[PATCH bpf-next] bpf, docs: Add signed comparison example

Dave Thaler
2023-03-10T23:38:26Z

From: Dave Thaler <dthaler@microsoft.com>

Improve clarity by adding an example of a signed comparison instruction

Signed-off-by: Dave Thaler <dthaler@microsoft.com>
---
Documentation/bpf/instruction-set.rst | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst
index 5e43e14abe8..b4464058905 100644
--- a/Documentation/bpf/instruction-set.rst
+++ b/Documentation/bpf/instruction-set.rst
@@ -11,7 +11,8 @@ Documentation conventions
=========================

For brevity, this document uses the type notion "u64", "u32", etc.
-to mean an unsigned integer whose width is the specified number of bits.
+to mean an unsigned integer whose width is the specified number of bits,
+and "s32", etc. to mean a signed integer of the specified number of bits.

Registers and calling convention
================================
@@ -264,6 +265,14 @@ BPF_JSLE 0xd0 PC += off if dst <= src signed
The eBPF program needs to store the return value into register R0 before doing a
BPF_EXIT.

+Example:
+
+``BPF_JSGE | BPF_X | BPF_JMP32`` (0x7e) means::
+
+ if (s32)dst s>= (s32)src goto +offset
+
+where 's>=' indicates a signed '>=' comparison.
+
Helper functions
~~~~~~~~~~~~~~~~

--
2.33.4