linux-kernel - Re: [RFC PATCH 4/4] objtool/powerpc: Add --mcount specific implementation

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Message-Id: <1655474054.lvnbqfz64f.naveen@linux.ibm.com>
Date:   Fri, 17 Jun 2022 19:34:48 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     "aik@...abs.ru" <aik@...abs.ru>,
        Chen Zhongjin <chenzhongjin@...wei.com>,
        "jpoimboe@...hat.com" <jpoimboe@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "mbenes@...e.cz" <mbenes@...e.cz>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        Sathvika Vasireddy <sv@...ux.ibm.com>,
        Sathvika Vasireddy <sv@...ux.vnet.ibm.com>
Subject: Re: [RFC PATCH 4/4] objtool/powerpc: Add --mcount specific
 implementation

Christophe Leroy wrote:
> 
> 
> Le 16/06/2022 à 15:57, Peter Zijlstra a écrit :
>> On Thu, Jun 16, 2022 at 01:40:34PM +0000, Christophe Leroy wrote:
>>> sizeof(u64) is always 8 by definition.
>>>
>>> So if size is 8 we are working on a binary file for a 64 bits target, if
>>> not it means we are working for a 32 bits target.
>> 
>> Cross-builds invalidate this I think. Best to look at something like:
>> 
>>    elf->ehdr.e_ident[EI_CLASS] == ELFCLASS32
>> 
>> 
> 
> Yes that's what it does indirectly:
> 
> 	int size = elf_class_size(elf);
> 
> 
> With
> 
> static inline int elf_class_size(struct elf *elf)
> {
> 	if (elf->ehdr.e_ident[EI_CLASS] == ELFCLASS32)
> 		return sizeof(u32);
> 	else
> 		return sizeof(u64);
> }

Ok, those come from the below patch:
https://lore.kernel.org/all/c4b06b5b314183d85615765a5ce421a057674bd8.1653398233.git.christophe.leroy@csgroup.eu/T/#u

I guess it would have been clearer if 'size' was named differently: 
'addr_size' perhaps?


- Naveen