1. 19 Mar, 2021 1 commit
    • Jean-Philippe Brucker's avatar
      libbpf: Fix BTF dump of pointer-to-array-of-struct · 901ee1d7
      Jean-Philippe Brucker authored
      The vmlinux.h generated from BTF is invalid when building
      drivers/phy/ti/phy-gmii-sel.c with clang:
      
      vmlinux.h:61702:27: error: array type has incomplete element type ‘struct reg_field’
      61702 |  const struct reg_field (*regfields)[3];
            |                           ^~~~~~~~~
      
      bpftool generates a forward declaration for this struct regfield, which
      compilers aren't happy about. Here's a simplified reproducer:
      
      	struct inner {
      		int val;
      	};
      	struct outer {
      		struct inner (*ptr_to_array)[2];
      	} A;
      
      After build with clang -> bpftool btf dump c -> clang/gcc:
      ./def-clang.h:11:23: error: array has incomplete element type 'struct inner'
              struct inner (*ptr_to_array)[2];
      
      Member ptr_to_array of struct outer is a pointer to an array of struct
      inner. In the DWARF generated by clang, struct outer appears before
      struct inner, so when converting BTF of struct outer into C, bpftool
      issues a forward declaration to struct inner. With GCC the DWARF info is
      reversed so struct inner gets fully defined.
      
      That forward declaration is not sufficient when compilers handle an
      array of the struct, even when it's only used through a pointer. Note
      that we can trigger the same issue with an intermediate typedef:
      
      	struct inner {
      	        int val;
      	};
      	typedef struct inner inner2_t[2];
      	struct outer {
      	        inner2_t *ptr_to_array;
      	} A;
      
      Becomes:
      
      	struct inner;
      	typedef struct inner inner2_t[2];
      
      And causes:
      
      ./def-clang.h:10:30: error: array has incomplete element type 'struct inner'
      	typedef struct inner inner2_t[2];
      
      To fix this, clear through_ptr whenever we encounter an intermediate
      array, to make the inner struct part of a strong link and force full
      declaration.
      
      Fixes: 351131b5 ("libbpf: add btf_dump API for BTF-to-C conversion")
      Signed-off-by: default avatarJean-Philippe Brucker <jean-philippe@linaro.org>
      Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
      Link: https://lore.kernel.org/bpf/20210319112554.794552-2-jean-philippe@linaro.org
      901ee1d7
  2. 18 Mar, 2021 2 commits
  3. 17 Mar, 2021 12 commits
  4. 16 Mar, 2021 25 commits