> On Jan 17, 2023, at 11:59 PM, Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote: > > On 1/17/23 3:22 PM, Tonghao Zhang wrote: >>> On Jan 17, 2023, at 3:30 PM, Christophe Leroy <christophe.leroy@xxxxxxxxxx> wrote: >>> >>> >>> >>> Le 17/01/2023 à 06:30, Tonghao Zhang a écrit : >>>> >>>> >>>>> On Jan 9, 2023, at 4:15 PM, Christophe Leroy <christophe.leroy@xxxxxxxxxx> wrote: >>>>> >>>>> >>>>> >>>>> Le 06/01/2023 à 16:37, Daniel Borkmann a écrit : >>>>>> On 1/5/23 6:53 PM, Christophe Leroy wrote: >>>>>>> Le 05/01/2023 à 04:06, tong@xxxxxxxxxxxxx a écrit : >>>>>>>> From: Tonghao Zhang <tong@xxxxxxxxxxxxx> >>>>>>>> >>>>>>>> The x86_64 can't dump the valid insn in this way. A test BPF prog >>>>>>>> which include subprog: >>>>>>>> >>>>>>>> $ llvm-objdump -d subprog.o >>>>>>>> Disassembly of section .text: >>>>>>>> 0000000000000000 <subprog>: >>>>>>>> 0: 18 01 00 00 73 75 62 70 00 00 00 00 72 6f 67 00 r1 >>>>>>>> = 29114459903653235 ll >>>>>>>> 2: 7b 1a f8 ff 00 00 00 00 *(u64 *)(r10 - 8) = r1 >>>>>>>> 3: bf a1 00 00 00 00 00 00 r1 = r10 >>>>>>>> 4: 07 01 00 00 f8 ff ff ff r1 += -8 >>>>>>>> 5: b7 02 00 00 08 00 00 00 r2 = 8 >>>>>>>> 6: 85 00 00 00 06 00 00 00 call 6 >>>>>>>> 7: 95 00 00 00 00 00 00 00 exit >>>>>>>> Disassembly of section raw_tp/sys_enter: >>>>>>>> 0000000000000000 <entry>: >>>>>>>> 0: 85 10 00 00 ff ff ff ff call -1 >>>>>>>> 1: b7 00 00 00 00 00 00 00 r0 = 0 >>>>>>>> 2: 95 00 00 00 00 00 00 00 exit >>>>>>>> >>>>>>>> kernel print message: >>>>>>>> [ 580.775387] flen=8 proglen=51 pass=3 image=ffffffffa000c20c >>>>>>>> from=kprobe-load pid=1643 >>>>>>>> [ 580.777236] JIT code: 00000000: cc cc cc cc cc cc cc cc cc cc cc >>>>>>>> cc cc cc cc cc >>>>>>>> [ 580.779037] JIT code: 00000010: cc cc cc cc cc cc cc cc cc cc cc >>>>>>>> cc cc cc cc cc >>>>>>>> [ 580.780767] JIT code: 00000020: cc cc cc cc cc cc cc cc cc cc cc >>>>>>>> cc cc cc cc cc >>>>>>>> [ 580.782568] JIT code: 00000030: cc cc cc >>>>>>>> >>>>>>>> $ bpf_jit_disasm >>>>>>>> 51 bytes emitted from JIT compiler (pass:3, flen:8) >>>>>>>> ffffffffa000c20c + <x>: >>>>>>>> 0: int3 >>>>>>>> 1: int3 >>>>>>>> 2: int3 >>>>>>>> 3: int3 >>>>>>>> 4: int3 >>>>>>>> 5: int3 >>>>>>>> ... >>>>>>>> >>>>>>>> Until bpf_jit_binary_pack_finalize is invoked, we copy rw_header to >>>>>>>> header >>>>>>>> and then image/insn is valid. BTW, we can use the "bpftool prog dump" >>>>>>>> JITed instructions. >>>>>>> >>>>>>> NACK. >>>>>>> >>>>>>> Because the feature is buggy on x86_64, you remove it for all >>>>>>> architectures ? >>>>>>> >>>>>>> On powerpc bpf_jit_enable == 2 works and is very usefull. >>>>>>> >>>>>>> Last time I tried to use bpftool on powerpc/32 it didn't work. I don't >>>>>>> remember the details, I think it was an issue with endianess. Maybe it >>>>>>> is fixed now, but it needs to be verified. >>>>>>> >>>>>>> So please, before removing a working and usefull feature, make sure >>>>>>> there is an alternative available to it for all architectures in all >>>>>>> configurations. >>>>>>> >>>>>>> Also, I don't think bpftool is usable to dump kernel BPF selftests. >>>>>>> That's vital when a selftest fails if you want to have a chance to >>>>>>> understand why it fails. >>>>>> >>>>>> If this is actively used by JIT developers and considered useful, I'd be >>>>>> ok to leave it for the time being. Overall goal is to reach feature parity >>>>>> among (at least major arch) JITs and not just have most functionality only >>>>>> available on x86-64 JIT. Could you however check what is not working with >>>>>> bpftool on powerpc/32? Perhaps it's not too much effort to just fix it, >>>>>> but details would be useful otherwise 'it didn't work' is too fuzzy. >>>>> >>>>> Sure I will try to test bpftool again in the coming days. >>>>> >>>>> Previous discussion about that subject is here: >>>>> https://patchwork.kernel.org/project/linux-riscv/patch/20210415093250.3391257-1-Jianlin.Lv@xxxxxxx/#24176847= >>>> Hi Christophe >>>> Any progress? We discuss to deprecate the bpf_jit_enable == 2 in 2021, but bpftool can not run on powerpc. >>>> Now can we fix this issue? >>> >>> Hi Tong, >>> >>> I have started to look at it but I don't have any fruitfull feedback yet. >>> >>> In the meantime, were you able to confirm that bpftool can also be used >>> to dump jitted tests from test_bpf.ko module on x86_64 ? In that can you >>> tell me how to proceed ? >> Now I do not test, but we can dump the insn after bpf_prog_select_runtime in test_bpf.ko. bpf_map_get_info_by_fd can copy the insn to userspace, but we can >> dump them in test_bpf.ko in the same way. > > Issue is that these progs are not consumable from userspace (and therefore not bpftool). > it's just simple bpf_prog_alloc + copy of test insns + bpf_prog_select_runtime() to test > JITs (see generate_filter()). Some of them could be converted over to test_verifier, but > not all might actually pass verifier, iirc. Don't think it's a good idea to allow exposing > them via fd tbh. Hi I mean that, can we invoke the bpf_jit_dump in test_bpf.ko directly ?. bpf_prog_get_info_by_fd copy the insn to userspace, but we only dump insn in test_bpf.ko if (bpf_dump_raw_ok(file->f_cred)) {// code copied from bpf_prog_get_info_by_fd, not tested /* for multi-function programs, copy the JITed * instructions for all the functions */ if (prog->aux->func_cnt) { for (i = 0; i < prog->aux->func_cnt; i++) { len = prog->aux->func[i]->jited_len; img = (u8 *) prog->aux->func[i]->bpf_func; bpf_jit_dump(1, len, 1, img); } } else { bpf_jit_dump(1, ulen, 1, prog->bpf_func); } }
