Message-ID: <4D086C1A.5000907@redhat.com>
Date: Wed, 15 Dec 2010 15:19:54 +0800
From: Cong Wang <amwang@redhat.com>
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To: "Suzuki K. Poulose" <suzuki@in.ibm.com>
CC: linux-kernel@vger.kernel.org,
        Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>,
        Christoph Hellwig <hch@lst.de>, Masami Hiramatsu <mhiramat@redhat.com>,
        Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
        Daisuke HATAYAMA <d.hatayama@jp.fujitsu.com>,
        Andi Kleen <andi@firstfloor.org>, Roland McGrath <roland@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [Patch 18/21] Generate the data sections for ELF Core
References: <20101214152259.67896960@suzukikp> <20101214155200.06b56e57@suzukikp>
In-Reply-To: <20101214155200.06b56e57@suzukikp>
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于 2010年12月14日 18:22, Suzuki K. Poulose 写道:
...
> +	/*
> +	 * Read from the vma segments
> +	 * a. verify if the *fpos is within a phdr
> +	 * b. Use access_process_vm() to get data page by page
> +	 * c. copy_to_user into user buffer
> +	 */


This kind of comments is useless, "code tells you how, comments tell you why."


> +
> +	while (buflen) {
> +		size_t bufsz, offset, bytes;
> +		char *readbuf;
> +		struct elf_phdr *phdr = get_pos_elfphdr(cp, *fpos);
> +
> +		if (!phdr)
> +			break;
> +
> +		bufsz = (buflen>  PAGE_SIZE) ? PAGE_SIZE : buflen;
> +		readbuf = kmalloc(bufsz, GFP_KERNEL);
> +		if (!readbuf) {
> +			ret = -ENOMEM;
> +			goto out;
> +		}
> +
> +		offset = *fpos - phdr->p_offset;
> +		bytes = access_process_vm(cp->task, (phdr->p_vaddr + offset),
> +						readbuf, bufsz, 0);
> +		if (!bytes) {
> +			ret = -EIO;
> +			goto out;


Why you don't kfree(readbuf) here?

> +		}
> +		if (copy_to_user(buffer, readbuf, bytes)) {
> +			ret = -EFAULT;
> +			kfree(readbuf);
> +			goto out;
> +		} else
> +			acc += bytes;
> +
> +		kfree(readbuf);
> +		buflen -= bytes;
> +		buffer += bytes;
> +		*fpos += bytes;
> +	}
> +
> +	/* Fill extnum section header if present */
> +	if (buflen&&
> +		elf_hdr->e_shoff&&
> +		(*fpos>= elf_hdr->e_shoff)&&
> +		(*fpos<  (elf_hdr->e_shoff + sizeof(struct elf_shdr)))) {


This indention seems ugly.

> +
> +		off_t offset = *fpos - elf_hdr->e_shoff;

Are you sure it is 'off_t' not 'loff_t'?

> +		size_t shdrsz = sizeof(struct elf_shdr) - offset;
> +
> +		shdrsz = (buflen<  shdrsz) ? buflen : shdrsz;
> +		if (copy_to_user(buffer, ((char *)cp->shdr) + offset, shdrsz)) {
> +			ret = -EFAULT;
> +			goto out;
> +		} else {
> +			acc += shdrsz;
> +			buflen -= shdrsz;
> +			buffer += shdrsz;
> +		}
> +	}
>
> +done:
> +	ret = acc;
>   out:
>   	return ret;
>   }

Thanks.
--
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