bpf, docs: Move sentence about returning R0 to abi.rst

As discussed at LSF/MM/BPF, the sentence about using R0 for returning
values from calls is part of the calling convention and belongs in
abi.rst.  Any further additions or clarifications to this text are left
for future patches on abi.rst.  The current patch is simply to unblock
progression of instruction-set.rst to a standard.

In contrast, the restriction of register numbers to the range 0-10
is untouched, left in the instruction-set.rst definition of the
src_reg and dst_reg fields.

Signed-off-by: Dave Thaler <dthaler1968@googlemail.com>
Link: https://lore.kernel.org/r/20240517153445.3914-1-dthaler1968@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/Documentation/bpf/standardization/abi.rst b/Documentation/bpf/standardization/abi.rst
index 0c2e10eeb89a05a10553a0cec5e826a110128a5f..41514137cb7b84924caf2e7aaf0bd3598682c0b7 100644 (file)
--- a/Documentation/bpf/standardization/abi.rst
+++ b/Documentation/bpf/standardization/abi.rst
@@ -23,3 +23,6 @@ The BPF calling convention is defined as:
 
 R0 - R5 are scratch registers and BPF programs needs to spill/fill them if
 necessary across calls.
+
+The BPF program needs to store the return value into register R0 before doing an
+``EXIT``.

diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst
index 00c93eb42613ed924a24c41bde2a2a42c04d4782..e2f6c0a4a559bc6ec49558df77077bf14776b1ba 100644 (file)
--- a/Documentation/bpf/standardization/instruction-set.rst
+++ b/Documentation/bpf/standardization/instruction-set.rst
@@ -476,9 +476,6 @@ the jump instruction.  Thus 'PC += 1' skips execution of the next
 instruction if it's a basic instruction or results in undefined behavior
 if the next instruction is a 128-bit wide instruction.
 
-The BPF program needs to store the return value into register R0 before doing an
-``EXIT``.
-
 Example:
 
 ``{JSGE, X, JMP32}`` means::