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From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ard Biesheuvel <ardb@kernel.org>,
	Mark-PK Tsai <mark-pk.tsai@mediatek.com>,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	linux-toolchains@vger.kernel.org,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-mediatek@lists.infradead.org,
	Matthias Brugger <matthias.bgg@gmail.com>,
	Matt Helsley <mhelsley@vmware.com>,
	Sami Tolvanen <samitolvanen@google.com>,
	yj.chiang@mediatek.com
Subject: Re: [PATCH] recordmcount: avoid using ABS symbol as reference
Date: Mon, 7 Jun 2021 09:44:33 -0400	[thread overview]
Message-ID: <20210607094433.473100d9@oasis.local.home> (raw)
In-Reply-To: <YL4GlbfMJiuLkRhR@hirez.programming.kicks-ass.net>

On Mon, 7 Jun 2021 13:44:21 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> There's an extended section header index section for just that. And
> recordmcount actually seems to use that as well.
> 
> I can't seem to find enough of the thread to figure out what the actual
> problem is though. The lore archive doesn't have anything prior to this
> message.
> 
> One should only use st_shndx when >SHN_UDEF and <SHN_LORESERVE. When
> SHN_XINDEX, then use .symtab_shndx.
> 
> Apparently you've found a case where neither is true? In that case
> objtool seems to use shndx 0. A matching recordmcount patch would be
> something like this.

Mark-PK,

Does the below patch fix it for you too (if you backport it to your
kernel). I much rather have recordmcount match objtool, as one day the
two will hopefully merge to one executable.

-- Steve


> 
> 
> diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h
> index f9b19524da11..d99cc0aed6fe 100644
> --- a/scripts/recordmcount.h
> +++ b/scripts/recordmcount.h
> @@ -194,13 +194,18 @@ static unsigned int get_symindex(Elf_Sym const *sym, Elf32_Word const *symtab,
>  	unsigned long offset;
>  	int index;
>  
> -	if (sym->st_shndx != SHN_XINDEX)
> +	if (sym->st_shndx > SHN_UDEF &&
> +	    sym->st_shndx < SHN_LORESERVE)
>  		return w2(sym->st_shndx);
>  
> -	offset = (unsigned long)sym - (unsigned long)symtab;
> -	index = offset / sizeof(*sym);
> +	if (sym->st_shndx == SHN_XINDEX) {
> +		offset = (unsigned long)sym - (unsigned long)symtab;
> +		index = offset / sizeof(*sym);
>  
> -	return w(symtab_shndx[index]);
> +		return w(symtab_shndx[index]);
> +	}
> +
> +	return 0;
>  }
>  
>  static unsigned int get_shnum(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0)


  parent reply	other threads:[~2021-06-07 13:44 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-07  2:38 [PATCH] recordmcount: avoid using ABS symbol as reference Mark-PK Tsai
2021-06-07  6:37 ` Ard Biesheuvel
2021-06-07  6:59   ` Mark-PK Tsai
2021-06-07  7:07     ` Ard Biesheuvel
2021-06-07  7:42       ` Mark-PK Tsai
2021-06-07  8:06         ` Mark-PK Tsai
2021-06-07  9:50           ` Ard Biesheuvel
2021-06-07 10:32             ` Mark-PK Tsai
2021-06-07 11:44             ` Peter Zijlstra
2021-06-07 13:18               ` Mark-PK Tsai
2021-06-07 13:44               ` Steven Rostedt [this message]
2021-06-07 17:31                 ` Mark-PK Tsai
2021-06-07 15:40               ` Peter Zijlstra
2021-06-08  1:15                 ` Mark-PK Tsai

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