[PATCH 3/3] ARM: early_printk: use printascii() rather than printch()

[Chris Brandt]

On Wednesday, November 01, 2017 1, Nicolas Pitre wrote:
> > > This patch worked for me.
> > > I get my carriage returns again.
> >
> > Sorry, but no.  This is crap.
> >
> > The kernelci.org test resulting from the tree I pushed out this evening
> > with both of the patches in is very unhappy:
> >
> >      42  arch/arm/kernel/debug.S:98: Error: immediate expression
> requires a # prefix -- `mov r1,10'
> >      42  arch/arm/kernel/debug.S:94: Error: immediate expression
> requires a # prefix -- `mov r1,13'
> >
> > I can't believe that anyone actually build-tested this patch as it
> > stands - maybe, Chris, you just think you did but you ended up
> > testing something else?  Or maybe your binutils is broken because
> > it now accepts constants without the preceding '#' ?
> 
> Well... I don't know what happened with Chris' testing either.


So, just to show I'm not crazy...


# Yes, patch was applied:
$ grep "mov        r1" arch/arm/kernel/debug.S
		mov	r1, #8
		mov	r1, #4
		mov	r1, #2
		mov	r1, #0
		mov	r1, '\r'    <<<<<<<<<<
		mov	r1, '\n'    <<<<<<<<<<
		mov	r1, r0
		mov	r1, r0

# Yes it builds:
$ touch arch/arm/kernel/debug.S
$ make -j8 O=.out uImage LOADADDR=0x08008000
make[1]: Entering directory '/home/renesas/tools/upstream/renesas-drivers/.out'
  CHK     include/config/kernel.release
  GEN     ./Makefile
  CHK     include/generated/uapi/linux/version.h
  CHK     scripts/mod/devicetable-offsets.h
  UPD     include/config/kernel.release
  Using .. as source for kernel
  CHK     include/generated/utsrelease.h
  UPD     include/generated/utsrelease.h
  CHK     include/generated/timeconst.h
  CHK     include/generated/bounds.h
  CHK     include/generated/asm-offsets.h
  CALL    ../scripts/checksyscalls.sh
  CHK     include/generated/compile.h
  CC      init/version.o
  AS      arch/arm/kernel/debug.o       <<<<<<<<<<


# Have a look at the output:
$ arm-linux-gnueabihf-objdump -SdCg .out/arch/arm/kernel/debug.o > /tmp/debug.lst
$ cat /tmp/debug.lst

------------------------------------------------------------
                mov     r1, '\r'           <<<<<<<<<<
  70:   f04f 010d       mov.w   r1, #13    <<<<<<<<<<
                waituart r2, r3
  74:   8a1a            ldrh    r2, [r3, #16]
  76:   f012 0f20       tst.w   r2, #32
  7a:   d0fb            beq.n   74 <printascii+0x2c>
                senduart r1, r3
  7c:   7319            strb    r1, [r3, #12]
  7e:   8a19            ldrh    r1, [r3, #16]
  80:   f021 0140       bic.w   r1, r1, #64     ; 0x40
  84:   8219            strh    r1, [r3, #16]
                busyuart r2, r3
  86:   8a1a            ldrh    r2, [r3, #16]
  88:   f012 0f40       tst.w   r2, #64 ; 0x40
  8c:   d0fb            beq.n   86 <printascii+0x3e>
                mov     r1, '\n'         <<<<<<<<<<
  8e:   f04f 010a       mov.w   r1, #10  <<<<<<<<<<
------------------------------------------------------------


So, the compiler realized what you wanted to do even if there wasn't a
# in front of the constant.


$ arm-linux-gnueabihf-gcc --version
arm-linux-gnueabihf-gcc (Linaro GCC 5.4-2017.01) 5.4.1 20161213
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.



Chris