On Wed, Mar 27, 2013 at 6:11 AM, <ch0.han@xxxxxxx> wrote: > From: Changhee Han <gyulkkajo@xxxxxxxxx> > > Add notes that caution users when passing arguments to syscall.2. > > Signed-off-by: Changhee Han <gyulkkajo@xxxxxxxxx> > --- > man2/syscall.2 | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/man2/syscall.2 b/man2/syscall.2 > index 0675943..2c823b6 100644 > --- a/man2/syscall.2 > +++ b/man2/syscall.2 > @@ -79,6 +79,15 @@ and an error code is stored in > .BR syscall () > first appeared in > 4BSD. > + > +On some architecture arguments should be passed with an appropriate way. > +The glibc wrapper function, described in > +.BR syscalls (2), > +copies arguments to the right registers denpend on the architecture but > +.BR syscall (2) > +needs arguments following ABI, which its architecture describes, to be passed manually by a user. > +For example, on ARM architecture, a long long type of argument is considered to be 8-byte aligned and to be split into two 4-byte arguments. Changhee, I think this is a very worthwhile patch, but needs a bit of clarification. How would text such as this be: [[ Each architecture ABI has its own requirements on how system call arguments are passed to the kernel. For system calls that have a glibc wrapper (i.e., most system calls) glibc handles the details of copy arguments to the right registers in a manner suitable for the architecture. However, when using .BR syscall () to make a system call, the caller may need to handle architecture-dependent details. For example, on the ARM architecture, a .I "long long" argument is considered to be 8-byte aligned and to be split into two 4-byte arguments. ]] Would that text be okay? And then, in addition to that it would be good to have an example of how one uses syscall() on ARM to invoke a system call with an 8-byte aligned argument. Could you provide an example? Cheers, Michael -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
