On Thu, 9 Mar 2023 at 16:38, 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, arm64_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 | 44 ++++++++++++++++++++++++++++++++++++++++++++ > arch/arm64/mm/pageattr.c | 5 ++--- > include/linux/kfence.h | 7 +++++++ > mm/kfence/core.c | 9 +++++++++ > 4 files changed, 62 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 6f9d889..46afe3f 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> > @@ -525,6 +526,33 @@ static int __init enable_crash_mem_map(char *arg) > } > early_param("crashkernel", enable_crash_mem_map); > > +#ifdef CONFIG_KFENCE > + > +static phys_addr_t arm64_kfence_alloc_pool(void) > +{ > + phys_addr_t kfence_pool = 0; > + > + if (!kfence_sample_interval) > + return 0; > + > + kfence_pool = memblock_phys_alloc(KFENCE_POOL_SIZE, PAGE_SIZE); > + if (!kfence_pool) { > + pr_err("failed to allocate kfence pool\n"); > + return 0; > + } > + > + return kfence_pool; > +} > + > +#else > + > +static phys_addr_t arm64_kfence_alloc_pool(void) > +{ > + return (phys_addr_t)NULL; Just return "0" - which the above function does as well on error. Or the above function should also do (phys_addr_t)NULL for consistency. > +} > + > +#endif > + > static void __init map_mem(pgd_t *pgdp) > { > static const u64 direct_map_end = _PAGE_END(VA_BITS_MIN); > @@ -532,6 +560,7 @@ 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; > + phys_addr_t kfence_pool = 0; > u64 i; > > /* > @@ -564,6 +593,10 @@ static void __init map_mem(pgd_t *pgdp) > } > #endif > > + kfence_pool = arm64_kfence_alloc_pool(); > + if (kfence_pool) > + memblock_mark_nomap(kfence_pool, KFENCE_POOL_SIZE); > + > /* map all the memory banks */ > for_each_mem_range(i, &start, &end) { > if (start >= end) > @@ -608,6 +641,17 @@ static void __init map_mem(pgd_t *pgdp) > } > } > #endif > + > + /* Kfence pool needs page-level mapping */ > + 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); > + } > } > > 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..d982ac2 100644 > --- a/include/linux/kfence.h > +++ b/include/linux/kfence.h > @@ -64,6 +64,11 @@ static __always_inline bool is_kfence_address(const void *addr) > void __init kfence_alloc_pool(void); > > /** > + * kfence_set_pool() - KFENCE pool mapped and can be used I don't understand the comment. Maybe just "allows an arch to set the KFENCE pool during early init" > + */ > +void __init kfence_set_pool(phys_addr_t addr); > + > +/** > * kfence_init() - perform KFENCE initialization at boot time > * > * Requires that kfence_alloc_pool() was called before. This sets up the > @@ -222,8 +227,10 @@ bool __kfence_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *sla > > #else /* CONFIG_KFENCE */ > > +#define KFENCE_POOL_SIZE 0 > static inline bool is_kfence_address(const void *addr) { return false; } > static inline void kfence_alloc_pool(void) { } > +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/mm/kfence/core.c b/mm/kfence/core.c > index 5349c37..a17c20c2 100644 > --- a/mm/kfence/core.c > +++ b/mm/kfence/core.c > @@ -814,12 +814,21 @@ void __init kfence_alloc_pool(void) > if (!kfence_sample_interval) > return; > > + /* if __kfence_pool already initialized in some arch, abort */ Abort sounds like it's a failure condition, but it's actually ok. Maybe just write: /* Check if the pool has already been initialized by arch; if so, skip the below. */ > + if (__kfence_pool) > + return; > + > __kfence_pool = memblock_alloc(KFENCE_POOL_SIZE, PAGE_SIZE); > > if (!__kfence_pool) > pr_err("failed to allocate pool\n"); > } > > +void __init kfence_set_pool(phys_addr_t addr) > +{ > + __kfence_pool = phys_to_virt(addr); > +} > + The rest looks good.
