blob: b4f2e7e9e90785534e10d017a94e787aa5e8fc03 [file] [log] [blame]
/**
* 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 "selftest.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)
{
#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
if (!kmemcheck_selftest()) {
printk(KERN_INFO "kmemcheck: self-tests failed; disabling\n");
kmemcheck_enabled = 0;
return -EINVAL;
}
printk(KERN_INFO "kmemcheck: Initialized\n");
return 0;
}
early_initcall(kmemcheck_init);
/*
* We need to parse the kmemcheck= option before any memory is allocated.
*/
static int __init param_kmemcheck(char *str)
{
int val;
int ret;
if (!str)
return -EINVAL;
ret = kstrtoint(str, 0, &val);
if (ret)
return ret;
kmemcheck_enabled = val;
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 = this_cpu_ptr(&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 = this_cpu_ptr(&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 = this_cpu_ptr(&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 = this_cpu_ptr(&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 = this_cpu_ptr(&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 = this_cpu_ptr(&kmemcheck_context);
int n;
BUG_ON(!irqs_disabled());
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);
}
bool kmemcheck_is_obj_initialized(unsigned long addr, size_t size)
{
enum kmemcheck_shadow status;
void *shadow;
shadow = kmemcheck_shadow_lookup(addr);
if (!shadow)
return true;
status = kmemcheck_shadow_test_all(shadow, size);
return status == KMEMCHECK_SHADOW_INITIALIZED;
}
/* 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 = this_cpu_ptr(&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;
/*
* 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 = kmemcheck_pte_lookup(address);
if (!pte)
return false;
WARN_ON_ONCE(in_nmi());
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;
}