On Thu, Mar 16, 2023 at 04:50:20PM +0800, Zhenhua Huang 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@xxxxxxx> > Signed-off-by: Zhenhua Huang <quic_zhenhuah@xxxxxxxxxxx> > --- > arch/arm64/include/asm/kfence.h | 16 +++++++++++ > arch/arm64/mm/mmu.c | 59 +++++++++++++++++++++++++++++++++++++++++ > arch/arm64/mm/pageattr.c | 9 +++++-- > include/linux/kfence.h | 1 + > mm/kfence/core.c | 4 +++ > 5 files changed, 87 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/include/asm/kfence.h b/arch/arm64/include/asm/kfence.h > index aa855c6..8143c91 100644 > --- a/arch/arm64/include/asm/kfence.h > +++ b/arch/arm64/include/asm/kfence.h > @@ -10,6 +10,22 @@ > > #include <asm/set_memory.h> > > +extern phys_addr_t early_kfence_pool; > + > +#ifdef CONFIG_KFENCE > + > +extern char *__kfence_pool; > +static inline void kfence_set_pool(phys_addr_t addr) > +{ > + __kfence_pool = phys_to_virt(addr); > +} > + > +#else > + > +static inline void kfence_set_pool(phys_addr_t addr) { } > + > +#endif > + > static inline bool arch_kfence_init_pool(void) { return true; } > > static inline bool kfence_protect_page(unsigned long addr, bool protect) > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 6f9d889..61944c70 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) > @@ -525,6 +527,48 @@ static int __init enable_crash_mem_map(char *arg) > } > early_param("crashkernel", enable_crash_mem_map); > > +#ifdef CONFIG_KFENCE > + > +static bool kfence_early_init __initdata = !!CONFIG_KFENCE_SAMPLE_INTERVAL; > +/* > + * early_param can be parsed before linear mapping > + * set up > + */ > +static int __init parse_kfence_early_init(char *p) > +{ > + int val; > + > + if (get_option(&p, &val)) > + kfence_early_init = !!val; > + return 0; > +} > +early_param("kfence.sample_interval", parse_kfence_early_init); > + > +static phys_addr_t 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"); > + > + return kfence_pool; > +} > + > +#else > + > +static phys_addr_t arm64_kfence_alloc_pool(void) > +{ > + return 0; > +} > + > +#endif > + > +phys_addr_t early_kfence_pool; > + > static void __init map_mem(pgd_t *pgdp) > { > static const u64 direct_map_end = _PAGE_END(VA_BITS_MIN); > @@ -543,6 +587,10 @@ 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 (early_kfence_pool) > + memblock_mark_nomap(early_kfence_pool, KFENCE_POOL_SIZE); > + > if (can_set_direct_map()) > flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; > > @@ -608,6 +656,17 @@ static void __init map_mem(pgd_t *pgdp) > } > } > #endif > + > + /* Kfence pool needs page-level mapping */ > + if (early_kfence_pool) { > + __map_memblock(pgdp, early_kfence_pool, > + early_kfence_pool + KFENCE_POOL_SIZE, > + pgprot_tagged(PAGE_KERNEL), > + NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS); > + memblock_clear_nomap(early_kfence_pool, KFENCE_POOL_SIZE); > + /* kfence_pool really mapped now */ > + kfence_set_pool(early_kfence_pool); > + } Why not wrap this under CONFIG_KFENCE ? early_kfence_pool can also go in there? Thanks, Pavan
