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Subject[PATCH 1/4] kmemcheck v4
Greetings,

I post the fourth revision of kmemcheck. It seems that we are slowly
converging towards something usable :-)

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.

Changes since v3:
- More clean-ups. Hopefully the SLUB bits are clearer now.
- Don't print directly from the page fault handler. Instead, we save all
errors on a ring queue and print them from a helper kernel thread.
- Some experimental support for graceful bit-field handling.
- Preliminary support for use-after-free detection.
- I've also separated the patch into logical chunks.

On my machine, the kmemcheck-enabled kernel now boots into full
graphical desktop. As expected, it is much, much slower than the vanilla
kernel, but still surprisingly usable. Unfortunately, the kernel
usually freezes hard after a couple of hours for unknown reasons --
ideas and/or patches are welcome ;-)

The patches apply to v2.6.25-rc1.


Kind regards,
Vegard Nossum


From 0fcca4341b6b1b277d936558aa3cab0f212bad9b Mon Sep 17 00:00:00 2001
From: Vegard Nossum <vegard.nossum@gmail.com>
Date: Thu, 14 Feb 2008 19:10:40 +0100
Subject: [PATCH] kmemcheck: add the core kmemcheck changes

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.

Signed-off-by: Vegard Nossum <vegardno@ifi.uio.no>
---
Documentation/kmemcheck.txt | 73 ++++
arch/x86/Kconfig.debug | 35 ++
arch/x86/kernel/Makefile | 2 +
arch/x86/kernel/kmemcheck_32.c | 781 ++++++++++++++++++++++++++++++++++++++++
include/asm-x86/kmemcheck.h | 3 +
include/asm-x86/kmemcheck_32.h | 22 ++
include/asm-x86/pgtable.h | 4 +-
include/asm-x86/pgtable_32.h | 1 +
include/linux/gfp.h | 3 +-
include/linux/kmemcheck.h | 17 +
include/linux/page-flags.h | 7 +
11 files changed, 945 insertions(+), 3 deletions(-)
create mode 100644 Documentation/kmemcheck.txt
create mode 100644 arch/x86/kernel/kmemcheck_32.c
create mode 100644 include/asm-x86/kmemcheck.h
create mode 100644 include/asm-x86/kmemcheck_32.h
create mode 100644 include/linux/kmemcheck.h
diff --git a/Documentation/kmemcheck.txt b/Documentation/kmemcheck.txt
new file mode 100644
index 0000000..d234571
--- /dev/null
+++ b/Documentation/kmemcheck.txt
@@ -0,0 +1,73 @@
+Technical description
+=====================
+
+kmemcheck works by marking memory pages non-present. This means that whenever
+somebody attempts to access the page, a page fault is generated. The page
+fault handler notices that the page was in fact only hidden, and so it calls
+on the kmemcheck code to make further investigations.
+
+When the investigations are completed, kmemcheck "shows" the page by marking
+it present (as it would be under normal circumstances). This way, the
+interrupted code can continue as usual.
+
+But after the instruction has been executed, we should hide the page again, so
+that we can catch the next access too! Now kmemcheck makes use of a debugging
+feature of the processor, namely single-stepping. When the processor has
+finished the one instruction that generated the memory access, a debug
+exception is raised. From here, we simply hide the page again and continue
+execution, this time with the single-stepping feature turned off.
+
+
+Changes to the memory allocator (SLUB)
+======================================
+
+kmemcheck requires some assistance from the memory allocator in order to work.
+The memory allocator needs to
+
+1. Request twice as much memory as would normally be needed. The bottom half
+ of the memory is what the user actually sees and uses; the upper half
+ contains the so-called shadow memory, which stores the status of each byte
+ in the bottom half, e.g. initialized or uninitialized.
+2. Tell kmemcheck which parts of memory that should be marked uninitialized.
+ There are actually a few more states, such as "not yet allocated" and
+ "recently freed".
+
+If a slab cache is set up using the SLAB_NOTRACK flag, it will never return
+memory that can take page faults because of kmemcheck.
+
+If a slab cache is NOT set up using the SLAB_NOTRACK flag, callers can still
+request memory with the __GFP_NOTRACK flag. This does not prevent the page
+faults from occuring, however, but marks the object in question as being
+initialized so that no warnings will ever be produced for this object.
+
+
+Problems
+========
+
+The most prominent problem seems to be that of bit-fields. kmemcheck can only
+track memory with byte granularity. Therefore, when gcc generates code to
+access only one bit in a bit-field, there is really no way for kmemcheck to
+know which of the other bits that will be used or thrown away. Consequently,
+there may be bogus warnings for bit-field accesses. There is some experimental
+support to detect this automatically, though it is probably better to work
+around this by explicitly initializing whole bit-fields at once.
+
+Some allocations are used for DMA. As DMA doesn't go through the paging
+mechanism, we have absolutely no way to detect DMA writes. This means that
+spurious warnings may be seen on access to DMA memory. DMA allocations should
+be annotated with the __GFP_NOTRACK flag or allocated from caches marked
+SLAB_NOTRACK to work around this problem.
+
+
+Future enhancements
+===================
+
+There is already some preliminary support for catching use-after-free errors.
+What still needs to be done is delaying kfree() so that memory is not
+reallocated immediately after freeing it. [Suggested by Pekka Enberg.]
+
+It should be possible to allow SMP systems by duplicating the page tables for
+each processor in the system. This is probably extremely difficult, however.
+[Suggested by Ingo Molnar.]
+
+Support for instruction set extensions like XMM, SSE2, etc.
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 864affc..f373c0e 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -134,6 +134,41 @@ config IOMMU_LEAK
Add a simple leak tracer to the IOMMU code. This is useful when you
are debugging a buggy device driver that leaks IOMMU mappings.

+config KMEMCHECK
+ bool "kmemcheck: trap use of uninitialized memory"
+ depends on M386 && !X86_GENERIC && !SMP
+ depends on !CC_OPTIMIZE_FOR_SIZE
+ depends on !DEBUG_PAGEALLOC && SLUB
+ select DEBUG_INFO
+ select FRAME_POINTER
+ select STACKTRACE
+ default n
+ help
+ This option enables tracing of dynamically allocated kernel memory
+ to see if memory is used before it has been given an initial value.
+ Be aware that this requires half of your memory for bookkeeping and
+ will insert extra code at *every* read and write to tracked memory
+ thus slow down the kernel code (but user code is unaffected).
+
+config KMEMCHECK_PARTIAL_OK
+ bool "kmemcheck: allow partially uninitialized memory"
+ depends on KMEMCHECK
+ default y
+ help
+ This option works around certain GCC optimizations that produce
+ 32-bit reads from 16-bit variables where the upper 16 bits are
+ thrown away afterwards. This may of course also hide some real
+ bugs.
+
+config KMEMCHECK_BITOPS_OK
+ bool "kmemcheck: allow bit-field manipulation"
+ depends on KMEMCHECK
+ default n
+ help
+ This option silences warnings that would be generated for bit-field
+ accesses where not all the bits are initialized at the same time.
+ This may also hide some real bugs.
+
#
# IO delay types:
#
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 76ec0f8..f302a8a 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -78,6 +78,8 @@ endif
obj-$(CONFIG_SCx200) += scx200.o
scx200-y += scx200_32.o

+obj-$(CONFIG_KMEMCHECK) += kmemcheck_32.o
+
###
# 64 bit specific files
ifeq ($(CONFIG_X86_64),y)
diff --git a/arch/x86/kernel/kmemcheck_32.c b/arch/x86/kernel/kmemcheck_32.c
new file mode 100644
index 0000000..0863ce2
--- /dev/null
+++ b/arch/x86/kernel/kmemcheck_32.c
@@ -0,0 +1,781 @@
+/**
+ * kmemcheck - a heavyweight memory checker
+ * 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/kallsyms.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/page-flags.h>
+#include <linux/stacktrace.h>
+
+#include <asm/cacheflush.h>
+#include <asm/kdebug.h>
+#include <asm/kmemcheck.h>
+#include <asm/pgtable.h>
+#include <asm/string.h>
+#include <asm/tlbflush.h>
+
+enum shadow {
+ SHADOW_UNALLOCATED,
+ SHADOW_UNINITIALIZED,
+ SHADOW_INITIALIZED,
+ SHADOW_FREED,
+};
+
+struct kmemcheck_error {
+ /* Kind of access that caused the error */
+ enum shadow state;
+ /* Address and size of the erroneous read */
+ uint32_t address;
+ unsigned int size;
+
+ struct pt_regs regs;
+ struct stack_trace trace;
+ unsigned long trace_entries[32];
+};
+
+/*
+ * 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[32];
+static unsigned int error_count;
+static unsigned int error_rd;
+static unsigned int error_wr;
+
+static struct task_struct *kmemcheck_thread;
+
+static struct kmemcheck_error *
+error_next_wr(void)
+{
+ struct kmemcheck_error *e;
+
+ if (error_count == ARRAY_SIZE(error_fifo))
+ 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;
+}
+
+/*
+ * Save the context of the error.
+ */
+static void
+error_save(enum shadow state, uint32_t address, unsigned int size,
+ struct pt_regs *regs)
+{
+ static uint32_t prev_ip;
+
+ struct kmemcheck_error *e;
+
+ /* 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->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 = 4;
+ save_stack_trace(&e->trace);
+
+ if (kmemcheck_thread)
+ wake_up_process(kmemcheck_thread);
+}
+
+static void
+error_recall(void)
+{
+ static const char *desc[] = {
+ [SHADOW_UNALLOCATED] = "unallocated",
+ [SHADOW_UNINITIALIZED] = "uninitialized",
+ [SHADOW_INITIALIZED] = "initialized",
+ [SHADOW_FREED] = "freed",
+ };
+
+ struct kmemcheck_error *e;
+
+ e = error_next_rd();
+ if (!e)
+ return;
+
+ printk(KERN_ALERT "kmemcheck: Caught %d-bit read from %s memory\n",
+ e->size, desc[e->state]);
+ printk(KERN_ALERT "=> address %08x\n", e->address);
+
+ __show_registers(&e->regs, 1);
+ print_stack_trace(&e->trace, 0);
+}
+
+/*
+ * The error reporter thread.
+ */
+static int
+kmemcheck_thread_run(void *data)
+{
+ while (true) {
+ while (error_count > 0)
+ error_recall();
+
+ /* Sleep */
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule();
+ }
+}
+
+static int
+init(void)
+{
+ struct task_struct *t;
+
+ printk(KERN_INFO "kmemcheck: \"Bugs, beware!\"\n");
+
+ t = kthread_create(&kmemcheck_thread_run, NULL,
+ "kmemcheck");
+ if (IS_ERR(t)) {
+ printk(KERN_ERR "kmemcheck: Couldn't start output thread\n");
+ return PTR_ERR(t);
+ }
+
+ kmemcheck_thread = t;
+ wake_up_process(kmemcheck_thread);
+ return 0;
+}
+
+core_initcall(init);
+
+/*
+ * Return the shadow address for the given address. Returns NULL if the
+ * address is not tracked.
+ */
+static void *
+address_get_shadow(unsigned long address)
+{
+ struct page *page;
+ struct page *head;
+
+ if (address < PAGE_OFFSET)
+ return NULL;
+ page = virt_to_page(address);
+ if (!page)
+ return NULL;
+ head = compound_head(page);
+ if (!head)
+ return NULL;
+ if (!PageSlab(head))
+ return NULL;
+ if (!PageTracked(head))
+ return NULL;
+ return (void *) address + (PAGE_SIZE << (compound_order(head) - 1));
+}
+
+static int
+show_addr(uint32_t addr)
+{
+ pte_t *pte;
+ int level;
+
+ if (!address_get_shadow(addr))
+ return 0;
+
+ pte = lookup_address(addr, &level);
+ BUG_ON(!pte);
+ BUG_ON(level != PG_LEVEL_4K);
+
+ pte->pte_low |= _PAGE_PRESENT;
+ __flush_tlb_one(addr);
+ return 1;
+}
+
+static int
+hide_addr(uint32_t addr)
+{
+ pte_t *pte;
+ int level;
+
+ if (!address_get_shadow(addr))
+ return 0;
+
+ pte = lookup_address(addr, &level);
+ BUG_ON(!pte);
+ BUG_ON(level != PG_LEVEL_4K);
+
+ pte->pte_low &= ~_PAGE_PRESENT;
+ __flush_tlb_one(addr);
+ return 1;
+}
+
+DEFINE_PER_CPU(bool, kmemcheck_busy) = false;
+DEFINE_PER_CPU(uint32_t, kmemcheck_addr1) = 0;
+DEFINE_PER_CPU(uint32_t, kmemcheck_addr2) = 0;
+DEFINE_PER_CPU(uint32_t, kmemcheck_reg_flags) = 0;
+
+DEFINE_PER_CPU(int, kmemcheck_num) = 0;
+DEFINE_PER_CPU(int, kmemcheck_balance) = 0;
+
+/*
+ * Called from the #PF handler.
+ */
+void
+kmemcheck_show(struct pt_regs *regs)
+{
+ int n;
+
+ BUG_ON(!irqs_disabled());
+
+ if (__get_cpu_var(kmemcheck_balance) != 0) {
+ oops_in_progress = 1;
+ panic("kmemcheck: extra #PF");
+ }
+
+ ++__get_cpu_var(kmemcheck_num);
+
+ BUG_ON(!__get_cpu_var(kmemcheck_addr1)
+ && !__get_cpu_var(kmemcheck_addr2));
+
+ n = 0;
+ n += show_addr(__get_cpu_var(kmemcheck_addr1));
+ n += show_addr(__get_cpu_var(kmemcheck_addr2));
+
+ /* None of the addresses actually belonged to kmemcheck. Note that
+ * this is not an error. */
+ if (n == 0)
+ return;
+
+ ++__get_cpu_var(kmemcheck_balance);
+ ++__get_cpu_var(kmemcheck_num);
+
+ /*
+ * 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 & TF_MASK))
+ __get_cpu_var(kmemcheck_reg_flags) = regs->flags;
+
+ regs->flags |= TF_MASK;
+ regs->flags &= ~IF_MASK;
+}
+
+/*
+ * Called from the #DB handler.
+ */
+void
+kmemcheck_hide(struct pt_regs *regs)
+{
+ BUG_ON(!irqs_disabled());
+
+ --__get_cpu_var(kmemcheck_balance);
+ if (unlikely(__get_cpu_var(kmemcheck_balance) != 0)) {
+ oops_in_progress = 1;
+ panic("kmemcheck: extra #DB");
+ }
+
+ hide_addr(__get_cpu_var(kmemcheck_addr1));
+ hide_addr(__get_cpu_var(kmemcheck_addr2));
+ __get_cpu_var(kmemcheck_addr1) = 0;
+ __get_cpu_var(kmemcheck_addr2) = 0;
+
+ if (!(__get_cpu_var(kmemcheck_reg_flags) & TF_MASK))
+ regs->flags &= ~TF_MASK;
+ if (__get_cpu_var(kmemcheck_reg_flags) & IF_MASK)
+ regs->flags |= IF_MASK;
+}
+
+void
+kmemcheck_prepare(struct pt_regs *regs)
+{
+ /*
+ * Detect and handle recursive pagefaults:
+ */
+ if (__get_cpu_var(kmemcheck_balance) > 0) {
+ panic_timeout++;
+ /*
+ * We can have multi-address faults from accesses like:
+ *
+ * rep movsb %ds:(%esi),%es:(%edi)
+ *
+ * So in this case, we hide the current in-progress fault
+ * and handle when we detect this recursion, we hide the
+ * currently in-progress addresses again.
+ */
+ kmemcheck_hide(regs);
+ }
+}
+
+void
+kmemcheck_show_pages(struct page *p, unsigned int n)
+{
+ unsigned int i;
+ struct page *head;
+
+ head = compound_head(p);
+ BUG_ON(!head);
+
+ ClearPageTracked(head);
+
+ for (i = 0; i < n; ++i) {
+ unsigned long address;
+ pte_t *pte;
+ int level;
+
+ address = (unsigned long) page_address(&p[i]);
+ pte = lookup_address(address, &level);
+ BUG_ON(!pte);
+ BUG_ON(level != PG_LEVEL_4K);
+
+ pte->pte_low |= _PAGE_PRESENT;
+ pte->pte_low &= ~_PAGE_HIDDEN;
+ __flush_tlb_one(address);
+ }
+}
+
+void
+kmemcheck_hide_pages(struct page *p, unsigned int n)
+{
+ unsigned int i;
+ struct page *head;
+
+ head = compound_head(p);
+ BUG_ON(!head);
+
+ SetPageTracked(head);
+
+ for (i = 0; i < n; ++i) {
+ unsigned long address;
+ pte_t *pte;
+ int level;
+
+ address = (unsigned long) page_address(&p[i]);
+ pte = lookup_address(address, &level);
+ BUG_ON(!pte);
+ BUG_ON(level != PG_LEVEL_4K);
+
+ pte->pte_low &= ~_PAGE_PRESENT;
+ pte->pte_low |= _PAGE_HIDDEN;
+ __flush_tlb_one(address);
+ }
+}
+
+static void
+mark_shadow(void *address, unsigned int n, enum shadow status)
+{
+ void *shadow;
+
+ shadow = address_get_shadow((unsigned long) address);
+ if (!shadow)
+ return;
+ __memset(shadow, status, n);
+}
+
+void
+kmemcheck_mark_unallocated(void *address, unsigned int n)
+{
+ mark_shadow(address, n, SHADOW_UNALLOCATED);
+}
+
+void
+kmemcheck_mark_uninitialized(void *address, unsigned int n)
+{
+ mark_shadow(address, n, 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, SHADOW_INITIALIZED);
+}
+
+void
+kmemcheck_mark_freed(void *address, unsigned int n)
+{
+ mark_shadow(address, n, 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);
+}
+
+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;
+}
+
+/* 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. */
+static unsigned int
+opcode_get_size(const uint8_t *op)
+{
+ /* Default operand size */
+ int operand_size_override = 32;
+
+ /* prefixes */
+ for (; opcode_is_prefix(*op); ++op) {
+ if (*op == 0x66)
+ operand_size_override = 16;
+ }
+
+ /* escape opcode */
+ if (*op == 0x0f) {
+ ++op;
+
+ if (*op == 0xb6)
+ return operand_size_override >> 1;
+ if (*op == 0xb7)
+ return 16;
+ }
+
+ return (*op & 1) ? operand_size_override : 8;
+}
+
+static const uint8_t *
+opcode_get_primary(const uint8_t *op)
+{
+ /* skip prefixes */
+ for (; opcode_is_prefix(*op); ++op);
+ return op;
+}
+
+static inline enum shadow
+test(void *shadow, unsigned int size)
+{
+ uint8_t *x;
+
+ x = shadow;
+
+#ifdef CONFIG_KMEMCHECK_PARTIAL_OK
+ /*
+ * Make sure _some_ bytes are initialized. Gcc frequently generates
+ * code to access neighboring bytes.
+ */
+ switch (size) {
+ case 32:
+ if (x[3] == SHADOW_INITIALIZED)
+ return x[3];
+ if (x[2] == SHADOW_INITIALIZED)
+ return x[2];
+ case 16:
+ if (x[1] == SHADOW_INITIALIZED)
+ return x[1];
+ case 8:
+ if (x[0] == SHADOW_INITIALIZED)
+ return x[0];
+ }
+#else
+ switch (size) {
+ case 32:
+ if (x[3] != SHADOW_INITIALIZED)
+ return x[3];
+ if (x[2] != SHADOW_INITIALIZED)
+ return x[2];
+ case 16:
+ if (x[1] != SHADOW_INITIALIZED)
+ return x[1];
+ case 8:
+ if (x[0] != SHADOW_INITIALIZED)
+ return x[0];
+ }
+#endif
+
+ return x[0];
+}
+
+static inline void
+set(void *shadow, unsigned int size)
+{
+ uint8_t *x;
+
+ x = shadow;
+
+ switch (size) {
+ case 32:
+ x[3] = SHADOW_INITIALIZED;
+ x[2] = SHADOW_INITIALIZED;
+ case 16:
+ x[1] = SHADOW_INITIALIZED;
+ case 8:
+ x[0] = SHADOW_INITIALIZED;
+ }
+
+ return;
+}
+
+static void
+kmemcheck_read(struct pt_regs *regs, uint32_t address, unsigned int size)
+{
+ void *shadow;
+ enum shadow status;
+
+ shadow = address_get_shadow(address);
+ if (!shadow)
+ return;
+
+ status = test(shadow, size);
+ if (status == SHADOW_INITIALIZED)
+ return;
+
+ /* Don't warn about it again. */
+ set(shadow, size);
+
+ oops_in_progress = 1;
+ error_save(status, address, size, regs);
+}
+
+static void
+kmemcheck_write(struct pt_regs *regs, uint32_t address, unsigned int size)
+{
+ void *shadow;
+
+ shadow = address_get_shadow(address);
+ if (!shadow)
+ return;
+ set(shadow, size);
+}
+
+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;
+
+ if (__get_cpu_var(kmemcheck_busy)) {
+ oops_in_progress = 1;
+ panic("kmemcheck: recursive fault");
+ }
+
+ __get_cpu_var(kmemcheck_busy) = true;
+
+ insn = (const uint8_t *) regs->ip;
+ insn_primary = opcode_get_primary(insn);
+
+ size = opcode_get_size(insn);
+
+ 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);
+ __get_cpu_var(kmemcheck_addr1) = fallback_address;
+ __get_cpu_var(kmemcheck_addr2) = 0;
+ __get_cpu_var(kmemcheck_busy) = false;
+ return;
+
+ /* 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_read(regs, regs->si, size);
+ kmemcheck_write(regs, regs->di, size);
+ __get_cpu_var(kmemcheck_addr1) = regs->si;
+ __get_cpu_var(kmemcheck_addr2) = regs->di;
+ __get_cpu_var(kmemcheck_busy) = false;
+ return;
+
+ /* CMPS, CMPSB, CMPSW, CMPSD */
+ case 0xa6:
+ case 0xa7:
+ kmemcheck_read(regs, regs->si, size);
+ kmemcheck_read(regs, regs->di, size);
+ __get_cpu_var(kmemcheck_addr1) = regs->si;
+ __get_cpu_var(kmemcheck_addr2) = regs->di;
+ __get_cpu_var(kmemcheck_busy) = false;
+ return;
+ }
+
+ /* 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);
+ __get_cpu_var(kmemcheck_addr1) = fallback_address;
+ __get_cpu_var(kmemcheck_addr2) = 0;
+ __get_cpu_var(kmemcheck_busy) = false;
+ return;
+ case KMEMCHECK_WRITE:
+ kmemcheck_write(regs, fallback_address, size);
+ __get_cpu_var(kmemcheck_addr1) = fallback_address;
+ __get_cpu_var(kmemcheck_addr2) = 0;
+ __get_cpu_var(kmemcheck_busy) = false;
+ return;
+ }
+}
+
+/*
+ * A faster implementation of memset() when tracking is enabled where the
+ * whole memory area is within a single page.
+ */
+static void
+memset_one_page(unsigned long s, int c, size_t n)
+{
+ void *x;
+ unsigned long flags;
+
+ x = address_get_shadow(s);
+ if (!x) {
+ /* The page isn't being tracked. */
+ __memset((void *) s, c, n);
+ return;
+ }
+
+ /* While we are not guarding the page in question, nobody else
+ * should be able to change them. */
+ local_irq_save(flags);
+
+ show_addr(s);
+ __memset((void *) s, c, n);
+ __memset((void *) x, SHADOW_INITIALIZED, n);
+ hide_addr(s);
+
+ local_irq_restore(flags);
+}
+
+/*
+ * A faster implementation of memset() when tracking is enabled. We cannot
+ * assume that all pages within the range are tracked, so copying has to be
+ * split into page-sized (or smaller, for the ends) chunks.
+ */
+void
+kmemcheck_memset(unsigned long s, int c, size_t n)
+{
+ unsigned long a_page, a_offset;
+ unsigned long b_page, b_offset;
+ unsigned long i;
+
+ if (!n)
+ return;
+
+ if (!slab_is_available()) {
+ __memset((void *) s, c, n);
+ return;
+ }
+
+ a_page = s & PAGE_MASK;
+ b_page = (s + n) & PAGE_MASK;
+
+ if (a_page == b_page) {
+ /* The entire area is within the same page. Good, we only
+ * need one memset(). */
+ memset_one_page(s, c, n);
+ return;
+ }
+
+ a_offset = s & ~PAGE_MASK;
+ b_offset = (s + n) & ~PAGE_MASK;
+
+ /* Clear the head, body, and tail of the memory area. */
+ if (a_offset < PAGE_SIZE)
+ memset_one_page(s, c, PAGE_SIZE - a_offset);
+ for (i = a_page + PAGE_SIZE; i < b_page; i += PAGE_SIZE)
+ memset_one_page(i, c, PAGE_SIZE);
+ if (b_offset > 0)
+ memset_one_page(b_page, c, b_offset);
+}
+
+EXPORT_SYMBOL(kmemcheck_memset);
diff --git a/include/asm-x86/kmemcheck.h b/include/asm-x86/kmemcheck.h
new file mode 100644
index 0000000..11de35a
--- /dev/null
+++ b/include/asm-x86/kmemcheck.h
@@ -0,0 +1,3 @@
+#ifdef CONFIG_X86_32
+# include "kmemcheck_32.h"
+#endif
diff --git a/include/asm-x86/kmemcheck_32.h b/include/asm-x86/kmemcheck_32.h
new file mode 100644
index 0000000..295e256
--- /dev/null
+++ b/include/asm-x86/kmemcheck_32.h
@@ -0,0 +1,22 @@
+#ifndef ASM_X86_KMEMCHECK_32_H
+#define ASM_X86_KMEMCHECK_32_H
+
+#include <linux/percpu.h>
+#include <asm/pgtable.h>
+
+enum kmemcheck_method {
+ KMEMCHECK_READ,
+ KMEMCHECK_WRITE,
+};
+
+#ifdef CONFIG_KMEMCHECK
+void kmemcheck_prepare(struct pt_regs *regs);
+
+void kmemcheck_show(struct pt_regs *regs);
+void kmemcheck_hide(struct pt_regs *regs);
+
+void kmemcheck_access(struct pt_regs *regs,
+ unsigned long address, enum kmemcheck_method method);
+#endif
+
+#endif
diff --git a/include/asm-x86/pgtable.h b/include/asm-x86/pgtable.h
index 174b877..eb64bbb 100644
--- a/include/asm-x86/pgtable.h
+++ b/include/asm-x86/pgtable.h
@@ -17,8 +17,8 @@
#define _PAGE_BIT_GLOBAL 8 /* Global TLB entry PPro+ */
#define _PAGE_BIT_UNUSED1 9 /* available for programmer */
#define _PAGE_BIT_UNUSED2 10
-#define _PAGE_BIT_UNUSED3 11
#define _PAGE_BIT_PAT_LARGE 12 /* On 2MB or 1GB pages */
+#define _PAGE_BIT_HIDDEN 11
#define _PAGE_BIT_NX 63 /* No execute: only valid after cpuid check */

/*
@@ -37,9 +37,9 @@
#define _PAGE_GLOBAL (_AC(1, L)<<_PAGE_BIT_GLOBAL) /* Global TLB entry */
#define _PAGE_UNUSED1 (_AC(1, L)<<_PAGE_BIT_UNUSED1)
#define _PAGE_UNUSED2 (_AC(1, L)<<_PAGE_BIT_UNUSED2)
-#define _PAGE_UNUSED3 (_AC(1, L)<<_PAGE_BIT_UNUSED3)
#define _PAGE_PAT (_AC(1, L)<<_PAGE_BIT_PAT)
#define _PAGE_PAT_LARGE (_AC(1, L)<<_PAGE_BIT_PAT_LARGE)
+#define _PAGE_HIDDEN (_AC(1, L)<<_PAGE_BIT_HIDDEN)

#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
#define _PAGE_NX (_AC(1, ULL) << _PAGE_BIT_NX)
diff --git a/include/asm-x86/pgtable_32.h b/include/asm-x86/pgtable_32.h
index a842c72..6830703 100644
--- a/include/asm-x86/pgtable_32.h
+++ b/include/asm-x86/pgtable_32.h
@@ -87,6 +87,7 @@ void paging_init(void);
extern unsigned long pg0[];

#define pte_present(x) ((x).pte_low & (_PAGE_PRESENT | _PAGE_PROTNONE))
+#define pte_hidden(x) ((x).pte_low & (_PAGE_HIDDEN))

/* To avoid harmful races, pmd_none(x) should check only the lower when PAE */
#define pmd_none(x) (!(unsigned long)pmd_val(x))
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 0c6ce51..2138d64 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -50,8 +50,9 @@ struct vm_area_struct;
#define __GFP_THISNODE ((__force gfp_t)0x40000u)/* No fallback, no policies */
#define __GFP_RECLAIMABLE ((__force gfp_t)0x80000u) /* Page is reclaimable */
#define __GFP_MOVABLE ((__force gfp_t)0x100000u) /* Page is movable */
+#define __GFP_NOTRACK ((__force gfp_t)0x200000u) /* Don't track with kmemcheck */

-#define __GFP_BITS_SHIFT 21 /* Room for 21 __GFP_FOO bits */
+#define __GFP_BITS_SHIFT 22 /* Room for 22 __GFP_FOO bits */
#define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))

/* This equals 0, but use constants in case they ever change */
diff --git a/include/linux/kmemcheck.h b/include/linux/kmemcheck.h
new file mode 100644
index 0000000..407bc5c
--- /dev/null
+++ b/include/linux/kmemcheck.h
@@ -0,0 +1,17 @@
+#ifndef LINUX_KMEMCHECK_H
+#define LINUX_KMEMCHECK_H
+
+#ifdef CONFIG_KMEMCHECK
+void kmemcheck_show_pages(struct page *p, unsigned int n);
+void kmemcheck_hide_pages(struct page *p, unsigned int n);
+
+void kmemcheck_mark_unallocated(void *address, unsigned int n);
+void kmemcheck_mark_uninitialized(void *address, unsigned int n);
+void kmemcheck_mark_initialized(void *address, unsigned int n);
+void kmemcheck_mark_freed(void *address, unsigned int n);
+
+void kmemcheck_mark_unallocated_pages(struct page *p, unsigned int n);
+void kmemcheck_mark_uninitialized_pages(struct page *p, unsigned int n);
+#endif
+
+#endif
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index bbad43f..1593859 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -90,6 +90,8 @@
#define PG_reclaim 17 /* To be reclaimed asap */
#define PG_buddy 19 /* Page is free, on buddy lists */

+#define PG_tracked 20 /* Page is tracked by kmemcheck */
+
/* PG_readahead is only used for file reads; PG_reclaim is only for writes */
#define PG_readahead PG_reclaim /* Reminder to do async read-ahead */

@@ -296,6 +298,11 @@ static inline void __ClearPageTail(struct page *page)
#define SetPageUncached(page) set_bit(PG_uncached, &(page)->flags)
#define ClearPageUncached(page) clear_bit(PG_uncached, &(page)->flags)

+#define PageTracked(page) test_bit(PG_tracked, &(page)->flags)
+#define SetPageTracked(page) set_bit(PG_tracked, &(page)->flags)
+#define ClearPageTracked(page) clear_bit(PG_tracked, &(page)->flags)
+
+
struct page; /* forward declaration */

extern void cancel_dirty_page(struct page *page, unsigned int account_size);
--
1.5.3.8

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