[PATCH] [7/16] POISON: Add basic support for poisoned pages in fault handler

From: Andi Kleen
Date: Tue Apr 07 2009 - 11:21:42 EST



- Add a new VM_FAULT_POISON error code to handle_mm_fault. Right now
architectures have to explicitely enable poison page support, so
this is forward compatible to all architectures. They only need
to add it when they enable poison page support.
- Add poison page handling in swap in fault code

Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>

---
include/linux/mm.h | 3 ++-
mm/memory.c | 17 ++++++++++++++---
2 files changed, 16 insertions(+), 4 deletions(-)

Index: linux/mm/memory.c
===================================================================
--- linux.orig/mm/memory.c 2009-04-07 16:39:24.000000000 +0200
+++ linux/mm/memory.c 2009-04-07 16:43:06.000000000 +0200
@@ -1315,7 +1315,8 @@
if (ret & VM_FAULT_ERROR) {
if (ret & VM_FAULT_OOM)
return i ? i : -ENOMEM;
- else if (ret & VM_FAULT_SIGBUS)
+ if (ret &
+ (VM_FAULT_POISON|VM_FAULT_SIGBUS))
return i ? i : -EFAULT;
BUG();
}
@@ -2426,8 +2427,15 @@
goto out;

entry = pte_to_swp_entry(orig_pte);
- if (is_migration_entry(entry)) {
- migration_entry_wait(mm, pmd, address);
+ if (unlikely(non_swap_entry(entry))) {
+ if (is_migration_entry(entry)) {
+ migration_entry_wait(mm, pmd, address);
+ } else if (is_poison_entry(entry)) {
+ ret = VM_FAULT_POISON;
+ } else {
+ print_bad_pte(vma, address, pte, NULL);
+ ret = VM_FAULT_OOM;
+ }
goto out;
}
delayacct_set_flag(DELAYACCT_PF_SWAPIN);
@@ -2451,6 +2459,9 @@
/* Had to read the page from swap area: Major fault */
ret = VM_FAULT_MAJOR;
count_vm_event(PGMAJFAULT);
+ } else if (PagePoison(page)) {
+ ret = VM_FAULT_POISON;
+ goto out;
}

lock_page(page);
Index: linux/include/linux/mm.h
===================================================================
--- linux.orig/include/linux/mm.h 2009-04-07 16:39:24.000000000 +0200
+++ linux/include/linux/mm.h 2009-04-07 16:43:05.000000000 +0200
@@ -702,11 +702,12 @@
#define VM_FAULT_SIGBUS 0x0002
#define VM_FAULT_MAJOR 0x0004
#define VM_FAULT_WRITE 0x0008 /* Special case for get_user_pages */
+#define VM_FAULT_POISON 0x0010 /* Hit poisoned page */

#define VM_FAULT_NOPAGE 0x0100 /* ->fault installed the pte, not return page */
#define VM_FAULT_LOCKED 0x0200 /* ->fault locked the returned page */

-#define VM_FAULT_ERROR (VM_FAULT_OOM | VM_FAULT_SIGBUS)
+#define VM_FAULT_ERROR (VM_FAULT_OOM | VM_FAULT_SIGBUS | VM_FAULT_POISON)

/*
* Can be called by the pagefault handler when it gets a VM_FAULT_OOM.
--
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