1. 30 Jul, 2021 13 commits
  2. 29 Jul, 2021 2 commits
    • Yonghong Song's avatar
      bpf: Emit better log message if bpf_iter ctx arg btf_id == 0 · d3621642
      Yonghong Song authored
      To avoid kernel build failure due to some missing .BTF-ids referenced
      functions/types, the patch ([1]) tries to fill btf_id 0 for
      these types.
      
      In bpf verifier, for percpu variable and helper returning btf_id cases,
      verifier already emitted proper warning with something like
        verbose(env, "Helper has invalid btf_id in R%d\n", regno);
        verbose(env, "invalid return type %d of func %s#%d\n",
                fn->ret_type, func_id_name(func_id), func_id);
      
      But this is not the case for bpf_iter context arguments.
      I hacked resolve_btfids to encode btf_id 0 for struct task_struct.
      With `./test_progs -n 7/5`, I got,
        0: (79) r2 = *(u64 *)(r1 +0)
        func 'bpf_iter_task' arg0 has btf_id 29739 type STRUCT 'bpf_iter_meta'
        ; struct seq_file *seq = ctx->meta->seq;
        1: (79) r6 = *(u64 *)(r2 +0)
        ; struct task_struct *task = ctx->task;
        2: (79) r7 = *(u64 *)(r1 +8)
        ; if (task == (void *)0) {
        3: (55) if r7 != 0x0 goto pc+11
        ...
        ; BPF_SEQ_PRINTF(seq, "%8d %8d\n", task->tgid, task->pid);
        26: (61) r1 = *(u32 *)(r7 +1372)
        Type '(anon)' is not a struct
      
      Basically, verifier will return btf_id 0 for task_struct.
      Later on, when the code tries to access task->tgid, the
      verifier correctly complains the type is '(anon)' and it is
      not a struct. Users still need to backtrace to find out
      what is going on.
      
      Let us catch the invalid btf_id 0 earlier
      and provide better message indicating btf_id is wrong.
      The new error message looks like below:
        R1 type=ctx expected=fp
        ; struct seq_file *seq = ctx->meta->seq;
        0: (79) r2 = *(u64 *)(r1 +0)
        func 'bpf_iter_task' arg0 has btf_id 29739 type STRUCT 'bpf_iter_meta'
        ; struct seq_file *seq = ctx->meta->seq;
        1: (79) r6 = *(u64 *)(r2 +0)
        ; struct task_struct *task = ctx->task;
        2: (79) r7 = *(u64 *)(r1 +8)
        invalid btf_id for context argument offset 8
        invalid bpf_context access off=8 size=8
      
      [1] https://lore.kernel.org/bpf/20210727132532.2473636-1-hengqi.chen@gmail.com/Signed-off-by: default avatarYonghong Song <yhs@fb.com>
      Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
      Link: https://lore.kernel.org/bpf/20210728183025.1461750-1-yhs@fb.com
      d3621642
    • Hengqi Chen's avatar
      tools/resolve_btfids: Emit warnings and patch zero id for missing symbols · 5aad0368
      Hengqi Chen authored
      Kernel functions referenced by .BTF_ids may be changed from global to static
      and get inlined or get renamed/removed, and thus disappears from BTF.
      This causes kernel build failure when resolve_btfids do id patch for symbols
      in .BTF_ids in vmlinux. Update resolve_btfids to emit warning messages and
      patch zero id for missing symbols instead of aborting kernel build process.
      Suggested-by: default avatarAndrii Nakryiko <andrii@kernel.org>
      Signed-off-by: default avatarHengqi Chen <hengqi.chen@gmail.com>
      Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
      Acked-by: default avatarYonghong Song <yhs@fb.com>
      Link: https://lore.kernel.org/bpf/20210727132532.2473636-2-hengqi.chen@gmail.com
      5aad0368
  3. 27 Jul, 2021 5 commits
  4. 26 Jul, 2021 6 commits
  5. 24 Jul, 2021 3 commits
  6. 23 Jul, 2021 11 commits