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Donglin Peng c276044f26 libbpf: Checking the btf_type kind when fixing variable offsets 
[ Upstream commit cc5083d1f3881624ad2de1f3cbb3a07e152cb254 ]

I encountered an issue when building the test_progs from the repository [1]:

  $ pwd
  /work/Qemu/x86_64/linux-6.10-rc2/tools/testing/selftests/bpf/

  $ make test_progs V=1
  [...]
  ./tools/sbin/bpftool gen object ./ip_check_defrag.bpf.linked2.o ./ip_check_defrag.bpf.linked1.o
  libbpf: failed to find symbol for variable 'bpf_dynptr_slice' in section '.ksyms'
  Error: failed to link './ip_check_defrag.bpf.linked1.o': No such file or directory (2)
  [...]

Upon investigation, I discovered that the btf_types referenced in the '.ksyms'
section had a kind of BTF_KIND_FUNC instead of BTF_KIND_VAR:

  $ bpftool btf dump file ./ip_check_defrag.bpf.linked1.o
  [...]
  [2] DATASEC '.ksyms' size=0 vlen=2
        type_id=16 offset=0 size=0 (FUNC 'bpf_dynptr_from_skb')
        type_id=17 offset=0 size=0 (FUNC 'bpf_dynptr_slice')
  [...]
  [16] FUNC 'bpf_dynptr_from_skb' type_id=82 linkage=extern
  [17] FUNC 'bpf_dynptr_slice' type_id=85 linkage=extern
  [...]

For a detailed analysis, please refer to [2]. We can add a kind checking to
fix the issue.

  [1] https://github.com/eddyz87/bpf/tree/binsort-btf-dedup
  [2] https://lore.kernel.org/all/0c0ef20c-c05e-4db9-bad7-2cbc0d6dfae7@oracle.com/

Fixes: 8fd27bf69b ("libbpf: Add BPF static linker BTF and BTF.ext support")
Signed-off-by: Donglin Peng <dolinux.peng@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20240619122355.426405-1-dolinux.peng@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
 		2024-08-03 08:53:39 +02:00
..
api libapi: Add missing linux/types.h header to get the __u64 type on io.h 2024-01-25 15:35:51 -08:00
bpf libbpf: Checking the btf_type kind when fixing variable offsets 2024-08-03 08:53:39 +02:00
perf perf evlist: Add perf_evlist__go_system_wide() helper 2024-06-12 11:13:02 +02:00
subcmd libsubcmd: Fix parse-options memory leak 2024-06-12 11:12:30 +02:00
symbol tools lib symbol: Add dependency test to install_headers 2022-12-14 11:16:12 -03:00
thermal tools/lib/thermal: Fix include path for libnl3 in pkg-config file. 2023-02-15 17:29:40 +01:00
argv_split.c
…
bitmap.c Bitmap patches for v6.0-rc1 2022-08-07 17:52:35 -07:00
ctype.c
…
find_bit.c tools: sync find_bit() implementation 2022-09-21 12:21:44 -07:00
hweight.c
…
list_sort.c tools lib: Adopt list_sort() from the kernel sources 2021-10-20 10:30:59 -03:00
rbtree.c tools/: replace HTTP links with HTTPS ones 2020-08-07 11:33:21 -07:00
slab.c tools: Move gfp.h and slab.h from radix-tree to lib 2022-02-20 08:44:37 +02:00
str_error_r.c
…
string.c tools lib: Adopt memchr_inv() from kernel 2020-11-27 08:34:52 -03:00
vsprintf.c
…
zalloc.c
…