From 2d71a90f7e0fa3cd348602a36f6eb1237ab7cebb Mon Sep 17 00:00:00 2001 From: Will Hawkins Date: Sat, 26 Aug 2023 01:32:54 -0400 Subject: [PATCH] bpf, docs: Correct source of offset for program-local call The offset to use when calculating the target of a program-local call is in the instruction's imm field, not its offset field. Signed-off-by: Will Hawkins Signed-off-by: Daniel Borkmann Acked-by: Eduard Zingerman Acked-by: David Vernet Link: https://lore.kernel.org/bpf/20230826053258.1860167-1-hawkinsw@obs.cr --- 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 4f73e9d..c5b0b20 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 =========================== -- 2.7.4