[bpf-next v2] bpf: drop deprecated bpf_jit_enable == 2
Christophe Leroy
christophe.leroy at csgroup.eu
Fri Jan 6 04:53:14 AEDT 2023
Le 05/01/2023 à 04:06, tong at infragraf.org a écrit :
> From: Tonghao Zhang <tong at infragraf.org>
>
> 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.
Thanks
Christophe
>
> Signed-off-by: Tonghao Zhang <tong at infragraf.org>
> Suggested-by: Alexei Starovoitov <ast at kernel.org>
> Cc: Alexei Starovoitov <ast at kernel.org>
> Cc: Daniel Borkmann <daniel at iogearbox.net>
> Cc: Andrii Nakryiko <andrii at kernel.org>
> Cc: Martin KaFai Lau <martin.lau at linux.dev>
> Cc: Song Liu <song at kernel.org>
> Cc: Yonghong Song <yhs at fb.com>
> Cc: John Fastabend <john.fastabend at gmail.com>
> Cc: KP Singh <kpsingh at kernel.org>
> Cc: Stanislav Fomichev <sdf at google.com>
> Cc: Hao Luo <haoluo at google.com>
> Cc: Jiri Olsa <jolsa at kernel.org>
> Cc: Hou Tao <houtao1 at huawei.com>
> ---
> Documentation/admin-guide/sysctl/net.rst | 1 +
> Documentation/networking/filter.rst | 98 +------
> arch/arm/net/bpf_jit_32.c | 4 -
> arch/arm64/net/bpf_jit_comp.c | 4 -
> arch/loongarch/net/bpf_jit.c | 4 -
> arch/mips/net/bpf_jit_comp.c | 3 -
> arch/powerpc/net/bpf_jit_comp.c | 11 -
> arch/riscv/net/bpf_jit_core.c | 3 -
> arch/s390/net/bpf_jit_comp.c | 4 -
> arch/sparc/net/bpf_jit_comp_32.c | 3 -
> arch/sparc/net/bpf_jit_comp_64.c | 13 -
> arch/x86/net/bpf_jit_comp.c | 3 -
> arch/x86/net/bpf_jit_comp32.c | 3 -
> net/core/sysctl_net_core.c | 12 +-
> tools/bpf/.gitignore | 1 -
> tools/bpf/Makefile | 10 +-
> tools/bpf/bpf_jit_disasm.c | 332 -----------------------
> 17 files changed, 9 insertions(+), 500 deletions(-)
> delete mode 100644 tools/bpf/bpf_jit_disasm.c
>
> diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst
> index 6394f5dc2303..82ca05ca6ed0 100644
> --- a/Documentation/admin-guide/sysctl/net.rst
> +++ b/Documentation/admin-guide/sysctl/net.rst
> @@ -88,6 +88,7 @@ Values:
> - 0 - disable the JIT (default value)
> - 1 - enable the JIT
> - 2 - enable the JIT and ask the compiler to emit traces on kernel log.
> + (deprecated since v6.3, use ``bpftool prog dump jited id <id>`` instead)
>
> bpf_jit_harden
> --------------
> diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
> index f69da5074860..5f51c050e88f 100644
> --- a/Documentation/networking/filter.rst
> +++ b/Documentation/networking/filter.rst
> @@ -520,102 +520,8 @@ been previously enabled by root::
>
> echo 1 > /proc/sys/net/core/bpf_jit_enable
>
> -For JIT developers, doing audits etc, each compile run can output the generated
> -opcode image into the kernel log via::
> -
> - echo 2 > /proc/sys/net/core/bpf_jit_enable
> -
> -Example output from dmesg::
> -
> - [ 3389.935842] flen=6 proglen=70 pass=3 image=ffffffffa0069c8f
> - [ 3389.935847] JIT code: 00000000: 55 48 89 e5 48 83 ec 60 48 89 5d f8 44 8b 4f 68
> - [ 3389.935849] JIT code: 00000010: 44 2b 4f 6c 4c 8b 87 d8 00 00 00 be 0c 00 00 00
> - [ 3389.935850] JIT code: 00000020: e8 1d 94 ff e0 3d 00 08 00 00 75 16 be 17 00 00
> - [ 3389.935851] JIT code: 00000030: 00 e8 28 94 ff e0 83 f8 01 75 07 b8 ff ff 00 00
> - [ 3389.935852] JIT code: 00000040: eb 02 31 c0 c9 c3
> -
> -When CONFIG_BPF_JIT_ALWAYS_ON is enabled, bpf_jit_enable is permanently set to 1 and
> -setting any other value than that will return in failure. This is even the case for
> -setting bpf_jit_enable to 2, since dumping the final JIT image into the kernel log
> -is discouraged and introspection through bpftool (under tools/bpf/bpftool/) is the
> -generally recommended approach instead.
> -
> -In the kernel source tree under tools/bpf/, there's bpf_jit_disasm for
> -generating disassembly out of the kernel log's hexdump::
> -
> - # ./bpf_jit_disasm
> - 70 bytes emitted from JIT compiler (pass:3, flen:6)
> - ffffffffa0069c8f + <x>:
> - 0: push %rbp
> - 1: mov %rsp,%rbp
> - 4: sub $0x60,%rsp
> - 8: mov %rbx,-0x8(%rbp)
> - c: mov 0x68(%rdi),%r9d
> - 10: sub 0x6c(%rdi),%r9d
> - 14: mov 0xd8(%rdi),%r8
> - 1b: mov $0xc,%esi
> - 20: callq 0xffffffffe0ff9442
> - 25: cmp $0x800,%eax
> - 2a: jne 0x0000000000000042
> - 2c: mov $0x17,%esi
> - 31: callq 0xffffffffe0ff945e
> - 36: cmp $0x1,%eax
> - 39: jne 0x0000000000000042
> - 3b: mov $0xffff,%eax
> - 40: jmp 0x0000000000000044
> - 42: xor %eax,%eax
> - 44: leaveq
> - 45: retq
> -
> - Issuing option `-o` will "annotate" opcodes to resulting assembler
> - instructions, which can be very useful for JIT developers:
> -
> - # ./bpf_jit_disasm -o
> - 70 bytes emitted from JIT compiler (pass:3, flen:6)
> - ffffffffa0069c8f + <x>:
> - 0: push %rbp
> - 55
> - 1: mov %rsp,%rbp
> - 48 89 e5
> - 4: sub $0x60,%rsp
> - 48 83 ec 60
> - 8: mov %rbx,-0x8(%rbp)
> - 48 89 5d f8
> - c: mov 0x68(%rdi),%r9d
> - 44 8b 4f 68
> - 10: sub 0x6c(%rdi),%r9d
> - 44 2b 4f 6c
> - 14: mov 0xd8(%rdi),%r8
> - 4c 8b 87 d8 00 00 00
> - 1b: mov $0xc,%esi
> - be 0c 00 00 00
> - 20: callq 0xffffffffe0ff9442
> - e8 1d 94 ff e0
> - 25: cmp $0x800,%eax
> - 3d 00 08 00 00
> - 2a: jne 0x0000000000000042
> - 75 16
> - 2c: mov $0x17,%esi
> - be 17 00 00 00
> - 31: callq 0xffffffffe0ff945e
> - e8 28 94 ff e0
> - 36: cmp $0x1,%eax
> - 83 f8 01
> - 39: jne 0x0000000000000042
> - 75 07
> - 3b: mov $0xffff,%eax
> - b8 ff ff 00 00
> - 40: jmp 0x0000000000000044
> - eb 02
> - 42: xor %eax,%eax
> - 31 c0
> - 44: leaveq
> - c9
> - 45: retq
> - c3
> -
> -For BPF JIT developers, bpf_jit_disasm, bpf_asm and bpf_dbg provides a useful
> -toolchain for developing and testing the kernel's JIT compiler.
> +For JIT developers, doing audits etc, should use `bpftool prog dump` to
> +veiw the JIT generated opcode image.
>
> BPF kernel internals
> --------------------
> diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
> index 6a1c9fca5260..39301d59b537 100644
> --- a/arch/arm/net/bpf_jit_32.c
> +++ b/arch/arm/net/bpf_jit_32.c
> @@ -1999,10 +1999,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> }
> flush_icache_range((u32)header, (u32)(ctx.target + ctx.idx));
>
> - if (bpf_jit_enable > 1)
> - /* there are 2 passes here */
> - bpf_jit_dump(prog->len, image_size, 2, ctx.target);
> -
> bpf_jit_binary_lock_ro(header);
> prog->bpf_func = (void *)ctx.target;
> prog->jited = 1;
> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
> index 62f805f427b7..59c35b4d77b7 100644
> --- a/arch/arm64/net/bpf_jit_comp.c
> +++ b/arch/arm64/net/bpf_jit_comp.c
> @@ -1567,10 +1567,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> goto out_off;
> }
>
> - /* And we're done. */
> - if (bpf_jit_enable > 1)
> - bpf_jit_dump(prog->len, prog_size, 2, ctx.image);
> -
> bpf_flush_icache(header, ctx.image + ctx.idx);
>
> if (!prog->is_func || extra_pass) {
> diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
> index bdcd0c7719a9..ea37f52faa6e 100644
> --- a/arch/loongarch/net/bpf_jit.c
> +++ b/arch/loongarch/net/bpf_jit.c
> @@ -1123,10 +1123,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> goto out_offset;
> }
>
> - /* And we're done */
> - if (bpf_jit_enable > 1)
> - bpf_jit_dump(prog->len, image_size, 2, ctx.image);
> -
> /* Update the icache */
> flush_icache_range((unsigned long)header, (unsigned long)(ctx.image + ctx.idx));
>
> diff --git a/arch/mips/net/bpf_jit_comp.c b/arch/mips/net/bpf_jit_comp.c
> index b17130d510d4..ccbb7c231cb0 100644
> --- a/arch/mips/net/bpf_jit_comp.c
> +++ b/arch/mips/net/bpf_jit_comp.c
> @@ -1012,9 +1012,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> flush_icache_range((unsigned long)header,
> (unsigned long)&ctx.target[ctx.jit_index]);
>
> - if (bpf_jit_enable > 1)
> - bpf_jit_dump(prog->len, image_size, 2, ctx.target);
> -
> prog->bpf_func = (void *)ctx.target;
> prog->jited = 1;
> prog->jited_len = image_size;
> diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
> index 43e634126514..f0f7d8ff2022 100644
> --- a/arch/powerpc/net/bpf_jit_comp.c
> +++ b/arch/powerpc/net/bpf_jit_comp.c
> @@ -262,20 +262,9 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
> goto out_addrs;
> }
> bpf_jit_build_epilogue(code_base, &cgctx);
> -
> - if (bpf_jit_enable > 1)
> - pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
> - proglen - (cgctx.idx * 4), cgctx.seen);
> }
>
> skip_codegen_passes:
> - if (bpf_jit_enable > 1)
> - /*
> - * Note that we output the base address of the code_base
> - * rather than image, since opcodes are in code_base.
> - */
> - bpf_jit_dump(flen, proglen, pass, code_base);
> -
> #ifdef CONFIG_PPC64_ELF_ABI_V1
> /* Function descriptor nastiness: Address + TOC */
> ((u64 *)image)[0] = (u64)code_base;
> diff --git a/arch/riscv/net/bpf_jit_core.c b/arch/riscv/net/bpf_jit_core.c
> index 737baf8715da..ff168c50d46a 100644
> --- a/arch/riscv/net/bpf_jit_core.c
> +++ b/arch/riscv/net/bpf_jit_core.c
> @@ -151,9 +151,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> }
> bpf_jit_build_epilogue(ctx);
>
> - if (bpf_jit_enable > 1)
> - bpf_jit_dump(prog->len, prog_size, pass, ctx->insns);
> -
> prog->bpf_func = (void *)ctx->insns;
> prog->jited = 1;
> prog->jited_len = prog_size;
> diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
> index af35052d06ed..13d996e27602 100644
> --- a/arch/s390/net/bpf_jit_comp.c
> +++ b/arch/s390/net/bpf_jit_comp.c
> @@ -1831,10 +1831,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
> fp = orig_fp;
> goto free_addrs;
> }
> - if (bpf_jit_enable > 1) {
> - bpf_jit_dump(fp->len, jit.size, pass, jit.prg_buf);
> - print_fn_code(jit.prg_buf, jit.size_prg);
> - }
> if (!fp->is_func || extra_pass) {
> bpf_jit_binary_lock_ro(header);
> } else {
> diff --git a/arch/sparc/net/bpf_jit_comp_32.c b/arch/sparc/net/bpf_jit_comp_32.c
> index a74e5004c6c8..08de0ed84831 100644
> --- a/arch/sparc/net/bpf_jit_comp_32.c
> +++ b/arch/sparc/net/bpf_jit_comp_32.c
> @@ -743,9 +743,6 @@ cond_branch: f_offset = addrs[i + filter[i].jf];
> oldproglen = proglen;
> }
>
> - if (bpf_jit_enable > 1)
> - bpf_jit_dump(flen, proglen, pass + 1, image);
> -
> if (image) {
> fp->bpf_func = (void *)image;
> fp->jited = 1;
> diff --git a/arch/sparc/net/bpf_jit_comp_64.c b/arch/sparc/net/bpf_jit_comp_64.c
> index fa0759bfe498..14c9e5ce4100 100644
> --- a/arch/sparc/net/bpf_jit_comp_64.c
> +++ b/arch/sparc/net/bpf_jit_comp_64.c
> @@ -1549,16 +1549,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> }
> build_epilogue(&ctx);
>
> - if (bpf_jit_enable > 1)
> - pr_info("Pass %d: size = %u, seen = [%c%c%c%c%c%c]\n", pass,
> - ctx.idx * 4,
> - ctx.tmp_1_used ? '1' : ' ',
> - ctx.tmp_2_used ? '2' : ' ',
> - ctx.tmp_3_used ? '3' : ' ',
> - ctx.saw_frame_pointer ? 'F' : ' ',
> - ctx.saw_call ? 'C' : ' ',
> - ctx.saw_tail_call ? 'T' : ' ');
> -
> if (ctx.idx * 4 == prev_image_size)
> break;
> prev_image_size = ctx.idx * 4;
> @@ -1596,9 +1586,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> goto out_off;
> }
>
> - if (bpf_jit_enable > 1)
> - bpf_jit_dump(prog->len, image_size, pass, ctx.image);
> -
> bpf_flush_icache(header, (u8 *)header + header->size);
>
> if (!prog->is_func || extra_pass) {
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index e3e2b57e4e13..197ff8651a56 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -2551,9 +2551,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> cond_resched();
> }
>
> - if (bpf_jit_enable > 1)
> - bpf_jit_dump(prog->len, proglen, pass + 1, image);
> -
> if (image) {
> if (!prog->is_func || extra_pass) {
> /*
> diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c
> index 429a89c5468b..ca53f20aca73 100644
> --- a/arch/x86/net/bpf_jit_comp32.c
> +++ b/arch/x86/net/bpf_jit_comp32.c
> @@ -2597,9 +2597,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> cond_resched();
> }
>
> - if (bpf_jit_enable > 1)
> - bpf_jit_dump(prog->len, proglen, pass + 1, image);
> -
> if (image) {
> bpf_jit_binary_lock_ro(header);
> prog->bpf_func = (void *)image;
> diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
> index 5b1ce656baa1..562ace48e1c9 100644
> --- a/net/core/sysctl_net_core.c
> +++ b/net/core/sysctl_net_core.c
> @@ -276,14 +276,10 @@ static int proc_dointvec_minmax_bpf_enable(struct ctl_table *table, int write,
> tmp.data = &jit_enable;
> ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
> if (write && !ret) {
> - if (jit_enable < 2 ||
> - (jit_enable == 2 && bpf_dump_raw_ok(current_cred()))) {
> - *(int *)table->data = jit_enable;
> - if (jit_enable == 2)
> - pr_warn("bpf_jit_enable = 2 was set! NEVER use this in production, only for JIT debugging!\n");
> - } else {
> - ret = -EPERM;
> - }
> + *(int *)table->data = jit_enable;
> +
> + if (jit_enable == 2)
> + pr_warn_once("bpf_jit_enable == 2 was deprecated! Use bpftool prog dump instead.\n");
> }
>
> if (write && ret && min == max)
> diff --git a/tools/bpf/.gitignore b/tools/bpf/.gitignore
> index cf53342175e7..5c70cfb9092e 100644
> --- a/tools/bpf/.gitignore
> +++ b/tools/bpf/.gitignore
> @@ -4,4 +4,3 @@ feature
> bpf_asm
> bpf_dbg
> bpf_exp.yacc.*
> -bpf_jit_disasm
> diff --git a/tools/bpf/Makefile b/tools/bpf/Makefile
> index 243b79f2b451..9264d7b0edf6 100644
> --- a/tools/bpf/Makefile
> +++ b/tools/bpf/Makefile
> @@ -74,14 +74,10 @@ $(OUTPUT)%.yacc.o: $(OUTPUT)%.yacc.c
> $(OUTPUT)%.lex.o: $(OUTPUT)%.lex.c
> $(QUIET_CC)$(CC) $(CFLAGS) -c -o $@ $<
>
> -PROGS = $(OUTPUT)bpf_jit_disasm $(OUTPUT)bpf_dbg $(OUTPUT)bpf_asm
> +PROGS = $(OUTPUT)bpf_dbg $(OUTPUT)bpf_asm
>
> all: $(PROGS) bpftool runqslower
>
> -$(OUTPUT)bpf_jit_disasm: CFLAGS += -DPACKAGE='bpf_jit_disasm'
> -$(OUTPUT)bpf_jit_disasm: $(OUTPUT)bpf_jit_disasm.o
> - $(QUIET_LINK)$(CC) $(CFLAGS) -o $@ $^ -lopcodes -lbfd -ldl
> -
> $(OUTPUT)bpf_dbg: $(OUTPUT)bpf_dbg.o
> $(QUIET_LINK)$(CC) $(CFLAGS) -o $@ $^ -lreadline
>
> @@ -94,16 +90,14 @@ $(OUTPUT)bpf_exp.lex.o: $(OUTPUT)bpf_exp.lex.c
>
> clean: bpftool_clean runqslower_clean resolve_btfids_clean
> $(call QUIET_CLEAN, bpf-progs)
> - $(Q)$(RM) -r -- $(OUTPUT)*.o $(OUTPUT)bpf_jit_disasm $(OUTPUT)bpf_dbg \
> + $(Q)$(RM) -r -- $(OUTPUT)*.o $(OUTPUT)bpf_dbg \
> $(OUTPUT)bpf_asm $(OUTPUT)bpf_exp.yacc.* $(OUTPUT)bpf_exp.lex.*
> $(call QUIET_CLEAN, core-gen)
> $(Q)$(RM) -- $(OUTPUT)FEATURE-DUMP.bpf
> $(Q)$(RM) -r -- $(OUTPUT)feature
>
> install: $(PROGS) bpftool_install
> - $(call QUIET_INSTALL, bpf_jit_disasm)
> $(Q)$(INSTALL) -m 0755 -d $(DESTDIR)$(prefix)/bin
> - $(Q)$(INSTALL) $(OUTPUT)bpf_jit_disasm $(DESTDIR)$(prefix)/bin/bpf_jit_disasm
> $(call QUIET_INSTALL, bpf_dbg)
> $(Q)$(INSTALL) $(OUTPUT)bpf_dbg $(DESTDIR)$(prefix)/bin/bpf_dbg
> $(call QUIET_INSTALL, bpf_asm)
> diff --git a/tools/bpf/bpf_jit_disasm.c b/tools/bpf/bpf_jit_disasm.c
> deleted file mode 100644
> index a90a5d110f92..000000000000
> --- a/tools/bpf/bpf_jit_disasm.c
> +++ /dev/null
> @@ -1,332 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0-only
> -/*
> - * Minimal BPF JIT image disassembler
> - *
> - * Disassembles BPF JIT compiler emitted opcodes back to asm insn's for
> - * debugging or verification purposes.
> - *
> - * To get the disassembly of the JIT code, do the following:
> - *
> - * 1) `echo 2 > /proc/sys/net/core/bpf_jit_enable`
> - * 2) Load a BPF filter (e.g. `tcpdump -p -n -s 0 -i eth1 host 192.168.20.0/24`)
> - * 3) Run e.g. `bpf_jit_disasm -o` to read out the last JIT code
> - *
> - * Copyright 2013 Daniel Borkmann <borkmann at redhat.com>
> - */
> -
> -#include <stdint.h>
> -#include <stdio.h>
> -#include <stdlib.h>
> -#include <assert.h>
> -#include <unistd.h>
> -#include <string.h>
> -#include <bfd.h>
> -#include <dis-asm.h>
> -#include <regex.h>
> -#include <fcntl.h>
> -#include <sys/klog.h>
> -#include <sys/types.h>
> -#include <sys/stat.h>
> -#include <limits.h>
> -#include <tools/dis-asm-compat.h>
> -
> -#define CMD_ACTION_SIZE_BUFFER 10
> -#define CMD_ACTION_READ_ALL 3
> -
> -static void get_exec_path(char *tpath, size_t size)
> -{
> - char *path;
> - ssize_t len;
> -
> - snprintf(tpath, size, "/proc/%d/exe", (int) getpid());
> - tpath[size - 1] = 0;
> -
> - path = strdup(tpath);
> - assert(path);
> -
> - len = readlink(path, tpath, size);
> - tpath[len] = 0;
> -
> - free(path);
> -}
> -
> -static void get_asm_insns(uint8_t *image, size_t len, int opcodes)
> -{
> - int count, i, pc = 0;
> - char tpath[PATH_MAX];
> - struct disassemble_info info;
> - disassembler_ftype disassemble;
> - bfd *bfdf;
> -
> - memset(tpath, 0, sizeof(tpath));
> - get_exec_path(tpath, sizeof(tpath));
> -
> - bfdf = bfd_openr(tpath, NULL);
> - assert(bfdf);
> - assert(bfd_check_format(bfdf, bfd_object));
> -
> - init_disassemble_info_compat(&info, stdout,
> - (fprintf_ftype) fprintf,
> - fprintf_styled);
> - info.arch = bfd_get_arch(bfdf);
> - info.mach = bfd_get_mach(bfdf);
> - info.buffer = image;
> - info.buffer_length = len;
> -
> - disassemble_init_for_target(&info);
> -
> -#ifdef DISASM_FOUR_ARGS_SIGNATURE
> - disassemble = disassembler(info.arch,
> - bfd_big_endian(bfdf),
> - info.mach,
> - bfdf);
> -#else
> - disassemble = disassembler(bfdf);
> -#endif
> - assert(disassemble);
> -
> - do {
> - printf("%4x:\t", pc);
> -
> - count = disassemble(pc, &info);
> -
> - if (opcodes) {
> - printf("\n\t");
> - for (i = 0; i < count; ++i)
> - printf("%02x ", (uint8_t) image[pc + i]);
> - }
> - printf("\n");
> -
> - pc += count;
> - } while(count > 0 && pc < len);
> -
> - bfd_close(bfdf);
> -}
> -
> -static char *get_klog_buff(unsigned int *klen)
> -{
> - int ret, len;
> - char *buff;
> -
> - len = klogctl(CMD_ACTION_SIZE_BUFFER, NULL, 0);
> - if (len < 0)
> - return NULL;
> -
> - buff = malloc(len);
> - if (!buff)
> - return NULL;
> -
> - ret = klogctl(CMD_ACTION_READ_ALL, buff, len);
> - if (ret < 0) {
> - free(buff);
> - return NULL;
> - }
> -
> - *klen = ret;
> - return buff;
> -}
> -
> -static char *get_flog_buff(const char *file, unsigned int *klen)
> -{
> - int fd, ret, len;
> - struct stat fi;
> - char *buff;
> -
> - fd = open(file, O_RDONLY);
> - if (fd < 0)
> - return NULL;
> -
> - ret = fstat(fd, &fi);
> - if (ret < 0 || !S_ISREG(fi.st_mode))
> - goto out;
> -
> - len = fi.st_size + 1;
> - buff = malloc(len);
> - if (!buff)
> - goto out;
> -
> - memset(buff, 0, len);
> - ret = read(fd, buff, len - 1);
> - if (ret <= 0)
> - goto out_free;
> -
> - close(fd);
> - *klen = ret;
> - return buff;
> -out_free:
> - free(buff);
> -out:
> - close(fd);
> - return NULL;
> -}
> -
> -static char *get_log_buff(const char *file, unsigned int *klen)
> -{
> - return file ? get_flog_buff(file, klen) : get_klog_buff(klen);
> -}
> -
> -static void put_log_buff(char *buff)
> -{
> - free(buff);
> -}
> -
> -static uint8_t *get_last_jit_image(char *haystack, size_t hlen,
> - unsigned int *ilen)
> -{
> - char *ptr, *pptr, *tmp;
> - off_t off = 0;
> - unsigned int proglen;
> - int ret, flen, pass, ulen = 0;
> - regmatch_t pmatch[1];
> - unsigned long base;
> - regex_t regex;
> - uint8_t *image;
> -
> - if (hlen == 0)
> - return NULL;
> -
> - ret = regcomp(®ex, "flen=[[:alnum:]]+ proglen=[[:digit:]]+ "
> - "pass=[[:digit:]]+ image=[[:xdigit:]]+", REG_EXTENDED);
> - assert(ret == 0);
> -
> - ptr = haystack;
> - memset(pmatch, 0, sizeof(pmatch));
> -
> - while (1) {
> - ret = regexec(®ex, ptr, 1, pmatch, 0);
> - if (ret == 0) {
> - ptr += pmatch[0].rm_eo;
> - off += pmatch[0].rm_eo;
> - assert(off < hlen);
> - } else
> - break;
> - }
> -
> - ptr = haystack + off - (pmatch[0].rm_eo - pmatch[0].rm_so);
> - ret = sscanf(ptr, "flen=%d proglen=%u pass=%d image=%lx",
> - &flen, &proglen, &pass, &base);
> - if (ret != 4) {
> - regfree(®ex);
> - return NULL;
> - }
> - if (proglen > 1000000) {
> - printf("proglen of %d too big, stopping\n", proglen);
> - return NULL;
> - }
> -
> - image = malloc(proglen);
> - if (!image) {
> - printf("Out of memory\n");
> - return NULL;
> - }
> - memset(image, 0, proglen);
> -
> - tmp = ptr = haystack + off;
> - while ((ptr = strtok(tmp, "\n")) != NULL && ulen < proglen) {
> - tmp = NULL;
> - if (!strstr(ptr, "JIT code"))
> - continue;
> - pptr = ptr;
> - while ((ptr = strstr(pptr, ":")))
> - pptr = ptr + 1;
> - ptr = pptr;
> - do {
> - image[ulen++] = (uint8_t) strtoul(pptr, &pptr, 16);
> - if (ptr == pptr) {
> - ulen--;
> - break;
> - }
> - if (ulen >= proglen)
> - break;
> - ptr = pptr;
> - } while (1);
> - }
> -
> - assert(ulen == proglen);
> - printf("%u bytes emitted from JIT compiler (pass:%d, flen:%d)\n",
> - proglen, pass, flen);
> - printf("%lx + <x>:\n", base);
> -
> - regfree(®ex);
> - *ilen = ulen;
> - return image;
> -}
> -
> -static void usage(void)
> -{
> - printf("Usage: bpf_jit_disasm [...]\n");
> - printf(" -o Also display related opcodes (default: off).\n");
> - printf(" -O <file> Write binary image of code to file, don't disassemble to stdout.\n");
> - printf(" -f <file> Read last image dump from file or stdin (default: klog).\n");
> - printf(" -h Display this help.\n");
> -}
> -
> -int main(int argc, char **argv)
> -{
> - unsigned int len, klen, opt, opcodes = 0;
> - char *kbuff, *file = NULL;
> - char *ofile = NULL;
> - int ofd;
> - ssize_t nr;
> - uint8_t *pos;
> - uint8_t *image = NULL;
> -
> - while ((opt = getopt(argc, argv, "of:O:")) != -1) {
> - switch (opt) {
> - case 'o':
> - opcodes = 1;
> - break;
> - case 'O':
> - ofile = optarg;
> - break;
> - case 'f':
> - file = optarg;
> - break;
> - default:
> - usage();
> - return -1;
> - }
> - }
> -
> - bfd_init();
> -
> - kbuff = get_log_buff(file, &klen);
> - if (!kbuff) {
> - fprintf(stderr, "Could not retrieve log buffer!\n");
> - return -1;
> - }
> -
> - image = get_last_jit_image(kbuff, klen, &len);
> - if (!image) {
> - fprintf(stderr, "No JIT image found!\n");
> - goto done;
> - }
> - if (!ofile) {
> - get_asm_insns(image, len, opcodes);
> - goto done;
> - }
> -
> - ofd = open(ofile, O_WRONLY | O_CREAT | O_TRUNC, DEFFILEMODE);
> - if (ofd < 0) {
> - fprintf(stderr, "Could not open file %s for writing: ", ofile);
> - perror(NULL);
> - goto done;
> - }
> - pos = image;
> - do {
> - nr = write(ofd, pos, len);
> - if (nr < 0) {
> - fprintf(stderr, "Could not write data to %s: ", ofile);
> - perror(NULL);
> - goto done;
> - }
> - len -= nr;
> - pos += nr;
> - } while (len);
> - close(ofd);
> -
> -done:
> - put_log_buff(kbuff);
> - free(image);
> - return 0;
> -}
> --
> 2.27.0
>
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