Messages in this thread Patch in this message | | | From | Arnd Bergmann <> | Subject | [PATCH] mm: extend max struct page size for kmsan | Date | Mon, 30 Jan 2023 14:07:26 +0100 |
| |
From: Arnd Bergmann <arnd@arndb.de>
After x86 has enabled support for KMSAN, it has become possible to have larger 'struct page' than was expected when commit 5470dea49f53 ("mm: use mm_zero_struct_page from SPARC on all 64b architectures") was merged:
include/linux/mm.h:156:10: warning: no case matching constant switch condition '96' switch (sizeof(struct page)) {
Extend the maximum accordingly.
Fixes: 5470dea49f53 ("mm: use mm_zero_struct_page from SPARC on all 64b architectures") Fixes: 4ca8cc8d1bbe ("x86: kmsan: enable KMSAN builds for x86") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- This seems to show up extremely rarely in randconfig builds, but enough to trigger my build machine.
I saw a related discussion at [1] about raising MAX_STRUCT_PAGE_SIZE, but as I understand it, that needs to be addressed separately.
[1] https://lore.kernel.org/lkml/20220701142310.2188015-11-glider@google.com/ --- include/linux/mm.h | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h index b73ba2e5cfd2..aa39d5ddace1 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -137,7 +137,7 @@ extern int mmap_rnd_compat_bits __read_mostly; * define their own version of this macro in <asm/pgtable.h> */ #if BITS_PER_LONG == 64 -/* This function must be updated when the size of struct page grows above 80 +/* This function must be updated when the size of struct page grows above 96 * or reduces below 56. The idea that compiler optimizes out switch() * statement, and only leaves move/store instructions. Also the compiler can * combine write statements if they are both assignments and can be reordered, @@ -148,12 +148,18 @@ static inline void __mm_zero_struct_page(struct page *page) { unsigned long *_pp = (void *)page; - /* Check that struct page is either 56, 64, 72, or 80 bytes */ + /* Check that struct page is either 56, 64, 72, 80, 88 or 96 bytes */ BUILD_BUG_ON(sizeof(struct page) & 7); BUILD_BUG_ON(sizeof(struct page) < 56); - BUILD_BUG_ON(sizeof(struct page) > 80); + BUILD_BUG_ON(sizeof(struct page) > 96); switch (sizeof(struct page)) { + case 96: + _pp[11] = 0; + fallthrough; + case 88: + _pp[10] = 0; + fallthrough; case 80: _pp[9] = 0; fallthrough; -- 2.39.0
| |