On Thu, 9 Mar 2023 at 12:04, Zhenhua Huang <quic_zhenhuah@xxxxxxxxxxx> wrote: > > Thanks Marco. > > On 2023/3/9 18:33, Marco Elver wrote: > > On Thu, 9 Mar 2023 at 09:05, Zhenhua Huang <quic_zhenhuah@xxxxxxxxxxx> wrote: > >> > >> Kfence only needs its pool to be mapped as page granularity, previous > >> judgement was a bit over protected. Decouple it from judgement and do > >> page granularity mapping for kfence pool only [1]. > >> > >> To implement this, also relocate the kfence pool allocation before the > >> linear mapping setting up, kfence_alloc_pool is to allocate phys addr, > >> __kfence_pool is to be set after linear mapping set up. > >> > >> LINK: [1] https://lore.kernel.org/linux-arm-kernel/1675750519-1064-1-git-send-email-quic_zhenhuah@xxxxxxxxxxx/T/ > >> Suggested-by: Mark Rutland <mark.rutland@xxxxxxx> > >> Signed-off-by: Zhenhua Huang <quic_zhenhuah@xxxxxxxxxxx> > >> --- > >> arch/arm64/mm/mmu.c | 24 ++++++++++++++++++++++++ > >> arch/arm64/mm/pageattr.c | 5 ++--- > >> include/linux/kfence.h | 10 ++++++++-- > >> init/main.c | 1 - > >> mm/kfence/core.c | 18 ++++++++++++++---- > >> 5 files changed, 48 insertions(+), 10 deletions(-) > >> > >> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > >> index 6f9d889..bd79691 100644 > >> --- a/arch/arm64/mm/mmu.c > >> +++ b/arch/arm64/mm/mmu.c > >> @@ -24,6 +24,7 @@ > >> #include <linux/mm.h> > >> #include <linux/vmalloc.h> > >> #include <linux/set_memory.h> > >> +#include <linux/kfence.h> > >> > >> #include <asm/barrier.h> > >> #include <asm/cputype.h> > >> @@ -532,6 +533,9 @@ static void __init map_mem(pgd_t *pgdp) > >> phys_addr_t kernel_end = __pa_symbol(__init_begin); > >> phys_addr_t start, end; > >> int flags = NO_EXEC_MAPPINGS; > >> +#ifdef CONFIG_KFENCE > >> + phys_addr_t kfence_pool = 0; > >> +#endif > >> u64 i; > >> > >> /* > >> @@ -564,6 +568,12 @@ static void __init map_mem(pgd_t *pgdp) > >> } > >> #endif > >> > >> +#ifdef CONFIG_KFENCE > >> + kfence_pool = kfence_alloc_pool(); > >> + if (kfence_pool) > >> + memblock_mark_nomap(kfence_pool, KFENCE_POOL_SIZE); > >> +#endif > >> + > >> /* map all the memory banks */ > >> for_each_mem_range(i, &start, &end) { > >> if (start >= end) > >> @@ -608,6 +618,20 @@ static void __init map_mem(pgd_t *pgdp) > >> } > >> } > >> #endif > >> + > >> + /* Kfence pool needs page-level mapping */ > >> +#ifdef CONFIG_KFENCE > >> + if (kfence_pool) { > >> + __map_memblock(pgdp, kfence_pool, > >> + kfence_pool + KFENCE_POOL_SIZE, > >> + pgprot_tagged(PAGE_KERNEL), > >> + NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS); > >> + memblock_clear_nomap(kfence_pool, KFENCE_POOL_SIZE); > >> + /* kfence_pool really mapped now */ > >> + kfence_set_pool(kfence_pool); > >> + } > >> +#endif > >> + > >> } > >> > >> void mark_rodata_ro(void) > >> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c > >> index 79dd201..61156d0 100644 > >> --- a/arch/arm64/mm/pageattr.c > >> +++ b/arch/arm64/mm/pageattr.c > >> @@ -22,12 +22,11 @@ bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED > >> bool can_set_direct_map(void) > >> { > >> /* > >> - * rodata_full, DEBUG_PAGEALLOC and KFENCE require linear map to be > >> + * rodata_full and DEBUG_PAGEALLOC require linear map to be > >> * mapped at page granularity, so that it is possible to > >> * protect/unprotect single pages. > >> */ > >> - return (rodata_enabled && rodata_full) || debug_pagealloc_enabled() || > >> - IS_ENABLED(CONFIG_KFENCE); > >> + return (rodata_enabled && rodata_full) || debug_pagealloc_enabled(); > >> } > >> > >> static int change_page_range(pte_t *ptep, unsigned long addr, void *data) > >> diff --git a/include/linux/kfence.h b/include/linux/kfence.h > >> index 726857a..0252e74 100644 > >> --- a/include/linux/kfence.h > >> +++ b/include/linux/kfence.h > >> @@ -61,7 +61,12 @@ static __always_inline bool is_kfence_address(const void *addr) > >> /** > >> * kfence_alloc_pool() - allocate the KFENCE pool via memblock > >> */ > >> -void __init kfence_alloc_pool(void); > >> +phys_addr_t __init kfence_alloc_pool(void); > >> + > >> +/** > >> + * kfence_set_pool() - KFENCE pool mapped and can be used > >> + */ > >> +void __init kfence_set_pool(phys_addr_t addr); > >> > >> /** > >> * kfence_init() - perform KFENCE initialization at boot time > >> @@ -223,7 +228,8 @@ bool __kfence_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *sla > >> #else /* CONFIG_KFENCE */ > >> > >> static inline bool is_kfence_address(const void *addr) { return false; } > >> -static inline void kfence_alloc_pool(void) { } > >> +static inline phys_addr_t kfence_alloc_pool(void) { return (phys_addr_t)NULL; } > >> +static inline void kfence_set_pool(phys_addr_t addr) { } > >> static inline void kfence_init(void) { } > >> static inline void kfence_shutdown_cache(struct kmem_cache *s) { } > >> static inline void *kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags) { return NULL; } > >> diff --git a/init/main.c b/init/main.c > >> index 4425d17..9aaf217 100644 > >> --- a/init/main.c > >> +++ b/init/main.c > >> @@ -839,7 +839,6 @@ static void __init mm_init(void) > >> */ > >> page_ext_init_flatmem(); > >> init_mem_debugging_and_hardening(); > >> - kfence_alloc_pool(); > > > > This breaks other architectures. > > Nice catch. Thanks! > > > > >> report_meminit(); > >> kmsan_init_shadow(); > >> stack_depot_early_init(); > >> diff --git a/mm/kfence/core.c b/mm/kfence/core.c > >> index 5349c37..dd5cdd5 100644 > >> --- a/mm/kfence/core.c > >> +++ b/mm/kfence/core.c > >> @@ -809,15 +809,25 @@ static void toggle_allocation_gate(struct work_struct *work) > >> > >> /* === Public interface ===================================================== */ > >> > >> -void __init kfence_alloc_pool(void) > >> +phys_addr_t __init kfence_alloc_pool(void) > >> { > > > > You could just return here: > > > > if (__kfence_pool) > > return; /* Initialized earlier by arch init code. */ > > Yeah. > > > > > ... and see my comments below. > > > >> + phys_addr_t kfence_pool; > >> if (!kfence_sample_interval) > >> - return; > >> + return 0; > >> > >> - __kfence_pool = memblock_alloc(KFENCE_POOL_SIZE, PAGE_SIZE); > >> + kfence_pool = memblock_phys_alloc(KFENCE_POOL_SIZE, PAGE_SIZE); > >> > >> - if (!__kfence_pool) > >> + if (!kfence_pool) { > >> pr_err("failed to allocate pool\n"); > >> + return 0; > >> + } > >> + > >> + return kfence_pool; > >> +} > >> + > >> +void __init kfence_set_pool(phys_addr_t addr) > >> +{ > >> + __kfence_pool = phys_to_virt(addr); > >> } > > > > I would suggest leaving kfence_alloc_pool() to return nothing (with > > the addition above), and just set __kfence_pool as before. > > __kfence_pool itself is exported by include/linux/kfence.h, so if you > > call kfence_alloc_pool() in arm64 earlier, you can access > > __kfence_pool to get the allocated pool. > > Shall we add one new function like arm64_kfence_alloc_pool() ? The > reason is linear mapping at that time not set up and we must alloc phys > addr based on memblock. We can't use common kfence_alloc_pool().. Ah right - well, you can initialize __kfence_pool however you like within arm64 init code. Just teaching kfence_alloc_pool() to do nothing if it's already initialized should be enough. Within arch/arm64/mm/mmu.c it might be nice to factor out some bits into a helper like arm64_kfence_alloc_pool(), but would just stick to whatever is simplest. Thanks, -- Marco
