Re: [PATCH] arm: ensure symbol is a thumb symbol in new binutils

[Russell King - ARM Linux <linux@armlinux.org.uk>]

On Tue, Nov 21, 2017 at 06:46:25PM +0100, Jason A. Donenfeld wrote:
> Hi Russell,
> 
> On Tue, Nov 21, 2017 at 6:38 PM, Russell King - ARM Linux
> <linux@armlinux.org.uk> wrote:
> > +toolcheck:
> > +       @$(CONFIG_SHELL) '$(srctree)/$(src)/toolcheck'
> 
> Perhaps faster to put the check for THUMB2_KERNEL around the make
> target, instead of doing it in the code?

Could do, I was debating about extending this for the buggy linker
problem too from a few weeks ago.

> > +if grep -q 'CONFIG_THUMB2_KERNEL=y' .config; then
> 
> See above.
> 
> > +   tmp=$(mktemp -d /tmp/binutils-test.XXXXXXXXXX)
> > +   cat <<EOF | $AS $ASFLAGS -o $tmp/test.o
> > +       .syntax unified
> > +       .thumb
> > +       .macro  badr, reg, sym
> > +       adr     \reg, \sym + 1
> > +       .endm
> > +
> > +test:
> > +       mov     r0, #0
> > +       badr    lr, test
> > +EOF
> > +   if ! $OBJDUMP -d $tmp/test.o | grep -q '4:\s*f2af 0e07'; then
> > +      echo "Error: your assembler version produces buggy kernels" >&2
> > +      $AS --version | head -n1 >&2
> > +      rm $tmp/*.o
> > +      rmdir $tmp
> > +      exit 1
> > +   fi
> > +   rm $tmp/*.o
> > +   rmdir $tmp
> > +fi
> 
> This doesn't actually catch the issues. In the buggy binutils, it
> appears that sometimes adr grabs the right symbol and sometimes it
> doesn't. I'm not yet able to figure out a minimal condition for it
> going one way or the other.

What if we locate the "badr" instruction to the same offset - does
that trigger the binutils bug?  Note that the grep expression will
need updating...

-- 
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