From: Ilya Leoshkevich Date: Thu, 7 Apr 2022 21:44:10 +0000 (+0200) Subject: libbpf: Make BPF-side of USDT support work on big-endian machines X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=6f403d9d530635f533577d37929c61474d6c5d7f;p=linux.git libbpf: Make BPF-side of USDT support work on big-endian machines BPF_USDT_ARG_REG_DEREF handling always reads 8 bytes, regardless of the actual argument size. On little-endian the relevant argument bits end up in the lower bits of val, and later on the code that handles all the argument types expects them to be there. On big-endian they end up in the upper bits of val, breaking that expectation. Fix by right-shifting val on big-endian. Signed-off-by: Ilya Leoshkevich Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20220407214411.257260-3-iii@linux.ibm.com --- diff --git a/tools/lib/bpf/usdt.bpf.h b/tools/lib/bpf/usdt.bpf.h index 420d743734e12..881a2422a8efb 100644 --- a/tools/lib/bpf/usdt.bpf.h +++ b/tools/lib/bpf/usdt.bpf.h @@ -177,6 +177,9 @@ int bpf_usdt_arg(struct pt_regs *ctx, __u64 arg_num, long *res) err = bpf_probe_read_user(&val, sizeof(val), (void *)val + arg_spec->val_off); if (err) return err; +#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ + val >>= arg_spec->arg_bitshift; +#endif break; default: return -EINVAL;