File fix-build-issue-when-using-UAPI-of-older-kernel... of Package bpftrace

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File fix-build-issue-when-using-UAPI-of-older-kernel.patch of Package bpftrace (Revision cafd358b26ac7bb181b662ac86c7e0cd)

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From f806ebc9ec9fadab368267ba910c4ca8c7327f59 Mon Sep 17 00:00:00 2001
From: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Date: Thu, 1 Feb 2024 15:22:18 +0800
Subject: [PATCH] Fix build issue with UAPI header of older kernel

322cdfa7 ("Fixup generated BTF for older kernels") allowed the generated
BTF to work stable v5.4 kernel. However, the newly added btf_type_size()
requires definition of struct btf_decl_tag (v5.16) and struct btf_enum64
(v6.0), which were not available in UAPI header of v5.4 kernel; which
will cause build to fail.

Similar to libbpf/libbpf@85f8b7c, we can fix this by treating the
structs as an array, and thus calculate their respective size without
require their definition being present in the kernel UAPI header.

Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 src/bpfbytecode.cpp | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/bpfbytecode.cpp b/src/bpfbytecode.cpp
index f8d5d03483e..7ef8d2cb703 100644
--- a/src/bpfbytecode.cpp
+++ b/src/bpfbytecode.cpp
@@ -49,7 +49,16 @@ static int btf_type_size(const struct btf_type *t)
     case BTF_KIND_ENUM:
       return base_size + vlen * sizeof(struct btf_enum);
     case BTF_KIND_ENUM64:
-      return base_size + vlen * sizeof(struct btf_enum64);
+      /* struct btf_enum64 is not available in UAPI header until v6.0,
+       * calculate its size with array instead. Its definition is:
+       *
+       * struct btf_enum64 {
+       *	__u32	name_off;
+       *	__u32	val_lo32;
+       *	__u32	val_hi32;
+       * };
+       */
+      return base_size + vlen * sizeof(__u32[3]);
     case BTF_KIND_ARRAY:
       return base_size + sizeof(struct btf_array);
     case BTF_KIND_STRUCT:
@@ -62,7 +71,14 @@ static int btf_type_size(const struct btf_type *t)
     case BTF_KIND_DATASEC:
       return base_size + vlen * sizeof(struct btf_var_secinfo);
     case BTF_KIND_DECL_TAG:
-      return base_size + sizeof(struct btf_decl_tag);
+      /* struct btf_decl_tag is not available until v5.16. Use the same trick
+       * as btf_enum64 above. Its definition is:
+       *
+       * struct btf_decl_tag {
+       *  __s32   component_idx;
+       * };
+       */
+      return base_size + sizeof(__s32);
     default:
       return -EINVAL;
   }

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File fix-build-issue-when-using-UAPI-of-older-kernel.patch of Package bpftrace (Revision cafd358b26ac7bb181b662ac86c7e0cd)

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