selftests/bpf: Stop using static variables for passing data to/from user-space

In preparation of skipping emitting static variables in BPF skeletons, switch
all current selftests uses of static variables to pass data between BPF and
user-space to use global variables.

All non-read-only `static volatile` variables become just plain global
variables by dropping `static volatile` part.

Read-only `static volatile const` variables, though, still require `volatile`
modifier, otherwise compiler will ignore whatever values are set from
user-space.

Few static linker tests are using name-conflicting static variables to
validate that static linker still properly handles static variables and
doesn't trip up on name conflicts.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210507054119.270888-4-andrii@kernel.org

1 files changed, 2 insertions, 2 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_check_mtu.c b/tools/testing/selftests/bpf/progs/test_check_mtu.c
index c4a9bae96e75..71184af57749 100644
--- a/tools/testing/selftests/bpf/progs/test_check_mtu.c
+++ b/tools/testing/selftests/bpf/progs/test_check_mtu.c
@@ -11,8 +11,8 @@
 char _license[] SEC("license") = "GPL";
 
 /* Userspace will update with MTU it can see on device */
-static volatile const int GLOBAL_USER_MTU;
-static volatile const __u32 GLOBAL_USER_IFINDEX;
+volatile const int GLOBAL_USER_MTU;
+volatile const __u32 GLOBAL_USER_IFINDEX;
 
 /* BPF-prog will update these with MTU values it can see */
 __u32 global_bpf_mtu_xdp = 0;