summaryrefslogtreecommitdiffstats
path: root/Documentation/bpf
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/bpf')
-rw-r--r--Documentation/bpf/instruction-set.rst9
1 files changed, 6 insertions, 3 deletions
diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst
index 492980ece1ab..6644842cd3ea 100644
--- a/Documentation/bpf/instruction-set.rst
+++ b/Documentation/bpf/instruction-set.rst
@@ -163,13 +163,13 @@ BPF_MUL 0x20 dst \*= src
BPF_DIV 0x30 dst = (src != 0) ? (dst / src) : 0
BPF_OR 0x40 dst \|= src
BPF_AND 0x50 dst &= src
-BPF_LSH 0x60 dst <<= src
-BPF_RSH 0x70 dst >>= src
+BPF_LSH 0x60 dst <<= (src & mask)
+BPF_RSH 0x70 dst >>= (src & mask)
BPF_NEG 0x80 dst = ~src
BPF_MOD 0x90 dst = (src != 0) ? (dst % src) : dst
BPF_XOR 0xa0 dst ^= src
BPF_MOV 0xb0 dst = src
-BPF_ARSH 0xc0 sign extending shift right
+BPF_ARSH 0xc0 sign extending dst >>= (src & mask)
BPF_END 0xd0 byte swap operations (see `Byte swap instructions`_ below)
======== ===== ==========================================================
@@ -204,6 +204,9 @@ for ``BPF_ALU64``, 'imm' is first sign extended to 64 bits and the result
interpreted as an unsigned 64-bit value. There are no instructions for
signed division or modulo.
+Shift operations use a mask of 0x3F (63) for 64-bit operations and 0x1F (31)
+for 32-bit operations.
+
Byte swap instructions
~~~~~~~~~~~~~~~~~~~~~~