On Sun, Mar 12, 2023 at 10:19:58PM +0000, Dave Thaler wrote: > From: Dave Thaler <dthaler@xxxxxxxxxxxxx> > > Add extended call instructions. Since BPF can be used in userland > or SmartNICs, this uses the more generic "Platform-specific helper functions" > term as suggested by David Vernet, rather than the kernel specific "kfuncs". > > --- > V1 -> V2: addressed comments from David Vernet > > V2 -> V3: make descriptions in table consistent with updated names > > Signed-off-by: Dave Thaler <dthaler@xxxxxxxxxxxxx> > --- > Documentation/bpf/instruction-set.rst | 63 +++++++++++++++++---------- > Documentation/bpf/linux-notes.rst | 4 ++ > 2 files changed, 44 insertions(+), 23 deletions(-) > > diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst > index 5e43e14abe8..f890bcd0dba 100644 > --- a/Documentation/bpf/instruction-set.rst > +++ b/Documentation/bpf/instruction-set.rst > @@ -242,35 +242,52 @@ Jump instructions > otherwise identical operations. > The 'code' field encodes the operation as below: > > -======== ===== ========================= ============ > -code value description notes > -======== ===== ========================= ============ > -BPF_JA 0x00 PC += off BPF_JMP only > -BPF_JEQ 0x10 PC += off if dst == src > -BPF_JGT 0x20 PC += off if dst > src unsigned > -BPF_JGE 0x30 PC += off if dst >= src unsigned > -BPF_JSET 0x40 PC += off if dst & src > -BPF_JNE 0x50 PC += off if dst != src > -BPF_JSGT 0x60 PC += off if dst > src signed > -BPF_JSGE 0x70 PC += off if dst >= src signed > -BPF_CALL 0x80 function call see `Helper functions`_ > -BPF_EXIT 0x90 function / program return BPF_JMP only > -BPF_JLT 0xa0 PC += off if dst < src unsigned > -BPF_JLE 0xb0 PC += off if dst <= src unsigned > -BPF_JSLT 0xc0 PC += off if dst < src signed > -BPF_JSLE 0xd0 PC += off if dst <= src signed > -======== ===== ========================= ============ > +======== ===== === =========================================== ========================================= > +code value src description notes > +======== ===== === =========================================== ========================================= > +BPF_JA 0x0 0x0 PC += offset BPF_JMP only > +BPF_JEQ 0x1 any PC += offset if dst == src > +BPF_JGT 0x2 any PC += offset if dst > src unsigned > +BPF_JGE 0x3 any PC += offset if dst >= src unsigned > +BPF_JSET 0x4 any PC += offset if dst & src > +BPF_JNE 0x5 any PC += offset if dst != src > +BPF_JSGT 0x6 any PC += offset if dst > src signed > +BPF_JSGE 0x7 any PC += offset if dst >= src signed > +BPF_CALL 0x8 0x0 call platform-agnostic helper function imm see `Platform-agnostic helper functions`_ > +BPF_CALL 0x8 0x1 call PC += offset see `BPF-local functions`_ > +BPF_CALL 0x8 0x2 call platform-specific helper function imm see `Platform-specific helper functions`_ > +BPF_EXIT 0x9 0x0 return BPF_JMP only > +BPF_JLT 0xa any PC += offset if dst < src unsigned > +BPF_JLE 0xb any PC += offset if dst <= src unsigned > +BPF_JSLT 0xc any PC += offset if dst < src signed > +BPF_JSLE 0xd any PC += offset if dst <= src signed > +======== ===== === =========================================== ========================================= > > The eBPF program needs to store the return value into register R0 before doing a > BPF_EXIT. > > -Helper functions > -~~~~~~~~~~~~~~~~ > +Platform-agnostic helper functions > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > -Helper functions are a concept whereby BPF programs can call into a > -set of function calls exposed by the runtime. Each helper > +Platform-agnostic helper functions are a concept whereby BPF programs can call > +into a set of function calls exposed by the runtime. Each helper > function is identified by an integer used in a ``BPF_CALL`` instruction. > -The available helper functions may differ for each program type. > +The available platform-agnostic helper functions may differ for each program > +type, but integer values are unique across all program types. > + > +Platform-specific helper functions > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > +Platform-specific helper functions are helper functions that are unique to > +a particular platform. They use a separate integer numbering space from > +platform-agnostic helper functions, but otherwise the same considerations > +apply. Platforms are not required to implement any platform-specific > +functions. I don't think it's a right distinction. helper vs kfunc are just different mechanisms. Like old approach and new. Both can be platform specific and agnostic. Take bpf_inode_storage_get() or bpf_find_vma(), I doubt anything like this will be available on non-Linux OS. While bpf_obj_new_impl() might very well be in every OS. > + > +BPF-local functions > +~~~~~~~~~~~~~~ > +BPF-local functions are functions exposed by the same BPF program as the caller, > +and are referenced by offset from the call instruction, similar to ``BPF_JA``. > +A ``BPF_EXIT`` within the BPF-local function will return to the caller. Instead of saying 'BPF-local' may be use 'program local' ?
