[all-commits] [llvm/llvm-project] 6d6750: [clang][BPF] support type exist/size and enum exis...

[yonghong-song via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 6d6750696400e7ce988d66a1a00e1d0cb32815f8
      https://github.com/llvm/llvm-project/commit/6d6750696400e7ce988d66a1a00e1d0cb32815f8
  Author: Yonghong Song <yhs at fb.com>
  Date:   2020-08-04 (Tue, 04 Aug 2020)

  Changed paths:
    M clang/include/clang/Basic/BuiltinsBPF.def
    M clang/include/clang/Basic/DiagnosticSemaKinds.td
    M clang/lib/CodeGen/CGBuiltin.cpp
    M clang/lib/Sema/SemaChecking.cpp
    A clang/test/CodeGen/builtins-bpf-preserve-field-info-3.c
    A clang/test/CodeGen/builtins-bpf-preserve-field-info-4.c
    M clang/test/Sema/builtins-bpf.c
    M llvm/include/llvm/IR/IntrinsicsBPF.td

  Log Message:
  -----------
  [clang][BPF] support type exist/size and enum exist/value relocations

This patch added the following additional compile-once
run-everywhere (CO-RE) relocations:
  - existence/size of typedef, struct/union or enum type
  - enum value and enum value existence

These additional relocations will make CO-RE bpf programs more
adaptive for potential kernel internal data structure changes.

For existence/size relocations, the following two code patterns
are supported:
  1. uint32_t __builtin_preserve_type_info(*(<type> *)0, flag);
  2. <type> var;
     uint32_t __builtin_preserve_field_info(var, flag);
flag = 0 for existence relocation and flag = 1 for size relocation.

For enum value existence and enum value relocations, the following code
pattern is supported:
  uint64_t __builtin_preserve_enum_value(*(<enum_type> *)<enum_value>,
                                         flag);
flag = 0 means existence relocation and flag = 1 for enum value.
relocation. In the above <enum_type> can be an enum type or
a typedef to enum type. The <enum_value> needs to be an enumerator
value from the same enum type. The return type is uint64_t to
permit potential 64bit enumerator values.

Differential Revision: https://reviews.llvm.org/D83242