Re: [PATCH v5 2/2] kasan: call kasan_init_generic in kasan_init

[Alexandre Ghiti <alex@ghiti.fr>]

On 8/8/25 08:44, Sabyrzhan Tasbolatov wrote:
> On Fri, Aug 8, 2025 at 10:07 AM Christophe Leroy
> <christophe.leroy@csgroup.eu> wrote:
>>
>>
>> Le 07/08/2025 à 21:40, Sabyrzhan Tasbolatov a écrit :
>>> Call kasan_init_generic() which handles Generic KASAN initialization.
>>> For architectures that do not select ARCH_DEFER_KASAN,
>>> this will be a no-op for the runtime flag but will
>>> print the initialization banner.
>>>
>>> For SW_TAGS and HW_TAGS modes, their respective init functions will
>>> handle the flag enabling, if they are enabled/implemented.
>>>
>>> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217049
>>> Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
>>> Tested-by: Alexandre Ghiti <alexghiti@rivosinc.com> # riscv
>>> Acked-by: Alexander Gordeev <agordeev@linux.ibm.com> # s390
>>> ---
>>> Changes in v5:
>>> - Unified arch patches into a single one, where we just call
>>>        kasan_init_generic()
>>> - Added Tested-by tag for riscv (tested the same change in v4)
>>> - Added Acked-by tag for s390 (tested the same change in v4)
>>> ---
>>>    arch/arm/mm/kasan_init.c    | 2 +-
>>>    arch/arm64/mm/kasan_init.c  | 4 +---
>>>    arch/riscv/mm/kasan_init.c  | 1 +
>>>    arch/s390/kernel/early.c    | 3 ++-
>>>    arch/x86/mm/kasan_init_64.c | 2 +-
>>>    arch/xtensa/mm/kasan_init.c | 2 +-
>>>    6 files changed, 7 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/arch/arm/mm/kasan_init.c b/arch/arm/mm/kasan_init.c
>>> index 111d4f70313..c6625e808bf 100644
>>> --- a/arch/arm/mm/kasan_init.c
>>> +++ b/arch/arm/mm/kasan_init.c
>>> @@ -300,6 +300,6 @@ void __init kasan_init(void)
>>>        local_flush_tlb_all();
>>>
>>>        memset(kasan_early_shadow_page, 0, PAGE_SIZE);
>>> -     pr_info("Kernel address sanitizer initialized\n");
>>>        init_task.kasan_depth = 0;
>>> +     kasan_init_generic();
>>>    }
>>> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
>>> index d541ce45dae..abeb81bf6eb 100644
>>> --- a/arch/arm64/mm/kasan_init.c
>>> +++ b/arch/arm64/mm/kasan_init.c
>>> @@ -399,14 +399,12 @@ void __init kasan_init(void)
>>>    {
>>>        kasan_init_shadow();
>>>        kasan_init_depth();
>>> -#if defined(CONFIG_KASAN_GENERIC)
>>> +     kasan_init_generic();
>>>        /*
>>>         * Generic KASAN is now fully initialized.
>>>         * Software and Hardware Tag-Based modes still require
>>>         * kasan_init_sw_tags() and kasan_init_hw_tags() correspondingly.
>>>         */
>>> -     pr_info("KernelAddressSanitizer initialized (generic)\n");
>>> -#endif
>>>    }
>>>
>>>    #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
>>> diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
>>> index 41c635d6aca..ba2709b1eec 100644
>>> --- a/arch/riscv/mm/kasan_init.c
>>> +++ b/arch/riscv/mm/kasan_init.c
>>> @@ -530,6 +530,7 @@ void __init kasan_init(void)
>>>
>>>        memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE);
>>>        init_task.kasan_depth = 0;
>>> +     kasan_init_generic();
>> I understood KASAN is really ready to function only once the csr_write()
>> and local_flush_tlb_all() below are done. Shouldn't kasan_init_generic()
>> be called after it ?
> I will try to test this in v6:
>
>          csr_write(CSR_SATP, PFN_DOWN(__pa(swapper_pg_dir)) | satp_mode);
>          local_flush_tlb_all();
>          kasan_init_generic();


Before setting the final kasan mapping, we still have the early one so 
we won't trap or anything on some kasan accesses. But if there is a v6, 
I agree it will be cleaner to do it this ^ way.

Thanks,

Alex


>
> Alexandre Ghiti said [1] it was not a problem, but I will check.
>
> [1] https://lore.kernel.org/all/20c1e656-512e-4424-9d4e-176af18bb7d6@ghiti.fr/
>
>>>        csr_write(CSR_SATP, PFN_DOWN(__pa(swapper_pg_dir)) | satp_mode);
>>>        local_flush_tlb_all();
>>> diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
>>> index 9adfbdd377d..544e5403dd9 100644
>>> --- a/arch/s390/kernel/early.c
>>> +++ b/arch/s390/kernel/early.c
>>> @@ -21,6 +21,7 @@
>>>    #include <linux/kernel.h>
>>>    #include <asm/asm-extable.h>
>>>    #include <linux/memblock.h>
>>> +#include <linux/kasan.h>
>>>    #include <asm/access-regs.h>
>>>    #include <asm/asm-offsets.h>
>>>    #include <asm/machine.h>
>>> @@ -65,7 +66,7 @@ static void __init kasan_early_init(void)
>>>    {
>>>    #ifdef CONFIG_KASAN
>>>        init_task.kasan_depth = 0;
>>> -     pr_info("KernelAddressSanitizer initialized\n");
>>> +     kasan_init_generic();
>>>    #endif
>>>    }
>>>
>>> diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
>>> index 0539efd0d21..998b6010d6d 100644
>>> --- a/arch/x86/mm/kasan_init_64.c
>>> +++ b/arch/x86/mm/kasan_init_64.c
>>> @@ -451,5 +451,5 @@ void __init kasan_init(void)
>>>        __flush_tlb_all();
>>>
>>>        init_task.kasan_depth = 0;
>>> -     pr_info("KernelAddressSanitizer initialized\n");
>>> +     kasan_init_generic();
>>>    }
>>> diff --git a/arch/xtensa/mm/kasan_init.c b/arch/xtensa/mm/kasan_init.c
>>> index f39c4d83173..0524b9ed5e6 100644
>>> --- a/arch/xtensa/mm/kasan_init.c
>>> +++ b/arch/xtensa/mm/kasan_init.c
>>> @@ -94,5 +94,5 @@ void __init kasan_init(void)
>>>
>>>        /* At this point kasan is fully initialized. Enable error messages. */
>>>        current->kasan_depth = 0;
>>> -     pr_info("KernelAddressSanitizer initialized\n");
>>> +     kasan_init_generic();
>>>    }
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