int
syscall(
int number
, ...
)
quad_t
__syscall(
quad_t number
, ...
)
)
performs the system call whose assembly language
interface has the specified
number
with the specified arguments.
Symbolic constants for system calls can be found in the header file
sys/syscall.h<.blm Pp
. >
The
__syscall
form should be used when one or more of the parameters is a
64-bit argument to ensure that argument alignment is correct.
This system call is useful for testing new system calls that
do not have entries in the C library.
)
function call appeared in
4.0BSD.
Since architectures return 32 bit and 64 bit results in different registers,
it may be impossible to portably convert the result of
__syscall()
to a 32bit value.
For instance sparc returns 32 bit values in %o0 and 64 bit values in %o0:%o1
(with %o0 containing the most significant part) so a 32 bit right shift
of the result is needed to get a correct 32 bit result.
Due to ABI implementation differences in passing struct or union
type arguments to system calls between different processors, all
system calls pass instead pointers to such structs or unions, even
when the documentation of the system call mentions otherwise.
The conversion between passing structs and unions is handled normally
via userland stubs.
The correct arguments for the kernel entry
points for each system call can be found in the header file
sys/syscallargs.h<.blm Pp
>