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

From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Christophe Leroy <christophe.leroy@csgroup.eu>,
	Peter Zijlstra <peterz@infradead.org>
Cc: "aik@ozlabs.ru" <aik@ozlabs.ru>,
	Chen Zhongjin <chenzhongjin@huawei.com>,
	"jpoimboe@redhat.com" <jpoimboe@redhat.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
	"mbenes@suse.cz" <mbenes@suse.cz>,
	"rostedt@goodmis.org" <rostedt@goodmis.org>,
	Sathvika Vasireddy <sv@linux.ibm.com>,
	Sathvika Vasireddy <sv@linux.vnet.ibm.com>
Subject: Re: [RFC PATCH 4/4] objtool/powerpc: Add --mcount specific implementation
Date: Fri, 17 Jun 2022 19:34:48 +0530	[thread overview]
Message-ID: <1655474054.lvnbqfz64f.naveen@linux.ibm.com> (raw)
In-Reply-To: <d095fe9d-e713-def1-6096-540c0d0da298@csgroup.eu>

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