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Mon, 13 Mar 2023 09:05:27 GMT Received: from [10.239.132.245] (10.80.80.8) by nalasex01a.na.qualcomm.com (10.47.209.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.41; Mon, 13 Mar 2023 02:05:23 -0700 Message-ID: <8b44b20d-675c-25d0-6ddb-9b02da1c72d2@quicinc.com> Date: Mon, 13 Mar 2023 17:05:19 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH v5] mm,kfence: decouple kfence from page granularity mapping judgement Content-Language: en-US To: Marco Elver CC: , , , , , , , , , , , , , , , References: <1678683825-11866-1-git-send-email-quic_zhenhuah@quicinc.com> From: Zhenhua Huang In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01b.na.qualcomm.com (10.46.141.250) To nalasex01a.na.qualcomm.com (10.47.209.196) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: YxZHp2RILOao7frQ2_6H3et8CPAlUy_Z X-Proofpoint-GUID: YxZHp2RILOao7frQ2_6H3et8CPAlUy_Z X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22 definitions=2023-03-13_01,2023-03-10_01,2023-02-09_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 impostorscore=0 phishscore=0 suspectscore=0 priorityscore=1501 clxscore=1015 malwarescore=0 mlxscore=0 adultscore=0 lowpriorityscore=0 mlxlogscore=999 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2303130074 X-Rspamd-Queue-Id: 3A4C4160011 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: j5rycf39i1md5j6jzc4k3kf74zyaryez X-HE-Tag: 1678698368-490922 X-HE-Meta: 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 6O61/1Ay IvJTHq91pmbdmPDkPSj776Cc/LXNiyNdoOw9vc5ZFQqvacZBrr/9Pzlt6iC49pMw3BZx8TfgSD6rIVHMXcb4bvHngTDrmS3e7IZzcD3WJP4lJduk01WUKrpk7chGXYetYGF4ZrqaLmI42hILjL4gc5T0BhdHvRWEg1hPOouXF4Hm0VEPkxuVFAOKs7QOZr918vjyGJ/ut2I5ZutK57cWpoNpYUkZA8EVPD0hrh3rSC5EgycIwoM/QkgpekznJIPdH0GUCc6O4EpCte7+JOxGVyMBeDXonJvq+uV7BI9Xi7MkCpmUL0HH0qgEaT9udE0DaKMi8p+f5zhM3StxqFecoWQkHaOeKDvL7cJbAeQyMnCHdLMu5wuVIbg1fNeKTnUJ1Gz5R33cyYvfJNHj+giAt8q96hA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Thanks Marco! On 2023/3/13 15:50, Marco Elver wrote: > On Mon, 13 Mar 2023 at 06:04, Zhenhua Huang wrote: >> >> Kfence only needs its pool to be mapped as page granularity, 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. >> >> 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. > > This patch still breaks the late-init capabilities that Kefeng pointed out. > > I think the only viable option is: > > 1. If KFENCE early init is requested on arm64, do what you're doing here. > > 2. If KFENCE is compiled in, but not enabled, do what was done > before, so it can be enabled late. I'm fine with above solution as well. The Disadvantage is if we want to dynamically disable kfence through kfence_sample_interval, it must be mapped into page granularity still. > > Am I missing an option? > Another option is what Kefeng firstly thought and I had proposed on comments of patchsetV3, actually I wanted to do in an separate patch: " So how about we raise another change, like you mentioned bootargs indicating to use late init of b33f778bba5e ("kfence: alloc kfence_pool after system startup"). 1. in arm64_kfence_alloc_pool(): if (!kfence_sample_interval && !using_late_init) return 0; else allocate pool 2. also do the check in late allocation,like if (do_allocation_late && !using_late_init) BUG(); " The thought is to allocate pool early as well if we need to using_late_init. Kefeng, Marco, How's your idea? >> >> LINK: [1] https://lore.kernel.org/linux-arm-kernel/Y+IsdrvDNILA59UN@FVFF77S0Q05N/ >> Suggested-by: Mark Rutland >> Signed-off-by: Zhenhua Huang >> --- >> arch/arm64/mm/mmu.c | 42 ++++++++++++++++++++++++++++++++++++++++++ >> arch/arm64/mm/pageattr.c | 5 ++--- >> include/linux/kfence.h | 8 ++++++++ >> mm/kfence/core.c | 9 +++++++++ >> 4 files changed, 61 insertions(+), 3 deletions(-) >> >> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >> index 6f9d889..ca5c932 100644 >> --- a/arch/arm64/mm/mmu.c >> +++ b/arch/arm64/mm/mmu.c >> @@ -24,6 +24,7 @@ >> #include >> #include >> #include >> +#include >> >> #include >> #include >> @@ -525,6 +526,31 @@ 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; >> + >> + 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 kfence_pool; >> +} >> + >> +#else >> + >> +static phys_addr_t arm64_kfence_alloc_pool(void) >> +{ >> + return 0; >> +} >> + >> +#endif >> + >> static void __init map_mem(pgd_t *pgdp) >> { >> static const u64 direct_map_end = _PAGE_END(VA_BITS_MIN); >> @@ -532,6 +558,7 @@ 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; >> u64 i; >> >> /* >> @@ -564,6 +591,10 @@ 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 +639,17 @@ 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 >> >