Subject: Re: [PATCH v1 05/10] asm-generic: Define 'funct_descr_t' to commonly describe function descriptors

From: Kees Cook <[email-masked]>
Date: Wed, 13 Oct 2021 00:01:48 -0700

On Mon, Oct 11, 2021 at 05:25:32PM +0200, Christophe Leroy wrote:
> We have three architectures using function descriptors, each with its
> own name.
> 
> Add a common typedef that can be used in generic code.
> 
> Also add a stub typedef for architecture without function descriptors,

nit: funct_descr_t reads weird to me. why not func_desc_t ? Either way:

Reviewed-by: Kees Cook <[email-masked]>

> to avoid a forest of #ifdefs.
> 
> Signed-off-by: Christophe Leroy <[email-masked]>
> ---
>  arch/ia64/include/asm/sections.h    | 1 +
>  arch/parisc/include/asm/sections.h  | 1 +
>  arch/powerpc/include/asm/sections.h | 1 +
>  include/asm-generic/sections.h      | 3 +++
>  4 files changed, 6 insertions(+)
> 
> diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
> index 80f5868afb06..929b5c535620 100644
> --- a/arch/ia64/include/asm/sections.h
> +++ b/arch/ia64/include/asm/sections.h
> @@ -8,6 +8,7 @@
>   */
>  
>  #define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> +typedef struct fdesc funct_descr_t;
>  
>  #include <linux/elf.h>
>  #include <linux/uaccess.h>
> diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
> index 2e781ee19b66..329e80f7af0a 100644
> --- a/arch/parisc/include/asm/sections.h
> +++ b/arch/parisc/include/asm/sections.h
> @@ -4,6 +4,7 @@
>  
>  #ifdef CONFIG_64BIT
>  #define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> +typedef Elf64_Fdesc funct_descr_t;
>  #endif
>  
>  /* nothing to see, move along */
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index b7f1ba04e756..d0d5287fa568 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -10,6 +10,7 @@
>  
>  #ifdef PPC64_ELF_ABI_v1
>  #define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> +typedef struct ppc64_opd_entry funct_descr_t;
>  #endif
>  
>  #include <asm-generic/sections.h>
> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
> index 1db5cfd69817..436412d94054 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -63,6 +63,9 @@ extern __visible const void __nosave_begin, __nosave_end;
>  #else
>  #define dereference_function_descriptor(p) ((void *)(p))
>  #define dereference_kernel_function_descriptor(p) ((void *)(p))
> +typedef struct {
> +	unsigned long addr;
> +} funct_descr_t;
>  #endif
>  
>  /* random extra sections (if any).  Override
> -- 
> 2.31.1
> 

-- 
Kees Cook