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

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Date:   Wed, 13 Oct 2021 09:23:56 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Kees Cook <keescook@...omium.org>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-ia64@...r.kernel.org, linux-parisc@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v1 05/10] asm-generic: Define 'funct_descr_t' to commonly
 describe function descriptors



Le 13/10/2021 à 09:01, Kees Cook a écrit :
> 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:

func_desc_t already exists in powerpc. I have a patch to remove it as it 
is redundant with struct ppc64_opd_entry, but I didnt' want to include 
it in this series.

But after all I can add it in this series, I'll add it in v2.

Christophe

> 
> Reviewed-by: Kees Cook <keescook@...omium.org>
> 
> 
>> to avoid a forest of #ifdefs.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
>> ---
>>   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
>>
>