path: root/Documentation/networking/filter.txt
diff options
authorAlexei Starovoitov <ast@plumgrid.com>2014-06-06 14:46:06 -0700
committerDavid S. Miller <davem@davemloft.net>2014-06-11 00:13:16 -0700
commite430f34ee5192c84bcabd3c79ab7e2388b5eec74 (patch)
tree4b4086b0ecf0c4d67c4ae28d493b5987430da143 /Documentation/networking/filter.txt
parentMerge branch 'bridge_multicast_exports' (diff)
net: filter: cleanup A/X name usage
The macro 'A' used in internal BPF interpreter: #define A regs[insn->a_reg] was easily confused with the name of classic BPF register 'A', since 'A' would mean two different things depending on context. This patch is trying to clean up the naming and clarify its usage in the following way: - A and X are names of two classic BPF registers - BPF_REG_A denotes internal BPF register R0 used to map classic register A in internal BPF programs generated from classic - BPF_REG_X denotes internal BPF register R7 used to map classic register X in internal BPF programs generated from classic - internal BPF instruction format: struct sock_filter_int { __u8 code; /* opcode */ __u8 dst_reg:4; /* dest register */ __u8 src_reg:4; /* source register */ __s16 off; /* signed offset */ __s32 imm; /* signed immediate constant */ }; - BPF_X/BPF_K is 1 bit used to encode source operand of instruction In classic: BPF_X - means use register X as source operand BPF_K - means use 32-bit immediate as source operand In internal: BPF_X - means use 'src_reg' register as source operand BPF_K - means use 32-bit immediate as source operand Suggested-by: Chema Gonzalez <chema@google.com> Signed-off-by: Alexei Starovoitov <ast@plumgrid.com> Acked-by: Daniel Borkmann <dborkman@redhat.com> Acked-by: Chema Gonzalez <chema@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to '')
1 files changed, 1 insertions, 1 deletions
diff --git a/Documentation/networking/filter.txt b/Documentation/networking/filter.txt
index 58c443926647..9f49b8690500 100644
--- a/Documentation/networking/filter.txt
+++ b/Documentation/networking/filter.txt
@@ -805,7 +805,7 @@ to seccomp_data, for converted BPF filters R1 points to a skb.
A program, that is translated internally consists of the following elements:
- op:16, jt:8, jf:8, k:32 ==> op:8, a_reg:4, x_reg:4, off:16, imm:32
+ op:16, jt:8, jf:8, k:32 ==> op:8, dst_reg:4, src_reg:4, off:16, imm:32
So far 87 internal BPF instructions were implemented. 8-bit 'op' opcode field
has room for new instructions. Some of them may use 16/24/32 byte encoding. New