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Subject: Re: [PATCH] riscv: Consistify
 protect_kernel_linear_mapping_text_rodata() use
To:     Geert Uytterhoeven <geert+renesas@glider.be>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Vitaly Wool <vitaly.wool@konsulko.com>
Cc:     linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
References: <b89a090317cf26bbe1caaa3cfa513a789ece1b19.1619708711.git.geert+renesas@glider.be>
From:   Alex Ghiti <alex@ghiti.fr>
Message-ID: <288c578a-d680-e2e8-33a1-004e11a4f6f0@ghiti.fr>
Date:   Sun, 2 May 2021 10:06:29 -0400
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Le 4/29/21 ? 11:10 AM, Geert Uytterhoeven a ?crit?:
> The various uses of protect_kernel_linear_mapping_text_rodata() are
> not consistent:
>    - Its definition depends on "64BIT && !XIP_KERNEL",
>    - Its forward declaration depends on MMU,
>    - Its single caller depends on "STRICT_KERNEL_RWX && 64BIT && MMU &&
>      !XIP_KERNEL".
> 
> Fix this by settling on the dependencies of the caller, which can be
> simplified as STRICT_KERNEL_RWX depends on "MMU && !XIP_KERNEL".
> Provide a dummy definition, as the caller is protected by
> "IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)" instead of "#ifdef
> CONFIG_STRICT_KERNEL_RWX".
> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> Only tested on K210 (SiPeed MAIX BiT).
> ---
>   arch/riscv/include/asm/set_memory.h | 7 ++++++-
>   arch/riscv/kernel/setup.c           | 2 --
>   arch/riscv/mm/init.c                | 2 +-
>   3 files changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/set_memory.h b/arch/riscv/include/asm/set_memory.h
> index a9c56776fa0e74d6..086f757e8ba3cc69 100644
> --- a/arch/riscv/include/asm/set_memory.h
> +++ b/arch/riscv/include/asm/set_memory.h
> @@ -17,7 +17,6 @@ int set_memory_x(unsigned long addr, int numpages);
>   int set_memory_nx(unsigned long addr, int numpages);
>   int set_memory_rw_nx(unsigned long addr, int numpages);
>   void protect_kernel_text_data(void);
> -void protect_kernel_linear_mapping_text_rodata(void);
>   #else
>   static inline int set_memory_ro(unsigned long addr, int numpages) { return 0; }
>   static inline int set_memory_rw(unsigned long addr, int numpages) { return 0; }
> @@ -27,6 +26,12 @@ static inline void protect_kernel_text_data(void) {}
>   static inline int set_memory_rw_nx(unsigned long addr, int numpages) { return 0; }
>   #endif
>   
> +#if defined(CONFIG_64BIT) && defined(CONFIG_STRICT_KERNEL_RWX)
> +void protect_kernel_linear_mapping_text_rodata(void);
> +#else
> +static inline void protect_kernel_linear_mapping_text_rodata(void) {}
> +#endif
> +
>   int set_direct_map_invalid_noflush(struct page *page);
>   int set_direct_map_default_noflush(struct page *page);
>   bool kernel_page_present(struct page *page);
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index 7b31779101f662e4..03901d3a8b027343 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -293,9 +293,7 @@ void __init setup_arch(char **cmdline_p)
>   
>   	if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)) {
>   		protect_kernel_text_data();
> -#if defined(CONFIG_64BIT) && defined(CONFIG_MMU) && !defined(CONFIG_XIP_KERNEL)
>   		protect_kernel_linear_mapping_text_rodata();
> -#endif
>   	}
>   
>   #ifdef CONFIG_SWIOTLB
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 3ebc0f5d2b73b42b..6cc0421a5d0ef4a3 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -646,7 +646,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>   #endif
>   }
>   
> -#if defined(CONFIG_64BIT) && !defined(CONFIG_XIP_KERNEL)
> +#if defined(CONFIG_64BIT) && defined(CONFIG_STRICT_KERNEL_RWX)
>   void protect_kernel_linear_mapping_text_rodata(void)
>   {
>   	unsigned long text_start = (unsigned long)lm_alias(_start);
> 

I tested this on the following configs:

- rv32_defconfig (build and valid on qemu)
- defconfig (with and without CONFIG_STRICT_KERNEL_RWX) (build and valid 
on qemu)
- xip kernel (build and valid on qemu)
- nommu_k210_defconfig (build only)

so you can add:

Tested-by: Alexandre Ghiti <alex@ghiti.fr>

Thank you for the cleanup!

Alex