Messages in this thread Patch in this message | | | Date | Fri, 04 Apr 2008 15:45:31 +0200 | From | Vegard Nossum <> | Subject | [PATCH 1/3] kmemcheck: add the kmemcheck core |
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From bb63a1de75a67ecd88c962c2616f0ab4217f27fe Mon Sep 17 00:00:00 2001 From: Vegard Nossum <vegard.nossum@gmail.com> Date: Fri, 4 Apr 2008 00:51:41 +0200 Subject: [PATCH] kmemcheck: add the kmemcheck core
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> Acked-by: Pekka Enberg <penberg@cs.helsinki.fi> Signed-off-by: Ingo Molnar <mingo@elte.hu> --- Documentation/kmemcheck.txt | 93 +++++ arch/x86/Kconfig.debug | 47 +++ arch/x86/kernel/Makefile | 2 + arch/x86/kernel/kmemcheck.c | 893 ++++++++++++++++++++++++++++++++++++++++++ include/asm-x86/kmemcheck.h | 30 ++ include/asm-x86/pgtable.h | 4 +- include/asm-x86/pgtable_32.h | 6 + include/linux/kmemcheck.h | 27 ++ include/linux/page-flags.h | 6 + init/main.c | 2 + kernel/sysctl.c | 12 + 11 files changed, 1120 insertions(+), 2 deletions(-) create mode 100644 Documentation/kmemcheck.txt create mode 100644 arch/x86/kernel/kmemcheck.c create mode 100644 include/asm-x86/kmemcheck.h create mode 100644 include/linux/kmemcheck.h
diff --git a/Documentation/kmemcheck.txt b/Documentation/kmemcheck.txt new file mode 100644 index 0000000..9d359d2 --- /dev/null +++ b/Documentation/kmemcheck.txt @@ -0,0 +1,93 @@ +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 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 occurring, 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 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. + + +Parameters +========== + +In addition to enabling CONFIG_KMEMCHECK before the kernel is compiled, the +parameter kmemcheck=1 must be passed to the kernel when it is started in order +to actually do the tracking. So by default, there is only a very small +(probably negligible) overhead for enabling the config option. + +Similarly, kmemcheck may be turned on or off at run-time using, respectively: + +echo 1 > /proc/sys/kernel/kmemcheck + and +echo 0 > /proc/sys/kernel/kmemcheck + +Note that this is a lazy setting; once turned off, the old allocations will +still have to take a single page fault exception before tracking is turned off +for that particular page. Enabling kmemcheck on will only enable tracking for +allocations made from that point onwards. + + +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 702eb39..a33683f 100644 --- a/arch/x86/Kconfig.debug +++ b/arch/x86/Kconfig.debug @@ -134,6 +134,53 @@ 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 X86_32 + depends on !X86_USE_3DNOW + depends on !CC_OPTIMIZE_FOR_SIZE + depends on !DEBUG_PAGEALLOC && SLUB + 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). + + The kernel may be started with kmemcheck=0 or kmemcheck=1 to disable + or enable kmemcheck at boot-time. If the kernel is started with + kmemcheck=0, the large memory and CPU overhead is not incurred. + +config KMEMCHECK_ENABLED_BY_DEFAULT + bool "kmemcheck: enable at boot by default" + depends on KMEMCHECK + default y + help + This option controls the default behaviour of kmemcheck when the + kernel boots and no kmemcheck= parameter is given. + +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 4eb5ce8..e1fcc1e 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -86,6 +86,8 @@ endif obj-$(CONFIG_SCx200) += scx200.o scx200-y += scx200_32.o
+obj-$(CONFIG_KMEMCHECK) += kmemcheck.o + ### # 64 bit specific files ifeq ($(CONFIG_X86_64),y) diff --git a/arch/x86/kernel/kmemcheck.c b/arch/x86/kernel/kmemcheck.c new file mode 100644 index 0000000..1dd79f5 --- /dev/null +++ b/arch/x86/kernel/kmemcheck.c @@ -0,0 +1,893 @@ +/** + * 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/kallsyms.h> +#include <linux/kdebug.h> +#include <linux/kernel.h> +#include <linux/mm.h> +#include <linux/module.h> +#include <linux/page-flags.h> +#include <linux/stacktrace.h> +#include <linux/timer.h> + +#include <asm/cacheflush.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, +}; + +enum kmemcheck_error_type { + ERROR_INVALID_ACCESS, + ERROR_BUG, +}; + +struct kmemcheck_error { + enum kmemcheck_error_type type; + + union { + /* ERROR_INVALID_ACCESS */ + struct { + /* 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 timer_list kmemcheck_timer; + +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 an 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->type = 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 = 1; + save_stack_trace(&e->trace); +} + +/* + * Save the context of a kmemcheck bug. + */ +static void +error_save_bug(struct pt_regs *regs) +{ + struct kmemcheck_error *e; + + e = error_next_wr(); + if (!e) + return; + + e->type = 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); +} + +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; + + switch (e->type) { + case ERROR_INVALID_ACCESS: + printk(KERN_ERR "kmemcheck: Caught %d-bit read " + "from %s memory (%08x)\n", + e->size, desc[e->state], e->address); + break; + case ERROR_BUG: + printk(KERN_EMERG "kmemcheck: Fatal error\n"); + break; + } + + __show_registers(&e->regs, 1); + print_stack_trace(&e->trace, 0); +} + +static void +do_wakeup(unsigned long data) +{ + while (error_count > 0) + error_recall(); + mod_timer(&kmemcheck_timer, kmemcheck_timer.expires + HZ); +} + +void __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 + + setup_timer(&kmemcheck_timer, &do_wakeup, 0); + mod_timer(&kmemcheck_timer, jiffies + HZ); +} + +#ifdef CONFIG_KMEMCHECK_ENABLED_BY_DEFAULT +int kmemcheck_enabled = 1; +#else +int kmemcheck_enabled = 0; +#endif + +static int __init +param_kmemcheck(char *str) +{ + if (!str) + return -EINVAL; + + switch (str[0]) { + case '0': + kmemcheck_enabled = 0; + return 0; + case '1': + kmemcheck_enabled = 1; + return 0; + } + + return -EINVAL; +} + +early_param("kmemcheck", param_kmemcheck); + +/* + * 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 (!PageHead(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); + + set_pte(pte, __pte(pte_val(*pte) | _PAGE_PRESENT)); + __flush_tlb_one(addr); + return 1; +} + +/* + * In case there's something seriously wrong with kmemcheck (like a recursive + * or looping page fault), we should disable tracking for the page as a last + * attempt to not hang the machine. + */ +static void +emergency_show_addr(uint32_t address) +{ + pte_t *pte; + int level; + + pte = lookup_address(address, &level); + if (!pte) + return; + if (level != PG_LEVEL_4K) + return; + + /* Don't change pages that weren't hidden in the first place -- they + * aren't ours to modify. */ + if (!(pte_val(*pte) & _PAGE_HIDDEN)) + return; + + set_pte(pte, __pte(pte_val(*pte) | _PAGE_PRESENT)); + __flush_tlb_one(address); +} + +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); + + set_pte(pte, __pte(pte_val(*pte) & ~_PAGE_PRESENT)); + __flush_tlb_one(addr); + return 1; +} + +struct kmemcheck_context { + bool busy; + int balance; + + uint32_t addr1; + uint32_t addr2; + uint32_t flags; +}; + +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; +} + +/* + * Called from the #PF handler. + */ +void +kmemcheck_show(struct pt_regs *regs) +{ + struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context); + int n; + + BUG_ON(!irqs_disabled()); + + if (unlikely(data->balance != 0)) { + emergency_show_addr(data->addr1); + emergency_show_addr(data->addr2); + error_save_bug(regs); + data->balance = 0; + return; + } + + n = 0; + n += show_addr(data->addr1); + n += show_addr(data->addr2); + + /* None of the addresses actually belonged to kmemcheck. Note that + * this is not an error. */ + if (n == 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 & TF_MASK)) + data->flags = regs->flags; + + regs->flags |= TF_MASK; + regs->flags &= ~IF_MASK; +} + +/* + * 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)) { + emergency_show_addr(data->addr1); + emergency_show_addr(data->addr2); + error_save_bug(regs); + data->addr1 = 0; + data->addr2 = 0; + data->balance = 0; + + if (!(data->flags & TF_MASK)) + regs->flags &= ~TF_MASK; + if (data->flags & IF_MASK) + regs->flags |= IF_MASK; + return; + } + + n = 0; + if (kmemcheck_enabled) { + n += hide_addr(data->addr1); + n += hide_addr(data->addr2); + } else { + n += show_addr(data->addr1); + n += show_addr(data->addr2); + } + + if (n == 0) + return; + + --data->balance; + + data->addr1 = 0; + data->addr2 = 0; + + if (!(data->flags & TF_MASK)) + regs->flags &= ~TF_MASK; + if (data->flags & IF_MASK) + regs->flags |= IF_MASK; +} + +void +kmemcheck_show_pages(struct page *p, unsigned int n) +{ + unsigned int i; + struct page *head; + + head = compound_head(p); + BUG_ON(!PageHead(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); + + set_pte(pte, __pte(pte_val(*pte) | _PAGE_PRESENT)); + set_pte(pte, __pte(pte_val(*pte) & ~_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(!PageHead(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); + + set_pte(pte, __pte(pte_val(*pte) & ~_PAGE_PRESENT)); + set_pte(pte, __pte(pte_val(*pte) | _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); + + 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; + + struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context); + + /* Recursive fault -- ouch. */ + if (data->busy) { + emergency_show_addr(fallback_address); + error_save_bug(regs); + return; + } + + data->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); + data->addr1 = fallback_address; + data->addr2 = 0; + data->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); + data->addr1 = regs->si; + data->addr2 = regs->di; + data->busy = false; + return; + + /* CMPS, CMPSB, CMPSW, CMPSD */ + case 0xa6: + case 0xa7: + kmemcheck_read(regs, regs->si, size); + kmemcheck_read(regs, regs->di, size); + data->addr1 = regs->si; + data->addr2 = regs->di; + data->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); + data->addr1 = fallback_address; + data->addr2 = 0; + data->busy = false; + return; + case KMEMCHECK_WRITE: + kmemcheck_write(regs, fallback_address, size); + data->addr1 = fallback_address; + data->addr2 = 0; + data->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(void *s, int c, size_t n) +{ + unsigned long addr; + void *x; + unsigned long flags; + + addr = (unsigned long) s; + + x = address_get_shadow(addr); + if (!x) { + /* The page isn't being tracked. */ + __memset(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(addr); + __memset(s, c, n); + __memset(x, SHADOW_INITIALIZED, n); + if (kmemcheck_enabled) + hide_addr(addr); + + 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(void *s, int c, size_t n) +{ + unsigned long addr; + unsigned long start_page, start_offset; + unsigned long end_page, end_offset; + unsigned long i; + + if (!n) + return s; + + if (!slab_is_available()) { + __memset(s, c, n); + return s; + } + + addr = (unsigned long) s; + + start_page = addr & PAGE_MASK; + end_page = (addr + n) & PAGE_MASK; + + if (start_page == end_page) { + /* The entire area is within the same page. Good, we only + * need one memset(). */ + memset_one_page(s, c, n); + return s; + } + + start_offset = addr & ~PAGE_MASK; + end_offset = (addr + n) & ~PAGE_MASK; + + /* Clear the head, body, and tail of the memory area. */ + if (start_offset < PAGE_SIZE) + memset_one_page(s, c, PAGE_SIZE - start_offset); + for (i = start_page + PAGE_SIZE; i < end_page; i += PAGE_SIZE) + memset_one_page((void *) i, c, PAGE_SIZE); + if (end_offset > 0) + memset_one_page((void *) end_page, c, end_offset); + + return s; +} + +EXPORT_SYMBOL(kmemcheck_memset); diff --git a/include/asm-x86/kmemcheck.h b/include/asm-x86/kmemcheck.h new file mode 100644 index 0000000..885b107 --- /dev/null +++ b/include/asm-x86/kmemcheck.h @@ -0,0 +1,30 @@ +#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 +bool kmemcheck_active(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); +#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 void kmemcheck_access(struct pt_regs *regs, + unsigned long address, enum kmemcheck_method method) { } +#endif /* CONFIG_KMEMCHECK */ + +#endif diff --git a/include/asm-x86/pgtable.h b/include/asm-x86/pgtable.h index 9cf472a..ebf285d 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 4e6a0fc..266a0f5 100644 --- a/include/asm-x86/pgtable_32.h +++ b/include/asm-x86/pgtable_32.h @@ -87,6 +87,12 @@ extern unsigned long pg0[];
#define pte_present(x) ((x).pte_low & (_PAGE_PRESENT | _PAGE_PROTNONE))
+#ifdef CONFIG_KMEMCHECK +#define pte_hidden(x) ((x).pte_low & (_PAGE_HIDDEN)) +#else +#define pte_hidden(x) 0 +#endif + /* To avoid harmful races, pmd_none(x) should check only the lower when PAE */ #define pmd_none(x) (!(unsigned long)pmd_val(x)) #define pmd_present(x) (pmd_val(x) & _PAGE_PRESENT) diff --git a/include/linux/kmemcheck.h b/include/linux/kmemcheck.h new file mode 100644 index 0000000..801da50 --- /dev/null +++ b/include/linux/kmemcheck.h @@ -0,0 +1,27 @@ +#ifndef LINUX_KMEMCHECK_H +#define LINUX_KMEMCHECK_H + +#ifdef CONFIG_KMEMCHECK +extern int kmemcheck_enabled; + +void kmemcheck_init(void); + +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 /* CONFIG_KMEMCHECK */ + + +#ifndef CONFIG_KMEMCHECK +#define kmemcheck_enabled 0 +static inline void kmemcheck_init(void) { } +#endif /* CONFIG_KMEMCHECK */ + +#endif /* LINUX_KMEMCHECK_H */ diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index b5b30f1..63f5fd8 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -89,6 +89,7 @@ #define PG_mappedtodisk 16 /* Has blocks allocated on-disk */ #define PG_reclaim 17 /* To be reclaimed asap */ #define PG_buddy 19 /* Page is free, on buddy lists */ +#define PG_tracked 20 /* 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 +297,11 @@ 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); diff --git a/init/main.c b/init/main.c index 99ce949..7f85ea2 100644 --- a/init/main.c +++ b/init/main.c @@ -58,6 +58,7 @@ #include <linux/kthread.h> #include <linux/sched.h> #include <linux/signal.h> +#include <linux/kmemcheck.h>
#include <asm/io.h> #include <asm/bugs.h> @@ -751,6 +752,7 @@ static void __init do_pre_smp_initcalls(void) { extern int spawn_ksoftirqd(void);
+ kmemcheck_init(); migration_init(); spawn_ksoftirqd(); if (!nosoftlockup) diff --git a/kernel/sysctl.c b/kernel/sysctl.c index b2a2d68..5381eb7 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -45,6 +45,7 @@ #include <linux/nfs_fs.h> #include <linux/acpi.h> #include <linux/reboot.h> +#include <linux/kmemcheck.h>
#include <asm/uaccess.h> #include <asm/processor.h> @@ -820,6 +821,17 @@ static struct ctl_table kern_table[] = { .proc_handler = &proc_dostring, .strategy = &sysctl_string, }, +#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 -- 1.5.4.1
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