linux-kernel - Re: [PATCH] tools lib bpf: Use official ELF e

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Date:	Tue, 26 Jul 2016 10:15:30 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	<acme@...nel.org>
CC:	<lizefan@...wei.com>, <linux-kernel@...r.kernel.org>,
	<pi3orama@....com>
Subject: Re: [PATCH] tools lib bpf: Use official ELF e_machine value

Hi Arnaldo,

Please don't forget this patch.

Thank you.

On 2016/7/19 5:37, Alexei Starovoitov wrote:
> On Mon, Jul 18, 2016 at 06:01:08AM +0000, Wang Nan wrote:
>> New LLVM will issue newly assigned EM_BPF machine code. The new code
>> will be propogated to glibc and libelf.
>>
>> This patch introduces the new machine code to libbpf.
>>
>> Signed-off-by: Wang Nan <wangnan0@...wei.com>
>> Cc: Alexei Starovoitov <ast@...nel.org>
>> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
>> Cc: Zefan Li <lizefan@...wei.com>
>> Cc: pi3orama@....com
>> ---
>>   tools/lib/bpf/libbpf.c | 7 ++++++-
>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>> index 32e6b6b..b699aea 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -37,6 +37,10 @@
>>   #include "libbpf.h"
>>   #include "bpf.h"
>>   
>> +#ifndef EM_BPF
>> +#define EM_BPF 247
>> +#endif
>> +
>>   #define __printf(a, b)	__attribute__((format(printf, a, b)))
>>   
>>   __printf(1, 2)
>> @@ -439,7 +443,8 @@ static int bpf_object__elf_init(struct bpf_object *obj)
>>   	}
>>   	ep = &obj->efile.ehdr;
>>   
>> -	if ((ep->e_type != ET_REL) || (ep->e_machine != 0)) {
>> +	/* Old LLVM set e_machine to EM_NONE */
>> +	if ((ep->e_type != ET_REL) || (ep->e_machine && (ep->e_machine != EM_BPF))) {
> Thanks for the fix. Didn't realize we already check for zero here.
> btw EM_BPF will be in llvm 3.9 release.
>
> Acked-by: Alexei Starovoitov <ast@...nel.org>
>