KVER macro - support 4.9.256+ kernelandroid-s-preview-1

Instead of doing 16/8/8 bits for major/minor/subver macro,
switch to 8/8/16 bits, since this gives plenty of space:
  - major versions are bumped every few years, so 256 last forever
  - minor versions are bumped every few months (~5-6 per year),
    so 256 lasts for decades, additionally Linus Torvalds doesn't
    like big numbers, and eventually bumps the major instead
  - sub versions are the problematic ones, because they're bumped
    on every LTS security release, however even at one release per day,
    16 bits lasts for 180 years

Note: before this change 4.9.256 was treated as equivalent to 4.10.0.

Luckily all our tests were only ever (by chance) against the LTS release
bases (ie. 4.9.0, 4.14.0, 4.19.0, 5.4.0) and thus we wouldn't have hit
an actually failure until 4.9.(5*256) === 4.14.0 which would have caused
the bpfloader to attempt to load bpf code requiring 4.14 on a 4.9 kernel,
and resulted in failure of device to successfully boot.

Test: atest, TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I0535ce081967af092f3342c0abfd05a1e5028eb6

2 files changed, 2 insertions, 2 deletions

diff --git a/libbpf_android/include/bpf/BpfUtils.h b/libbpf_android/include/bpf/BpfUtils.h
index 413d3ff..9671b8a 100644
--- a/libbpf_android/include/bpf/BpfUtils.h
+++ b/libbpf_android/include/bpf/BpfUtils.h
@@ -37,7 +37,7 @@ uint64_t getSocketCookie(int sockFd);
 int synchronizeKernelRCU();
 int setrlimitForTest();
 
-#define KVER(a, b, c) ((a)*65536 + (b)*256 + (c))
+#define KVER(a, b, c) (((a) << 24) + ((b) << 16) + (c))
 
 unsigned kernelVersion();
 
diff --git a/progs/include/bpf_helpers.h b/progs/include/bpf_helpers.h
index a45b6fb..075ea94 100644
--- a/progs/include/bpf_helpers.h
+++ b/progs/include/bpf_helpers.h
@@ -109,7 +109,7 @@ static unsigned long long (*bpf_get_current_uid_gid)(void) = (void*) BPF_FUNC_ge
 static unsigned long long (*bpf_get_smp_processor_id)(void) = (void*) BPF_FUNC_get_smp_processor_id;
 
 #define KVER_NONE 0
-#define KVER(a, b, c) ((a)*65536 + (b)*256 + (c))
+#define KVER(a, b, c) (((a) << 24) + ((b) << 16) + (c))
 #define KVER_INF 0xFFFFFFFF
 
 #define DEFINE_BPF_PROG_KVER_RANGE_OPT(SECTION_NAME, prog_uid, prog_gid, the_prog, min_kv, max_kv, \