linux-kernel - Re: [RFC PATCH v4 09/29] bpf tools: Collect version and license from ELF sections

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Date:	Thu, 28 May 2015 11:34:37 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>
CC:	<paulus@...ba.org>, <a.p.zijlstra@...llo.nl>, <mingo@...hat.com>,
	<acme@...nel.org>, <namhyung@...nel.org>, <jolsa@...nel.org>,
	<dsahern@...il.com>, <daniel@...earbox.net>,
	<brendan.d.gregg@...il.com>, <masami.hiramatsu.pt@...achi.com>,
	<lizefan@...wei.com>, <linux-kernel@...r.kernel.org>,
	<pi3orama@....com>
Subject: Re: [RFC PATCH v4 09/29] bpf tools: Collect version and license from
 ELF sections



On 2015/5/28 9:48, Alexei Starovoitov wrote:
> On Wed, May 27, 2015 at 05:19:44AM +0000, Wang Nan wrote:
>> Expand bpf_obj_elf_collect() to collect license and kernel version
>> information in eBPF object file. eBPF object file should have a section
>> named 'license', which contains a string. It should also have a section
>> named 'version', contains a u32 LINUX_VERSION_CODE.
>>
>> bpf_obj_validate() is introduced to validate object file after loaded.
>> Currently it only check existance of 'version' section.
>>
>> Signed-off-by: Wang Nan <wangnan0@...wei.com>
>> ---
> ...
>> +static int
>> +bpf_object__init_kversion(struct bpf_object *obj,
>> +			  void *data, size_t size)
>> +{
>> +	u32 kver;
>> +	if (size < sizeof(kver)) {
> shouldn't it be '!=' ?

Is it possible that LLVM pads 'version' section so the size of it becomes
longer than sizeof(u32)?

Thank you.

>> +		pr_warning("invalid kver section in %s\n", obj->path);
>> +		return -EINVAL;
>> +	}
>> +	memcpy(&kver, data, sizeof(kver));
>> +	obj->kern_version = kver;
>> +	pr_debug("kernel version of %s is %x\n", obj->path,
>> +		 obj->kern_version);
>> +	return 0;
>> +}
>> +


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