On 03/21/2018 07:37 PM, Jiri Olsa wrote:
> On Wed, Mar 21, 2018 at 05:25:33PM +0000, Quentin Monnet wrote:
>> 2018-03-21 16:02 UTC+0100 ~ Jiri Olsa <jo...@kernel.org>
>>> We use print_bpf_insn in user space (bpftool and soon perf),
>>> so it'd be nice to keep it generic and strip it off the kernel
>>> struct bpf_verifier_env argument.
>>>
>>> This argument can be safely removed, because its users can
>>> use the struct bpf_insn_cbs::private_data to pass it.
>>>
>>> Signed-off-by: Jiri Olsa <jo...@kernel.org>
>>> ---
>>> kernel/bpf/disasm.c | 52
>>> +++++++++++++++++++++++++--------------------------
>>> kernel/bpf/disasm.h | 5 +----
>>> kernel/bpf/verifier.c | 6 +++---
>>> 3 files changed, 30 insertions(+), 33 deletions(-)
>>
>> [...]
>>
>>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
>>> index c6eff108aa99..9f27d3fa7259 100644
>>> --- a/kernel/bpf/verifier.c
>>> +++ b/kernel/bpf/verifier.c
>>> @@ -202,8 +202,7 @@ EXPORT_SYMBOL_GPL(bpf_verifier_log_write);
>>> * generic for symbol export. The function was renamed, but not the calls
>>> in
>>> * the verifier to avoid complicating backports. Hence the alias below.
>>> */
>>> -static __printf(2, 3) void verbose(struct bpf_verifier_env *env,
>>> - const char *fmt, ...)
>>> +static __printf(2, 3) void verbose(void *private_data, const char *fmt,
>>> ...)
>>> __attribute__((alias("bpf_verifier_log_write")));
>>
>> Just as a note, verbose() will be aliased to a function whose prototype
>> differs (bpf_verifier_log_write() still expects a struct
>> bpf_verifier_env as its first argument). I am not so familiar with
>> function aliases, could this change be a concern?
>
> yea, but as it was pointer for pointer switch I did not
> see any problem with that.. I'll check more
Ok, holding off for now until we have clarification. Other option could also
be to make it void *private_data everywhere and for the kernel writer then
do struct bpf_verifier_env *env = private_data.
