Le 17/01/2023 à 15:18, Tonghao Zhang a écrit : > > >> 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 > Yes, must be something wrong with the build, I get same as you : $ LANG= readelf -h 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 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: 34704 (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 Whereas I expect the same as bpftool I suppose, which is : $ LANG= readelf -h bpftool ELF Header: Magic: 7f 45 4c 46 01 02 01 00 00 00 00 00 00 00 00 00 Class: ELF32 Data: 2's complement, big endian Version: 1 (current) OS/ABI: UNIX - System V ABI Version: 0 Type: EXEC (Executable file) Machine: PowerPC Version: 0x1 Entry point address: 0x100027d0 Start of program headers: 52 (bytes into file) Start of section headers: 1842896 (bytes into file) Flags: 0x0 Size of this header: 52 (bytes) Size of program headers: 32 (bytes) Number of program headers: 9 Size of section headers: 40 (bytes) Number of section headers: 39 Section header string table index: 38 Thanks Christophe
