Re: arm-uboot: misc.S:56: Error: r13 not allowed here -- `sub sp, fp, #4'

[Vladimir 'φ-coder/phcoder' Serbinenko]

On 13.11.2013 16:36, Leif Lindholm wrote:
> On Wed, Nov 13, 2013 at 04:15:53PM +0100, Vladimir 'φ-coder/phcoder' 
> Serbinenko wrote:
>> On 13.11.2013 15:49, Colin Watson wrote:
>>> After my previous fix, arm-uboot still fails to build with:
>>>
>>>   arm-linux-gnueabihf-gcc -DHAVE_CONFIG_H -I. -I../../../grub-core -I..  
>>> -Wall -W -I../../../include -I../include  -DGRUB_MACHINE_UBOOT=1 
>>> -DGRUB_MACHINE_ARM=1 -DGRUB_MACHINE=ARM_UBOOT -DGRUB_TARGET_CPU_ARM=1 
>>> -nostdinc -isystem /usr/lib/gcc-cross/arm-linux-gnueabihf/4.8/include 
>>> -DGRUB_FILE=\"lib/arg.c\" -I. -I../../../grub-core -I.. -I../../.. 
>>> -I../../../include -I../include 
>>> -I../../../grub-core/lib/libgcrypt-grub/include 
>>> -I../../../grub-core/lib/libgcrypt-grub/src/   -DGRUB_KERNEL=1   -Os -Wall 
>>> -W -Wshadow -Wold-style-definition -Wpointer-arith -Wundef -Wextra 
>>> -Wattributes -Wchar-subscripts -Wcomment -Wdeprecated-declarations 
>>> -Wdisabled-optimization -Wdiv-by-zero -Wendif-labels -Wfloat-equal 
>>> -Wformat-extra-args -Wformat-security -Wformat-y2k -Wimplicit 
>>> -Wimplicit-function-declaration -Wimplicit-int -Winit-self 
>>> -Wint-to-pointer-cast -Winvalid-pch -Wmain -Wmissing-braces 
>>> -Wmissing-field-initializers -Wmissing-format-attribute -Wmultichar 
>>> -Wnonnull -Woverflow -Wparentheses -Wpointer-
ar
>> ith -Wpointer-to-int-cast -Wreturn-type -Wsequence-point -Wshadow 
>> -Wsign-compare -Wstrict-aliasing -Wswitch -Wtrigraphs -Wundef 
>> -Wunknown-pragmas -Wunused -Wunused-function -Wunused-label 
>> -Wunused-parameter -Wunused-value  -Wunused-variable -Wvariadic-macros 
>> -Wvolatile-register-var -Wwrite-strings -Wnested-externs -Wstrict-prototypes 
>> -Wpointer-sign -g -Wredundant-decls -Wmissing-prototypes 
>> -Wmissing-declarations -Wcast-align -freg-struct-return -fno-dwarf2-cfi-asm 
>> -fno-asynchronous-unwind-tables -fno-stack-protector -mno-unaligned-access 
>> -Wtrampolines -Werror -DUSE_ASCII_FALLBACK=1 -DHAVE_UNIFONT_WIDTHSPEC=1     
>> -mthumb-interwork -mlong-calls -ffreestanding   -MT lib/kernel_exec-arg.o 
>> -MD -MP -MF lib/.deps-core/kernel_exec-arg.Tpo -c -o lib/kernel_exec-arg.o 
>> `test -f 'lib/arg.c' || echo '../../../grub-core/'`lib/arg.c
>>>   misc.S: Assembler messages:
>>>   misc.S:56: Error: r13 not allowed here -- `sub sp,fp,#4'
>>>   make[3]: *** [kern/arm/kernel_exec-misc.o] Error 1
>>>
>>> I don't think SP can be used that way in Thumb mode?
>>>
>> I think that our asm routines should be in full ARM. Attached patch
>> follows this strategy. One remaining problem is to make sure that thumb
>> flags in TARGET_CFLAGS and TARGET_CCASFLAGS match.
> 
> There should be no need for this - the only thing is to ensure the
> -mthumb-interwork is set in CCASFLAGS_PLATFORM as well as
> CFLAGS_PLATFORM, and even that is just to prevent linker warnings..
> 
> There is no special ARM_PROLOGUE needed, and (on armv5te onwards)
> pop {..., pc} is an interworking branch.
> 
> If we want to force a file to build as ARM (which I'm not sure is
> necessary now that we have split up armv6 separate from later
> architectures), all that is required is a .arm directive up top.
> 
Hm. I'm confused. According to
http://stuff.mit.edu/afs/sipb/project/egcs/src/egcs/gcc/config/arm/README-interworking:
"Note that specifying -mthumb-interwork does result in slightly larger,
slower code being produced.  This is why interworking support must be
specifically enabled by a switch."

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