On Tue, Nov 30, 2021 at 11:13 PM Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote: > > Hm... I'd actually try to keep kprobe BTF-free. We have fentry for > cases where BTF is present and the function is simple enough (like <=6 > args, etc). Kprobe is an escape hatch mechanism when all the BTF > fanciness just gets in the way (retsnoop being a primary example from > my side). What I meant here was that bpf_get_arg(int n) would read > correct fields from pt_regs that map to first N arguments passed in > the registers. What we currently have with PT_REGS_PARM macros in > bpf_tracing.h, but with a proper unified BPF helper. and these macros are arch specific. which means that it won't be a trivial patch to add bpf_get_arg() support for kprobes. Plenty of things to consider. Like should it return an error at run-time or verification time when a particular arch is not supported. Or argument 6 might be available on one arch, but not on the other. 32-bit CPU regs vs 64-bit regs of BPF, etc. I wouldn't attempt to mix this work with current patches.
