Re: [RFC PATCH bpf-next 0/6] bpf, printk: add BTF-based type printing
From: Arnaldo Carvalho de Melo
Date: Mon Apr 20 2020 - 16:54:32 EST
Em Sat, Apr 18, 2020 at 09:05:36AM -0700, Alexei Starovoitov escreveu:
> On Fri, Apr 17, 2020 at 11:42:34AM +0100, Alan Maguire wrote:
> > ...gives us:
> >
> > {{{.next=00000000c7916e9c,.prev=00000000c7916e9c,{.dev=00000000c7916e9c|.dev_scratch=0}}|.rbnode={.__rb_parent_color=0,
> This is unreadable.
> I like the choice of C style output, but please format it similar to drgn. Like:
> *(struct task_struct *)0xffff889ff8a08000 = {
> .thread_info = (struct thread_info){
> .flags = (unsigned long)0,
> .status = (u32)0,
> },
> .state = (volatile long)1,
> .stack = (void *)0xffffc9000c4dc000,
> .usage = (refcount_t){
> .refs = (atomic_t){
> .counter = (int)2,
> },
> },
> .flags = (unsigned int)4194560,
> .ptrace = (unsigned int)0,
> I like Arnaldo's idea as well, but I prefer zeros to be dropped by default.
> Just like %d doesn't print leading zeros by default.
> "%p0<struct sk_buff>" would print them.
I was thinking about another way to compress the output of a given data
structure someone is tracking, having to print it from time to time,
which is to store a copy of the struct as you print it and then, when
printing it again, print just its pointer, i.e. that:
*(struct task_struct *)0xffff889ff8a08000 = {
Line, then just printing the fields that changed, say just that refcount
was bumped, so it first print:
*(struct task_struct *)0xffff889ff8a08000 = {
.thread_info = (struct thread_info){
.flags = (unsigned long)0,
.status = (u32)0,
},
.state = (volatile long)1,
.stack = (void *)0xffffc9000c4dc000,
.usage = (refcount_t){
.refs = (atomic_t){
.counter = (int)2,
},
},
.flags = (unsigned int)4194560,
.ptrace = (unsigned int)0,
Then, the next time it would print:
*(struct task_struct *)0xffff889ff8a08000 = {
.usage = (refcount_t){
.refs = (atomic_t){
.counter = (int)3,
},
},
},
- Arnaldo