On Mon, Jan 24, 2022 at 10:27 AM Song Liu <songliubraving@xxxxxx> wrote: > > > > Are arches expected to allocate rw buffers in different ways? If not, > > I would consider putting this into the common code as well. Then > > arch-specific code would do something like > > > > header = bpf_jit_binary_alloc_pack(size, &prg_buf, &prg_addr, ...); > > ... > > /* > > * Generate code into prg_buf, the code should assume that its first > > * byte is located at prg_addr. > > */ > > ... > > bpf_jit_binary_finalize_pack(header, prg_buf); > > > > where bpf_jit_binary_finalize_pack() would copy prg_buf to header and > > free it. It feels right, but bpf_jit_binary_finalize_pack() sounds 100% arch dependent. The only thing it will do is perform a copy via text_poke. What else? > I think this should work. > > We will need an API like: bpf_arch_text_copy, which uses text_poke_copy() > for x86_64 and s390_kernel_write() for x390. We will use bpf_arch_text_copy > to > 1) write header->size; > 2) do finally copy in bpf_jit_binary_finalize_pack(). we can combine all text_poke operations into one. Can we add an 'image' pointer into struct bpf_binary_header ? Then do: int bpf_jit_binary_alloc_pack(size, &ro_hdr, &rw_hdr); ro_hdr->image would be the address used to compute offsets by JIT. rw_hdr->image would point to kvmalloc-ed area for emitting insns. rw_hdr->size would already be populated. The JITs would write insns into rw_hdr->image including 'int 3' insns. At the end the JIT will do text_poke_copy(ro_hdr, rw_hdr, rw_hdr->size); That would be the only copy that will transfer everything into final location. Then kvfree(rw_hdr) wdyt?
