[Linux-ia64] 2.4.14 Missing asm clobbers

[Linux-ia64] 2.4.14 Missing asm clobbers

[Keith Owens]

A comment of Linus's on l-k promoted me to check ia64 inline asm for
predicates.  I was surprised to find what look like missing asm
clobbers.  I am not 100% sure that these are errors (gcc clobbers are a
black art ;) so there is no patch.

include/asm-ia64/spinlock.h.

  spin_lock() changes ar.ccv, p7 without a clobber (!NEW_LOCK version).
  read_lock() changes p6 without a clobber.
  write_lock() changes ar.ccv, p7 without a clobber.

arch/ia64/kernel/traps.c

  fp_emulate() does ldf f10, f11 without a clobber.

arch/ia64/kernel/unaligned.c

  invala_gr() and invala_fr() do invala without a "memory" clobber.
  Not sure if it is necessary or not.

Re: [Linux-ia64] 2.4.14 Missing asm clobbers

[David Mosberger]

Thanks for reporting on this.  I'm certain some of asm need to be
fixed given not-so-recent compiler developments, though I'm not aware
of there being any real problems in this area at the moment.  I'll
look into it next week.

	--david

>>>>> On Wed, 21 Nov 2001 11:40:56 +1100, Keith Owens <kaos@ocs.com.au> said:

  Keith> A comment of Linus's on l-k promoted me to check ia64 inline
  Keith> asm for predicates.  I was surprised to find what look like
  Keith> missing asm clobbers.  I am not 100% sure that these are
  Keith> errors (gcc clobbers are a black art ;) so there is no patch.

  Keith> include/asm-ia64/spinlock.h.

  Keith>   spin_lock() changes ar.ccv, p7 without a clobber (!NEW_LOCK
  Keith> version).  read_lock() changes p6 without a clobber.
  Keith> write_lock() changes ar.ccv, p7 without a clobber.

  Keith> arch/ia64/kernel/traps.c

  Keith>   fp_emulate() does ldf f10, f11 without a clobber.

  Keith> arch/ia64/kernel/unaligned.c

  Keith>   invala_gr() and invala_fr() do invala without a "memory"
  Keith> clobber.  Not sure if it is necessary or not.

Re: [Linux-ia64] 2.4.14 Missing asm clobbers

[David Mosberger]

>>>>> On Wed, 21 Nov 2001 11:40:56 +1100, Keith Owens <kaos@ocs.com.au> said:

  Keith> include/asm-ia64/spinlock.h.

  Keith>   spin_lock() changes ar.ccv, p7 without a clobber (!NEW_LOCK
  Keith> version).  read_lock() changes p6 without a clobber.
  Keith> write_lock() changes ar.ccv, p7 without a clobber.

Ok, those should be fixed now.  They clearly are needed, though I
don't think the missing ar.ccv really had any effect because gcc uses
that register only for the builtin synchronization ops use them (which
we don't use in the kernel).

  Keith> arch/ia64/kernel/traps.c

  Keith>   fp_emulate() does ldf f10, f11 without a clobber.

That's fine because f10 and f11 are marked "fixed" on the command
line.

  Keith> arch/ia64/kernel/unaligned.c

  Keith>   invala_gr() and invala_fr() do invala without a "memory"
  Keith> clobber.  Not sure if it is necessary or not.

This is fine because the instructions affect the code that caused the
unaliged access, not the unaligned handler itself.  However, we
shouldn't need that code anymore because we now do an "invala" on
entry to the kernel.  I'll remove it in 2.5.xx.

Thanks,

	--david