On Fri, Sep 17, 2021 at 11:29 AM Dave Marchevsky [off-list ref] wrote:

This series introduces a new helper, bpf_trace_vprintk, which functions
like bpf_trace_printk but supports > 3 arguments via a pseudo-vararg u64
array. The bpf_printk libbpf convenience macro is modified to use
bpf_trace_vprintk when > 3 varargs are passed, otherwise the previous
behavior - using bpf_trace_printk - is retained.

Helper functions and macros added during the implementation of
bpf_seq_printf and bpf_snprintf do most of the heavy lifting for
bpf_trace_vprintk. There's no novel format string wrangling here.

Usecase here is straightforward: Giving BPF program writers a more
powerful printk will ease development of BPF programs, particularly
during debugging and testing, where printk tends to be used.

This feature was proposed by Andrii in libbpf mirror's issue tracker
[1].

[1] https://github.com/libbpf/libbpf/issues/315

v5 -> v6: Rebase to pick up newly-added helper

Applied. Thanks!