On Sat, 2023-08-26 at 01:32 -0400, Will Hawkins wrote: > The offset to use when calculating the target of a program-local call is > in the instruction's imm field, not its offset field. Indeed, this is the case, e.g. see kernel/bpf/verifier.c:add_subprog_and_kfunc(). Acked-by: Eduard Zingerman <eddyz87@xxxxxxxxx> > > Signed-off-by: Will Hawkins <hawkinsw@xxxxxx> > --- > Documentation/bpf/standardization/instruction-set.rst | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst > index 4f73e9dc8d9e..c5b0b2011f16 100644 > --- a/Documentation/bpf/standardization/instruction-set.rst > +++ b/Documentation/bpf/standardization/instruction-set.rst > @@ -373,7 +373,7 @@ 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 helper function by address see `Helper functions`_ > -BPF_CALL 0x8 0x1 call PC += offset see `Program-local functions`_ > +BPF_CALL 0x8 0x1 call PC += imm see `Program-local functions`_ > BPF_CALL 0x8 0x2 call helper function by BTF ID see `Helper functions`_ > BPF_EXIT 0x9 0x0 return BPF_JMP only > BPF_JLT 0xa any PC += offset if dst < src unsigned > @@ -424,8 +424,8 @@ Program-local functions > ~~~~~~~~~~~~~~~~~~~~~~~ > Program-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 program-local function will return to > -the caller. > +``BPF_JA``. The offset is encoded in the imm field of the call instruction. > +A ``BPF_EXIT`` within the program-local function will return to the caller. > > Load and store instructions > ===========================
