> On Jan 17, 2023, at 7:36 PM, Christophe Leroy <christophe.leroy@xxxxxxxxxx> wrote: > > > > Le 17/01/2023 à 08:30, Christophe Leroy a écrit : >> >> >> 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. > > Hi Again, > > I tested again, the problem is still the same as one year ago: > > root@vgoip:~# ./bpftool prog > libbpf: elf: endianness mismatch in pid_iter_bpf. It seem to be not right ehdr->e_ident[EI_DATA]. Do we can print the real value? /* * e_ident[EI_DATA] */ #define ELFDATANONE 0 #define ELFDATA2LSB 1 #define ELFDATA2MSB 2 #define ELFDATANUM 3 bpf_object__elf_init: obj->efile.ehdr = ehdr = elf64_getehdr(elf); > libbpf: failed to initialize skeleton BPF object 'pid_iter_bpf': -4003 > Error: failed to open PID iterator skeleton > > root@vgoip:~# uname -a > Linux vgoip 6.2.0-rc3-02596-g1c2c9c13e256 #242 PREEMPT Tue Jan 17 > 09:36:08 CET 2023 ppc GNU/Linux On my pc, elf is little endian. # readelf -h tools/bpf/bpftool/pid_iter.bpf.o ELF Header: Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 Class: ELF64 Data: 2's complement, little endian # x86_64 Version: 1 (current) OS/ABI: UNIX - System V ABI Version: 0 Type: REL (Relocatable file) Machine: Linux BPF Version: 0x1 Entry point address: 0x0 Start of program headers: 0 (bytes into file) Start of section headers: 64832 (bytes into file) Flags: 0x0 Size of this header: 64 (bytes) Size of program headers: 0 (bytes) Number of program headers: 0 Size of section headers: 64 (bytes) Number of section headers: 13 Section header string table index: 1 > >> >> 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 ? >> >> Thanks >> Christophe >> > > > Christophe
