| Message ID | 1678979429-25815-1-git-send-email-quic_zhenhuah@quicinc.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v11] mm,kfence: decouple kfence from page granularity mapping judgement | expand |
On Thu, 16 Mar 2023 at 16:10, Zhenhua Huang <quic_zhenhuah@quicinc.com> wrote: > > Kfence only needs its pool to be mapped as page granularity, if it is > inited early. Previous judgement was a bit over protected. From [1], Mark > suggested to "just map the KFENCE region a page granularity". So I > decouple it from judgement and do page granularity mapping for kfence > pool only. Need to be noticed that late init of kfence pool still requires > page granularity mapping. > > Page granularity mapping in theory cost more(2M per 1GB) memory on arm64 > platform. Like what I've tested on QEMU(emulated 1GB RAM) with > gki_defconfig, also turning off rodata protection: > Before: > [root@liebao ]# cat /proc/meminfo > MemTotal: 999484 kB > After: > [root@liebao ]# cat /proc/meminfo > MemTotal: 1001480 kB > > 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/Y+IsdrvDNILA59UN@FVFF77S0Q05N/ > Suggested-by: Mark Rutland <mark.rutland@arm.com> > Signed-off-by: Zhenhua Huang <quic_zhenhuah@quicinc.com> > Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com> Reviewed-by: Marco Elver <elver@google.com> One question: what happens if the page-granular direct map is requested either way, is there any downside with this patch? Does it mean map_mem() just does a little extra work it shouldn't have? (Not saying that's a problem, just trying to ask you to double-check it's ok.) However, please also wait for an arm64 maintainer to have a look. I'm assuming that because it touches mostly arm64 code, this patch ought to go through the arm64 tree? Thanks, -- Marco
On 2023/3/17 5:43, Marco Elver wrote: > On Thu, 16 Mar 2023 at 16:10, Zhenhua Huang <quic_zhenhuah@quicinc.com> wrote: >> >> Kfence only needs its pool to be mapped as page granularity, if it is >> inited early. Previous judgement was a bit over protected. From [1], Mark >> suggested to "just map the KFENCE region a page granularity". So I >> decouple it from judgement and do page granularity mapping for kfence >> pool only. Need to be noticed that late init of kfence pool still requires >> page granularity mapping. >> >> Page granularity mapping in theory cost more(2M per 1GB) memory on arm64 >> platform. Like what I've tested on QEMU(emulated 1GB RAM) with >> gki_defconfig, also turning off rodata protection: >> Before: >> [root@liebao ]# cat /proc/meminfo >> MemTotal: 999484 kB >> After: >> [root@liebao ]# cat /proc/meminfo >> MemTotal: 1001480 kB >> >> 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/Y+IsdrvDNILA59UN@FVFF77S0Q05N/ >> Suggested-by: Mark Rutland <mark.rutland@arm.com> >> Signed-off-by: Zhenhua Huang <quic_zhenhuah@quicinc.com> >> Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com> > > Reviewed-by: Marco Elver <elver@google.com> > > One question: what happens if the page-granular direct map is > requested either way, is there any downside with this patch? Does it > mean map_mem() just does a little extra work it shouldn't have? (Not > saying that's a problem, just trying to ask you to double-check it's > ok.) > Yeah.. I think so Marco. Seems the extra work in map_mem() is we did judgement there.. Other side is we added one early param. > However, please also wait for an arm64 maintainer to have a look. I'm > assuming that because it touches mostly arm64 code, this patch ought > to go through the arm64 tree? Yeah, sure. We will wait for arm64 maintainers' comments. Thanks, Zhenhua > > Thanks, > -- Marco
diff --git a/arch/arm64/include/asm/kfence.h b/arch/arm64/include/asm/kfence.h index aa855c6..a81937f 100644 --- a/arch/arm64/include/asm/kfence.h +++ b/arch/arm64/include/asm/kfence.h @@ -19,4 +19,14 @@ static inline bool kfence_protect_page(unsigned long addr, bool protect) return true; } +#ifdef CONFIG_KFENCE +extern bool kfence_early_init; +static inline bool arm64_kfence_can_set_direct_map(void) +{ + return !kfence_early_init; +} +#else /* CONFIG_KFENCE */ +static inline bool arm64_kfence_can_set_direct_map(void) { return false; } +#endif /* CONFIG_KFENCE */ + #endif /* __ASM_KFENCE_H */ diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 6f9d889..9813f2a 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> @@ -38,6 +39,7 @@ #include <asm/ptdump.h> #include <asm/tlbflush.h> #include <asm/pgalloc.h> +#include <asm/kfence.h> #define NO_BLOCK_MAPPINGS BIT(0) #define NO_CONT_MAPPINGS BIT(1) @@ -525,12 +527,67 @@ static int __init enable_crash_mem_map(char *arg) } early_param("crashkernel", enable_crash_mem_map); +#ifdef CONFIG_KFENCE + +bool __ro_after_init kfence_early_init = !!CONFIG_KFENCE_SAMPLE_INTERVAL; + +/* early_param() will be parsed before map_mem() below. */ +static int __init parse_kfence_early_init(char *arg) +{ + int val; + + if (get_option(&arg, &val)) + kfence_early_init = !!val; + return 0; +} +early_param("kfence.sample_interval", parse_kfence_early_init); + +static phys_addr_t __init arm64_kfence_alloc_pool(void) +{ + phys_addr_t kfence_pool; + + if (!kfence_early_init) + return 0; + + kfence_pool = memblock_phys_alloc(KFENCE_POOL_SIZE, PAGE_SIZE); + if (!kfence_pool) { + pr_err("failed to allocate kfence pool\n"); + kfence_early_init = false; + return 0; + } + + /* Temporarily mark as NOMAP. */ + memblock_mark_nomap(kfence_pool, KFENCE_POOL_SIZE); + + return kfence_pool; +} + +static void __init arm64_kfence_map_pool(phys_addr_t kfence_pool, pgd_t *pgdp) +{ + if (!kfence_pool) + return; + + /* KFENCE pool needs page-level mapping. */ + __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 = phys_to_virt(kfence_pool); +} +#else /* CONFIG_KFENCE */ + +static inline phys_addr_t arm64_kfence_alloc_pool(void) { return 0; } +static inline void arm64_kfence_map_pool(phys_addr_t kfence_pool, pgd_t *pgdp) { } + +#endif /* CONFIG_KFENCE */ + static void __init map_mem(pgd_t *pgdp) { static const u64 direct_map_end = _PAGE_END(VA_BITS_MIN); phys_addr_t kernel_start = __pa_symbol(_stext); phys_addr_t kernel_end = __pa_symbol(__init_begin); phys_addr_t start, end; + phys_addr_t early_kfence_pool; int flags = NO_EXEC_MAPPINGS; u64 i; @@ -543,6 +600,8 @@ static void __init map_mem(pgd_t *pgdp) */ BUILD_BUG_ON(pgd_index(direct_map_end - 1) == pgd_index(direct_map_end)); + early_kfence_pool = arm64_kfence_alloc_pool(); + if (can_set_direct_map()) flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; @@ -608,6 +667,8 @@ static void __init map_mem(pgd_t *pgdp) } } #endif + + arm64_kfence_map_pool(early_kfence_pool, pgdp); } void mark_rodata_ro(void) diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c index 79dd201..8e2017b 100644 --- a/arch/arm64/mm/pageattr.c +++ b/arch/arm64/mm/pageattr.c @@ -11,6 +11,7 @@ #include <asm/cacheflush.h> #include <asm/set_memory.h> #include <asm/tlbflush.h> +#include <asm/kfence.h> struct page_change_data { pgprot_t set_mask; @@ -22,12 +23,14 @@ 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. + * + * KFENCE pool requires page-granular mapping if initialized late. */ return (rodata_enabled && rodata_full) || debug_pagealloc_enabled() || - IS_ENABLED(CONFIG_KFENCE); + arm64_kfence_can_set_direct_map(); } static int change_page_range(pte_t *ptep, unsigned long addr, void *data) diff --git a/mm/kfence/core.c b/mm/kfence/core.c index 5349c37..5abc79f 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -814,6 +814,10 @@ 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)