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Subject[PATCH 2/3] mm/page_table_check: Do WARN_ON instead of BUG_ON by default
Date
Currently, page_table_check when detects errors panics kernel. Instead,
print a warning, and panic only when specifically requested via kernel
parameter:

page_table_check=panic

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
mm/page_table_check.c | 53 +++++++++++++++++++++++++++++++------------
1 file changed, 39 insertions(+), 14 deletions(-)

diff --git a/mm/page_table_check.c b/mm/page_table_check.c
index 665ece0d55d4..881f19d0714c 100644
--- a/mm/page_table_check.c
+++ b/mm/page_table_check.c
@@ -17,13 +17,37 @@ struct page_table_check {

static bool __page_table_check_enabled __initdata =
IS_ENABLED(CONFIG_PAGE_TABLE_CHECK_ENFORCED);
+static bool __page_table_check_panic;

DEFINE_STATIC_KEY_TRUE(page_table_check_disabled);
EXPORT_SYMBOL(page_table_check_disabled);

+#define PAGE_TABLE_CHECK_BUG(v) \
+ do { \
+ bool __bug = !!(v); \
+ \
+ if (__page_table_check_panic) \
+ BUG_ON(__bug); \
+ else if (WARN_ON_ONCE(__bug)) \
+ static_branch_enable(&page_table_check_disabled); \
+ } while (false)
+
static int __init early_page_table_check_param(char *buf)
{
- return strtobool(buf, &__page_table_check_enabled);
+ int rc = strtobool(buf, &__page_table_check_enabled);
+
+ if (rc) {
+ if (!strcmp(buf, "panic")) {
+ __page_table_check_enabled = true;
+ __page_table_check_panic = true;
+ rc = 0;
+ }
+ }
+
+ if (rc)
+ pr_warn("Invalid option string: '%s'\n", buf);
+
+ return rc;
}

early_param("page_table_check", early_page_table_check_param);
@@ -48,7 +72,8 @@ struct page_ext_operations page_table_check_ops = {

static struct page_table_check *get_page_table_check(struct page_ext *page_ext)
{
- BUG_ON(!page_ext);
+ PAGE_TABLE_CHECK_BUG(!page_ext);
+
return (void *)(page_ext) + page_table_check_ops.offset;
}

@@ -75,11 +100,11 @@ static void page_table_check_clear(struct mm_struct *mm, unsigned long addr,
struct page_table_check *ptc = get_page_table_check(page_ext);

if (anon) {
- BUG_ON(atomic_read(&ptc->file_map_count));
- BUG_ON(atomic_dec_return(&ptc->anon_map_count) < 0);
+ PAGE_TABLE_CHECK_BUG(atomic_read(&ptc->file_map_count));
+ PAGE_TABLE_CHECK_BUG(atomic_dec_return(&ptc->anon_map_count) < 0);
} else {
- BUG_ON(atomic_read(&ptc->anon_map_count));
- BUG_ON(atomic_dec_return(&ptc->file_map_count) < 0);
+ PAGE_TABLE_CHECK_BUG(atomic_read(&ptc->anon_map_count));
+ PAGE_TABLE_CHECK_BUG(atomic_dec_return(&ptc->file_map_count) < 0);
}
page_ext = page_ext_next(page_ext);
}
@@ -102,7 +127,7 @@ static void page_table_check_set(struct mm_struct *mm, unsigned long addr,
if (!pfn_valid(pfn))
return;

- BUG_ON(is_zero_pfn(pfn) && rw);
+ PAGE_TABLE_CHECK_BUG(!is_zero_pfn(pfn) && rw);

page = pfn_to_page(pfn);
page_ext = lookup_page_ext(page);
@@ -112,11 +137,11 @@ static void page_table_check_set(struct mm_struct *mm, unsigned long addr,
struct page_table_check *ptc = get_page_table_check(page_ext);

if (anon) {
- BUG_ON(atomic_read(&ptc->file_map_count));
- BUG_ON(atomic_inc_return(&ptc->anon_map_count) > 1 && rw);
+ PAGE_TABLE_CHECK_BUG(atomic_read(&ptc->file_map_count));
+ PAGE_TABLE_CHECK_BUG(atomic_inc_return(&ptc->anon_map_count) > 1 && rw);
} else {
- BUG_ON(atomic_read(&ptc->anon_map_count));
- BUG_ON(atomic_inc_return(&ptc->file_map_count) < 0);
+ PAGE_TABLE_CHECK_BUG(atomic_read(&ptc->anon_map_count));
+ PAGE_TABLE_CHECK_BUG(atomic_inc_return(&ptc->file_map_count) < 0);
}
page_ext = page_ext_next(page_ext);
}
@@ -131,12 +156,12 @@ void __page_table_check_zero(struct page *page, unsigned int order)
struct page_ext *page_ext = lookup_page_ext(page);
unsigned long i;

- BUG_ON(!page_ext);
+ PAGE_TABLE_CHECK_BUG(!page_ext);
for (i = 0; i < (1ul << order); i++) {
struct page_table_check *ptc = get_page_table_check(page_ext);

- BUG_ON(atomic_read(&ptc->anon_map_count));
- BUG_ON(atomic_read(&ptc->file_map_count));
+ PAGE_TABLE_CHECK_BUG(atomic_read(&ptc->anon_map_count));
+ PAGE_TABLE_CHECK_BUG(atomic_read(&ptc->file_map_count));
page_ext = page_ext_next(page_ext);
}
}
--
2.37.2.789.g6183377224-goog
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