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SubjectRe: [PATCH bpf-next v2 1/2] bpf: Unify data extension operation of jited_ksyms and jited_linfo
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On 2022/5/7 4:52, John Fastabend wrote:
> Pu Lehui wrote:
>> We found that 32-bit environment can not print bpf line info due
>> to data inconsistency between jited_ksyms[0] and jited_linfo[0].
>>
>> For example:
>> jited_kyms[0] = 0xb800067c, jited_linfo[0] = 0xffffffffb800067c
>>
>> We know that both of them store bpf func address, but due to the
>> different data extension operations when extended to u64, they may
>> not be the same. We need to unify the data extension operations of
>> them.
>>
>> Signed-off-by: Pu Lehui <pulehui@huawei.com>
>> ---
>> kernel/bpf/syscall.c | 5 ++++-
>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
>> index e9e3e49c0eb7..18137ea5190d 100644
>> --- a/kernel/bpf/syscall.c
>> +++ b/kernel/bpf/syscall.c
>> @@ -3871,13 +3871,16 @@ static int bpf_prog_get_info_by_fd(struct file *file,
>> info.nr_jited_line_info = 0;
>> if (info.nr_jited_line_info && ulen) {
>> if (bpf_dump_raw_ok(file->f_cred)) {
>> + unsigned long jited_linfo_addr;
>> __u64 __user *user_linfo;
>> u32 i;
>>
>> user_linfo = u64_to_user_ptr(info.jited_line_info);
>> ulen = min_t(u32, info.nr_jited_line_info, ulen);
>> for (i = 0; i < ulen; i++) {
>> - if (put_user((__u64)(long)prog->aux->jited_linfo[i],
>> + jited_linfo_addr = (unsigned long)
>> + prog->aux->jited_linfo[i];
>> + if (put_user((__u64) jited_linfo_addr,
>> &user_linfo[i]))
>
> the logic is fine but i'm going to nitpick a bit this 4 lines is ugly
> just make it slightly longer than 80chars or use a shoarter name? For
> example,
>
> for (i = 0; i < ulen; i++) {
> unsigned long l;
>
> l = (unsigned long) prog->aux->jited_linfo[i];
> if (put_user((__u64) l, &user_linfo[i]))
>
> is much nicer -- no reason to smash single assignment across multiple
> lines. My $.02.
>

Okay, It sounds good. I will make change in next version. Thanks.

> Thanks,
> John
> .
>

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