linux-kernel - Re: [PATCH 1/3] init: Declare rodata_enabled and mark_rodata

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Date: Thu, 21 Dec 2023 23:16:56 +1100
From: Michael Ellerman <mpe@...erman.id.au>
To: Christophe Leroy <christophe.leroy@...roup.eu>, Nicholas Piggin
 <npiggin@...il.com>, Arnd Bergmann <arnd@...db.de>, Luis Chamberlain
 <mcgrof@...nel.org>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
 linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
 linux-modules@...r.kernel.org, Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH 1/3] init: Declare rodata_enabled and mark_rodata_ro()
 at all time

Cc +Kees

Christophe Leroy <christophe.leroy@...roup.eu> writes:
> Declaring rodata_enabled and mark_rodata_ro() at all time
> helps removing related #ifdefery in C files.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
>  include/linux/init.h |  4 ----
>  init/main.c          | 21 +++++++--------------
>  2 files changed, 7 insertions(+), 18 deletions(-)
>
> diff --git a/include/linux/init.h b/include/linux/init.h
> index 01b52c9c7526..d2b47be38a07 100644
> --- a/include/linux/init.h
> +++ b/include/linux/init.h
> @@ -168,12 +168,8 @@ extern initcall_entry_t __initcall_end[];
>  
>  extern struct file_system_type rootfs_fs_type;
>  
> -#if defined(CONFIG_STRICT_KERNEL_RWX) || defined(CONFIG_STRICT_MODULE_RWX)
>  extern bool rodata_enabled;
> -#endif
> -#ifdef CONFIG_STRICT_KERNEL_RWX
>  void mark_rodata_ro(void);
> -#endif
>  
>  extern void (*late_time_init)(void);
>  
> diff --git a/init/main.c b/init/main.c
> index e24b0780fdff..807df08c501f 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -1396,10 +1396,9 @@ static int __init set_debug_rodata(char *str)
>  early_param("rodata", set_debug_rodata);
>  #endif
>  
> -#ifdef CONFIG_STRICT_KERNEL_RWX
>  static void mark_readonly(void)
>  {
> -	if (rodata_enabled) {
> +	if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX) && rodata_enabled) {
>  		/*
>  		 * load_module() results in W+X mappings, which are cleaned
>  		 * up with call_rcu().  Let's make sure that queued work is
> @@ -1409,20 +1408,14 @@ static void mark_readonly(void)
>  		rcu_barrier();
>  		mark_rodata_ro();
>  		rodata_test();
> -	} else
> +	} else if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)) {
>  		pr_info("Kernel memory protection disabled.\n");
> +	} else if (IS_ENABLED(CONFIG_ARCH_HAS_STRICT_KERNEL_RWX)) {
> +		pr_warn("Kernel memory protection not selected by kernel config.\n");
> +	} else {
> +		pr_warn("This architecture does not have kernel memory protection.\n");
> +	}
>  }
> -#elif defined(CONFIG_ARCH_HAS_STRICT_KERNEL_RWX)
> -static inline void mark_readonly(void)
> -{
> -	pr_warn("Kernel memory protection not selected by kernel config.\n");
> -}
> -#else
> -static inline void mark_readonly(void)
> -{
> -	pr_warn("This architecture does not have kernel memory protection.\n");
> -}
> -#endif
>  
>  void __weak free_initmem(void)
>  {
> -- 
> 2.41.0