[kvm-unit-tests,v2,2/2] powerpc: select endianness
diff mbox

Message ID 1456506526-10803-3-git-send-email-lvivier@redhat.com
State Superseded
Headers show

Commit Message

Laurent Vivier Feb. 26, 2016, 5:08 p.m. UTC
This patch allows to build tests for ppc64 little endian target
(ppc64le) on big and little endian hosts.

We add a new parameter to configure to select the endianness of the
tests (--endian=little or --endian=big).

I have built and tested big and little endian tests on a little
endian host, a big endian host, with kvm_hv and kvm_pr, and on
x86_64 with ppc64 as a TCG target.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
v2: replace FIXUP_ENDIAN from linux by a home made version
    (B_BE and RETURN_FROM_BE)

 Makefile                  | 11 ++++++-----
 configure                 |  6 ++++++
 lib/powerpc/asm/ppc_asm.h | 36 ++++++++++++++++++++++++++++++++++++
 lib/ppc64/asm/io.h        |  8 ++++++++
 lib/ppc64/asm/ppc_asm.h   |  1 +
 powerpc/Makefile          |  2 +-
 powerpc/Makefile.big      | 21 +++++++++++++++++++++
 powerpc/Makefile.common   | 18 ++++++++++--------
 powerpc/Makefile.little   | 21 +++++++++++++++++++++
 powerpc/Makefile.ppc64    | 22 ----------------------
 powerpc/cstart64.S        | 14 ++++++++++----
 11 files changed, 120 insertions(+), 40 deletions(-)
 create mode 100644 lib/powerpc/asm/ppc_asm.h
 create mode 100644 lib/ppc64/asm/ppc_asm.h
 create mode 100644 powerpc/Makefile.big
 create mode 100644 powerpc/Makefile.little
 delete mode 100644 powerpc/Makefile.ppc64

Comments

Andrew Jones Feb. 26, 2016, 6:45 p.m. UTC | #1
On Fri, Feb 26, 2016 at 06:08:46PM +0100, Laurent Vivier wrote:
> This patch allows to build tests for ppc64 little endian target
> (ppc64le) on big and little endian hosts.
> 
> We add a new parameter to configure to select the endianness of the
> tests (--endian=little or --endian=big).
> 
> I have built and tested big and little endian tests on a little
> endian host, a big endian host, with kvm_hv and kvm_pr, and on
> x86_64 with ppc64 as a TCG target.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
> v2: replace FIXUP_ENDIAN from linux by a home made version
>     (B_BE and RETURN_FROM_BE)
> 
>  Makefile                  | 11 ++++++-----
>  configure                 |  6 ++++++
>  lib/powerpc/asm/ppc_asm.h | 36 ++++++++++++++++++++++++++++++++++++
>  lib/ppc64/asm/io.h        |  8 ++++++++
>  lib/ppc64/asm/ppc_asm.h   |  1 +
>  powerpc/Makefile          |  2 +-
>  powerpc/Makefile.big      | 21 +++++++++++++++++++++
>  powerpc/Makefile.common   | 18 ++++++++++--------
>  powerpc/Makefile.little   | 21 +++++++++++++++++++++
>  powerpc/Makefile.ppc64    | 22 ----------------------
>  powerpc/cstart64.S        | 14 ++++++++++----

By renaming Makefile.ppc64 to Makefile.{little,big} we lose the
'ppc64' information. Since you've defined the ENDIAN config
variable, then how about just doing

ifeq ($(ENDIAN),little)
    CFLAGS = -mlittle-endian
    LDFLAGS = -EL
else
    CFLAGS = -mbig-endian
    LDFLAGS = -EB
endif

Or even just substitute $(ENDIAN) when you want "big"/"little",
such as in the CFLAGS.

>  11 files changed, 120 insertions(+), 40 deletions(-)
>  create mode 100644 lib/powerpc/asm/ppc_asm.h
>  create mode 100644 lib/ppc64/asm/ppc_asm.h
>  create mode 100644 powerpc/Makefile.big
>  create mode 100644 powerpc/Makefile.little
>  delete mode 100644 powerpc/Makefile.ppc64
> 
> diff --git a/Makefile b/Makefile
> index ddba941..8ed244a 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -40,12 +40,13 @@ include $(TEST_DIR)/Makefile
>  cc-option = $(shell if $(CC) $(1) -S -o /dev/null -xc /dev/null \
>                > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
>  
> -CFLAGS += -g
> -CFLAGS += $(autodepend-flags) -Wall
> -CFLAGS += $(call cc-option, -fomit-frame-pointer, "")
> -CFLAGS += $(call cc-option, -fno-stack-protector, "")
> -CFLAGS += $(call cc-option, -fno-stack-protector-all, "")
> +main_CFLAGS = -g
> +main_CFLAGS += $(autodepend-flags) -Wall
> +main_CFLAGS += $(call cc-option, -fomit-frame-pointer, "")
> +main_CFLAGS += $(call cc-option, -fno-stack-protector, "")
> +main_CFLAGS += $(call cc-option, -fno-stack-protector-all, "")

I guess this is because cc-option doesn't work well with cross-endian
compiling? Can we fix the function instead? In any case, do we have
drop '-g -Wall and -MMD -MF $(dir $*).$(notdir $*).d' too?

>  
> +CFLAGS += $(main_CFLAGS)
>  CXXFLAGS += $(CFLAGS)
>  
>  autodepend-flags = -MMD -MF $(dir $*).$(notdir $*).d
> diff --git a/configure b/configure
> index a685cca..0043ee9 100755
> --- a/configure
> +++ b/configure
> @@ -10,6 +10,7 @@ ar=ar
>  arch=`uname -m | sed -e 's/i.86/i386/;s/arm.*/arm/;s/ppc64.*/ppc64/'`
>  host=$arch
>  cross_prefix=
> +endian=big # default for ppc64, the only user

If we default to 'little', then we don't have to worry about the current
architectures using it. Is big the better default for some reason? Also,
as both big and little work on both big and little, then maybe we should
require it to be explicitly added (to make sure the user knows which
they're using).

>  
>  usage() {
>      cat <<-EOF
> @@ -23,6 +24,7 @@ usage() {
>  	    --ld=LD		   ld linker to use ($ld)
>  	    --prefix=PREFIX        where to install things ($prefix)
>  	    --kerneldir=DIR        kernel build directory for kvm.h ($kerneldir)
> +	    --endian=ENDIAN        endianness to compile for (little or big)
>  EOF
>      exit 1
>  }
> @@ -50,6 +52,9 @@ while [[ "$1" = -* ]]; do
>  	--cross-prefix)
>  	    cross_prefix="$arg"
>  	    ;;
> +        --endian)
> +            endian="$arg"
> +            ;;

Looks like a inconsistent whitespace here (should use tabs).

>  	--cc)
>  	    cc="$arg"
>  	    ;;
> @@ -139,4 +144,5 @@ AR=$cross_prefix$ar
>  API=$api
>  TEST_DIR=$testdir
>  FIRMWARE=$firmware
> +ENDIAN=$endian
>  EOF
> diff --git a/lib/powerpc/asm/ppc_asm.h b/lib/powerpc/asm/ppc_asm.h
> new file mode 100644
> index 0000000..f0ab241
> --- /dev/null
> +++ b/lib/powerpc/asm/ppc_asm.h
> @@ -0,0 +1,36 @@
> +#ifndef _ASMPOWERPC_PPC_ASM_H
> +#define _ASMPOWERPC_PPC_ASM_H

Adding this file is a good idea, we should probably move
LOAD_REG_IMMEDIATE and LOAD_REG_ADDR here too.

> +
> +#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
> +
> +#define B_BE(addr)				\
> +	mtctr	addr;				\
> +	nop;					\
> +	bctr
> +
> +#define RETURN_FROM_BE
> +
> +#elif __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
> +
> +#define B_BE(addr)				\
> +	mfmsr	r11;				\
> +	xori	r11,r11,1;			\
> +	mtsrr0	addr;				\
> +	mtsrr1	r11;				\
> +	rfid;					\
> +	b       .
> +
> +#define RETURN_FROM_BE				\
> +	.long 0x05000048; /* bl . + 4        */ \
> +	.long 0xa602487d; /* mflr r10        */	\
> +	.long 0x20004a39; /* addi r10,r10,32 */	\
> +	.long 0xa600607d; /* mfmsr r11       */	\
> +	.long 0x01006b69; /* xori r11,r11,1  */	\
> +	.long 0xa6035a7d; /* mtsrr0 r10	     */	\
> +	.long 0xa6037b7d; /* mtsrr1 r11      */	\
> +	.long 0x2400004c; /* rfid            */ \
> +	.long 0x00000048; /* b .             */ \

I think we only need RETURN_FROM_BE. B_BE is currently only used
in enter_rtas, where it's fine now, but based on some of David's
comments, I think we may eventually want to change even more
state before the rtas call, which means the BE version will need
the rfid anyway. Thus we can just drop the LE version straight into
enter_rtas, replacing the xor with explicitly setting BE mode.

> +
> +#endif /* __BYTE_ORDER__ */
> +
> +#endif /* _ASMPOWERPC_PPC_ASM_H */
> diff --git a/lib/ppc64/asm/io.h b/lib/ppc64/asm/io.h
> index c0801d4..4f2c31b 100644
> --- a/lib/ppc64/asm/io.h
> +++ b/lib/ppc64/asm/io.h
> @@ -1,5 +1,13 @@
>  #ifndef _ASMPPC64_IO_H_
>  #define _ASMPPC64_IO_H_
> +
> +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
> +#define __cpu_is_be() (0)
> +#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
>  #define __cpu_is_be() (1)
> +#else
> +#error Undefined byte order
> +#endif
> +
>  #include <asm-generic/io.h>
>  #endif
> diff --git a/lib/ppc64/asm/ppc_asm.h b/lib/ppc64/asm/ppc_asm.h
> new file mode 100644
> index 0000000..e3929ee
> --- /dev/null
> +++ b/lib/ppc64/asm/ppc_asm.h
> @@ -0,0 +1 @@
> +#include "../../powerpc/asm/ppc_asm.h"
> diff --git a/powerpc/Makefile b/powerpc/Makefile
> index 369a38b..cc39a09 100644
> --- a/powerpc/Makefile
> +++ b/powerpc/Makefile
> @@ -1 +1 @@
> -include $(TEST_DIR)/Makefile.$(ARCH)
> +include $(TEST_DIR)/Makefile.$(ENDIAN)
> diff --git a/powerpc/Makefile.big b/powerpc/Makefile.big
> new file mode 100644
> index 0000000..d81c52d
> --- /dev/null
> +++ b/powerpc/Makefile.big
> @@ -0,0 +1,21 @@
> +#
> +# ppc64 big-endian makefile
> +#
> +# Authors: Andrew Jones <drjones@redhat.com>
> +#
> +bits = 64
> +
> +arch_CFLAGS = -mbig-endian
> +arch_LDFLAGS = -EB
> +
> +cstart.o = $(TEST_DIR)/cstart64.o
> +reloc.o  = $(TEST_DIR)/reloc64.o
> +cflatobjs += lib/ppc64/spinlock.o
> +
> +# ppc64 specific tests
> +tests =
> +
> +include $(TEST_DIR)/Makefile.common
> +
> +arch_clean: powerpc_clean
> +	$(RM) lib/ppc64/.*.d
> diff --git a/powerpc/Makefile.common b/powerpc/Makefile.common
> index cc27ac8..b088af6 100644
> --- a/powerpc/Makefile.common
> +++ b/powerpc/Makefile.common
> @@ -11,14 +11,15 @@ all: $(TEST_DIR)/boot_rom.bin test_cases
>  
>  ##################################################################
>  
> -CFLAGS += $(arch_CFLAGS)
> -CFLAGS += -std=gnu99
> -CFLAGS += -ffreestanding
> -CFLAGS += -Wextra
> -CFLAGS += -O2
> -CFLAGS += -I lib -I lib/libfdt
> -CFLAGS += -Wa,-mregnames
> -CFLAGS += -fpie
> +common_CFLAGS = -std=gnu99
> +common_CFLAGS += -ffreestanding
> +common_CFLAGS += -Wextra
> +common_CFLAGS += -O2
> +common_CFLAGS += -I lib -I lib/libfdt
> +common_CFLAGS += -Wa,-mregnames
> +common_CFLAGS += -fpie
> +
> +CFLAGS += $(arch_CFLAGS) $(common_CFLAGS)

I'm not sure what we gain by renaming to common_CFLAGS. Doesn't just

%.elf: CFLAGS += $(arch_CFLAGS)

work?

>  
>  asm-offsets = lib/$(ARCH)/asm-offsets.h
>  include scripts/asm-offsets.mak
> @@ -48,6 +49,7 @@ $(TEST_DIR)/boot_rom.bin: $(TEST_DIR)/boot_rom.elf
>  	dd if=/dev/zero of=$@ bs=256 count=1
>  	$(OBJCOPY) -O binary $^ >(cat - >>$@)
>  
> +$(TEST_DIR)/boot_rom.elf: CFLAGS = -mbig-endian $(common_CFLAGS) $(main_CFLAGS)

And just
$(TEST_DIR)/boot_rom.elf: CFLAGS += -mbig-endian

>  $(TEST_DIR)/boot_rom.elf: $(TEST_DIR)/boot_rom.o
>  	$(LD) -EB -nostdlib -Ttext=0x100 --entry=start --build-id=none -o $@ $<
>  
> diff --git a/powerpc/Makefile.little b/powerpc/Makefile.little
> new file mode 100644
> index 0000000..c37d2fc
> --- /dev/null
> +++ b/powerpc/Makefile.little
> @@ -0,0 +1,21 @@
> +#
> +# ppc64 little-endian makefile
> +#
> +# Authors: Andrew Jones <drjones@redhat.com>
> +#
> +bits = 64
> +
> +arch_CFLAGS = -mlittle-endian
> +arch_LDFLAGS = -EL
> +
> +cstart.o = $(TEST_DIR)/cstart64.o
> +reloc.o  = $(TEST_DIR)/reloc64.o
> +cflatobjs += lib/ppc64/spinlock.o
> +
> +# ppc64 specific tests
> +tests =
> +
> +include $(TEST_DIR)/Makefile.common
> +
> +arch_clean: powerpc_clean
> +	$(RM) lib/ppc64/.*.d
> diff --git a/powerpc/Makefile.ppc64 b/powerpc/Makefile.ppc64
> deleted file mode 100644
> index 1cf277e..0000000
> --- a/powerpc/Makefile.ppc64
> +++ /dev/null
> @@ -1,22 +0,0 @@
> -#
> -# ppc64 makefile
> -#
> -# Authors: Andrew Jones <drjones@redhat.com>
> -#
> -bits = 64
> -ldarch = elf64-powerpc
> -
> -arch_CFLAGS = -mbig-endian
> -arch_LDFLAGS = -EB
> -
> -cstart.o = $(TEST_DIR)/cstart64.o
> -reloc.o  = $(TEST_DIR)/reloc64.o
> -cflatobjs += lib/ppc64/spinlock.o
> -
> -# ppc64 specific tests
> -tests =
> -
> -include $(TEST_DIR)/Makefile.common
> -
> -arch_clean: powerpc_clean
> -	$(RM) lib/ppc64/.*.d
> diff --git a/powerpc/cstart64.S b/powerpc/cstart64.S
> index f5530fb..60557a9 100644
> --- a/powerpc/cstart64.S
> +++ b/powerpc/cstart64.S
> @@ -7,6 +7,7 @@
>   */
>  #define __ASSEMBLY__
>  #include <asm/hcall.h>
> +#include <asm/ppc_asm.h>
>  
>  #define LOAD_REG_IMMEDIATE(reg,expr)		\
>  	lis	reg,(expr)@highest;		\
> @@ -25,6 +26,7 @@
>   */
>  .globl start
>  start:
> +	RETURN_FROM_BE
>  	/*
>  	 * We were loaded at QEMU's kernel load address, but we're not
>  	 * allowed to link there due to how QEMU deals with linker VMAs,
> @@ -93,11 +95,15 @@ halt:
>  enter_rtas:
>  	mflr	r0
>  	std	r0, 16(r1)
> +
> +	LOAD_REG_ADDR(r10,rtas_return_loc)
> +	mtlr	r10
> +
>  	LOAD_REG_ADDR(r10, rtas_blob)
> -//FIXME: change this bctrl to an rtas-prep, rfid, rtas-return sequence
> -	mtctr	r10
> -	nop
> -	bctrl
> +	B_BE(r10)
> +
> +rtas_return_loc:
> +	RETURN_FROM_BE
>  	ld	r0, 16(r1)
>  	mtlr	r0
>  	blr

Besides my earlier comment about always needing rfid to prep for the
rtas call (which my FIXUP comment here poorly indicated), then this
looks good to me. Although I'm not sure I like the name RETURN_FROM_BE,
as sometimes we're returning to LE, and sometimes we're not. In the
not case, it's a bit confusing.

Thanks,
drew
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Laurent Vivier Feb. 29, 2016, 1:24 p.m. UTC | #2
On 26/02/2016 19:45, Andrew Jones wrote:
> On Fri, Feb 26, 2016 at 06:08:46PM +0100, Laurent Vivier wrote:
>> This patch allows to build tests for ppc64 little endian target
>> (ppc64le) on big and little endian hosts.
>>
>> We add a new parameter to configure to select the endianness of the
>> tests (--endian=little or --endian=big).
>>
>> I have built and tested big and little endian tests on a little
>> endian host, a big endian host, with kvm_hv and kvm_pr, and on
>> x86_64 with ppc64 as a TCG target.
>>
>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>> ---
>> v2: replace FIXUP_ENDIAN from linux by a home made version
>>     (B_BE and RETURN_FROM_BE)
>>
>>  Makefile                  | 11 ++++++-----
>>  configure                 |  6 ++++++
>>  lib/powerpc/asm/ppc_asm.h | 36 ++++++++++++++++++++++++++++++++++++
>>  lib/ppc64/asm/io.h        |  8 ++++++++
>>  lib/ppc64/asm/ppc_asm.h   |  1 +
>>  powerpc/Makefile          |  2 +-
>>  powerpc/Makefile.big      | 21 +++++++++++++++++++++
>>  powerpc/Makefile.common   | 18 ++++++++++--------
>>  powerpc/Makefile.little   | 21 +++++++++++++++++++++
>>  powerpc/Makefile.ppc64    | 22 ----------------------
>>  powerpc/cstart64.S        | 14 ++++++++++----
> 
> By renaming Makefile.ppc64 to Makefile.{little,big} we lose the
> 'ppc64' information. Since you've defined the ENDIAN config
> variable, then how about just doing
> 
> ifeq ($(ENDIAN),little)
>     CFLAGS = -mlittle-endian
>     LDFLAGS = -EL
> else
>     CFLAGS = -mbig-endian
>     LDFLAGS = -EB
> endif
> 
> Or even just substitute $(ENDIAN) when you want "big"/"little",
> such as in the CFLAGS.

I need the LDFLAGS too, so I will rename the file to Makefile.ppc64 and
use the "ifeq".

> 
>>  11 files changed, 120 insertions(+), 40 deletions(-)
>>  create mode 100644 lib/powerpc/asm/ppc_asm.h
>>  create mode 100644 lib/ppc64/asm/ppc_asm.h
>>  create mode 100644 powerpc/Makefile.big
>>  create mode 100644 powerpc/Makefile.little
>>  delete mode 100644 powerpc/Makefile.ppc64
>>
>> diff --git a/Makefile b/Makefile
>> index ddba941..8ed244a 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -40,12 +40,13 @@ include $(TEST_DIR)/Makefile
>>  cc-option = $(shell if $(CC) $(1) -S -o /dev/null -xc /dev/null \
>>                > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
>>  
>> -CFLAGS += -g
>> -CFLAGS += $(autodepend-flags) -Wall
>> -CFLAGS += $(call cc-option, -fomit-frame-pointer, "")
>> -CFLAGS += $(call cc-option, -fno-stack-protector, "")
>> -CFLAGS += $(call cc-option, -fno-stack-protector-all, "")
>> +main_CFLAGS = -g
>> +main_CFLAGS += $(autodepend-flags) -Wall
>> +main_CFLAGS += $(call cc-option, -fomit-frame-pointer, "")
>> +main_CFLAGS += $(call cc-option, -fno-stack-protector, "")
>> +main_CFLAGS += $(call cc-option, -fno-stack-protector-all, "")
> 
> I guess this is because cc-option doesn't work well with cross-endian
> compiling? Can we fix the function instead? In any case, do we have
> drop '-g -Wall and -MMD -MF $(dir $*).$(notdir $*).d' too?

In fact, my problem here is to always compile the boot_rom in gin endian
mode and the other files using the provided endianness.

So I have to extract all the common flags and add the good endianness
according the file to build.

But I agree, I did a minimalist change (renaming): I can try to extract
flags needed to build boot_rom to not change the common CFLAGS.

>>  
>> +CFLAGS += $(main_CFLAGS)
>>  CXXFLAGS += $(CFLAGS)
>>  
>>  autodepend-flags = -MMD -MF $(dir $*).$(notdir $*).d
>> diff --git a/configure b/configure
>> index a685cca..0043ee9 100755
>> --- a/configure
>> +++ b/configure
>> @@ -10,6 +10,7 @@ ar=ar
>>  arch=`uname -m | sed -e 's/i.86/i386/;s/arm.*/arm/;s/ppc64.*/ppc64/'`
>>  host=$arch
>>  cross_prefix=
>> +endian=big # default for ppc64, the only user
> 
> If we default to 'little', then we don't have to worry about the current
> architectures using it. Is big the better default for some reason? Also,
> as both big and little work on both big and little, then maybe we should
> require it to be explicitly added (to make sure the user knows which
> they're using).

This is not true: on old PowerPC machines, using ppc970 (like my
PowerMac G5), the little endian mode doesn't work. It's why I set the
default to big endian.

But I agree: it's a good idea to have it added explicitly to know what
we are using.

>>  
>>  usage() {
>>      cat <<-EOF
>> @@ -23,6 +24,7 @@ usage() {
>>  	    --ld=LD		   ld linker to use ($ld)
>>  	    --prefix=PREFIX        where to install things ($prefix)
>>  	    --kerneldir=DIR        kernel build directory for kvm.h ($kerneldir)
>> +	    --endian=ENDIAN        endianness to compile for (little or big)
>>  EOF
>>      exit 1
>>  }
>> @@ -50,6 +52,9 @@ while [[ "$1" = -* ]]; do
>>  	--cross-prefix)
>>  	    cross_prefix="$arg"
>>  	    ;;
>> +        --endian)
>> +            endian="$arg"
>> +            ;;
> 
> Looks like a inconsistent whitespace here (should use tabs).
> 
>>  	--cc)
>>  	    cc="$arg"
>>  	    ;;
>> @@ -139,4 +144,5 @@ AR=$cross_prefix$ar
>>  API=$api
>>  TEST_DIR=$testdir
>>  FIRMWARE=$firmware
>> +ENDIAN=$endian
>>  EOF
>> diff --git a/lib/powerpc/asm/ppc_asm.h b/lib/powerpc/asm/ppc_asm.h
>> new file mode 100644
>> index 0000000..f0ab241
>> --- /dev/null
>> +++ b/lib/powerpc/asm/ppc_asm.h
>> @@ -0,0 +1,36 @@
>> +#ifndef _ASMPOWERPC_PPC_ASM_H
>> +#define _ASMPOWERPC_PPC_ASM_H
> 
> Adding this file is a good idea, we should probably move
> LOAD_REG_IMMEDIATE and LOAD_REG_ADDR here too.

I can add them in the series.

>> +
>> +#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
>> +
>> +#define B_BE(addr)				\
>> +	mtctr	addr;				\
>> +	nop;					\
>> +	bctr
>> +
>> +#define RETURN_FROM_BE
>> +
>> +#elif __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
>> +
>> +#define B_BE(addr)				\
>> +	mfmsr	r11;				\
>> +	xori	r11,r11,1;			\
>> +	mtsrr0	addr;				\
>> +	mtsrr1	r11;				\
>> +	rfid;					\
>> +	b       .
>> +
>> +#define RETURN_FROM_BE				\
>> +	.long 0x05000048; /* bl . + 4        */ \
>> +	.long 0xa602487d; /* mflr r10        */	\
>> +	.long 0x20004a39; /* addi r10,r10,32 */	\
>> +	.long 0xa600607d; /* mfmsr r11       */	\
>> +	.long 0x01006b69; /* xori r11,r11,1  */	\
>> +	.long 0xa6035a7d; /* mtsrr0 r10	     */	\
>> +	.long 0xa6037b7d; /* mtsrr1 r11      */	\
>> +	.long 0x2400004c; /* rfid            */ \
>> +	.long 0x00000048; /* b .             */ \
> 
> I think we only need RETURN_FROM_BE. B_BE is currently only used
> in enter_rtas, where it's fine now, but based on some of David's
> comments, I think we may eventually want to change even more
> state before the rtas call, which means the BE version will need
> the rfid anyway. Thus we can just drop the LE version straight into
> enter_rtas, replacing the xor with explicitly setting BE mode.

OK

>> +
>> +#endif /* __BYTE_ORDER__ */
>> +
>> +#endif /* _ASMPOWERPC_PPC_ASM_H */
>> diff --git a/lib/ppc64/asm/io.h b/lib/ppc64/asm/io.h
>> index c0801d4..4f2c31b 100644
>> --- a/lib/ppc64/asm/io.h
>> +++ b/lib/ppc64/asm/io.h
>> @@ -1,5 +1,13 @@
>>  #ifndef _ASMPPC64_IO_H_
>>  #define _ASMPPC64_IO_H_
>> +
>> +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
>> +#define __cpu_is_be() (0)
>> +#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
>>  #define __cpu_is_be() (1)
>> +#else
>> +#error Undefined byte order
>> +#endif
>> +
>>  #include <asm-generic/io.h>
>>  #endif
>> diff --git a/lib/ppc64/asm/ppc_asm.h b/lib/ppc64/asm/ppc_asm.h
>> new file mode 100644
>> index 0000000..e3929ee
>> --- /dev/null
>> +++ b/lib/ppc64/asm/ppc_asm.h
>> @@ -0,0 +1 @@
>> +#include "../../powerpc/asm/ppc_asm.h"
>> diff --git a/powerpc/Makefile b/powerpc/Makefile
>> index 369a38b..cc39a09 100644
>> --- a/powerpc/Makefile
>> +++ b/powerpc/Makefile
>> @@ -1 +1 @@
>> -include $(TEST_DIR)/Makefile.$(ARCH)
>> +include $(TEST_DIR)/Makefile.$(ENDIAN)
>> diff --git a/powerpc/Makefile.big b/powerpc/Makefile.big
>> new file mode 100644
>> index 0000000..d81c52d
>> --- /dev/null
>> +++ b/powerpc/Makefile.big
>> @@ -0,0 +1,21 @@
>> +#
>> +# ppc64 big-endian makefile
>> +#
>> +# Authors: Andrew Jones <drjones@redhat.com>
>> +#
>> +bits = 64
>> +
>> +arch_CFLAGS = -mbig-endian
>> +arch_LDFLAGS = -EB
>> +
>> +cstart.o = $(TEST_DIR)/cstart64.o
>> +reloc.o  = $(TEST_DIR)/reloc64.o
>> +cflatobjs += lib/ppc64/spinlock.o
>> +
>> +# ppc64 specific tests
>> +tests =
>> +
>> +include $(TEST_DIR)/Makefile.common
>> +
>> +arch_clean: powerpc_clean
>> +	$(RM) lib/ppc64/.*.d
>> diff --git a/powerpc/Makefile.common b/powerpc/Makefile.common
>> index cc27ac8..b088af6 100644
>> --- a/powerpc/Makefile.common
>> +++ b/powerpc/Makefile.common
>> @@ -11,14 +11,15 @@ all: $(TEST_DIR)/boot_rom.bin test_cases
>>  
>>  ##################################################################
>>  
>> -CFLAGS += $(arch_CFLAGS)
>> -CFLAGS += -std=gnu99
>> -CFLAGS += -ffreestanding
>> -CFLAGS += -Wextra
>> -CFLAGS += -O2
>> -CFLAGS += -I lib -I lib/libfdt
>> -CFLAGS += -Wa,-mregnames
>> -CFLAGS += -fpie
>> +common_CFLAGS = -std=gnu99
>> +common_CFLAGS += -ffreestanding
>> +common_CFLAGS += -Wextra
>> +common_CFLAGS += -O2
>> +common_CFLAGS += -I lib -I lib/libfdt
>> +common_CFLAGS += -Wa,-mregnames
>> +common_CFLAGS += -fpie
>> +
>> +CFLAGS += $(arch_CFLAGS) $(common_CFLAGS)
> 
> I'm not sure what we gain by renaming to common_CFLAGS. Doesn't just
> 
> %.elf: CFLAGS += $(arch_CFLAGS)
> 
> work?
> 
>>  
>>  asm-offsets = lib/$(ARCH)/asm-offsets.h
>>  include scripts/asm-offsets.mak
>> @@ -48,6 +49,7 @@ $(TEST_DIR)/boot_rom.bin: $(TEST_DIR)/boot_rom.elf
>>  	dd if=/dev/zero of=$@ bs=256 count=1
>>  	$(OBJCOPY) -O binary $^ >(cat - >>$@)
>>  
>> +$(TEST_DIR)/boot_rom.elf: CFLAGS = -mbig-endian $(common_CFLAGS) $(main_CFLAGS)
> 
> And just
> $(TEST_DIR)/boot_rom.elf: CFLAGS += -mbig-endian

I can try.

> 
>>  $(TEST_DIR)/boot_rom.elf: $(TEST_DIR)/boot_rom.o
>>  	$(LD) -EB -nostdlib -Ttext=0x100 --entry=start --build-id=none -o $@ $<
>>  
>> diff --git a/powerpc/Makefile.little b/powerpc/Makefile.little
>> new file mode 100644
>> index 0000000..c37d2fc
>> --- /dev/null
>> +++ b/powerpc/Makefile.little
>> @@ -0,0 +1,21 @@
>> +#
>> +# ppc64 little-endian makefile
>> +#
>> +# Authors: Andrew Jones <drjones@redhat.com>
>> +#
>> +bits = 64
>> +
>> +arch_CFLAGS = -mlittle-endian
>> +arch_LDFLAGS = -EL
>> +
>> +cstart.o = $(TEST_DIR)/cstart64.o
>> +reloc.o  = $(TEST_DIR)/reloc64.o
>> +cflatobjs += lib/ppc64/spinlock.o
>> +
>> +# ppc64 specific tests
>> +tests =
>> +
>> +include $(TEST_DIR)/Makefile.common
>> +
>> +arch_clean: powerpc_clean
>> +	$(RM) lib/ppc64/.*.d
>> diff --git a/powerpc/Makefile.ppc64 b/powerpc/Makefile.ppc64
>> deleted file mode 100644
>> index 1cf277e..0000000
>> --- a/powerpc/Makefile.ppc64
>> +++ /dev/null
>> @@ -1,22 +0,0 @@
>> -#
>> -# ppc64 makefile
>> -#
>> -# Authors: Andrew Jones <drjones@redhat.com>
>> -#
>> -bits = 64
>> -ldarch = elf64-powerpc
>> -
>> -arch_CFLAGS = -mbig-endian
>> -arch_LDFLAGS = -EB
>> -
>> -cstart.o = $(TEST_DIR)/cstart64.o
>> -reloc.o  = $(TEST_DIR)/reloc64.o
>> -cflatobjs += lib/ppc64/spinlock.o
>> -
>> -# ppc64 specific tests
>> -tests =
>> -
>> -include $(TEST_DIR)/Makefile.common
>> -
>> -arch_clean: powerpc_clean
>> -	$(RM) lib/ppc64/.*.d
>> diff --git a/powerpc/cstart64.S b/powerpc/cstart64.S
>> index f5530fb..60557a9 100644
>> --- a/powerpc/cstart64.S
>> +++ b/powerpc/cstart64.S
>> @@ -7,6 +7,7 @@
>>   */
>>  #define __ASSEMBLY__
>>  #include <asm/hcall.h>
>> +#include <asm/ppc_asm.h>
>>  
>>  #define LOAD_REG_IMMEDIATE(reg,expr)		\
>>  	lis	reg,(expr)@highest;		\
>> @@ -25,6 +26,7 @@
>>   */
>>  .globl start
>>  start:
>> +	RETURN_FROM_BE
>>  	/*
>>  	 * We were loaded at QEMU's kernel load address, but we're not
>>  	 * allowed to link there due to how QEMU deals with linker VMAs,
>> @@ -93,11 +95,15 @@ halt:
>>  enter_rtas:
>>  	mflr	r0
>>  	std	r0, 16(r1)
>> +
>> +	LOAD_REG_ADDR(r10,rtas_return_loc)
>> +	mtlr	r10
>> +
>>  	LOAD_REG_ADDR(r10, rtas_blob)
>> -//FIXME: change this bctrl to an rtas-prep, rfid, rtas-return sequence
>> -	mtctr	r10
>> -	nop
>> -	bctrl
>> +	B_BE(r10)
>> +
>> +rtas_return_loc:
>> +	RETURN_FROM_BE
>>  	ld	r0, 16(r1)
>>  	mtlr	r0
>>  	blr
> 
> Besides my earlier comment about always needing rfid to prep for the
> rtas call (which my FIXUP comment here poorly indicated), then this
> looks good to me. Although I'm not sure I like the name RETURN_FROM_BE,
> as sometimes we're returning to LE, and sometimes we're not. In the
> not case, it's a bit confusing.
> 
> Thanks,
> drew
> 
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Paolo Bonzini Feb. 29, 2016, 4:06 p.m. UTC | #3
On 26/02/2016 19:45, Andrew Jones wrote:
>> > +	LOAD_REG_ADDR(r10,rtas_return_loc)
>> > +	mtlr	r10
>> > +
>> >  	LOAD_REG_ADDR(r10, rtas_blob)
>> > -//FIXME: change this bctrl to an rtas-prep, rfid, rtas-return sequence
>> > -	mtctr	r10
>> > -	nop
>> > -	bctrl
>> > +	B_BE(r10)

Note that this doesn't apply.  I've applied patch 1 though.

Paolo

>> > +
>> > +rtas_return_loc:
>> > +	RETURN_FROM_BE
>> >  	ld	r0, 16(r1)
>> >  	mtlr	r0
>> >  	blr
> Besides my earlier comment about always needing rfid to prep for the
> rtas call (which my FIXUP comment here poorly indicated), then this
> looks good to me. Although I'm not sure I like the name RETURN_FROM_BE,
> as sometimes we're returning to LE, and sometimes we're not. In the
> not case, it's a bit confusing.
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Laurent Vivier Feb. 29, 2016, 4:44 p.m. UTC | #4
On 29/02/2016 17:06, Paolo Bonzini wrote:
> 
> 
> On 26/02/2016 19:45, Andrew Jones wrote:
>>>> +	LOAD_REG_ADDR(r10,rtas_return_loc)
>>>> +	mtlr	r10
>>>> +
>>>>  	LOAD_REG_ADDR(r10, rtas_blob)
>>>> -//FIXME: change this bctrl to an rtas-prep, rfid, rtas-return sequence
>>>> -	mtctr	r10
>>>> -	nop
>>>> -	bctrl
>>>> +	B_BE(r10)
> 
> Note that this doesn't apply.  I've applied patch 1 though.

Yes, Drew has changed this part, and anyway I have to rework this.

Thanks,
Laurent

> Paolo
> 
>>>> +
>>>> +rtas_return_loc:
>>>> +	RETURN_FROM_BE
>>>>  	ld	r0, 16(r1)
>>>>  	mtlr	r0
>>>>  	blr
>> Besides my earlier comment about always needing rfid to prep for the
>> rtas call (which my FIXUP comment here poorly indicated), then this
>> looks good to me. Although I'm not sure I like the name RETURN_FROM_BE,
>> as sometimes we're returning to LE, and sometimes we're not. In the
>> not case, it's a bit confusing.
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Laurent Vivier Feb. 29, 2016, 5:53 p.m. UTC | #5
On 26/02/2016 19:45, Andrew Jones wrote:
...
>> diff --git a/powerpc/Makefile.common b/powerpc/Makefile.common
>> > index cc27ac8..b088af6 100644
>> > --- a/powerpc/Makefile.common
>> > +++ b/powerpc/Makefile.common
>> > @@ -11,14 +11,15 @@ all: $(TEST_DIR)/boot_rom.bin test_cases
>> >  
>> >  ##################################################################
>> >  
>> > -CFLAGS += $(arch_CFLAGS)
>> > -CFLAGS += -std=gnu99
>> > -CFLAGS += -ffreestanding
>> > -CFLAGS += -Wextra
>> > -CFLAGS += -O2
>> > -CFLAGS += -I lib -I lib/libfdt
>> > -CFLAGS += -Wa,-mregnames
>> > -CFLAGS += -fpie
>> > +common_CFLAGS = -std=gnu99
>> > +common_CFLAGS += -ffreestanding
>> > +common_CFLAGS += -Wextra
>> > +common_CFLAGS += -O2
>> > +common_CFLAGS += -I lib -I lib/libfdt
>> > +common_CFLAGS += -Wa,-mregnames
>> > +common_CFLAGS += -fpie
>> > +
>> > +CFLAGS += $(arch_CFLAGS) $(common_CFLAGS)
> I'm not sure what we gain by renaming to common_CFLAGS. Doesn't just
> 
> %.elf: CFLAGS += $(arch_CFLAGS)
> 
> work?
> 
>> >  
>> >  asm-offsets = lib/$(ARCH)/asm-offsets.h
>> >  include scripts/asm-offsets.mak
>> > @@ -48,6 +49,7 @@ $(TEST_DIR)/boot_rom.bin: $(TEST_DIR)/boot_rom.elf
>> >  	dd if=/dev/zero of=$@ bs=256 count=1
>> >  	$(OBJCOPY) -O binary $^ >(cat - >>$@)
>> >  
>> > +$(TEST_DIR)/boot_rom.elf: CFLAGS = -mbig-endian $(common_CFLAGS) $(main_CFLAGS)
> And just
> $(TEST_DIR)/boot_rom.elf: CFLAGS += -mbig-endian
> 

We can't do that because boot_rom.elf is also a .elf, so the both rules
apply and we end up with in the case of boot_rom.elf (and --endian=little):

  CFLAGS += -mlittle-endian -mbig-endian

and it doesn't work. We must overwrite CFLAGS in the case of boot_rom.elf.

But boot_rom.S is a one line of assembly language, we don't need the
other flags, in fact...

Laurent
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Patch
diff mbox

diff --git a/Makefile b/Makefile
index ddba941..8ed244a 100644
--- a/Makefile
+++ b/Makefile
@@ -40,12 +40,13 @@  include $(TEST_DIR)/Makefile
 cc-option = $(shell if $(CC) $(1) -S -o /dev/null -xc /dev/null \
               > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
 
-CFLAGS += -g
-CFLAGS += $(autodepend-flags) -Wall
-CFLAGS += $(call cc-option, -fomit-frame-pointer, "")
-CFLAGS += $(call cc-option, -fno-stack-protector, "")
-CFLAGS += $(call cc-option, -fno-stack-protector-all, "")
+main_CFLAGS = -g
+main_CFLAGS += $(autodepend-flags) -Wall
+main_CFLAGS += $(call cc-option, -fomit-frame-pointer, "")
+main_CFLAGS += $(call cc-option, -fno-stack-protector, "")
+main_CFLAGS += $(call cc-option, -fno-stack-protector-all, "")
 
+CFLAGS += $(main_CFLAGS)
 CXXFLAGS += $(CFLAGS)
 
 autodepend-flags = -MMD -MF $(dir $*).$(notdir $*).d
diff --git a/configure b/configure
index a685cca..0043ee9 100755
--- a/configure
+++ b/configure
@@ -10,6 +10,7 @@  ar=ar
 arch=`uname -m | sed -e 's/i.86/i386/;s/arm.*/arm/;s/ppc64.*/ppc64/'`
 host=$arch
 cross_prefix=
+endian=big # default for ppc64, the only user
 
 usage() {
     cat <<-EOF
@@ -23,6 +24,7 @@  usage() {
 	    --ld=LD		   ld linker to use ($ld)
 	    --prefix=PREFIX        where to install things ($prefix)
 	    --kerneldir=DIR        kernel build directory for kvm.h ($kerneldir)
+	    --endian=ENDIAN        endianness to compile for (little or big)
 EOF
     exit 1
 }
@@ -50,6 +52,9 @@  while [[ "$1" = -* ]]; do
 	--cross-prefix)
 	    cross_prefix="$arg"
 	    ;;
+        --endian)
+            endian="$arg"
+            ;;
 	--cc)
 	    cc="$arg"
 	    ;;
@@ -139,4 +144,5 @@  AR=$cross_prefix$ar
 API=$api
 TEST_DIR=$testdir
 FIRMWARE=$firmware
+ENDIAN=$endian
 EOF
diff --git a/lib/powerpc/asm/ppc_asm.h b/lib/powerpc/asm/ppc_asm.h
new file mode 100644
index 0000000..f0ab241
--- /dev/null
+++ b/lib/powerpc/asm/ppc_asm.h
@@ -0,0 +1,36 @@ 
+#ifndef _ASMPOWERPC_PPC_ASM_H
+#define _ASMPOWERPC_PPC_ASM_H
+
+#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+
+#define B_BE(addr)				\
+	mtctr	addr;				\
+	nop;					\
+	bctr
+
+#define RETURN_FROM_BE
+
+#elif __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+
+#define B_BE(addr)				\
+	mfmsr	r11;				\
+	xori	r11,r11,1;			\
+	mtsrr0	addr;				\
+	mtsrr1	r11;				\
+	rfid;					\
+	b       .
+
+#define RETURN_FROM_BE				\
+	.long 0x05000048; /* bl . + 4        */ \
+	.long 0xa602487d; /* mflr r10        */	\
+	.long 0x20004a39; /* addi r10,r10,32 */	\
+	.long 0xa600607d; /* mfmsr r11       */	\
+	.long 0x01006b69; /* xori r11,r11,1  */	\
+	.long 0xa6035a7d; /* mtsrr0 r10	     */	\
+	.long 0xa6037b7d; /* mtsrr1 r11      */	\
+	.long 0x2400004c; /* rfid            */ \
+	.long 0x00000048; /* b .             */ \
+
+#endif /* __BYTE_ORDER__ */
+
+#endif /* _ASMPOWERPC_PPC_ASM_H */
diff --git a/lib/ppc64/asm/io.h b/lib/ppc64/asm/io.h
index c0801d4..4f2c31b 100644
--- a/lib/ppc64/asm/io.h
+++ b/lib/ppc64/asm/io.h
@@ -1,5 +1,13 @@ 
 #ifndef _ASMPPC64_IO_H_
 #define _ASMPPC64_IO_H_
+
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define __cpu_is_be() (0)
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
 #define __cpu_is_be() (1)
+#else
+#error Undefined byte order
+#endif
+
 #include <asm-generic/io.h>
 #endif
diff --git a/lib/ppc64/asm/ppc_asm.h b/lib/ppc64/asm/ppc_asm.h
new file mode 100644
index 0000000..e3929ee
--- /dev/null
+++ b/lib/ppc64/asm/ppc_asm.h
@@ -0,0 +1 @@ 
+#include "../../powerpc/asm/ppc_asm.h"
diff --git a/powerpc/Makefile b/powerpc/Makefile
index 369a38b..cc39a09 100644
--- a/powerpc/Makefile
+++ b/powerpc/Makefile
@@ -1 +1 @@ 
-include $(TEST_DIR)/Makefile.$(ARCH)
+include $(TEST_DIR)/Makefile.$(ENDIAN)
diff --git a/powerpc/Makefile.big b/powerpc/Makefile.big
new file mode 100644
index 0000000..d81c52d
--- /dev/null
+++ b/powerpc/Makefile.big
@@ -0,0 +1,21 @@ 
+#
+# ppc64 big-endian makefile
+#
+# Authors: Andrew Jones <drjones@redhat.com>
+#
+bits = 64
+
+arch_CFLAGS = -mbig-endian
+arch_LDFLAGS = -EB
+
+cstart.o = $(TEST_DIR)/cstart64.o
+reloc.o  = $(TEST_DIR)/reloc64.o
+cflatobjs += lib/ppc64/spinlock.o
+
+# ppc64 specific tests
+tests =
+
+include $(TEST_DIR)/Makefile.common
+
+arch_clean: powerpc_clean
+	$(RM) lib/ppc64/.*.d
diff --git a/powerpc/Makefile.common b/powerpc/Makefile.common
index cc27ac8..b088af6 100644
--- a/powerpc/Makefile.common
+++ b/powerpc/Makefile.common
@@ -11,14 +11,15 @@  all: $(TEST_DIR)/boot_rom.bin test_cases
 
 ##################################################################
 
-CFLAGS += $(arch_CFLAGS)
-CFLAGS += -std=gnu99
-CFLAGS += -ffreestanding
-CFLAGS += -Wextra
-CFLAGS += -O2
-CFLAGS += -I lib -I lib/libfdt
-CFLAGS += -Wa,-mregnames
-CFLAGS += -fpie
+common_CFLAGS = -std=gnu99
+common_CFLAGS += -ffreestanding
+common_CFLAGS += -Wextra
+common_CFLAGS += -O2
+common_CFLAGS += -I lib -I lib/libfdt
+common_CFLAGS += -Wa,-mregnames
+common_CFLAGS += -fpie
+
+CFLAGS += $(arch_CFLAGS) $(common_CFLAGS)
 
 asm-offsets = lib/$(ARCH)/asm-offsets.h
 include scripts/asm-offsets.mak
@@ -48,6 +49,7 @@  $(TEST_DIR)/boot_rom.bin: $(TEST_DIR)/boot_rom.elf
 	dd if=/dev/zero of=$@ bs=256 count=1
 	$(OBJCOPY) -O binary $^ >(cat - >>$@)
 
+$(TEST_DIR)/boot_rom.elf: CFLAGS = -mbig-endian $(common_CFLAGS) $(main_CFLAGS)
 $(TEST_DIR)/boot_rom.elf: $(TEST_DIR)/boot_rom.o
 	$(LD) -EB -nostdlib -Ttext=0x100 --entry=start --build-id=none -o $@ $<
 
diff --git a/powerpc/Makefile.little b/powerpc/Makefile.little
new file mode 100644
index 0000000..c37d2fc
--- /dev/null
+++ b/powerpc/Makefile.little
@@ -0,0 +1,21 @@ 
+#
+# ppc64 little-endian makefile
+#
+# Authors: Andrew Jones <drjones@redhat.com>
+#
+bits = 64
+
+arch_CFLAGS = -mlittle-endian
+arch_LDFLAGS = -EL
+
+cstart.o = $(TEST_DIR)/cstart64.o
+reloc.o  = $(TEST_DIR)/reloc64.o
+cflatobjs += lib/ppc64/spinlock.o
+
+# ppc64 specific tests
+tests =
+
+include $(TEST_DIR)/Makefile.common
+
+arch_clean: powerpc_clean
+	$(RM) lib/ppc64/.*.d
diff --git a/powerpc/Makefile.ppc64 b/powerpc/Makefile.ppc64
deleted file mode 100644
index 1cf277e..0000000
--- a/powerpc/Makefile.ppc64
+++ /dev/null
@@ -1,22 +0,0 @@ 
-#
-# ppc64 makefile
-#
-# Authors: Andrew Jones <drjones@redhat.com>
-#
-bits = 64
-ldarch = elf64-powerpc
-
-arch_CFLAGS = -mbig-endian
-arch_LDFLAGS = -EB
-
-cstart.o = $(TEST_DIR)/cstart64.o
-reloc.o  = $(TEST_DIR)/reloc64.o
-cflatobjs += lib/ppc64/spinlock.o
-
-# ppc64 specific tests
-tests =
-
-include $(TEST_DIR)/Makefile.common
-
-arch_clean: powerpc_clean
-	$(RM) lib/ppc64/.*.d
diff --git a/powerpc/cstart64.S b/powerpc/cstart64.S
index f5530fb..60557a9 100644
--- a/powerpc/cstart64.S
+++ b/powerpc/cstart64.S
@@ -7,6 +7,7 @@ 
  */
 #define __ASSEMBLY__
 #include <asm/hcall.h>
+#include <asm/ppc_asm.h>
 
 #define LOAD_REG_IMMEDIATE(reg,expr)		\
 	lis	reg,(expr)@highest;		\
@@ -25,6 +26,7 @@ 
  */
 .globl start
 start:
+	RETURN_FROM_BE
 	/*
 	 * We were loaded at QEMU's kernel load address, but we're not
 	 * allowed to link there due to how QEMU deals with linker VMAs,
@@ -93,11 +95,15 @@  halt:
 enter_rtas:
 	mflr	r0
 	std	r0, 16(r1)
+
+	LOAD_REG_ADDR(r10,rtas_return_loc)
+	mtlr	r10
+
 	LOAD_REG_ADDR(r10, rtas_blob)
-//FIXME: change this bctrl to an rtas-prep, rfid, rtas-return sequence
-	mtctr	r10
-	nop
-	bctrl
+	B_BE(r10)
+
+rtas_return_loc:
+	RETURN_FROM_BE
 	ld	r0, 16(r1)
 	mtlr	r0
 	blr