Use PT_REGS_RC(ctx) instead of ctx->rax, which is not present on s390. This patch series consists of three preparatory commits, which make it possible to use PT_REGS_RC in BPF selftests, followed by the actual fix. Since the last time, I've tested it with x86_64-linux-gnu-, aarch64-linux-gnu-, arm-linux-gnueabihf-, mips64el-linux-gnuabi64-, powerpc64le-linux-gnu-, s390x-linux-gnu- and sparc64-linux-gnu- compilers, and found that I also need to add arm64 support. Like s390, arm64 exports user_pt_regs instead of struct pt_regs to userspace. I've also made fixes for a few unrelated build problems, which I will post separately. v1->v2: Split into multiple patches. v2->v3: Added arm64 support. Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
