On Tue, Aug 24, 2021 at 10:57 AM Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > > On Mon, Aug 23, 2021 at 9:50 PM Andrii Nakryiko > <andrii.nakryiko@xxxxxxxxx> wrote: > > > > On Fri, Aug 20, 2021 at 7:59 PM Dave Marchevsky <davemarchevsky@xxxxxx> wrote: > > > > > > This helper is meant to be "bpf_trace_printk, but with proper vararg > > > > We have bpf_snprintf() and bpf_seq_printf() names for other BPF > > helpers using the same approach. How about we call this one simply > > `bpf_printf`? It will be in line with other naming, it is logical BPF > > equivalent of user-space printf (which outputs to stderr, which in BPF > > land is /sys/kernel/debug/tracing/trace_pipe). And it will be logical > > to have a nice and short BPF_PRINTF() convenience macro provided by > > libbpf. > > > > > support". Follow bpf_snprintf's example and take a u64 pseudo-vararg > > > array. Write to dmesg using the same mechanism as bpf_trace_printk. > > > > Are you sure about the dmesg part?... bpf_trace_printk is outputting > > into /sys/kernel/debug/tracing/trace_pipe. > > Actually I like bpf_trace_vprintk() name, since it makes it obvious that It's the inconsistency with bpf_snprintf() and bpf_seq_printf() that's mildly annoying (it's f at the end, and no v- prefix). Maybe bpf_trace_printf() then? Or is it too close to bpf_trace_printk()? But either way you would be using BPF_PRINTF() macro for this. And we can make that macro use bpf_trace_printk() transparently for <3 args, so that new macro works on old kernels. > it's a flavor of bpf_trace_printk() and its quirks that users learned > to deal with. > I would reserve bpf_printf() for the future. We might have standalone > bpf programs in the future (without user space component) and a better > equivalent > of stdin/stdout. clang -target bpf hello_world.c -o a.out; ./a.out > should print to a terminal. Such future hello world in bpf would be > using bpf_printf() > or bpf_dprintf().
