diff options
| author | Peter Collingbourne <pcc@google.com> | 2021-06-02 16:52:29 -0700 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2021-06-04 19:32:21 +0100 |
| commit | 013bb59dbb7cf876449df860946458a595a96d51 (patch) | |
| tree | 2c086b293dc8c5d6e33881248aa49b0dbe698808 /mm | |
| parent | 7a3b835371883558eb63e069d891bd87f562380d (diff) | |
arm64: mte: handle tags zeroing at page allocation time
Currently, on an anonymous page fault, the kernel allocates a zeroed
page and maps it in user space. If the mapping is tagged (PROT_MTE),
set_pte_at() additionally clears the tags. It is, however, more
efficient to clear the tags at the same time as zeroing the data on
allocation. To avoid clearing the tags on any page (which may not be
mapped as tagged), only do this if the vma flags contain VM_MTE. This
requires introducing a new GFP flag that is used to determine whether
to clear the tags.
The DC GZVA instruction with a 0 top byte (and 0 tag) requires
top-byte-ignore. Set the TCR_EL1.{TBI1,TBID1} bits irrespective of
whether KASAN_HW is enabled.
Signed-off-by: Peter Collingbourne <pcc@google.com>
Co-developed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://linux-review.googlesource.com/id/Id46dc94e30fe11474f7e54f5d65e7658dbdddb26
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Link: https://lore.kernel.org/r/20210602235230.3928842-4-pcc@google.com
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/kasan/hw_tags.c | 9 | ||||
| -rw-r--r-- | mm/page_alloc.c | 13 |
2 files changed, 18 insertions, 4 deletions
diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c index 9d0f6f934016..41fd5326ee0a 100644 --- a/mm/kasan/hw_tags.c +++ b/mm/kasan/hw_tags.c @@ -246,7 +246,14 @@ void kasan_alloc_pages(struct page *page, unsigned int order, gfp_t flags) */ bool init = !want_init_on_free() && want_init_on_alloc(flags); - kasan_unpoison_pages(page, order, init); + if (flags & __GFP_ZEROTAGS) { + int i; + + for (i = 0; i != 1 << order; ++i) + tag_clear_highpage(page + i); + } else { + kasan_unpoison_pages(page, order, init); + } } void kasan_free_pages(struct page *page, unsigned int order) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 4fddb7cac3c6..13937e793fda 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1219,10 +1219,16 @@ out: return ret; } -static void kernel_init_free_pages(struct page *page, int numpages) +static void kernel_init_free_pages(struct page *page, int numpages, bool zero_tags) { int i; + if (zero_tags) { + for (i = 0; i < numpages; i++) + tag_clear_highpage(page + i); + return; + } + /* s390's use of memset() could override KASAN redzones. */ kasan_disable_current(); for (i = 0; i < numpages; i++) { @@ -1314,7 +1320,7 @@ static __always_inline bool free_pages_prepare(struct page *page, bool init = want_init_on_free(); if (init) - kernel_init_free_pages(page, 1 << order); + kernel_init_free_pages(page, 1 << order, false); if (!skip_kasan_poison) kasan_poison_pages(page, order, init); } @@ -2349,7 +2355,8 @@ inline void post_alloc_hook(struct page *page, unsigned int order, kasan_unpoison_pages(page, order, init); if (init) - kernel_init_free_pages(page, 1 << order); + kernel_init_free_pages(page, 1 << order, + gfp_flags & __GFP_ZEROTAGS); } set_page_owner(page, order, gfp_flags); |