[BPF] Allow struct pointee member btf generation with annotations #141719
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Currently, to avoid generating too much BTF types, for a struct type like
struct foo {
int val;
struct bar *ptr;
};
if the BTF generation reaches 'struct foo', it will not generate actual
type for 'struct bar' and instead a forward decl is generated. The
'struct bar' is actual generated in BTF unless it is reached through a
non-struct pointer member.
Such a limitation forces bpf developer to hack and workaround this problem.
See [1] and [2]. For example in [1], we have
struct map_value {
struct prog_test_ref_kfunc *not_kptr;
struct prog_test_ref_kfunc __kptr *val;
struct node_data __kptr *node;
};
The BTF type for 'struct node_data' is not generated. Note that we have
a '__kptr' annotation. Similar problem for [2] with a '__uptr' annotation.
Note that the issue in [1] has been resolved later but the hack in [2]
is still needed.
This patch relaxed the struct type (with struct pointer member) BTF generation
if the struct pointer has a btf_type_tag annotation.
[1] https://lore.kernel.org/r/20230310230743.2320707-4-davemarchevsky@fb.com
[2] https://lore.kernel.org/r/20241023234759.860539-9-martin.lau@linux.dev
|
I noticed a single significant change in BTF generated for selftests: Happens because of a From logic pow, I think this code change is fine, however, I'm curious, would it be possible to use a single flag (e.g. |
eddyz87
approved these changes
May 28, 2025
Indeed, this is the reason.
Not sure. I guess we can do this later for refactoring only if we want. |
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/138/builds/13811 Here is the relevant piece of the build log for the reference |
google-yfyang
pushed a commit
to google-yfyang/llvm-project
that referenced
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May 29, 2025
…vm#141719) Currently, to avoid generating too much BTF types, for a struct type like ``` struct foo { int val; struct bar *ptr; }; ``` if the BTF generation reaches 'struct foo', it will not generate actual type for 'struct bar' and instead a forward decl is generated. The 'struct bar' is actual generated in BTF unless it is reached through a non-struct pointer member. Such a limitation forces bpf developer to hack and workaround this problem. See [1] and [2]. For example in [1], we have ``` struct map_value { struct prog_test_ref_kfunc *not_kptr; struct prog_test_ref_kfunc __kptr *val; struct node_data __kptr *node; }; ``` The BTF type for 'struct node_data' is not generated. Note that we have a '__kptr' annotation. Similar problem for [2] with a '__uptr' annotation. Note that the issue in [1] has been resolved later but the hack in [2] is still needed. This patch relaxed the struct type (with struct pointer member) BTF generation if the struct pointer has a btf_type_tag annotation. [1] https://lore.kernel.org/r/20230310230743.2320707-4-davemarchevsky@fb.com [2] https://lore.kernel.org/r/20241023234759.860539-9-martin.lau@linux.dev
sivan-shani
pushed a commit
to sivan-shani/llvm-project
that referenced
this pull request
Jun 3, 2025
…vm#141719) Currently, to avoid generating too much BTF types, for a struct type like ``` struct foo { int val; struct bar *ptr; }; ``` if the BTF generation reaches 'struct foo', it will not generate actual type for 'struct bar' and instead a forward decl is generated. The 'struct bar' is actual generated in BTF unless it is reached through a non-struct pointer member. Such a limitation forces bpf developer to hack and workaround this problem. See [1] and [2]. For example in [1], we have ``` struct map_value { struct prog_test_ref_kfunc *not_kptr; struct prog_test_ref_kfunc __kptr *val; struct node_data __kptr *node; }; ``` The BTF type for 'struct node_data' is not generated. Note that we have a '__kptr' annotation. Similar problem for [2] with a '__uptr' annotation. Note that the issue in [1] has been resolved later but the hack in [2] is still needed. This patch relaxed the struct type (with struct pointer member) BTF generation if the struct pointer has a btf_type_tag annotation. [1] https://lore.kernel.org/r/20230310230743.2320707-4-davemarchevsky@fb.com [2] https://lore.kernel.org/r/20241023234759.860539-9-martin.lau@linux.dev
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Currently, to avoid generating too much BTF types, for a struct type like
if the BTF generation reaches 'struct foo', it will not generate actual type for 'struct bar' and instead a forward decl is generated. The 'struct bar' is actual generated in BTF unless it is reached through a non-struct pointer member.
Such a limitation forces bpf developer to hack and workaround this problem. See [1] and [2]. For example in [1], we have
The BTF type for 'struct node_data' is not generated. Note that we have a '__kptr' annotation. Similar problem for [2] with a '__uptr' annotation. Note that the issue in [1] has been resolved later but the hack in [2] is still needed.
This patch relaxed the struct type (with struct pointer member) BTF generation if the struct pointer has a btf_type_tag annotation.
[1] https://lore.kernel.org/r/20230310230743.2320707-4-davemarchevsky@fb.com
[2] https://lore.kernel.org/r/20241023234759.860539-9-martin.lau@linux.dev