imm is defined as a 32-bit signed integer.
{MOV, K, ALU64} says it does "dst = src" (where src is 'imm') and it
does do dst = (s64)imm, which in that sense does sign extend imm. The MOVSX
instruction is explained as sign extending, so added the example of
{MOV, K, ALU64} to make this more clear.
{JLE, K, JMP} says it does "PC += offset if dst <= src" (where src is 'imm',
and the comparison is unsigned). This was apparently ambiguous to some
readers as to whether the comparison was "dst <= (u64)(u32)imm" or
"dst <= (u64)(s64)imm" so added an example to make this more clear.
v1 -> v2: Address comments from Yonghong
Signed-off-by: Dave Thaler <dthaler1968@xxxxxxxxxxxxxx>
---
.../bpf/standardization/instruction-set.rst | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst
index 997560aba..7bb1281c5 100644
--- a/Documentation/bpf/standardization/instruction-set.rst
+++ b/Documentation/bpf/standardization/instruction-set.rst
@@ -385,6 +385,19 @@ The ``MOVSX`` instruction does a move operation with sign extension.
operands into 64-bit operands. Unlike other arithmetic instructions,
``MOVSX`` is only defined for register source operands (``X``).
+``{MOV, K, ALU64}`` means::
+
+ dst = (s64)imm
+
+``{MOV, X, ALU}`` means::
+
+ dst = (u32)src
+
+``{MOVSX, X, ALU}`` with 'offset' 8 means::
+
+ dst = (u32)(s32)(s8)src
+
+
The ``NEG`` instruction is only defined when the source bit is clear
(``K``).
@@ -486,6 +499,10 @@ Example:
where 's>=' indicates a signed '>=' comparison.
+``{JLE, K, JMP}`` means::
+
+ if dst <= (u64)(s64)imm goto +offset
+
``{JA, K, JMP32}`` means::
gotol +imm
--
2.40.1
