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authorPavel Emelyanov <xemul@parallels.com>2013-07-03 15:01:20 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-07-03 16:07:26 -0700
commit0f8975ec4db2c8b5bd111b211292ca9be0feb6b8 (patch)
tree47bb0acc9fc3e783ad9cf33097a6636190f5e42b /arch/x86
parent2b0a9f017548f05e42fbf7e67c4a626c1ebd5e12 (diff)
mm: soft-dirty bits for user memory changes tracking
The soft-dirty is a bit on a PTE which helps to track which pages a task writes to. In order to do this tracking one should 1. Clear soft-dirty bits from PTEs ("echo 4 > /proc/PID/clear_refs) 2. Wait some time. 3. Read soft-dirty bits (55'th in /proc/PID/pagemap2 entries) To do this tracking, the writable bit is cleared from PTEs when the soft-dirty bit is. Thus, after this, when the task tries to modify a page at some virtual address the #PF occurs and the kernel sets the soft-dirty bit on the respective PTE. Note, that although all the task's address space is marked as r/o after the soft-dirty bits clear, the #PF-s that occur after that are processed fast. This is so, since the pages are still mapped to physical memory, and thus all the kernel does is finds this fact out and puts back writable, dirty and soft-dirty bits on the PTE. Another thing to note, is that when mremap moves PTEs they are marked with soft-dirty as well, since from the user perspective mremap modifies the virtual memory at mremap's new address. Signed-off-by: Pavel Emelyanov <xemul@parallels.com> Cc: Matt Mackall <mpm@selenic.com> Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Cc: Glauber Costa <glommer@parallels.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/Kconfig1
-rw-r--r--arch/x86/include/asm/pgtable.h24
-rw-r--r--arch/x86/include/asm/pgtable_types.h12
3 files changed, 35 insertions, 2 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b094816a7e0..10764a3d62c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -102,6 +102,7 @@ config X86
select HAVE_ARCH_SECCOMP_FILTER
select BUILDTIME_EXTABLE_SORT
select GENERIC_CMOS_UPDATE
+ select HAVE_ARCH_SOFT_DIRTY
select CLOCKSOURCE_WATCHDOG
select GENERIC_CLOCKEVENTS
select ARCH_CLOCKSOURCE_DATA if X86_64
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 5b0818bc896..7dc305a4605 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -207,7 +207,7 @@ static inline pte_t pte_mkexec(pte_t pte)
static inline pte_t pte_mkdirty(pte_t pte)
{
- return pte_set_flags(pte, _PAGE_DIRTY);
+ return pte_set_flags(pte, _PAGE_DIRTY | _PAGE_SOFT_DIRTY);
}
static inline pte_t pte_mkyoung(pte_t pte)
@@ -271,7 +271,7 @@ static inline pmd_t pmd_wrprotect(pmd_t pmd)
static inline pmd_t pmd_mkdirty(pmd_t pmd)
{
- return pmd_set_flags(pmd, _PAGE_DIRTY);
+ return pmd_set_flags(pmd, _PAGE_DIRTY | _PAGE_SOFT_DIRTY);
}
static inline pmd_t pmd_mkhuge(pmd_t pmd)
@@ -294,6 +294,26 @@ static inline pmd_t pmd_mknotpresent(pmd_t pmd)
return pmd_clear_flags(pmd, _PAGE_PRESENT);
}
+static inline int pte_soft_dirty(pte_t pte)
+{
+ return pte_flags(pte) & _PAGE_SOFT_DIRTY;
+}
+
+static inline int pmd_soft_dirty(pmd_t pmd)
+{
+ return pmd_flags(pmd) & _PAGE_SOFT_DIRTY;
+}
+
+static inline pte_t pte_mksoft_dirty(pte_t pte)
+{
+ return pte_set_flags(pte, _PAGE_SOFT_DIRTY);
+}
+
+static inline pmd_t pmd_mksoft_dirty(pmd_t pmd)
+{
+ return pmd_set_flags(pmd, _PAGE_SOFT_DIRTY);
+}
+
/*
* Mask out unsupported bits in a present pgprot. Non-present pgprots
* can use those bits for other purposes, so leave them be.
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index e6423002c10..c98ac63aae4 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -55,6 +55,18 @@
#define _PAGE_HIDDEN (_AT(pteval_t, 0))
#endif
+/*
+ * The same hidden bit is used by kmemcheck, but since kmemcheck
+ * works on kernel pages while soft-dirty engine on user space,
+ * they do not conflict with each other.
+ */
+
+#ifdef CONFIG_MEM_SOFT_DIRTY
+#define _PAGE_SOFT_DIRTY (_AT(pteval_t, 1) << _PAGE_BIT_HIDDEN)
+#else
+#define _PAGE_SOFT_DIRTY (_AT(pteval_t, 0))
+#endif
+
#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
#define _PAGE_NX (_AT(pteval_t, 1) << _PAGE_BIT_NX)
#else