Add a debug Kconfig option that will make page allocator verify
that pages that were supposed to be scrubbed are, in fact, clean.
Signed-off-by: Boris Ostrovsky
Reviewed-by: Jan Beulich
---
xen/Kconfig.debug | 7 ++
xen/common/page_alloc.c | 63 -
2 files changed, 69 insertions(+), 1 deletion(-)
diff --git a/xen/Kconfig.debug b/xen/Kconfig.debug
index 689f297..195d504 100644
--- a/xen/Kconfig.debug
+++ b/xen/Kconfig.debug
@@ -114,6 +114,13 @@ config DEVICE_TREE_DEBUG
logged in the Xen ring buffer.
If unsure, say N here.
+config SCRUB_DEBUG
+ bool "Page scrubbing test"
+ default DEBUG
+ ---help---
+ Verify that pages that need to be scrubbed before being allocated to
+ a guest are indeed scrubbed.
+
endif # DEBUG || EXPERT
endmenu
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 34c45be..388b121 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -170,6 +170,10 @@ boolean_param("bootscrub", opt_bootscrub);
static unsigned long __initdata opt_bootscrub_chunk = MB(128);
size_param("bootscrub_chunk", opt_bootscrub_chunk);
+#ifdef CONFIG_SCRUB_DEBUG
+static bool __read_mostly boot_scrub_done;
+#endif
+
/*
* Bit width of the DMA heap -- used to override NUMA-node-first.
* allocation strategy, which can otherwise exhaust low memory.
@@ -694,6 +698,43 @@ static void page_list_add_scrub(struct page_info *pg,
unsigned int node,
page_list_add(pg, &heap(node, zone, order));
}
+/* SCRUB_PATTERN needs to be a repeating series of bytes. */
+#ifndef NDEBUG
+#define SCRUB_PATTERN0xc2c2c2c2c2c2c2c2ULL
+#else
+#define SCRUB_PATTERN0ULL
+#endif
+#define SCRUB_BYTE_PATTERN (SCRUB_PATTERN & 0xff)
+
+static void poison_one_page(struct page_info *pg)
+{
+#ifdef CONFIG_SCRUB_DEBUG
+mfn_t mfn = _mfn(page_to_mfn(pg));
+uint64_t *ptr;
+
+ptr = map_domain_page(mfn);
+*ptr = ~SCRUB_PATTERN;
+unmap_domain_page(ptr);
+#endif
+}
+
+static void check_one_page(struct page_info *pg)
+{
+#ifdef CONFIG_SCRUB_DEBUG
+mfn_t mfn = _mfn(page_to_mfn(pg));
+const uint64_t *ptr;
+unsigned int i;
+
+if ( !boot_scrub_done )
+return;
+
+ptr = map_domain_page(mfn);
+for ( i = 0; i < PAGE_SIZE / sizeof (*ptr); i++ )
+ASSERT(ptr[i] == SCRUB_PATTERN);
+unmap_domain_page(ptr);
+#endif
+}
+
static void check_and_stop_scrub(struct page_info *head)
{
if ( head->u.free.scrub_state == BUDDY_SCRUBBING )
@@ -928,6 +969,9 @@ static struct page_info *alloc_heap_pages(
* guest can control its own visibility of/through the cache.
*/
flush_page_to_ram(page_to_mfn(&pg[i]), !(memflags &
MEMF_no_icache_flush));
+
+if ( !(memflags & MEMF_no_scrub) )
+check_one_page(&pg[i]);
}
spin_unlock(&heap_lock);
@@ -1291,7 +1335,10 @@ static void free_heap_pages(
set_gpfn_from_mfn(mfn + i, INVALID_M2P_ENTRY);
if ( need_scrub )
+{
pg[i].count_info |= PGC_need_scrub;
+poison_one_page(&pg[i]);
+}
}
avail[node][zone] += 1 << order;
@@ -1649,7 +1696,12 @@ static void init_heap_pages(
nr_pages -= n;
}
+#ifndef CONFIG_SCRUB_DEBUG
free_heap_pages(pg + i, 0, false);
+#else
+free_heap_pages(pg + i, 0, boot_scrub_done);
+#endif
+
}
}
@@ -1915,6 +1967,10 @@ void __init scrub_heap_pages(void)
printk("done.\n");
+#ifdef CONFIG_SCRUB_DEBUG
+boot_scrub_done = true;
+#endif
+
/* Now that the heap is initialized, run checks and set bounds
* for the low mem virq algorithm. */
setup_low_mem_virq();
@@ -2188,12 +2244,16 @@ void free_domheap_pages(struct page_info *pg, unsigned
int order)
spin_unlock_recursive(&d->page_alloc_lock);
+#ifndef CONFIG_SCRUB_DEBUG
/*
* Normally we expect a domain to clear pages before freeing them,
* if it cares about the secrecy of their contents. However, after
* a domain has died we assume responsibility for erasure.
*/
scrub = !!d->is_dying;
+#else
+scrub = true;
+#endif
}
else
{
@@ -2285,7 +2345,8 @@ void scrub_one_page(struct page_info *pg)
#ifndef NDEBUG
/* Avoid callers relying on allocations returning zeroed pages. */
-unmap_domain_page(memset(__map_domain_page(pg), 0xc2, PAGE_SIZE));
+unmap_domain_page(memset(__map_domain_page(pg),
+ SCRUB_BYTE_PATTERN, PAGE_SIZE));
#else
/* For a production build, clear_page() is the fastest way to scrub. */
clear_domain_page(_mfn(page_to_mfn(pg)));
--
1.8.3.1
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