On 04/21/2017, 09:32 PM, Alexei Starovoitov wrote:
> On Fri, Apr 21, 2017 at 04:12:43PM +0200, Jiri Slaby wrote:
>> Do not use a custom macro FUNC for starts of the global functions, use
>> ENTRY instead.
>>
>> And while at it, annotate also ends of the functions by ENDPROC.
>>
>> Signed-off-by: Jiri Slaby <jsl...@suse.cz>
>> Cc: "David S. Miller" <da...@davemloft.net>
>> Cc: Alexey Kuznetsov <kuz...@ms2.inr.ac.ru>
>> Cc: James Morris <jmor...@namei.org>
>> Cc: Hideaki YOSHIFUJI <yoshf...@linux-ipv6.org>
>> Cc: Patrick McHardy <ka...@trash.net>
>> Cc: Thomas Gleixner <t...@linutronix.de>
>> Cc: Ingo Molnar <mi...@redhat.com>
>> Cc: "H. Peter Anvin" <h...@zytor.com>
>> Cc: x...@kernel.org
>> Cc: net...@vger.kernel.org
>> ---
>> arch/x86/net/bpf_jit.S | 32 ++++++++++++++++++--------------
>> 1 file changed, 18 insertions(+), 14 deletions(-)
>>
>> diff --git a/arch/x86/net/bpf_jit.S b/arch/x86/net/bpf_jit.S
>> index f2a7faf4706e..762c29fb8832 100644
>> --- a/arch/x86/net/bpf_jit.S
>> +++ b/arch/x86/net/bpf_jit.S
>> @@ -23,16 +23,12 @@
>> 32 /* space for rbx,r13,r14,r15 */ + \
>> 8 /* space for skb_copy_bits */)
>>
>> -#define FUNC(name) \
>> - .globl name; \
>> - .type name, @function; \
>> - name:
>> -
>> -FUNC(sk_load_word)
>> +ENTRY(sk_load_word)
>> test %esi,%esi
>> js bpf_slow_path_word_neg
>> +ENDPROC(sk_load_word)
>
> this doens't look right.
> It will add alignment nops in critical paths of these pseudo functions.
> I'm also not sure whether it will still work afterwards.
> Was it tested?
> I'd prefer if this code kept as-is.
It cannot stay as-is simply because we want to know where the functions
end to inject debuginfo properly. The code above does not warrant for
any exception.
Executing a nop takes a little and having externally-callable functions
aligned can actually help performance (no, I haven't measured nor tested
the code). But sure, the tool is generic, so I can introduce a local
macros to avoid alignments in the functions:
#define BPF_FUNC_START_LOCAL(name) \
SYM_START(name, SYM_V_LOCAL, SYM_A_NONE)
#define BPF_FUNC_START(name) \
SYM_START(name, SYM_V_GLOBAL, SYM_A_NONE)
#define BPF_FUNC_END(name) SYM_FUNC_END(name)
thanks,
--
js
suse labs
