[Linux-ia64] get_scratch_regs in bk 2.4 unwind.c

[Linux-ia64] get_scratch_regs in bk 2.4 unwind.c

[Keith Owens]

The bk version of unwind.c has some changes from my patch which do not
look right.

static inline struct pt_regs *
get_scratch_regs (struct unw_frame_info *info)
{
	if (!info->pt) {
		/* This should not happen with valid unwind info.  */
		UNW_DPRINT(0, "unwind.%s: bad unwind info: resetting info->pt\n", __FUNCTION__);
		info->pt = info->sp - 16;
	}
	UNW_DPRINT(3, "unwind.%s: sp 0x%lx pt 0x%lx\n", __FUNCTION__, info->sp, info->pt);
	return info->pt;
}

__FUNCTION__ will always print get_scratch_regs which is of no use, we
need the calling function.  My patch passed in the calling function
name as a parameter.  Please revert to passing in the function name or
make get_scratch_regs a #define so it gets the calling function name.
Also I printed the new value of info->pt, it is useful when debugging
bad unwind data.

unw_access_gr has

			/* access a scratch register */
			if (!info->pt) {
				UNW_DPRINT(0, "unwind.%s: no pt-regs; cannot access r%d\n",
					   __FUNCTION__, regnum);
				return -1;
			}
			pt = get_scratch_regs(info);

Why the test for !info->pt?  No other use of get_scratch_regs has that
test, unw_access_[abf]r will continue with whatever data get_scratch_regs
returns, using pt_regs on top of stack if info->pt is undefined.  The
code is inconsistent.

Re: [Linux-ia64] get_scratch_regs in bk 2.4 unwind.c

[David Mosberger]

>>>>> On Sat, 08 Mar 2003 14:57:11 +1100, Keith Owens <kaos@sgi.com> said:

  Keith> UNW_DPRINT(3, "unwind.%s: sp 0x%lx pt 0x%lx\n", __FUNCTION__, info->sp, info->pt);

  Keith> __FUNCTION__ will always print get_scratch_regs which is of no use, we
  Keith> need the calling function.  My patch passed in the calling function
  Keith> name as a parameter.  Please revert to passing in the function name or
  Keith> make get_scratch_regs a #define so it gets the calling function name.
  Keith> Also I printed the new value of info->pt, it is useful when debugging
  Keith> bad unwind data.

We're not going to pass around arguments that are only used for
debugging.  If you want to, we could print __builtin_return_address(0)
along with the function name (or we could use the kernel symbol table
to print the symbolic name).

  Keith> unw_access_gr has

  Keith> /* access a scratch register */
  Keith> if (!info->pt) {
  Keith> UNW_DPRINT(0, "unwind.%s: no pt-regs; cannot access r%d\n",
  Keith> __FUNCTION__, regnum);
  Keith> return -1;
  Keith> }
  Keith> pt = get_scratch_regs(info);

  Keith> Why the test for !info->pt?  No other use of get_scratch_regs
  Keith> has that test, unw_access_[abf]r will continue with whatever
  Keith> data get_scratch_regs returns, using pt_regs on top of stack
  Keith> if info->pt is undefined.  The code is inconsistent.

I agree.  Looks like something went wrong during the merge.  I'll fix
that.

	--david