Adding upstream version 6.7.7.upstream/6.7.7

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst
index c5d53a6e8c..245b6defc2 100644
--- a/Documentation/bpf/standardization/instruction-set.rst
+++ b/Documentation/bpf/standardization/instruction-set.rst
@@ -283,6 +283,14 @@ For signed operations (``BPF_SDIV`` and ``BPF_SMOD``), for ``BPF_ALU``,
 is first :term:`sign extended<Sign Extend>` from 32 to 64 bits, and then
 interpreted as a 64-bit signed value.
 
+Note that there are varying definitions of the signed modulo operation
+when the dividend or divisor are negative, where implementations often
+vary by language such that Python, Ruby, etc.  differ from C, Go, Java,
+etc. This specification requires that signed modulo use truncated division
+(where -13 % 3 == -1) as implemented in C, Go, etc.:
+
+   a % n = a - n * trunc(a / n)
+
 The ``BPF_MOVSX`` instruction does a move operation with sign extension.
 ``BPF_ALU | BPF_MOVSX`` :term:`sign extends<Sign Extend>` 8-bit and 16-bit operands into 32
 bit operands, and zeroes the remaining upper 32 bits.