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 | 8 ++++++++ mm/kfence/core.c | 9 +++++++++ 4 files changed, 63 insertions(+), 3 deletions(-) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 6f9d889..9f06a29e 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 (phys_addr_t)NULL; + + kfence_pool = memblock_phys_alloc(KFENCE_POOL_SIZE, PAGE_SIZE); + if (!kfence_pool) { + pr_err("failed to allocate kfence pool\n"); + return (phys_addr_t)NULL; + } + + return kfence_pool; +} + +#else + +static phys_addr_t arm64_kfence_alloc_pool(void) +{ + return (phys_addr_t)NULL; +} + +#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..570d4e3 100644 --- a/include/linux/kfence.h +++ b/include/linux/kfence.h @@ -64,6 +64,12 @@ static __always_inline bool is_kfence_address(const void *addr) void __init kfence_alloc_pool(void); /** + * kfence_set_pool() - 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 +228,10 @@ 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..0765395 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 the pool has already been initialized by arch, 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); +} + static void kfence_init_enable(void) { if (!IS_ENABLED(CONFIG_KFENCE_STATIC_KEYS)) -- 2.7.4
