diff options
Diffstat (limited to 'Documentation/bpf/instruction-set.rst')
| -rw-r--r-- | Documentation/bpf/instruction-set.rst | 38 |
1 files changed, 3 insertions, 35 deletions
diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst index 1b0e6711dec9..352f25a1eb17 100644 --- a/Documentation/bpf/instruction-set.rst +++ b/Documentation/bpf/instruction-set.rst @@ -282,8 +282,6 @@ arithmetic operations in the imm field to encode the atomic operation: *(u64 *)(dst_reg + off16) += src_reg -``BPF_XADD`` is a deprecated name for ``BPF_ATOMIC | BPF_ADD``. - In addition to the simple atomic operations, there also is a modifier and two complex atomic operations: @@ -331,36 +329,6 @@ There is currently only one such instruction. Legacy BPF Packet access instructions ------------------------------------- -eBPF has special instructions for access to packet data that have been -carried over from classic BPF to retain the performance of legacy socket -filters running in the eBPF interpreter. - -The instructions come in two forms: ``BPF_ABS | <size> | BPF_LD`` and -``BPF_IND | <size> | BPF_LD``. - -These instructions are used to access packet data and can only be used when -the program context is a pointer to networking packet. ``BPF_ABS`` -accesses packet data at an absolute offset specified by the immediate data -and ``BPF_IND`` access packet data at an offset that includes the value of -a register in addition to the immediate data. - -These instructions have seven implicit operands: - - * Register R6 is an implicit input that must contain pointer to a - struct sk_buff. - * Register R0 is an implicit output which contains the data fetched from - the packet. - * Registers R1-R5 are scratch registers that are clobbered after a call to - ``BPF_ABS | BPF_LD`` or ``BPF_IND | BPF_LD`` instructions. - -These instructions have an implicit program exit condition as well. When an -eBPF program is trying to access the data beyond the packet boundary, the -program execution will be aborted. - -``BPF_ABS | BPF_W | BPF_LD`` means:: - - R0 = ntohl(*(u32 *) (((struct sk_buff *) R6)->data + imm32)) - -``BPF_IND | BPF_W | BPF_LD`` means:: - - R0 = ntohl(*(u32 *) (((struct sk_buff *) R6)->data + src_reg + imm32)) +eBPF previously introduced special instructions for access to packet data that were +carried over from classic BPF. However, these instructions are +deprecated and should no longer be used. |