System call numbers differ among different operating
systems. For example, on Linux machines, the read syscall number is
0 but on Darwin machines, it is 3. The x86 model
currently supports syscall numbers for Linux and Darwin operating
systems only.
For the x86isa model, we define the syscall numbers based on the
contents of the os-info field of the x86 state. Currently
supported values of this field are :linux and :darwin, with
:linux being the default value. Note that the field os-info
is meaningful only in the app-view.
