[PATCH v2] btf_encoder: Make BTF_KIND_TAG conditional

[PATCH v2] btf_encoder: Make BTF_KIND_TAG conditional

[Ian Rogers]

BTF_KIND_TAG is present in libbtf 6.0 but not libbtf in 5.15rc4. Make
the code requiring it conditionally compiled in.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 btf_encoder.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/btf_encoder.c b/btf_encoder.c
index c341f95..1694679 100644
--- a/btf_encoder.c
+++ b/btf_encoder.c
@@ -31,6 +31,15 @@
 #include <errno.h>
 #include <stdint.h>
 
+#ifndef LIBBPF_MINOR_VERSION
+/*
+ * The libbpf version is not defined in older versions, workaround by assuming
+ * version 0.5.
+ */
+#define LIBBPF_MAJOR_VERSION 0
+#define LIBBPF_MINOR_VERSION 5
+#endif
+
 struct elf_function {
 	const char	*name;
 	bool		 generated;
@@ -141,7 +150,9 @@ static const char * const btf_kind_str[NR_BTF_KINDS] = {
 	[BTF_KIND_VAR]          = "VAR",
 	[BTF_KIND_DATASEC]      = "DATASEC",
 	[BTF_KIND_FLOAT]        = "FLOAT",
+#if LIBBPF_MINOR_VERSION > 5
 	[BTF_KIND_TAG]          = "TAG",
+#endif
 };
 
 static const char *btf__printable_name(const struct btf *btf, uint32_t offset)
@@ -648,6 +659,7 @@ static int32_t btf_encoder__add_datasec(struct btf_encoder *encoder, const char
 static int32_t btf_encoder__add_tag(struct btf_encoder *encoder, const char *value, uint32_t type,
 				    int component_idx)
 {
+#if LIBBPF_MINOR_VERSION > 5
 	struct btf *btf = encoder->btf;
 	const struct btf_type *t;
 	int32_t id;
@@ -663,6 +675,10 @@ static int32_t btf_encoder__add_tag(struct btf_encoder *encoder, const char *val
 	}
 
 	return id;
+#else
+        fprintf(stderr, "error: unable to encode BTF_KIND_TAG due to old libbtf\n");
+        return -ENOTSUP;
+#endif
 }
 
 /*
-- 
2.33.0.1079.g6e70778dc9-goog

Re: [PATCH v2] btf_encoder: Make BTF_KIND_TAG conditional

[Andrii Nakryiko]

On Thu, Oct 21, 2021 at 10:09 AM Ian Rogers <irogers@google.com> wrote:
>
> BTF_KIND_TAG is present in libbtf 6.0 but not libbtf in 5.15rc4. Make
> the code requiring it conditionally compiled in.
>
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  btf_encoder.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/btf_encoder.c b/btf_encoder.c
> index c341f95..1694679 100644
> --- a/btf_encoder.c
> +++ b/btf_encoder.c
> @@ -31,6 +31,15 @@
>  #include <errno.h>
>  #include <stdint.h>
>
> +#ifndef LIBBPF_MINOR_VERSION
> +/*
> + * The libbpf version is not defined in older versions, workaround by assuming
> + * version 0.5.
> + */
> +#define LIBBPF_MAJOR_VERSION 0
> +#define LIBBPF_MINOR_VERSION 5
> +#endif
> +
>  struct elf_function {
>         const char      *name;
>         bool             generated;
> @@ -141,7 +150,9 @@ static const char * const btf_kind_str[NR_BTF_KINDS] = {
>         [BTF_KIND_VAR]          = "VAR",
>         [BTF_KIND_DATASEC]      = "DATASEC",
>         [BTF_KIND_FLOAT]        = "FLOAT",
> +#if LIBBPF_MINOR_VERSION > 5

this will break on 1.0

>         [BTF_KIND_TAG]          = "TAG",
> +#endif
>  };
>
>  static const char *btf__printable_name(const struct btf *btf, uint32_t offset)
> @@ -648,6 +659,7 @@ static int32_t btf_encoder__add_datasec(struct btf_encoder *encoder, const char
>  static int32_t btf_encoder__add_tag(struct btf_encoder *encoder, const char *value, uint32_t type,
>                                     int component_idx)
>  {
> +#if LIBBPF_MINOR_VERSION > 5
>         struct btf *btf = encoder->btf;
>         const struct btf_type *t;
>         int32_t id;
> @@ -663,6 +675,10 @@ static int32_t btf_encoder__add_tag(struct btf_encoder *encoder, const char *val
>         }
>
>         return id;
> +#else
> +        fprintf(stderr, "error: unable to encode BTF_KIND_TAG due to old libbtf\n");
> +        return -ENOTSUP;
> +#endif
>  }
>
>  /*
> --
> 2.33.0.1079.g6e70778dc9-goog
>