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

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Date:   Thu, 16 Jun 2022 14:06:33 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Sathvika Vasireddy <sv@...ux.vnet.ibm.com>,
        "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>
Subject: Re: [RFC PATCH 4/4] objtool/powerpc: Add --mcount specific
 implementation



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);
}