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

H.J. Lu
2012-06-09T14:30:41Z

On Tue, Jun 5, 2012 at 6:16 AM, Mark Kettenis <mark.kettenis@xs4all.nl> wrote:
>> 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.

Hi Mark,

Have you got time to review my change?

Thanks.

--
H.J.