netdev - Re: [PATCH v3 04/13] mm/execmem, arch: convert remaining overrides of module

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Date: Wed, 4 Oct 2023 00:29:36 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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Subject: Re: [PATCH v3 04/13] mm/execmem, arch: convert remaining overrides of
 module_alloc to execmem

On Mon, 2023-09-18 at 10:29 +0300, Mike Rapoport wrote:
> diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
> index 5f71a0cf4399..9d37375e2f05 100644
> --- a/arch/x86/kernel/module.c
> +++ b/arch/x86/kernel/module.c
> @@ -19,6 +19,7 @@
>  #include <linux/jump_label.h>
>  #include <linux/random.h>
>  #include <linux/memory.h>
> +#include <linux/execmem.h>
>  
>  #include <asm/text-patching.h>
>  #include <asm/page.h>
> @@ -36,55 +37,30 @@ do
> {                                                        \
>  } while (0)
>  #endif
>  
> -#ifdef CONFIG_RANDOMIZE_BASE
> -static unsigned long module_load_offset;
> +static struct execmem_params execmem_params __ro_after_init = {
> +       .ranges = {
> +               [EXECMEM_DEFAULT] = {
> +                       .flags = EXECMEM_KASAN_SHADOW,
> +                       .alignment = MODULE_ALIGN,
> +               },
> +       },
> +};
>  
> -/* Mutex protects the module_load_offset. */
> -static DEFINE_MUTEX(module_kaslr_mutex);
> -
> -static unsigned long int get_module_load_offset(void)
> -{
> -       if (kaslr_enabled()) {
> -               mutex_lock(&module_kaslr_mutex);
> -               /*
> -                * Calculate the module_load_offset the first time
> this
> -                * code is called. Once calculated it stays the same
> until
> -                * reboot.
> -                */
> -               if (module_load_offset == 0)
> -                       module_load_offset =
> -                               get_random_u32_inclusive(1, 1024) *
> PAGE_SIZE;
> -               mutex_unlock(&module_kaslr_mutex);
> -       }
> -       return module_load_offset;
> -}
> -#else
> -static unsigned long int get_module_load_offset(void)
> -{
> -       return 0;
> -}
> -#endif
> -
> -void *module_alloc(unsigned long size)
> +struct execmem_params __init *execmem_arch_params(void)
>  {
> -       gfp_t gfp_mask = GFP_KERNEL;
> -       void *p;
> -
> -       if (PAGE_ALIGN(size) > MODULES_LEN)
> -               return NULL;
> +       unsigned long module_load_offset = 0;
> +       unsigned long start;
>  
> -       p = __vmalloc_node_range(size, MODULE_ALIGN,
> -                                MODULES_VADDR +
> get_module_load_offset(),
> -                                MODULES_END, gfp_mask, PAGE_KERNEL,
> -                                VM_FLUSH_RESET_PERMS |
> VM_DEFER_KMEMLEAK,
> -                                NUMA_NO_NODE,
> __builtin_return_address(0));
> +       if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && kaslr_enabled())
> +               module_load_offset =
> +                       get_random_u32_inclusive(1, 1024) *
> PAGE_SIZE;

Minor:
I think you can skip the IS_ENABLED(CONFIG_RANDOMIZE_BASE) part because
CONFIG_RANDOMIZE_MEMORY depends on CONFIG_RANDOMIZE_BASE (which is
checked in kaslr_enabled()).