1. 26 Dec, 2019 1 commit
    • Andrii Nakryiko's avatar
      libbpf: Support CO-RE relocations for LDX/ST/STX instructions · 8ab9da57
      Andrii Nakryiko authored
      Clang patch [0] enables emitting relocatable generic ALU/ALU64 instructions
      (i.e, shifts and arithmetic operations), as well as generic load/store
      instructions. The former ones are already supported by libbpf as is. This
      patch adds further support for load/store instructions. Relocatable field
      offset is encoded in BPF instruction's 16-bit offset section and are adjusted
      by libbpf based on target kernel BTF.
      
      These Clang changes and corresponding libbpf changes allow for more succinct
      generated BPF code by encoding relocatable field reads as a single
      ST/LDX/STX instruction. It also enables relocatable access to BPF context.
      Previously, if context struct (e.g., __sk_buff) was accessed with CO-RE
      relocations (e.g., due to preserve_access_index attribute), it would be
      rejected by BPF verifier due to modified context pointer dereference. With
      Clang patch, such context accesses are both relocatable and have a fixed
      offset from the point of view of BPF verifier.
      
        [0] https://reviews.llvm.org/D71790Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      Acked-by: default avatarYonghong Song <yhs@fb.com>
      Link: https://lore.kernel.org/bpf/20191223180305.86417-1-andriin@fb.com
      8ab9da57
  2. 21 Dec, 2019 22 commits
  3. 20 Dec, 2019 16 commits
  4. 19 Dec, 2019 1 commit