The introduced header file linux/version.h in libbpf_probes.c may have a wrong macro KERNEL_VERSION for calculating LINUX_VERSION_CODE in some old kernel (Debian9,10). Below is a version info example from Debian 10.

release: 4.19.0-22-amd64
version: #1 SMP Debian 4.19.260-1 (2022-09-29)

The macro KERNEL_VERSION is defined to (((a) << 16) + ((b) << 8)) + (c)), which a, b, and c stand for major, minor and patch version. So in example here, the major is 4, minor is 19, patch is 260, the LINUX_VERSION(4, 19, 260) which is 267268 should be matched to LINUX_VERSION_CODE. However, the KERNEL_VERSION_CODE in linux/version.h is defined to 267263.

I noticed that the macro KERNEL_VERSION in linux/version.h of some new kernel is defined to (((a) << 16) + ((b) << 8) + ((c) > 255 ? 255 : (c))). And KERNEL_VERSION(4, 19, 260) is equal to 267263 which is the right LINUX_VERSION_CODE.

The mismatched LINUX_VERSION_CODE which will cause failing to load kprobe BPF programs in the version check of BPF syscall.

The return value of get_kernel_version in libbpf_probes.c should be matched to LINUX_VERSION_CODE by correcting the macro KERNEL_VERSION.

Signed-off-by: songrui.771 <songrui.771@bytedance.com>
---
Changes since v1:
- reintroduce header file linux/version.h
- define a new macro LIBBPF_KERNEL_VERSION to get kernel version rather than KERNEL_VERSION
---
 tools/lib/bpf/libbpf_probes.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index 4f3bc968ff8e..5b22a880c7e7 100644
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -18,6 +18,10 @@
 #include "libbpf.h"
 #include "libbpf_internal.h"
 
+#ifndef LIBBPF_KERNEL_VERSION
+#define LIBBPF_KERNEL_VERSION(a, b, c) (((a) << 16) + ((b) << 8) + ((c) > 255 ? 255 : (c)))
+#endif
+
 /* On Ubuntu LINUX_VERSION_CODE doesn't correspond to info.release,
  * but Ubuntu provides /proc/version_signature file, as described at
  * https://ubuntu.com/kernel, with an example contents below, which we
@@ -47,7 +51,7 @@ static __u32 get_ubuntu_kernel_version(void)
 	if (ret != 3)
 		return 0;
 
-	return KERNEL_VERSION(major, minor, patch);
+	return LIBBPF_KERNEL_VERSION(major, minor, patch);
 }
 
 /* On Debian LINUX_VERSION_CODE doesn't correspond to info.release.
@@ -74,7 +78,7 @@ static __u32 get_debian_kernel_version(struct utsname *info)
 	if (sscanf(p, "Debian %u.%u.%u", &major, &minor, &patch) != 3)
 		return 0;
 
-	return KERNEL_VERSION(major, minor, patch);
+	return LIBBPF_KERNEL_VERSION(major, minor, patch);
 }
 
 __u32 get_kernel_version(void)
@@ -97,7 +101,7 @@ __u32 get_kernel_version(void)
 	if (sscanf(info.release, "%u.%u.%u", &major, &minor, &patch) != 3)
 		return 0;
 
-	return KERNEL_VERSION(major, minor, patch);
+	return LIBBPF_KERNEL_VERSION(major, minor, patch);
 }
 
 static int probe_prog_load(enum bpf_prog_type prog_type,
-- 
2.39.2 (Apple Git-143)

Hi songrui.771,

kernel test robot noticed the following build warnings:

[auto build test WARNING on bpf-next/master]
[also build test WARNING on bpf/master linus/master v6.3-rc6 next-20230413]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/songrui-771/libbpf-correct-the-macro-KERNEL_VERSION-for-old-kernel/20230414-164547
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/20230414084353.36545-1-songrui.771%40bytedance.com
patch subject: [PATCH v2] libbpf: correct the macro KERNEL_VERSION for old kernel
reproduce:
        make versioncheck

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202304141932.JnvYvgv5-lkp@intel.com/

versioncheck warnings: (new ones prefixed by >>)
   INFO PATH=/opt/cross/clang/bin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
   /usr/bin/timeout -k 100 3h /usr/bin/make W=1 --keep-going HOSTCC=gcc-11 CC=gcc-11 -j32 ARCH=x86_64 versioncheck
   find ./* \( -name SCCS -o -name BitKeeper -o -name .svn -o -name CVS -o -name .pc -o -name .hg -o -name .git \) -prune -o \
   	-name '*.[hcS]' -type f -print | sort \
   	| xargs perl -w ./scripts/checkversion.pl
   ./drivers/accessibility/speakup/genmap.c: 13 linux/version.h not needed.
   ./drivers/accessibility/speakup/makemapdata.c: 13 linux/version.h not needed.
   ./drivers/soc/tegra/cbb/tegra-cbb.c: 19 linux/version.h not needed.
   ./drivers/soc/tegra/cbb/tegra194-cbb.c: 26 linux/version.h not needed.
   ./drivers/soc/tegra/cbb/tegra234-cbb.c: 27 linux/version.h not needed.
   ./drivers/staging/media/atomisp/include/linux/atomisp.h: 23 linux/version.h not needed.
   ./samples/trace_events/trace_custom_sched.c: 11 linux/version.h not needed.
   ./sound/soc/codecs/cs42l42.c: 14 linux/version.h not needed.
   ./tools/lib/bpf/bpf_helpers.h: 294: need linux/version.h
>> ./tools/lib/bpf/libbpf_probes.c: 15 linux/version.h not needed.
   ./tools/perf/tests/bpf-script-example.c: 60: need linux/version.h
   ./tools/perf/tests/bpf-script-test-kbuild.c: 21: need linux/version.h
   ./tools/perf/tests/bpf-script-test-prologue.c: 49: need linux/version.h
   ./tools/perf/tests/bpf-script-test-relocation.c: 51: need linux/version.h
   ./tools/testing/selftests/bpf/progs/dev_cgroup.c: 9 linux/version.h not needed.
   ./tools/testing/selftests/bpf/progs/netcnt_prog.c: 3 linux/version.h not needed.
   ./tools/testing/selftests/bpf/progs/test_map_lock.c: 4 linux/version.h not needed.
   ./tools/testing/selftests/bpf/progs/test_send_signal_kern.c: 4 linux/version.h not needed.
   ./tools/testing/selftests/bpf/progs/test_spin_lock.c: 4 linux/version.h not needed.
   ./tools/testing/selftests/bpf/progs/test_tcp_estats.c: 37 linux/version.h not needed.
   ./tools/testing/selftests/wireguard/qemu/init.c: 27 linux/version.h not needed.

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests