Re: x32 ABI Support (was Re: Three weeks to branching (gdb 7.5 release))

Mark Kettenis
2012-06-05T13:16:49Z

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> Date: Tue, 5 Jun 2012 05:58:18 -0700
> From: "H.J. Lu" <hjl.tools@gmail.com>
>
> On Thu, May 31, 2012 at 11:18 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> > On Mon, May 28, 2012 at 2:18 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> >> On Mon, May 28, 2012 at 1:26 PM, Mark Kettenis <mark.kettenis@xs4all.nl> wrote:
> >>>> Date: Sun, 20 May 2012 15:48:54 -0700
> >>>> From: "H.J. Lu" <hjl.tools@gmail.com>
> >>>>
> >>>> Does this one look OK.  I extracted x32_init_abi from amd64_x32_init_abi
> >>>> since amd64_x32_linux_init_abi can't call amd64_init_abi after
> >>>> calling amd64_linux_init_abi.
> >>>
> >>> I guess multiple-inheritance is a bad idea, even when implemented in C ;)
> >>>
> >>> I really do think that amd64_x32_linux_init_abi() should call
> >>> amd64_x32_init_abi().  That way it is immediately obvious that the OS-specific ABI inherits everything from the generic ABI.
> >>
> >> X32 kernel interface are highly OS specific.  Different OSes can implement
> >> very different kernel interfaces.  The only generic x32 bits are
> >>
> >>  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
> >>
> >>  tdep->num_dword_regs = 17;
> >>
> >>  set_tdesc_pseudo_register_type (gdbarch, amd64_x32_pseudo_register_type);
> >>
> >>  set_gdbarch_long_bit (gdbarch, 32);
> >>  set_gdbarch_ptr_bit (gdbarch, 32);
> >>
> >> They are the same for all x32 OSes since they are determined by
> >> hardware, not OS.
> >>
> >>> In order too avoid too much code duplication, the common bits should
> >>> be split out from amd64_linux_init_abi() into a seperate function that
> >>> gets called from both amd64_linux_init_abi() and
> >>> amd64_x32_linux_init_abi().  As I wrote earlier, it isn't entirely
> >>> obvious that everything in amd64_linix_init_abi() applies to the x32
> >>> ABI.  So we should be conservative in moving stuff into the common
> >>> function.  In fact it might be a good idea to start out with something
> >>> like the attached diff, and gradually move things over.
> >>
> >> Linux x32 kernel interface shares > 90% of Linux amd64 kernel
> >> interface (309 system calls out of 337 are the same).  See
> >> 64-bit system call table in Linux kernel 3.4:
> >>
> >> http://git.kernel.org/?p=linux/kernel/git/stable/linux-stable.git;a=blob;f=arch/x86/syscalls/syscall_64.tbl;h=dd29a9ea27c560a9d2fcb6e1c2983f8b8e9be407;hb=HEAD
> >>
> >> I believe we should start with sharing everything between Linux/x32
> >> and Linux/amd64.  We can update x32 part as we go.
> >>
> >
> >
> > Here is the updated patch.  I added amd64_x32_init for generic x32
> > setting.  It can be used by all x32 init_abi functions.  Since
> > tdep->tdesc can't be changed after being used, I renamed
> > amd64_init_abi/amd64_init_abi to amd64_init/amd64_linux_init
> > to take an  argument to set tdep->tdesc properly.  OK for trunk?
> >
> > Thanks.
> >
>
> Hi Mark,
>
> Do you have a chance to take a look at this?

Sorry, no. Unliekly to be able to look at it until Thrusday evening.