Re: Three weeks to branching (gdb 7.5 release)

Mark Kettenis
2012-05-20T21:39:07Z

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> Date: Sun, 20 May 2012 14:24:46 -0700
> From: "H.J. Lu" <hjl.tools@gmail.com>
>
> On Sun, May 20, 2012 at 1:43 PM, Mark Kettenis <mark.kettenis@xs4all.nl> wrote:
> >> Date: Sun, 20 May 2012 08:40:26 -0700
> >> From: "H.J. Lu" <hjl.tools@gmail.com>
> >>
> >> On Fri, May 11, 2012 at 11:43 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> >> > On Fri, May 11, 2012 at 11:17 AM, Joel Brobecker <brobecker@adacore.com> wrote:
> >> >> Hello,
> >> >>
> >> >> Just a quick heads up: The current tentative date for branching
> >> >> GDB (7.5 release) is Mon Jun 4th, which is a little over three weeks
> >> >> away.
> >> >>
> >> >> I've created a wiki page for known issues that need to be fixed
> >> >> before then:
> >> >>
> >> >>    http://sourceware.org/gdb/wiki/GDB_7.5_Release
> >> >>
> >> >> When you add an issue, please make sure you add a name so we know
> >> >> who is coordinating the effort.  If you don't know who can work
> >> >> on it, please just post the issue here, and we'll try to find some
> >> >> help.
> >> >>
> >> >> I only know of one issue, which is a noticeable performance degradation
> >> >> that was reported a while ago:
> >> >>
> >> >
> >> > I'd like to merge x32 into GDB 7.5.  My x32 change is on hjl/x32/master
> >> > branch at
> >> >
> >> > http://sourceware.org/git/?p=gdb.git;a=summary
> >> >
> >> > The current diff only has 864 lines.  One patch:
> >> >
> >> > http://sourceware.org/ml/gdb-patches/2012-05/msg00097.html
> >> >
> >> > isn't reviewed yet.  I will open a meta bug for x32 integration.
> >> >
> >>
> >> I opened:
> >>
> >> http://sourceware.org/bugzilla/show_bug.cgi?id=14099
> >>
> >> Thanks for help from everyone.  The full GDBserver x32 support
> >> as well as partial GDB x32 support have been checked in.  The
> >> remaining patches are:
> >>
> >> http://sourceware.org/ml/gdb-patches/2012-04/msg00195.html
> >> http://sourceware.org/ml/gdb-patches/2012-04/msg00191.html
> >> http://sourceware.org/ml/gdb-patches/2012-05/msg00744.html
> >> http://sourceware.org/ml/gdb-patches/2012-05/msg00531.html
> >> http://sourceware.org/ml/gdb-patches/2012-05/msg00533.html
> >> http://sourceware.org/ml/gdb-patches/2012-05/msg00489.html
> >> http://sourceware.org/ml/gdb-patches/2012-05/msg00438.html
> >> http://sourceware.org/ml/gdb-patches/2012-05/msg00097.html
> >>
> >> I would appreciate help to get them reviewed and approved.
> >
> > As I wrote before, I don't think adding lots if if-statements is the
> > proper way to add a new ABI to GDB.  The proper way is to do it like
> > the diff below.  In that diff, I'm not entirely confident that calling
> > amd64_linux_init_abi() from amd64_x32_linux_init_abi() makes all that
> > much sense.  For example the amd64_linux_record_tdep stuff probably
> > isn't right for the x32 ABI.  But at least this will give us a
> > starting point where we won't end up adding
> >
> >  if (gdbarch_ptr_bit (gdbarch) == 32)
> >    {
> >      ...
> >    }
>
> Please take a look at
>
> http://sourceware.org/ml/gdb-patches/2012-04/msg00195.html
>
> It doesn't add any (gdbarch_ptr_bit (gdbarch) == 32). It just changes
> it to bits_per_word. I add one "gdbarch_ptr_bit (gdbarch) == 32" in
> amd64_linux_sigtramp_start and I will remove them from
>
> http://sourceware.org/ml/gdb-patches/2012-05/msg00744.html

Well, I'm also thining about the future here. Stuff you haven't
addressed yet in your diff series and stuff that will be added later.

> > Index: amd64-linux-tdep.c
> > ===================================================================
> > RCS file: /cvs/src/src/gdb/amd64-linux-tdep.c,v
> > retrieving revision 1.50
> > diff -u -p -r1.50 amd64-linux-tdep.c
> > --- amd64-linux-tdep.c  12 May 2012 08:54:03 -0000      1.50
> > +++ amd64-linux-tdep.c  20 May 2012 20:31:53 -0000
> > @@ -1543,6 +1543,24 @@ amd64_linux_init_abi (struct gdbarch_inf
> >
> >   tdep->i386_syscall_record = amd64_linux_syscall_record;
> >  }
> > +
> > +static void
> > +amd64_x32_linux_init_abi(struct gdbarch_info info, struct gdbarch *gdbarch)
> > +{
> > +  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
> > +  const struct target_desc *tdesc = info.target_desc;
> > +
> > +  amd64_linux_init_abi (info, gdbarch);
> > +  amd64_x32_init_abi (info, gdbarch);
> > +
> > +  if (! tdesc_has_registers (tdesc))
> > +    tdesc = tdesc_amd64_linux;
>
> I assume you meant tdesc_x32_linux here. The problem is
> when we reach here, if (! tdesc_has_registers (tdesc)) will always
> be false since tdep->tdesc has been set by amd64_linux_init_abi.
>
> > +  tdep->tdesc = tdesc;
> > +
> > +  /* GNU/Linux uses SVR4-style shared libraries.  */
> > +  set_solib_svr4_fetch_link_map_offsets
> > +    (gdbarch, svr4_ilp32_fetch_link_map_offsets);
> > +}
> >
> >
> >  /* Provide a prototype to silence -Wmissing-prototypes.  */
> > @@ -1553,6 +1571,8 @@ _initialize_amd64_linux_tdep (void)
> >  {
> >   gdbarch_register_osabi (bfd_arch_i386, bfd_mach_x86_64,
> >                          GDB_OSABI_LINUX, amd64_linux_init_abi);
> > +  gdbarch_register_osabi (bfd_arch_i386, bfd_mach_x64_32,
> > +                         GDB_OSABI_LINUX, amd64_x32_linux_init_abi);
> >
> >   /* Initialize the Linux target description.  */
> >   initialize_tdesc_amd64_linux ();
> > Index: amd64-tdep.c
> > ===================================================================
> > RCS file: /cvs/src/src/gdb/amd64-tdep.c,v
> > retrieving revision 1.104
> > diff -u -p -r1.104 amd64-tdep.c
> > --- amd64-tdep.c        14 May 2012 18:56:40 -0000      1.104
> > +++ amd64-tdep.c        20 May 2012 20:31:54 -0000
> > @@ -258,7 +258,8 @@ static const char *amd64_word_names[] =
> >  static const char *amd64_dword_names[] =
> >  {
> >   "eax", "ebx", "ecx", "edx", "esi", "edi", "ebp", "esp",
> > -  "r8d", "r9d", "r10d", "r11d", "r12d", "r13d", "r14d", "r15d"
> > +  "r8d", "r9d", "r10d", "r11d", "r12d", "r13d", "r14d", "r15d",
> > +  "eip"
> >  };
> >
> >  /* Return the name of register REGNUM.  */
> > @@ -2729,6 +2730,43 @@ amd64_init_abi (struct gdbarch_info info
> >   set_gdbarch_stap_parse_special_token (gdbarch,
> >                                        i386_stap_parse_special_token);
> >  }
> > +
> > +
> > +static struct type *
> > +amd64_x32_pseudo_register_type (struct gdbarch *gdbarch, int regnum)
> > +{
> > +  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
> > +
> > +  switch (regnum - tdep->eax_regnum)
> > +    {
> > +    case AMD64_RBP_REGNUM:     /* %ebp */
> > +    case AMD64_RSP_REGNUM:     /* %esp */
> > +      return builtin_type (gdbarch)->builtin_data_ptr;
> > +    case AMD64_RIP_REGNUM:     /* %eip */
> > +      return builtin_type (gdbarch)->builtin_func_ptr;
> > +    }
> > +
> > +  return i386_pseudo_register_type (gdbarch, regnum);
> > +}
> > +
> > +void
> > +amd64_x32_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
> > +{
> > +  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
> > +  const struct target_desc *tdesc = info.target_desc;
> > +
> > +  amd64_init_abi (info, gdbarch);
> > +
> > +  if (! tdesc_has_registers (tdesc))
> > +    tdesc = tdesc_x32;
>
> Again, " if (! tdesc_has_registers (tdesc))" will always false
> since tdep->tdesc has been set in amd64_init_abi.

I don't think that's true. Here tdesc comes from info.target_desc,
not tdep->tdesc, so the check should still do the right thing. In
fact it must do the right thing, since amd64_linux_init_abi() does the
same thing already.