diff options
Diffstat (limited to 'gas/doc/c-bpf.texi')
| -rw-r--r-- | gas/doc/c-bpf.texi | 56 |
1 files changed, 51 insertions, 5 deletions
diff --git a/gas/doc/c-bpf.texi b/gas/doc/c-bpf.texi index 0756796..917e0dc 100644 --- a/gas/doc/c-bpf.texi +++ b/gas/doc/c-bpf.texi @@ -377,14 +377,60 @@ Terminate the eBPF program. @subsubsection Atomic instructions -Atomic exchange-and-add instructions are provided in two flavors: one -for swapping 64-bit quantities and another for 32-bit quantities. +BPF provides a set of instructions to perform arithmetic and logical +operations on stored data atomically. These are: @table @code -@item xadddw [%d+offset16],%s -Exchange-and-add a 64-bit value at the specified location. @item xaddw [%d+offset16],%s -Exchange-and-add a 32-bit value at the specified location. +@itemx xadddw [%d+offset16],%s +Add @code{%s} to the 32 or 64 bit signed integer stored in the +specified memory location and store the result, atomically. +@item xorw [%d+offset16],%s +@itemx xordw [%d+offset16],%s +Perform a bit-wise or operation between @code{%s} and the 32 or 64 bit +signed integer stored in the specified memory location and store the +result, atomically. +@item xxorw [%d+offset16],%s +@itemx xxordw [%d+offset16],%s +Perform a bit-wise xor operation between @code{%s} and the 32 or 64 bit +signed integer stored in the specified memory location and store the +result, atomically. +@end table + +@noindent +Additionally, the following instructions allow to perform arithmetic +and logical operations on stored data and then fetching the original +stored value in a register, atomically: + +@table @code +@item xfaddw [%d+offset16],%s +@itemx xfadddw [%d+offset16],%s +Add @code{%s} to the 32 or 64 bit signed integer stored in the +specified memory location, store the result, and set @code{%s} to the +value originally stored in the memory location, atomically. +@item xforw [%d+offset16],%s +@itemx xfordw [%d+offset16],%s +Perform a bit-wise or operation between @code{%s} and the 32 or 64 bit +signed integer stored in the specified memory location, store the +result, and set @code{%s} to the value originally stored in the memory +location, atomically. +@item xfxorw [%d+offset16],%s +@itemx xfxordw [%d+offset16],%s +Perform a bit-wise xor operation between @code{%s} and the 32 or 64 +bit signed integer stored in the specified memory location, store the +result, and set @code{%s} to the value originally stored in the memory +location, atomically. +@item xchgw [%d+offset16],%s +@itemx xchgdw [%d+offset16],%s +Exchange the 32 or 64 bit values in @code{%s} and the specified memory +location, atomically. +@item xcmpw [%d+offset16],%s +@itemx xcmpdw [%d+offset16],%s +Compare and exchange operation. Compare the 32 or 64 bit value stored +in the specified memory location to the contents of the @code{%r0} +register. If they are equal, store @code{%s} in the memory location. +In any case, update @code{%r0} with the original contents of the +memory location. @end table @node BPF Pseudo-C Syntax |