Messages in this thread | | | Date | Wed, 21 Sep 2022 18:19:12 +0300 | From | Mike Rapoport <> | Subject | Re: [PATCH] arm64/mm: fold check for KFENCE into can_set_direct_map() |
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Hi Anshuman,
On Wed, Sep 21, 2022 at 05:09:19PM +0530, Anshuman Khandual wrote: > > > On 9/21/22 13:18, Mike Rapoport wrote: > > From: Mike Rapoport <rppt@linux.ibm.com> > > > > KFENCE requires linear map to be mapped at page granularity, so that it > > is possible to protect/unprotect single pages, just like with > > rodata_full and DEBUG_PAGEALLOC. > > > > Instead of repating > > > > can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE) > > > > make can_set_direct_map() handle the KFENCE case. > > > > This also prevents potential false positives in kernel_page_present() > > that may return true for non-present page if CONFIG_KFENCE is enabled. > > > > Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> > > --- > > arch/arm64/mm/mmu.c | 8 ++------ > > arch/arm64/mm/pageattr.c | 8 +++++++- > > 2 files changed, 9 insertions(+), 7 deletions(-) > > > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > > index e7ad44585f40..c5065abec55a 100644 > > --- a/arch/arm64/mm/mmu.c > > +++ b/arch/arm64/mm/mmu.c > > @@ -535,7 +535,7 @@ static void __init map_mem(pgd_t *pgdp) > > */ > > BUILD_BUG_ON(pgd_index(direct_map_end - 1) == pgd_index(direct_map_end)); > > > > - if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE)) > > + if (can_set_direct_map()) > > flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; > > > > /* > > @@ -1547,11 +1547,7 @@ int arch_add_memory(int nid, u64 start, u64 size, > > > > VM_BUG_ON(!mhp_range_allowed(start, size, true)); > > > > - /* > > - * KFENCE requires linear map to be mapped at page granularity, so that > > - * it is possible to protect/unprotect single pages in the KFENCE pool. > > - */ > > - if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE)) > > + if (can_set_direct_map()) > > flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; > > > > __create_pgd_mapping(swapper_pg_dir, start, __phys_to_virt(start), > > diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c > > index 64e985eaa52d..d107c3d434e2 100644 > > --- a/arch/arm64/mm/pageattr.c > > +++ b/arch/arm64/mm/pageattr.c > > @@ -21,7 +21,13 @@ bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED > > > > bool can_set_direct_map(void) > > { > > - return rodata_full || debug_pagealloc_enabled(); > > + /* > > + * rodata_full, DEBUG_PAGEALLOC and KFENCE require linear map to be > > + * mapped at page granularity, so that it is possible to > > + * protect/unprotect single pages. > > + */ > > + return rodata_full || debug_pagealloc_enabled() || > > + IS_ENABLED(CONFIG_KFENCE); > > } > > Changing can_set_direct_map() also changes behaviour for other functions such as > > set_direct_map_default_noflush() > set_direct_map_invalid_noflush() > __kernel_map_pages() > > Is that okay ?
Yes. Since KFENCE disables block mappings, these will actually change the page tables. Actually, before this change the test for can_set_direct_map() in these functions was false negative when CONFIG_KFENCE=y
> > static int change_page_range(pte_t *ptep, unsigned long addr, void *data)
-- Sincerely yours, Mike.
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