On Wed, 13 May 2020, Yonghong Song wrote: > > > + while (isbtffmt(fmt[i])) > > + i++; > > The pointer passed to the helper may not be valid pointer. I think you > need to do a probe_read_kernel() here. Do an atomic memory allocation > here should be okay as this is mostly for debugging only. >
Are there other examples of doing allocations in program execution context? I'd hate to be the first to introduce one if not. I was hoping I could get away with some per-CPU scratch space. Most data structures will fit within a small per-CPU buffer, but if multiple copies are required, performance isn't the key concern. It will make traversing the buffer during display a bit more complex but I think avoiding allocation might make that complexity worth it. The other thought I had was we could carry out an allocation associated with the attach, but that's messy as it's possible run-time might determine the type for display (and thus the amount of the buffer we need to copy safely). Great news about LLVM support for __builtin_btf_type_id()! Thanks! Alan
