Le 18/01/2023 à 03:21, Alexei Starovoitov a écrit : > On Tue, Jan 17, 2023 at 6:13 PM Tonghao Zhang <tong@xxxxxxxxxxxxx> wrote: >> >> >> >>> 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); >> } >> } > > Let's not reinvent the wheel. > bpftool prog dump jited > is our supported command. > ppc issue with bpftool is related to endianness of embedded skeleton. > which means that none of the bpftool prog commands work on ppc. > It's a bigger issue to address with cross compilation of bpftool. > > bpftool supports gnu and llvm disassembler. It retrieves and > prints BTF, line info and source code along with asm. > The user experience is at different level comparing to bpf_jit_dump. Hi Alexei, Fair enough, we are going to try and fix bpftool. But for test_bpf.ko module, how do you use bpftool to dump the BPF tests ? Even on x86 I have not been able to use bpftool for that until now. Can you tell me how you do ? Thanks Christophe
