linux-kernel - Re: [PATCH 2/2] livepatch: Fix the bug if the function name is larger than KSYM_NAME

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Message-ID: <20150413231305.GD4412@treble.hsd1.ky.comcast.net>
Date:	Mon, 13 Apr 2015 18:13:05 -0500
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Minfei Huang <minfei.huang@...mail.com>
Cc:	sjenning@...hat.com, jkosina@...e.cz, vojtech@...e.cz,
	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] livepatch: Fix the bug if the function name is
 larger than KSYM_NAME_LEN-1

On Sun, Apr 12, 2015 at 09:15:54PM +0800, Minfei Huang wrote:
> For now, the kallsyms will only store the first (KSYM_NAME_LEN-1). The
> kallsyms name is same for the function which first (KSYM_NAME_LEN-1) is
> same, but the rest is not.
> 
> Then function will never be patched, although function name and address
> are provided both. The reason caused this bug is livepatch cannt
> recognize the function name.
> 
> Now, livepatch will verify the function name with first (KSYM_NAME_LEN-1)
> and address, if provided. Once they are matched, we can confirm that the
> patched function is found.

>From scripts/kallsyms.c:

	if (strlen(str) > KSYM_NAME_LEN) {
		fprintf(stderr, "Symbol %s too long for kallsyms (%zu vs %d).\n"
				"Please increase KSYM_NAME_LEN both in kernel and kallsyms.c\n",
			str, strlen(str), KSYM_NAME_LEN);
		return -1;
	}

So I think such a long symbol name wouldn't be added to the kallsyms
database in the first place.

-- 
Josh
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