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    Subject[PATCH AUTOSEL 5.9 067/147] selftests/bpf: Define string const as global for test_sysctl_prog.c
    Date
    From: Yonghong Song <yhs@fb.com>

    [ Upstream commit 6e057fc15a2da4ee03eb1fa6889cf687e690106e ]

    When tweaking llvm optimizations, I found that selftest build failed
    with the following error:
    libbpf: elf: skipping unrecognized data section(6) .rodata.str1.1
    libbpf: prog 'sysctl_tcp_mem': bad map relo against '.L__const.is_tcp_mem.tcp_mem_name'
    in section '.rodata.str1.1'
    Error: failed to open BPF object file: Relocation failed
    make: *** [/work/net-next/tools/testing/selftests/bpf/test_sysctl_prog.skel.h] Error 255
    make: *** Deleting file `/work/net-next/tools/testing/selftests/bpf/test_sysctl_prog.skel.h'

    The local string constant "tcp_mem_name" is put into '.rodata.str1.1' section
    which libbpf cannot handle. Using untweaked upstream llvm, "tcp_mem_name"
    is completely inlined after loop unrolling.

    Commit 7fb5eefd7639 ("selftests/bpf: Fix test_sysctl_loop{1, 2}
    failure due to clang change") solved a similar problem by defining
    the string const as a global. Let us do the same here
    for test_sysctl_prog.c so it can weather future potential llvm changes.

    Signed-off-by: Yonghong Song <yhs@fb.com>
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>
    Acked-by: Andrii Nakryiko <andriin@fb.com>
    Link: https://lore.kernel.org/bpf/20200910202718.956042-1-yhs@fb.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    tools/testing/selftests/bpf/progs/test_sysctl_prog.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/tools/testing/selftests/bpf/progs/test_sysctl_prog.c b/tools/testing/selftests/bpf/progs/test_sysctl_prog.c
    index 50525235380e8..5489823c83fc2 100644
    --- a/tools/testing/selftests/bpf/progs/test_sysctl_prog.c
    +++ b/tools/testing/selftests/bpf/progs/test_sysctl_prog.c
    @@ -19,11 +19,11 @@
    #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
    #endif

    +const char tcp_mem_name[] = "net/ipv4/tcp_mem";
    static __always_inline int is_tcp_mem(struct bpf_sysctl *ctx)
    {
    - char tcp_mem_name[] = "net/ipv4/tcp_mem";
    unsigned char i;
    - char name[64];
    + char name[sizeof(tcp_mem_name)];
    int ret;

    memset(name, 0, sizeof(name));
    --
    2.25.1
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