linux-kernel - Re: [PATCH v2] RISC-V: Don't mark init section as non-executable

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Date:   Mon, 1 Jun 2020 11:23:11 -0700
From:   Atish Patra <atishp@...shpatra.org>
To:     Anup Patel <anup.patel@....com>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <anup@...infault.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        stable@...r.kernel.org, Atish Patra <atish.patra@....com>,
        Alistair Francis <Alistair.Francis@....com>,
        linux-riscv <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH v2] RISC-V: Don't mark init section as non-executable

On Sun, May 31, 2020 at 10:07 PM Anup Patel <anup.patel@....com> wrote:
>
> The head text section (i.e. _start, secondary_start_sbi, etc) and the
> init section fall under same page table level-1 mapping.
>
> Currently, the runtime CPU hotplug is broken because we are marking
> init section as non-executable which in-turn marks head text section
> as non-executable.
>
> Further investigating other architectures, it seems marking the init
> section as non-executable is redundant because the init section pages
> are anyway poisoned and freed.
>
> To fix broken runtime CPU hotplug, we simply remove the code marking
> the init section as non-executable.
>
> Fixes: d27c3c90817e ("riscv: add STRICT_KERNEL_RWX support")
> Cc: stable@...r.kernel.org
> Signed-off-by: Anup Patel <anup.patel@....com>
> ---
> Changes since v1:
>  - Updated free_initmem() is same as generic free_initmem() defined in
>    init/main.c so we completely remove free_initmem() from arch/riscv
> ---
>  arch/riscv/mm/init.c | 11 -----------
>  1 file changed, 11 deletions(-)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 736de6c8739f..fdc772f57edc 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -479,17 +479,6 @@ static void __init setup_vm_final(void)
>         csr_write(CSR_SATP, PFN_DOWN(__pa_symbol(swapper_pg_dir)) | SATP_MODE);
>         local_flush_tlb_all();
>  }
> -
> -void free_initmem(void)
> -{
> -       unsigned long init_begin = (unsigned long)__init_begin;
> -       unsigned long init_end = (unsigned long)__init_end;
> -
> -       /* Make the region as non-execuatble. */
> -       set_memory_nx(init_begin, (init_end - init_begin) >> PAGE_SHIFT);
> -       free_initmem_default(POISON_FREE_INITMEM);
> -}
> -
>  #else
>  asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>  {
> --
> 2.25.1
>
>

Reviewed-by: Atish Patra <atish.patra@....com>
-- 
Regards,
Atish