5.15-stable review patch. If anyone has any objections, please let me know.

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From: Andrii Nakryiko andrii@kernel.org

commit 70bc793382a0e37ba4e35e4d1a317b280b829a44 upstream.

PT_REGS*() macro on some architectures force-cast struct pt_regs to other types (user_pt_regs, etc) and might drop volatile modifiers, if any. Volatile isn't really required as pt_regs value isn't supposed to change during the BPF program run, so this is correct behavior.

But progs/loop3.c relies on that volatile modifier to ensure that loop is preserved. Fix loop3.c by declaring i and sum variables as volatile instead. It preserves the loop and makes the test pass on all architectures (including s390x which is currently broken).

Fixes: 3cc31d794097 ("libbpf: Normalize PT_REGS_xxx() macro definitions") Signed-off-by: Andrii Nakryiko andrii@kernel.org Signed-off-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/bpf/20220106205156.955373-1-andrii@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- tools/testing/selftests/bpf/progs/loop3.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/tools/testing/selftests/bpf/progs/loop3.c +++ b/tools/testing/selftests/bpf/progs/loop3.c @@ -12,9 +12,9 @@ char _license[] SEC("license") = "GPL";

SEC("raw_tracepoint/consume_skb") -int while_true(volatile struct pt_regs* ctx) +int while_true(struct pt_regs *ctx) { - __u64 i = 0, sum = 0; + volatile __u64 i = 0, sum = 0; do { i++; sum += PT_REGS_RC(ctx);