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Date: Wed, 3 Feb 2010 18:56:20 -0800 (PST)
From: Neelkanth Natu <neelnatu@yahoo.com>
To: "C. Jayachandran" <c.jayachandran@gmail.com>
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Cc: freebsd-mips@freebsd.org
Subject: Re: mips ptrace.S fix
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Hi JC,

--- On Wed, 2/3/10, C. Jayachandran <c.jayachandran@gmail.com> wrote:

> From: C. Jayachandran <c.jayachandran@gmail.com>
> Subject: Re: mips ptrace.S fix
> To: "Neelkanth Natu" <neelnatu@yahoo.com>
> Cc: "Rui Paulo" <rpaulo@freebsd.org>, freebsd-mips@freebsd.org
> Date: Wednesday, February 3, 2010, 6:09 PM
> On Thu, Feb 4, 2010 at 1:01 AM,
> Neelkanth Natu <neelnatu@yahoo.com>
> wrote:
> > Your patch looks good. I have a few comments though.
> See inline:
> >
> > Index: lib/libc/mips/sys/ptrace.S
> >
> ===================================================================
> > --- lib/libc/mips/sys/ptrace.S  (revision 203379)
> > +++ lib/libc/mips/sys/ptrace.S  (working copy)
> > @@ -42,14 +42,26 @@
> >  #endif /* LIBC_SCCS and not lint */
> >
> >  LEAF(ptrace)
> > +       .frame  sp,40,ra
> >
> >>> space missing after the ','
> >
> > +       .mask   0x80000000, -8
> >  #ifdef __ABICALLS__
> >        .set    noreorder
> >        .cpload t9
> >        .set    reorder
> >  #endif
> > +       subu    sp, sp, 40
> > +       sw      ra,  32(sp)
> > +#ifdef __ABICALLS__
> > +       .cprestore 16
> > +#endif
> >        la      t9, _C_LABEL(__error)   #
> locate address of errno
> > -       jalr    t9
> > +       jalr    t9
> >
> >>> this change is not required - the newly added
> line has a tab at the end.
> >
> > +#ifdef __ABICALLS__
> > +       lw      gp, 16(sp)
> > +#endif
> >
> >>> this is redundant - the assembler will
> generate exactly the same line of
> >>> code due to the .cprestore directive above.
> 
> Are you sure about this?  I think the assembler
> generates the gp load
> only for the 'jal' and 'bal' not for 'jalr'.
> 
> Probably the two lines(la and jalr) can be replaced by a
> jal.
> 

You are right. My eyes glossed over between the 'jal' and 'jalr'. I think
combining the two instructions into a single 'jal' is the way to go.

best
Neel

> Regards,
> JC.
>