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.

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>

3 files changed, 53 insertions, 2 deletions

diff --git a/arch/x86/include/asm/kmemcheck.h b/arch/x86/include/asm/kmemcheck.h
new file mode 100644
index 000000000000..ed01518f297e
--- /dev/null
+++ b/arch/x86/include/asm/kmemcheck.h
@@ -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
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 18ef7ebf2631..c5a08079ad5e 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -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;
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 4d258ad76a0f..9b5c92140aab 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -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)