kern/189845: [kvm] UnNecessary Copy of Error Buffer in _kvm_open

Jilles Tjoelker jilles at stack.nl
Sun May 18 22:10:01 UTC 2014


The following reply was made to PR kern/189845; it has been noted by GNATS.

From: Jilles Tjoelker <jilles at stack.nl>
To: bug-followup at FreeBSD.org, myron.walker at emc.com
Cc:  
Subject: Re: kern/189845: [kvm] UnNecessary Copy of Error Buffer in _kvm_open
Date: Mon, 19 May 2014 00:05:07 +0200

 In FreeBSD PR kern/189845, you wrote:
 > _kvm_open in libkvm always returns 0 on a failure. So writing a
 > message to kd is pointless because it is immediately passed to
 > kvm_close() and the memory is freed. Se the code snippet below from
 > _kvm_open.
 
 >	/*
 >	 * Copy out the error if doing sane error semantics.
 >	 */
 >	if (errout != 0)
 >		strlcpy(errout, kd->errbuf, _POSIX2_LINE_MAX);
 >	(void)kvm_close(kd);
 >	return (0);
 
 The error message is written to errout (if _kvm_open() was called via
 kvm_openfiles()), which stays around.
 
 It may be a bit strange to write an error message to kd->errbuf first
 and then copy it to the user's buffer, but it works fine and may
 slightly reduce code duplication from the two types of error handling
 available to the API client.
 
 -- 
 Jilles Tjoelker


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