same EIP. */
if (regs->ip == prev_ip)
return;
prev_ip = regs->ip;
e = error_next_wr();
if (!e)
return;
e->type = KMEMCHECK_ERROR_INVALID_ACCESS;
e->state = state;
e->address = address;
e->size = size;
/* Save regs */
memcpy(&e->regs, regs, sizeof(*regs));
/* Save stack trace */
e->trace.nr_entries = 0;
e->trace.entries = e->trace_entries;
e->trace.max_entries = ARRAY_SIZE(e->trace_entries);
e->trace.skip = 0;
save_stack_trace_bp(&e->trace, regs->bp);
/* Round address down to nearest 16 bytes */
shadow_copy = kmemcheck_shadow_lookup(address
& ~(SHADOW_COPY_SIZE - 1));
BUG_ON(!shadow_copy);
memcpy(e->shadow_copy, shadow_copy, SHADOW_COPY_SIZE);
kmemcheck_show_addr(address);
memory_copy = (void *) (address & ~(SHADOW_COPY_SIZE - 1));
memcpy(e->memory_copy, memory_copy, SHADOW_COPY_SIZE);
kmemcheck_hide_addr(address);
tasklet_hi_schedule_first(&kmemcheck_tasklet);
}
/*
* Save the context of a kmemcheck bug.
*/
void kmemcheck_error_save_bug(struct pt_regs *regs)
{
struct kmemcheck_error *e;
e = error_next_wr();
if (!e)
return;
e->type = KMEMCHECK_ERROR_BUG;
memcpy(&e->regs, regs, sizeof(*regs));
e->trace.nr_entries = 0;
e->trace.entries = e->trace_entries;
e->trace.max_entries = ARRAY_SIZE(e->trace_entries);
e->trace.skip = 1;
save_stack_trace(&e->trace);
tasklet_hi_schedule_first(&kmemcheck_tasklet);
}
void kmemcheck_error_recall(void)
{
static const char *desc[] = {
[KMEMCHECK_SHADOW_UNALLOCATED] = "unallocated",
[KMEMCHECK_SHADOW_UNINITIALIZED] = "uninitialized",
[KMEMCHECK_SHADOW_INITIALIZED] = "initialized",
[KMEMCHECK_SHADOW_FREED] = "freed",
};
static const char short_desc[] = {
[KMEMCHECK_SHADOW_UNALLOCATED] = 'a',
[KMEMCHECK_SHADOW_UNINITIALIZED] = 'u',
[KMEMCHECK_SHADOW_INITIALIZED] = 'i',
[KMEMCHECK_SHADOW_FREED] = 'f',
};
struct kmemcheck_error *e;
unsigned int i;
e = error_next_rd();
if (!e)
return;
switch (e->type) {
case KMEMCHECK_ERROR_INVALID_ACCESS:
printk(KERN_ERR "WARNING: kmemcheck: Caught %d-bit read "
"from %s memory (%p)\n",
8 * e->size, e->state < ARRAY_SIZE(desc) ?
desc[e->state] : "(invalid shadow state)",
(void *) e->address);
printk(KERN_INFO);
for (i = 0; i < SHADOW_COPY_SIZE; ++i)
printk("%02x", e->memory_copy[i]);
printk("\n");
printk(KERN_INFO);
for (i = 0; i < SHADOW_COPY_SIZE; ++i) {
if (e->shadow_copy[i] < ARRAY_SIZE(short_desc))
printk(" %c", short_desc[e->shadow_copy[i]]);
else
printk(" ?");
}
printk("\n");
printk(KERN_INFO "%*c\n", 2 + 2
* (int) (e->address & (SHADOW_COPY_SIZE - 1)), '^');
break;
case KMEMCHECK_ERROR_BUG:
printk(KERN_EMERG "ERROR: kmemcheck: Fatal error\n");
break;
}
__show_regs(&e->regs, 1);
print_stack_trace(&e->trace, 0);
}
static void do_wakeup(unsigned long data)
{
while (error_count > 0)
kmemcheck_error_recall();
if (error_missed_count > 0) {
printk(KERN_WARNING "kmemcheck: Lost %d error reports because "
"the queue was too small\n", error_missed_count);
error_missed_count = 0;
}
}

15
arch/x86/mm/kmemcheck/error.h Normal file
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@ -0,0 +1,15 @@
#ifndef ARCH__X86__MM__KMEMCHECK__ERROR_H
#define ARCH__X86__MM__KMEMCHECK__ERROR_H
#include <linux/ptrace.h>
#include "shadow.h"
void kmemcheck_error_save(enum kmemcheck_shadow state,
unsigned long address, unsigned int size, struct pt_regs *regs);
void kmemcheck_error_save_bug(struct pt_regs *regs);
void kmemcheck_error_recall(void);
#endif

650
arch/x86/mm/kmemcheck/kmemcheck.c Normal file
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@ -0,0 +1,650 @@
/**
* kmemcheck - a heavyweight memory checker for the linux kernel
* Copyright (C) 2007, 2008 Vegard Nossum <vegardno@ifi.uio.no>
* (With a lot of help from Ingo Molnar and Pekka Enberg.)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License (version 2) as
* published by the Free Software Foundation.
*/
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kallsyms.h>
#include <linux/kernel.h>
#include <linux/kmemcheck.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/page-flags.h>
#include <linux/percpu.h>
#include <linux/ptrace.h>
#include <linux/string.h>
#include <linux/types.h>
#include <asm/cacheflush.h>
#include <asm/kmemcheck.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include "error.h"
#include "opcode.h"
#include "pte.h"
#include "shadow.h"
#ifdef CONFIG_KMEMCHECK_DISABLED_BY_DEFAULT
# define KMEMCHECK_ENABLED 0
#endif
#ifdef CONFIG_KMEMCHECK_ENABLED_BY_DEFAULT
# define KMEMCHECK_ENABLED 1
#endif
#ifdef CONFIG_KMEMCHECK_ONESHOT_BY_DEFAULT
# define KMEMCHECK_ENABLED 2
#endif
int kmemcheck_enabled = KMEMCHECK_ENABLED;
int __init kmemcheck_init(void)
{
printk(KERN_INFO "kmemcheck: \"Bugs, beware!\"\n");
#ifdef CONFIG_SMP
/*
* Limit SMP to use a single CPU. We rely on the fact that this code
* runs before SMP is set up.
*/
if (setup_max_cpus > 1) {
printk(KERN_INFO
"kmemcheck: Limiting number of CPUs to 1.\n");
setup_max_cpus = 1;
}
#endif
return 0;
}
early_initcall(kmemcheck_init);
#ifdef CONFIG_KMEMCHECK_DISABLED_BY_DEFAULT
int kmemcheck_enabled = 0;
#endif
#ifdef CONFIG_KMEMCHECK_ENABLED_BY_DEFAULT
int kmemcheck_enabled = 1;
#endif
#ifdef CONFIG_KMEMCHECK_ONESHOT_BY_DEFAULT
int kmemcheck_enabled = 2;
#endif
/*
* We need to parse the kmemcheck= option before any memory is allocated.
*/
static int __init param_kmemcheck(char *str)
{
if (!str)
return -EINVAL;
sscanf(str, "%d", &kmemcheck_enabled);
return 0;
}
early_param("kmemcheck", param_kmemcheck);
int kmemcheck_show_addr(unsigned long address)
{
pte_t *pte;
pte = kmemcheck_pte_lookup(address);
if (!pte)
return 0;
set_pte(pte, __pte(pte_val(*pte) | _PAGE_PRESENT));
__flush_tlb_one(address);
return 1;
}
int kmemcheck_hide_addr(unsigned long address)
{
pte_t *pte;
pte = kmemcheck_pte_lookup(address);
if (!pte)
return 0;
set_pte(pte, __pte(pte_val(*pte) & ~_PAGE_PRESENT));
__flush_tlb_one(address);
return 1;
}
struct kmemcheck_context {
bool busy;
int balance;
/*
* There can be at most two memory operands to an instruction, but
* each address can cross a page boundary -- so we may need up to
* four addresses that must be hidden/revealed for each fault.
*/
unsigned long addr[4];
unsigned long n_addrs;
unsigned long flags;
/* Data size of the instruction that caused a fault. */
unsigned int size;
};
static DEFINE_PER_CPU(struct kmemcheck_context, kmemcheck_context);
bool kmemcheck_active(struct pt_regs *regs)
{
struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context);
return data->balance > 0;
}
/* Save an address that needs to be shown/hidden */
static void kmemcheck_save_addr(unsigned long addr)
{
struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context);
BUG_ON(data->n_addrs >= ARRAY_SIZE(data->addr));
data->addr[data->n_addrs++] = addr;
}
static unsigned int kmemcheck_show_all(void)
{
struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context);
unsigned int i;
unsigned int n;
n = 0;
for (i = 0; i < data->n_addrs; ++i)
n += kmemcheck_show_addr(data->addr[i]);
return n;
}
static unsigned int kmemcheck_hide_all(void)
{
struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context);
unsigned int i;
unsigned int n;
n = 0;
for (i = 0; i < data->n_addrs; ++i)
n += kmemcheck_hide_addr(data->addr[i]);
return n;
}
/*
* Called from the #PF handler.
*/
void kmemcheck_show(struct pt_regs *regs)
{
struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context);
BUG_ON(!irqs_disabled());
if (unlikely(data->balance != 0)) {
kmemcheck_show_all();
kmemcheck_error_save_bug(regs);
data->balance = 0;
return;
}
/*
* None of the addresses actually belonged to kmemcheck. Note that
* this is not an error.
*/
if (kmemcheck_show_all() == 0)
return;
++data->balance;
/*
* The IF needs to be cleared as well, so that the faulting
* instruction can run "uninterrupted". Otherwise, we might take
* an interrupt and start executing that before we've had a chance
* to hide the page again.
*
* NOTE: In the rare case of multiple faults, we must not override
* the original flags:
*/
if (!(regs->flags & X86_EFLAGS_TF))
data->flags = regs->flags;
regs->flags |= X86_EFLAGS_TF;
regs->flags &= ~X86_EFLAGS_IF;
}
/*
* Called from the #DB handler.
*/
void kmemcheck_hide(struct pt_regs *regs)
{
struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context);
int n;
BUG_ON(!irqs_disabled());
if (data->balance == 0)
return;
if (unlikely(data->balance != 1)) {
kmemcheck_show_all();
kmemcheck_error_save_bug(regs);
data->n_addrs = 0;
data->balance = 0;
if (!(data->flags & X86_EFLAGS_TF))
regs->flags &= ~X86_EFLAGS_TF;
if (data->flags & X86_EFLAGS_IF)
regs->flags |= X86_EFLAGS_IF;
return;
}
if (kmemcheck_enabled)
n = kmemcheck_hide_all();
else
n = kmemcheck_show_all();
if (n == 0)
return;
--data->balance;
data->n_addrs = 0;
if (!(data->flags & X86_EFLAGS_TF))
regs->flags &= ~X86_EFLAGS_TF;
if (data->flags & X86_EFLAGS_IF)
regs->flags |= X86_EFLAGS_IF;
}
void kmemcheck_show_pages(struct page *p, unsigned int n)
{
unsigned int i;
for (i = 0; i < n; ++i) {
unsigned long address;
pte_t *pte;
unsigned int level;
address = (unsigned long) page_address(&p[i]);
pte = lookup_address(address, &level);
BUG_ON(!pte);
BUG_ON(level != PG_LEVEL_4K);
set_pte(pte, __pte(pte_val(*pte) | _PAGE_PRESENT));
set_pte(pte, __pte(pte_val(*pte) & ~_PAGE_HIDDEN));
__flush_tlb_one(address);
}
}
bool kmemcheck_page_is_tracked(struct page *p)
{
/* This will also check the "hidden" flag of the PTE. */
return kmemcheck_pte_lookup((unsigned long) page_address(p));
}
void kmemcheck_hide_pages(struct page *p, unsigned int n)
{
unsigned int i;
for (i = 0; i < n; ++i) {
unsigned long address;
pte_t *pte;
unsigned int level;
address = (unsigned long) page_address(&p[i]);
pte = lookup_address(address, &level);
BUG_ON(!pte);
BUG_ON(level != PG_LEVEL_4K);
set_pte(pte, __pte(pte_val(*pte) & ~_PAGE_PRESENT));
set_pte(pte, __pte(pte_val(*pte) | _PAGE_HIDDEN));
__flush_tlb_one(address);
}
}
/* Access may NOT cross page boundary */
static void kmemcheck_read_strict(struct pt_regs *regs,
unsigned long addr, unsigned int size)
{
void *shadow;
enum kmemcheck_shadow status;
shadow = kmemcheck_shadow_lookup(addr);
if (!shadow)
return;
kmemcheck_save_addr(addr);
status = kmemcheck_shadow_test(shadow, size);
if (status == KMEMCHECK_SHADOW_INITIALIZED)
return;
if (kmemcheck_enabled)
kmemcheck_error_save(status, addr, size, regs);
if (kmemcheck_enabled == 2)
kmemcheck_enabled = 0;
/* Don't warn about it again. */
kmemcheck_shadow_set(shadow, size);
}
/* Access may cross page boundary */
static void kmemcheck_read(struct pt_regs *regs,
unsigned long addr, unsigned int size)
{
unsigned long page = addr & PAGE_MASK;
unsigned long next_addr = addr + size - 1;
unsigned long next_page = next_addr & PAGE_MASK;
if (likely(page == next_page)) {
kmemcheck_read_strict(regs, addr, size);
return;
}
/*
* What we do is basically to split the access across the
* two pages and handle each part separately. Yes, this means
* that we may now see reads that are 3 + 5 bytes, for
* example (and if both are uninitialized, there will be two
* reports), but it makes the code a lot simpler.
*/
kmemcheck_read_strict(regs, addr, next_page - addr);
kmemcheck_read_strict(regs, next_page, next_addr - next_page);
}
static void kmemcheck_write_strict(struct pt_regs *regs,
unsigned long addr, unsigned int size)
{
void *shadow;
shadow = kmemcheck_shadow_lookup(addr);
if (!shadow)
return;
kmemcheck_save_addr(addr);
kmemcheck_shadow_set(shadow, size);
}
static void kmemcheck_write(struct pt_regs *regs,
unsigned long addr, unsigned int size)
{
unsigned long page = addr & PAGE_MASK;
unsigned long next_addr = addr + size - 1;
unsigned long next_page = next_addr & PAGE_MASK;
if (likely(page == next_page)) {
kmemcheck_write_strict(regs, addr, size);
return;
}
/* See comment in kmemcheck_read(). */
kmemcheck_write_strict(regs, addr, next_page - addr);
kmemcheck_write_strict(regs, next_page, next_addr - next_page);
}
/*
* Copying is hard. We have two addresses, each of which may be split across
* a page (and each page will have different shadow addresses).
*/
static void kmemcheck_copy(struct pt_regs *regs,
unsigned long src_addr, unsigned long dst_addr, unsigned int size)
{
uint8_t shadow[8];
enum kmemcheck_shadow status;
unsigned long page;
unsigned long next_addr;
unsigned long next_page;
uint8_t *x;
unsigned int i;
unsigned int n;
BUG_ON(size > sizeof(shadow));
page = src_addr & PAGE_MASK;
next_addr = src_addr + size - 1;
next_page = next_addr & PAGE_MASK;
if (likely(page == next_page)) {
/* Same page */
x = kmemcheck_shadow_lookup(src_addr);
if (x) {
kmemcheck_save_addr(src_addr);
for (i = 0; i < size; ++i)
shadow[i] = x[i];
} else {
for (i = 0; i < size; ++i)
shadow[i] = KMEMCHECK_SHADOW_INITIALIZED;
}
} else {
n = next_page - src_addr;
BUG_ON(n > sizeof(shadow));
/* First page */
x = kmemcheck_shadow_lookup(src_addr);
if (x) {
kmemcheck_save_addr(src_addr);
for (i = 0; i < n; ++i)
shadow[i] = x[i];
} else {
/* Not tracked */
for (i = 0; i < n; ++i)
shadow[i] = KMEMCHECK_SHADOW_INITIALIZED;
}
/* Second page */
x = kmemcheck_shadow_lookup(next_page);
if (x) {
kmemcheck_save_addr(next_page);
for (i = n; i < size; ++i)
shadow[i] = x[i - n];
} else {
/* Not tracked */
for (i = n; i < size; ++i)
shadow[i] = KMEMCHECK_SHADOW_INITIALIZED;
}
}
page = dst_addr & PAGE_MASK;
next_addr = dst_addr + size - 1;
next_page = next_addr & PAGE_MASK;
if (likely(page == next_page)) {
/* Same page */
x = kmemcheck_shadow_lookup(dst_addr);
if (x) {
kmemcheck_save_addr(dst_addr);
for (i = 0; i < size; ++i) {
x[i] = shadow[i];
shadow[i] = KMEMCHECK_SHADOW_INITIALIZED;
}
}
} else {
n = next_page - dst_addr;
BUG_ON(n > sizeof(shadow));
/* First page */
x = kmemcheck_shadow_lookup(dst_addr);
if (x) {
kmemcheck_save_addr(dst_addr);
for (i = 0; i < n; ++i) {
x[i] = shadow[i];
shadow[i] = KMEMCHECK_SHADOW_INITIALIZED;
}
}
/* Second page */
x = kmemcheck_shadow_lookup(next_page);
if (x) {
kmemcheck_save_addr(next_page);
for (i = n; i < size; ++i) {
x[i - n] = shadow[i];
shadow[i] = KMEMCHECK_SHADOW_INITIALIZED;
}
}
}
status = kmemcheck_shadow_test(shadow, size);
if (status == KMEMCHECK_SHADOW_INITIALIZED)
return;
if (kmemcheck_enabled)
kmemcheck_error_save(status, src_addr, size, regs);
if (kmemcheck_enabled == 2)
kmemcheck_enabled = 0;
}
enum kmemcheck_method {
KMEMCHECK_READ,
KMEMCHECK_WRITE,
};
static void kmemcheck_access(struct pt_regs *regs,
unsigned long fallback_address, enum kmemcheck_method fallback_method)
{
const uint8_t *insn;
const uint8_t *insn_primary;
unsigned int size;
struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context);
/* Recursive fault -- ouch. */
if (data->busy) {
kmemcheck_show_addr(fallback_address);
kmemcheck_error_save_bug(regs);
return;
}
data->busy = true;
insn = (const uint8_t *) regs->ip;
insn_primary = kmemcheck_opcode_get_primary(insn);
kmemcheck_opcode_decode(insn, &size);
switch (insn_primary[0]) {
#ifdef CONFIG_KMEMCHECK_BITOPS_OK
/* AND, OR, XOR */
/*
* Unfortunately, these instructions have to be excluded from
* our regular checking since they access only some (and not
* all) bits. This clears out "bogus" bitfield-access warnings.
*/
case 0x80:
case 0x81:
case 0x82:
case 0x83:
switch ((insn_primary[1] >> 3) & 7) {
/* OR */
case 1:
/* AND */
case 4:
/* XOR */
case 6:
kmemcheck_write(regs, fallback_address, size);
goto out;
/* ADD */
case 0:
/* ADC */
case 2:
/* SBB */
case 3:
/* SUB */
case 5:
/* CMP */
case 7:
break;
}
break;
#endif
/* MOVS, MOVSB, MOVSW, MOVSD */
case 0xa4:
case 0xa5:
/*
* These instructions are special because they take two
* addresses, but we only get one page fault.
*/
kmemcheck_copy(regs, regs->si, regs->di, size);
goto out;
/* CMPS, CMPSB, CMPSW, CMPSD */
case 0xa6:
case 0xa7:
kmemcheck_read(regs, regs->si, size);
kmemcheck_read(regs, regs->di, size);
goto out;
}
/*
* If the opcode isn't special in any way, we use the data from the
* page fault handler to determine the address and type of memory
* access.
*/
switch (fallback_method) {
case KMEMCHECK_READ:
kmemcheck_read(regs, fallback_address, size);
goto out;
case KMEMCHECK_WRITE:
kmemcheck_write(regs, fallback_address, size);
goto out;
}
out:
data->busy = false;
}
bool kmemcheck_fault(struct pt_regs *regs, unsigned long address,
unsigned long error_code)
{
pte_t *pte;
unsigned int level;
/*
* XXX: Is it safe to assume that memory accesses from virtual 86
* mode or non-kernel code segments will _never_ access kernel
* memory (e.g. tracked pages)? For now, we need this to avoid
* invoking kmemcheck for PnP BIOS calls.
*/
if (regs->flags & X86_VM_MASK)
return false;
if (regs->cs != __KERNEL_CS)
return false;
pte = lookup_address(address, &level);
if (!pte)
return false;
if (level != PG_LEVEL_4K)
return false;
if (!pte_hidden(*pte))
return false;
if (error_code & 2)
kmemcheck_access(regs, address, KMEMCHECK_WRITE);
else
kmemcheck_access(regs, address, KMEMCHECK_READ);
kmemcheck_show(regs);
return true;
}
bool kmemcheck_trap(struct pt_regs *regs)
{
if (!kmemcheck_active(regs))
return false;
/* We're done. */
kmemcheck_hide(regs);
return true;
}

101
arch/x86/mm/kmemcheck/opcode.c Normal file
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@ -0,0 +1,101 @@
#include <linux/types.h>
#include "opcode.h"
static bool opcode_is_prefix(uint8_t b)
{
return
/* Group 1 */
b == 0xf0 || b == 0xf2 || b == 0xf3
/* Group 2 */
|| b == 0x2e || b == 0x36 || b == 0x3e || b == 0x26
|| b == 0x64 || b == 0x65 || b == 0x2e || b == 0x3e
/* Group 3 */
|| b == 0x66
/* Group 4 */
|| b == 0x67;
}
static bool opcode_is_rex_prefix(uint8_t b)
{
return (b & 0xf0) == 0x40;
}
#define REX_W (1 << 3)
/*
* This is a VERY crude opcode decoder. We only need to find the size of the
* load/store that caused our #PF and this should work for all the opcodes
* that we care about. Moreover, the ones who invented this instruction set
* should be shot.
*/
void kmemcheck_opcode_decode(const uint8_t *op, unsigned int *size)
{
/* Default operand size */
int operand_size_override = 4;
/* prefixes */
for (; opcode_is_prefix(*op); ++op) {
if (*op == 0x66)
operand_size_override = 2;
}
#ifdef CONFIG_X86_64
/* REX prefix */
if (opcode_is_rex_prefix(*op)) {
uint8_t rex = *op;
++op;
if (rex & REX_W) {
switch (*op) {
case 0x63:
*size = 4;
return;
case 0x0f:
++op;
switch (*op) {
case 0xb6:
case 0xbe:
*size = 1;
return;
case 0xb7:
case 0xbf:
*size = 2;
return;
}
break;
}
*size = 8;
return;
}
}
#endif
/* escape opcode */
if (*op == 0x0f) {
++op;
/*
* This is move with zero-extend and sign-extend, respectively;
* we don't have to think about 0xb6/0xbe, because this is
* already handled in the conditional below.
*/
if (*op == 0xb7 || *op == 0xbf)
operand_size_override = 2;
}
*size = (*op & 1) ? operand_size_override : 1;
}
const uint8_t *kmemcheck_opcode_get_primary(const uint8_t *op)
{
/* skip prefixes */
while (opcode_is_prefix(*op))
++op;
if (opcode_is_rex_prefix(*op))
++op;
return op;
}

9
arch/x86/mm/kmemcheck/opcode.h Normal file
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@ -0,0 +1,9 @@
#ifndef ARCH__X86__MM__KMEMCHECK__OPCODE_H
#define ARCH__X86__MM__KMEMCHECK__OPCODE_H
#include <linux/types.h>
void kmemcheck_opcode_decode(const uint8_t *op, unsigned int *size);
const uint8_t *kmemcheck_opcode_get_primary(const uint8_t *op);
#endif

22
arch/x86/mm/kmemcheck/pte.c Normal file
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@ -0,0 +1,22 @@
#include <linux/mm.h>
#include <asm/pgtable.h>
#include "pte.h"
pte_t *kmemcheck_pte_lookup(unsigned long address)
{
pte_t *pte;
unsigned int level;
pte = lookup_address(address, &level);
if (!pte)
return NULL;
if (level != PG_LEVEL_4K)
return NULL;
if (!pte_hidden(*pte))
return NULL;
return pte;
}

10
arch/x86/mm/kmemcheck/pte.h Normal file
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@ -0,0 +1,10 @@
#ifndef ARCH__X86__MM__KMEMCHECK__PTE_H
#define ARCH__X86__MM__KMEMCHECK__PTE_H
#include <linux/mm.h>
#include <asm/pgtable.h>
pte_t *kmemcheck_pte_lookup(unsigned long address);
#endif

153
arch/x86/mm/kmemcheck/shadow.c Normal file
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@ -0,0 +1,153 @@
#include <linux/kmemcheck.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include "pte.h"
#include "shadow.h"
/*
* Return the shadow address for the given address. Returns NULL if the
* address is not tracked.
*
* We need to be extremely careful not to follow any invalid pointers,
* because this function can be called for *any* possible address.
*/
void *kmemcheck_shadow_lookup(unsigned long address)
{
pte_t *pte;
struct page *page;
if (!virt_addr_valid(address))
return NULL;
pte = kmemcheck_pte_lookup(address);
if (!pte)
return NULL;
page = virt_to_page(address);
if (!page->shadow)
return NULL;
return page->shadow + (address & (PAGE_SIZE - 1));
}
static void mark_shadow(void *address, unsigned int n,
enum kmemcheck_shadow status)
{
unsigned long addr = (unsigned long) address;
unsigned long last_addr = addr + n - 1;
unsigned long page = addr & PAGE_MASK;
unsigned long last_page = last_addr & PAGE_MASK;
unsigned int first_n;
void *shadow;
/* If the memory range crosses a page boundary, stop there. */
if (page == last_page)
first_n = n;
else
first_n = page + PAGE_SIZE - addr;
shadow = kmemcheck_shadow_lookup(addr);
if (shadow)
memset(shadow, status, first_n);
addr += first_n;
n -= first_n;
/* Do full-page memset()s. */
while (n >= PAGE_SIZE) {
shadow = kmemcheck_shadow_lookup(addr);
if (shadow)
memset(shadow, status, PAGE_SIZE);
addr += PAGE_SIZE;
n -= PAGE_SIZE;
}
/* Do the remaining page, if any. */
if (n > 0) {
shadow = kmemcheck_shadow_lookup(addr);
if (shadow)
memset(shadow, status, n);
}
}
void kmemcheck_mark_unallocated(void *address, unsigned int n)
{
mark_shadow(address, n, KMEMCHECK_SHADOW_UNALLOCATED);
}
void kmemcheck_mark_uninitialized(void *address, unsigned int n)
{
mark_shadow(address, n, KMEMCHECK_SHADOW_UNINITIALIZED);
}
/*
* Fill the shadow memory of the given address such that the memory at that
* address is marked as being initialized.
*/
void kmemcheck_mark_initialized(void *address, unsigned int n)
{
mark_shadow(address, n, KMEMCHECK_SHADOW_INITIALIZED);
}
EXPORT_SYMBOL_GPL(kmemcheck_mark_initialized);
void kmemcheck_mark_freed(void *address, unsigned int n)
{
mark_shadow(address, n, KMEMCHECK_SHADOW_FREED);
}
void kmemcheck_mark_unallocated_pages(struct page *p, unsigned int n)
{
unsigned int i;
for (i = 0; i < n; ++i)
kmemcheck_mark_unallocated(page_address(&p[i]), PAGE_SIZE);
}
void kmemcheck_mark_uninitialized_pages(struct page *p, unsigned int n)
{
unsigned int i;
for (i = 0; i < n; ++i)
kmemcheck_mark_uninitialized(page_address(&p[i]), PAGE_SIZE);
}
enum kmemcheck_shadow kmemcheck_shadow_test(void *shadow, unsigned int size)
{
uint8_t *x;
unsigned int i;
x = shadow;
#ifdef CONFIG_KMEMCHECK_PARTIAL_OK
/*
* Make sure _some_ bytes are initialized. Gcc frequently generates
* code to access neighboring bytes.
*/
for (i = 0; i < size; ++i) {
if (x[i] == KMEMCHECK_SHADOW_INITIALIZED)
return x[i];
}
#else
/* All bytes must be initialized. */
for (i = 0; i < size; ++i) {
if (x[i] != KMEMCHECK_SHADOW_INITIALIZED)
return x[i];
}
#endif
return x[0];
}
void kmemcheck_shadow_set(void *shadow, unsigned int size)
{
uint8_t *x;
unsigned int i;
x = shadow;
for (i = 0; i < size; ++i)
x[i] = KMEMCHECK_SHADOW_INITIALIZED;
}

16
arch/x86/mm/kmemcheck/shadow.h Normal file
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@ -0,0 +1,16 @@
#ifndef ARCH__X86__MM__KMEMCHECK__SHADOW_H
#define ARCH__X86__MM__KMEMCHECK__SHADOW_H
enum kmemcheck_shadow {
KMEMCHECK_SHADOW_UNALLOCATED,
KMEMCHECK_SHADOW_UNINITIALIZED,
KMEMCHECK_SHADOW_INITIALIZED,
KMEMCHECK_SHADOW_FREED,
};
void *kmemcheck_shadow_lookup(unsigned long address);
enum kmemcheck_shadow kmemcheck_shadow_test(void *shadow, unsigned int size);
void kmemcheck_shadow_set(void *shadow, unsigned int size);
#endif

17
include/linux/kmemcheck.h Normal file
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@ -0,0 +1,17 @@
#ifndef LINUX_KMEMCHECK_H
#define LINUX_KMEMCHECK_H
#include <linux/mm_types.h>
#include <linux/types.h>
#ifdef CONFIG_KMEMCHECK
extern int kmemcheck_enabled;
int kmemcheck_show_addr(unsigned long address);
int kmemcheck_hide_addr(unsigned long address);
#else
#define kmemcheck_enabled 0
#endif /* CONFIG_KMEMCHECK */
#endif /* LINUX_KMEMCHECK_H */

8
include/linux/mm_types.h
View File

@ -98,6 +98,14 @@ struct page {
#ifdef CONFIG_WANT_PAGE_DEBUG_FLAGS
unsigned long debug_flags; /* Use atomic bitops on this */
#endif
#ifdef CONFIG_KMEMCHECK
/*
* kmemcheck wants to track the status of each byte in a page; this
* is a pointer to such a status block. NULL if not tracked.
*/
void *shadow;
#endif
};
/*

1
init/main.c
View File

@ -65,6 +65,7 @@
#include <linux/idr.h>
#include <linux/ftrace.h>
#include <linux/async.h>
#include <linux/kmemcheck.h>
#include <linux/kmemtrace.h>
#include <trace/boot.h>

12
kernel/sysctl.c
View File

@ -27,6 +27,7 @@
#include <linux/security.h>
#include <linux/ctype.h>
#include <linux/utsname.h>
#include <linux/kmemcheck.h>
#include <linux/smp_lock.h>
#include <linux/fs.h>
#include <linux/init.h>
@ -959,6 +960,17 @@ static struct ctl_table kern_table[] = {
.proc_handler = &proc_dointvec,
},
#endif
#ifdef CONFIG_KMEMCHECK
{
.ctl_name = CTL_UNNUMBERED,
.procname = "kmemcheck",
.data = &kmemcheck_enabled,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = &proc_dointvec,
},
#endif
/*
* NOTE: do not add new entries to this table unless you have read
* Documentation/sysctl/ctl_unnumbered.txt