When vma tracing is ON, the vma memory is remaped to read-only
state. Later in the pagefault handlers the event is sent via
tracing engine.
With the existing on/off events this makes it possible to monitor
how processes modify their memory contents.
Signed-off-by: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
---
include/linux/mm.h | 3 +++
include/trace/events/mmu.h | 18 ++++++++++++++++++
mm/huge_memory.c | 4 ++++
mm/madvise.c | 11 +++++++++++
mm/memory.c | 2 ++
mm/mprotect.c | 2 +-
6 files changed, 39 insertions(+), 1 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c7fad8d..7e5fe10 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1082,6 +1082,9 @@ extern unsigned long do_mremap(unsigned long addr,
extern int mprotect_fixup(struct vm_area_struct *vma,
struct vm_area_struct **pprev, unsigned long start,
unsigned long end, unsigned long newflags);
+void change_protection(struct vm_area_struct *vma,
+ unsigned long addr, unsigned long end, pgprot_t newprot,
+ int dirty_accountable);
/*
* doesn't attempt to fault and will return short.
diff --git a/include/trace/events/mmu.h b/include/trace/events/mmu.h
index 71b1ba6..d1bff37 100644
--- a/include/trace/events/mmu.h
+++ b/include/trace/events/mmu.h
@@ -24,6 +24,24 @@ TRACE_EVENT_CONDITION(mmu_trace_on,
TP_printk("start %#lx", __entry->start)
);
+TRACE_EVENT_CONDITION(mmu_page_mod,
+ TP_PROTO(struct vm_area_struct *vma, unsigned long vaddr),
+
+ TP_ARGS(vma, vaddr),
+
+ TP_CONDITION(vma->vm_flags & VM_TRACE),
+
+ TP_STRUCT__entry(
+ __field(unsigned long, vaddr)
+ ),
+
+ TP_fast_assign(
+ __entry->vaddr = vaddr;
+ ),
+
+ TP_printk("vaddr %#lx", __entry->vaddr)
+);
+
TRACE_EVENT_CONDITION(mmu_trace_off,
TP_PROTO(struct vm_area_struct *vma),
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 40f17c3..7a93683 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -22,6 +22,8 @@
#include <asm/pgalloc.h>
#include "internal.h"
+#include <trace/events/mmu.h>
+
/*
* By default transparent hugepage support is enabled for all mappings
* and khugepaged scans all mappings. Defrag is only invoked by
@@ -888,6 +890,8 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long mmun_start; /* For mmu_notifiers */
unsigned long mmun_end; /* For mmu_notifiers */
+ trace_mmu_page_mod(vma, address);
+
VM_BUG_ON(!vma->anon_vma);
spin_lock(&mm->page_table_lock);
if (unlikely(!pmd_same(*pmd, orig_pmd)))
diff --git a/mm/madvise.c b/mm/madvise.c
index 65633e9..05361c2 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -64,6 +64,17 @@ static long madvise_behavior(struct vm_area_struct * vma,
new_flags |= VM_DONTCOPY;
break;
case MADV_DOTRACE:
+ /*
+ * Protect pages to be read-only and force tasks to generate
+ * #PFs on modification.
+ *
+ * It should be done before issuing trace-on event. Otherwise
+ * we're leaving a short window after the 'on' event when tasks
+ * can still modify pages.
+ */
+ change_protection(vma, start, end,
+ vm_get_page_prot(vma->vm_flags & ~VM_READ),
+ vma_wants_writenotify(vma));
trace_mmu_trace_on(vma);
new_flags |= VM_TRACE;
break;
diff --git a/mm/memory.c b/mm/memory.c
index a6f5951..1dd30ae 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2533,6 +2533,8 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long mmun_start = 0; /* For mmu_notifiers */
unsigned long mmun_end = 0; /* For mmu_notifiers */
+ trace_mmu_page_mod(vma, address);
+
old_page = vm_normal_page(vma, address, orig_pte);
if (!old_page) {
/*
diff --git a/mm/mprotect.c b/mm/mprotect.c
index a409926..91c2266 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -119,7 +119,7 @@ static inline void change_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
} while (pud++, addr = next, addr != end);
}
-static void change_protection(struct vm_area_struct *vma,
+void change_protection(struct vm_area_struct *vma,
unsigned long addr, unsigned long end, pgprot_t newprot,
int dirty_accountable)
{
--
1.7.6.5
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