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Message-ID: <7cc30f38-55e5-ff7e-03a4-5cae2fa69587@redhat.com>
Date: Tue, 5 Jun 2018 14:56:46 -0700
From: Laura Abbott <labbott@...hat.com>
To: Jun Yao <yaojun8558363@...il.com>, linux-arm-kernel@...ts.infradead.org
Cc: catalin.marinas@....com, will.deacon@....com, james.morse@....com,
robin.murphy@....com, linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v2 1/3] arm64/mm: pass swapper_pg_dir as an argument to
__enable_mmu()
On 06/05/2018 02:33 AM, Jun Yao wrote:
> Introduce __pa_swapper_pg_dir to save physical address of
> swapper_pg_dir. And pass it as an argument to __enable_mmu().
>
> Signed-off-by: Jun Yao <yaojun8558363@...il.com>
> ---
> arch/arm64/include/asm/mmu_context.h | 4 +---
> arch/arm64/include/asm/pgtable.h | 1 +
> arch/arm64/kernel/cpufeature.c | 2 +-
> arch/arm64/kernel/head.S | 6 ++++--
> arch/arm64/kernel/hibernate.c | 2 +-
> arch/arm64/kernel/sleep.S | 1 +
> arch/arm64/mm/kasan_init.c | 4 ++--
> arch/arm64/mm/mmu.c | 11 +++++++++--
> 8 files changed, 20 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
> index 39ec0b8a689e..3eddb871f251 100644
> --- a/arch/arm64/include/asm/mmu_context.h
> +++ b/arch/arm64/include/asm/mmu_context.h
> @@ -141,14 +141,12 @@ static inline void cpu_install_idmap(void)
> * Atomically replaces the active TTBR1_EL1 PGD with a new VA-compatible PGD,
> * avoiding the possibility of conflicting TLB entries being allocated.
> */
> -static inline void cpu_replace_ttbr1(pgd_t *pgdp)
> +static inline void cpu_replace_ttbr1(phys_addr_t pgd_phys)
> {
> typedef void (ttbr_replace_func)(phys_addr_t);
> extern ttbr_replace_func idmap_cpu_replace_ttbr1;
> ttbr_replace_func *replace_phys;
>
> - phys_addr_t pgd_phys = virt_to_phys(pgdp);
> -
> replace_phys = (void *)__pa_symbol(idmap_cpu_replace_ttbr1);
>
> cpu_install_idmap();
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 7c4c8f318ba9..519ab5581b08 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -722,6 +722,7 @@ extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
> extern pgd_t swapper_pg_end[];
> extern pgd_t idmap_pg_dir[PTRS_PER_PGD];
> extern pgd_t tramp_pg_dir[PTRS_PER_PGD];
> +extern volatile phys_addr_t __pa_swapper_pg_dir;
>
> /*
> * Encode and decode a swap entry:
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index d2856b129097..e3d76a9dd67a 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -917,7 +917,7 @@ kpti_install_ng_mappings(const struct arm64_cpu_capabilities *__unused)
> remap_fn = (void *)__pa_symbol(idmap_kpti_install_ng_mappings);
>
> cpu_install_idmap();
> - remap_fn(cpu, num_online_cpus(), __pa_symbol(swapper_pg_dir));
> + remap_fn(cpu, num_online_cpus(), __pa_swapper_pg_dir);
> cpu_uninstall_idmap();
>
> if (!cpu)
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index b0853069702f..2e871b1cb75f 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -706,6 +706,7 @@ secondary_startup:
> * Common entry point for secondary CPUs.
> */
> bl __cpu_setup // initialise processor
> + ldr_l x26, __pa_swapper_pg_dir
> bl __enable_mmu
> ldr x8, =__secondary_switched
> br x8
> @@ -748,6 +749,7 @@ ENDPROC(__secondary_switched)
> * Enable the MMU.
> *
> * x0 = SCTLR_EL1 value for turning on the MMU.
> + * x26 = TTBR1 value for turning on the MMU.
> *
> * Returns to the caller via x30/lr. This requires the caller to be covered
> * by the .idmap.text section.
> @@ -762,9 +764,8 @@ ENTRY(__enable_mmu)
> b.ne __no_granule_support
> update_early_cpu_boot_status 0, x1, x2
> adrp x1, idmap_pg_dir
> - adrp x2, swapper_pg_dir
> phys_to_ttbr x3, x1
> - phys_to_ttbr x4, x2
> + phys_to_ttbr x4, x26
> msr ttbr0_el1, x3 // load TTBR0
> msr ttbr1_el1, x4 // load TTBR1
> isb
> @@ -823,6 +824,7 @@ __primary_switch:
> mrs x20, sctlr_el1 // preserve old SCTLR_EL1 value
> #endif
>
> + adrp x26, swapper_pg_dir
> bl __enable_mmu
> #ifdef CONFIG_RELOCATABLE
> bl __relocate_kernel
> diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
> index 6b2686d54411..0a0a0ca19f9b 100644
> --- a/arch/arm64/kernel/hibernate.c
> +++ b/arch/arm64/kernel/hibernate.c
> @@ -125,7 +125,7 @@ int arch_hibernation_header_save(void *addr, unsigned int max_size)
> return -EOVERFLOW;
>
> arch_hdr_invariants(&hdr->invariants);
> - hdr->ttbr1_el1 = __pa_symbol(swapper_pg_dir);
> + hdr->ttbr1_el1 = __pa_swapper_pg_dir;
> hdr->reenter_kernel = _cpu_resume;
>
> /* We can't use __hyp_get_vectors() because kvm may still be loaded */
> diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
> index bebec8ef9372..03854c329449 100644
> --- a/arch/arm64/kernel/sleep.S
> +++ b/arch/arm64/kernel/sleep.S
> @@ -101,6 +101,7 @@ ENTRY(cpu_resume)
> bl el2_setup // if in EL2 drop to EL1 cleanly
> bl __cpu_setup
> /* enable the MMU early - so we can access sleep_save_stash by va */
> + ldr_l x26, __pa_swapper_pg_dir
> bl __enable_mmu
> ldr x8, =_cpu_resume
> br x8
> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> index 12145874c02b..dd4f28c19165 100644
> --- a/arch/arm64/mm/kasan_init.c
> +++ b/arch/arm64/mm/kasan_init.c
> @@ -199,7 +199,7 @@ void __init kasan_init(void)
> */
> memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir));
> dsb(ishst);
> - cpu_replace_ttbr1(lm_alias(tmp_pg_dir));
> + cpu_replace_ttbr1(__pa_symbol(tmp_pg_dir));
>
> clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
>
> @@ -236,7 +236,7 @@ void __init kasan_init(void)
> pfn_pte(sym_to_pfn(kasan_zero_page), PAGE_KERNEL_RO));
>
> memset(kasan_zero_page, 0, PAGE_SIZE);
> - cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
> + cpu_replace_ttbr1(__pa_swapper_pg_dir);
>
> /* At this point kasan is fully initialized. Enable error messages */
> init_task.kasan_depth = 0;
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 2dbb2c9f1ec1..c7df2f0d2e85 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -55,6 +55,9 @@ u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
> u64 kimage_voffset __ro_after_init;
> EXPORT_SYMBOL(kimage_voffset);
>
> +volatile phys_addr_t __section(".mmuoff.data.read")
> +__pa_swapper_pg_dir;
> +
> /*
> * Empty_zero_page is a special page that is used for zero-initialized data
> * and COW.
> @@ -631,6 +634,10 @@ void __init paging_init(void)
> phys_addr_t pgd_phys = early_pgtable_alloc();
> pgd_t *pgdp = pgd_set_fixmap(pgd_phys);
>
> + __pa_swapper_pg_dir = __pa_symbol(swapper_pg_dir);
> + __flush_dcache_area((void *)&__pa_swapper_pg_dir,
> + sizeof(__pa_swapper_pg_dir));
> +
Can you add a comment here explaining why the flush is needed and
also why the variable gets placed in the particular section?
A brief summary of https://www.spinics.net/lists/kernel/msg2819594.html
would be fine.
Thanks,
Laura
> map_kernel(pgdp);
> map_mem(pgdp);
>
> @@ -642,9 +649,9 @@ void __init paging_init(void)
> *
> * To do this we need to go via a temporary pgd.
> */
> - cpu_replace_ttbr1(__va(pgd_phys));
> + cpu_replace_ttbr1(pgd_phys);
> memcpy(swapper_pg_dir, pgdp, PGD_SIZE);
> - cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
> + cpu_replace_ttbr1(__pa_swapper_pg_dir);
>
> pgd_clear_fixmap();
> memblock_free(pgd_phys, PAGE_SIZE);
>
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