[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Peter Tyser]

Previously, standalone applications were compiled with gcc flags that
produced relocatable executables on the PowerPC architecture (eg with
the -mrelocatable and -fPIC flags).  There's no reason for these
applications to be fully relocatable at this time since no relocation
fixups are performed on standalone applications.

Additionally, removing the gcc relocation flags results in the entry
point of applications residing at the base of the image.  When
a standalone application was relocatable, the entry point was generally
located at an offset into the image which was confusing and prone to
errors.

This change moves the entry point of PowerPC standalone applications
from 0x40004 (usually) to 0x40000.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
---
I tested this on an 8548-based board and it worked as described above.  It
wouldn't hurt if a few others tried it out to validate that the new entry
point is always 0x40000.

 examples/standalone/Makefile |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/examples/standalone/Makefile b/examples/standalone/Makefile
index 6ea3b93..0c8dbe7 100644
--- a/examples/standalone/Makefile
+++ b/examples/standalone/Makefile
@@ -72,6 +72,14 @@ gcclibdir := $(shell dirname `$(CC) -print-libgcc-file-name`)
 
 CPPFLAGS += -I..
 
+# For PowerPC there's no need to compile standalone applications as a
+# relocatable executable.  The relocation data is not needed, and
+# also causes the entry point of the standalone application to be
+# inconsistent.
+ifeq ($(ARCH),powerpc)
+CFLAGS := $(filter-out $(RELFLAGS),$(CFLAGS))
+endif
+
 all:	$(obj).depend $(OBJS) $(LIB) $(SREC) $(BIN) $(ELF)
 
 #########################################################################
-- 
1.7.0.4

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Timur Tabi]

Peter Tyser wrote:
> Previously, standalone applications were compiled with gcc flags that 
> produced relocatable executables on the PowerPC architecture (eg with the
> -mrelocatable and -fPIC flags).  There's no reason for these applications
> to be fully relocatable at this time since no relocation fixups are
> performed on standalone applications.

This didn't work for me.  The entry point for my application in 401b4.
Here's the build output:

make[1]: Entering directory `/home/b04825/git/u-boot.4737/examples/standalone'
powerpc-linux-gnu-gcc  -g  -Os   -mrelocatable -fPIC -ffixed-r14 -meabi
-D__KERNEL__ -DTEXT_BASE=0xeff80000 -DRESET_VECTOR_ADDRESS=0xeffffffc
-I/home/b04825/git/u-boot.4737/include -fno-builtin -ffreestanding -nostdinc
-isystem
/opt/freescale/usr/local/gcc-4.3.74-eglibc-2.8.74-6/powerpc-linux-gnu/bin/../lib/gcc/powerpc-linux-gnu/4.3.2/include
-pipe  -DCONFIG_PPC -D__powerpc__ -ffixed-r2 -Wa,-me500 -msoft-float
-mno-string -mspe=yes -mno-spe -Wall -Wstrict-prototypes
-fno-stack-protector   -o flash_wp.o flash_wp.c -c
powerpc-linux-gnu-ar crv libstubs.a ppc_longjmp.o ppc_setjmp.o stubs.o
r - ppc_longjmp.o
r - ppc_setjmp.o
r - stubs.o
powerpc-linux-gnu-ld -g -Ttext 0x40000 \
			-o hello_world -e hello_world hello_world.o libstubs.a \
		
-L/opt/freescale/usr/local/gcc-4.3.74-eglibc-2.8.74-6/powerpc-linux-gnu/bin/../lib/gcc/powerpc-linux-gnu/4.3.2
-lgcc
powerpc-linux-gnu-objcopy -O srec hello_world hello_world.srec 2>/dev/null
powerpc-linux-gnu-ld -g -Ttext 0x40000 \
			-o flash_wp -e flash_wp flash_wp.o libstubs.a \
		
-L/opt/freescale/usr/local/gcc-4.3.74-eglibc-2.8.74-6/powerpc-linux-gnu/bin/../lib/gcc/powerpc-linux-gnu/4.3.2
-lgcc
powerpc-linux-gnu-objcopy -O srec flash_wp flash_wp.srec 2>/dev/null
powerpc-linux-gnu-ld -g -Ttext 0x40000 \
			-o sched -e sched sched.o libstubs.a \
		
-L/opt/freescale/usr/local/gcc-4.3.74-eglibc-2.8.74-6/powerpc-linux-gnu/bin/../lib/gcc/powerpc-linux-gnu/4.3.2
-lgcc
powerpc-linux-gnu-objcopy -O srec sched sched.srec 2>/dev/null
powerpc-linux-gnu-objcopy -O binary hello_world hello_world.bin 2>/dev/null
powerpc-linux-gnu-objcopy -O binary flash_wp flash_wp.bin 2>/dev/null
powerpc-linux-gnu-objcopy -O binary sched sched.bin 2>/dev/null
make[1]: Leaving directory `/home/b04825/git/u-boot.4737/examples/standalone'

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Timur Tabi]

Timur Tabi wrote:
> Peter Tyser wrote:
>> Previously, standalone applications were compiled with gcc flags that 
>> produced relocatable executables on the PowerPC architecture (eg with the
>> -mrelocatable and -fPIC flags).  There's no reason for these applications
>> to be fully relocatable at this time since no relocation fixups are
>> performed on standalone applications.
> 
> This didn't work for me.  The entry point for my application in 401b4.

So if I comment-out the ifeq, like this:

#ifeq ($(ARCH),powerpc)
CFLAGS := $(filter-out $(RELFLAGS),$(CFLAGS))
#endif

and build, I get these errors:

powerpc-linux-gnu-ld: libstubs.a(ppc_longjmp.o): compiled with -mrelocatable
and linked with modules compiled normally
powerpc-linux-gnu-ld: failed to merge target specific data of file
libstubs.a(ppc_longjmp.o)
powerpc-linux-gnu-ld: libstubs.a(ppc_setjmp.o): compiled with -mrelocatable
and linked with modules compiled normally
powerpc-linux-gnu-ld: failed to merge target specific data of file
libstubs.a(ppc_setjmp.o)

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Peter Tyser]

On Tue, 2010-06-15 at 14:05 -0500, Timur Tabi wrote:
> Timur Tabi wrote:
> > Peter Tyser wrote:
> >> Previously, standalone applications were compiled with gcc flags that 
> >> produced relocatable executables on the PowerPC architecture (eg with the
> >> -mrelocatable and -fPIC flags).  There's no reason for these applications
> >> to be fully relocatable at this time since no relocation fixups are
> >> performed on standalone applications.
> > 
> > This didn't work for me.  The entry point for my application in 401b4.
> 
> So if I comment-out the ifeq, like this:
> 
> #ifeq ($(ARCH),powerpc)
> CFLAGS := $(filter-out $(RELFLAGS),$(CFLAGS))
> #endif
> 
> and build, I get these errors:
> 
> powerpc-linux-gnu-ld: libstubs.a(ppc_longjmp.o): compiled with -mrelocatable
> and linked with modules compiled normally
> powerpc-linux-gnu-ld: failed to merge target specific data of file
> libstubs.a(ppc_longjmp.o)
> powerpc-linux-gnu-ld: libstubs.a(ppc_setjmp.o): compiled with -mrelocatable
> and linked with modules compiled normally
> powerpc-linux-gnu-ld: failed to merge target specific data of file
> libstubs.a(ppc_setjmp.o)

Can you do a 'make clean', then recompile?

Thanks,
Peter

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Timur Tabi]

Peter Tyser wrote:
> Can you do a 'make clean', then recompile?

That *was* with a 'make clean'.

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Peter Tyser]

On Tue, 2010-06-15 at 14:20 -0500, Timur Tabi wrote:
> Peter Tyser wrote:
> > Can you do a 'make clean', then recompile?
> 
> That *was* with a 'make clean'.

Just to be sure, where did the output in your first email come from?  It
looked like a successful compile, but libstubs wasn't recompiled (I
didn't see it in your pasted output).  What changed between that 1st
email and the 2nd email?

For reference, this is the relevant part of the build I see on my end:
make[1]: Entering directory `/home/ptyser/u-boot/u-boot/examples/standalone'
powerpc-linux-gcc  -g -Os -D__KERNEL__ -DTEXT_BASE=0xfff80000 -I/home/ptyser/u-boot/u-boot/include -fno-builtin -ffreestanding -nostdinc -isystem /opt/xes/devkit/ppc/eldk_gcc4.2.2-glibc20070515T2025/bin/../lib/gcc/powerpc-linux/4.2.2/include -pipe -DCONFIG_PPC -D__powerpc__ -ffixed-r2 -Wa,-me500 -msoft-float -mno-string -mspe=yes -mno-spe -Wall -Wstrict-prototypes -fno-stack-protector   \
		-o hello_world.o hello_world.c -c
powerpc-linux-gcc  -g -Os -D__KERNEL__ -DTEXT_BASE=0xfff80000 -I/home/ptyser/u-boot/u-boot/include -fno-builtin -ffreestanding -nostdinc -isystem /opt/xes/devkit/ppc/eldk_gcc4.2.2-glibc20070515T2025/bin/../lib/gcc/powerpc-linux/4.2.2/include -pipe -DCONFIG_PPC -D__powerpc__ -ffixed-r2 -Wa,-me500 -msoft-float -mno-string -mspe=yes -mno-spe -Wall -Wstrict-prototypes -fno-stack-protector   \
		-o stubs.o stubs.c -c
powerpc-linux-ar crv libstubs.a stubs.o
a - stubs.o
powerpc-linux-ld -g -Ttext 0x40000 \
			-o hello_world -e hello_world hello_world.o libstubs.a \
			-L/opt/xes/devkit/ppc/eldk_gcc4.2.2-glibc20070515T2025/bin/../lib/gcc/powerpc-linux/4.2.2 -lgcc
....

ptyser at petert u-boot $ readelf -h examples/standalone/hello_world
ELF Header:
  Magic:   7f 45 4c 46 01 02 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF32
  Data:                              2's complement, big endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           PowerPC
  Version:                           0x1
  Entry point address:               0x40000
  Start of program headers:          52 (bytes into file)
  Start of section headers:          265304 (bytes into file)
  Flags:                             0x0
  Size of this header:               52 (bytes)
  Size of program headers:           32 (bytes)
  Number of program headers:         2
  Size of section headers:           40 (bytes)
  Number of section headers:         15
  Section header string table index: 12

Could you paste similar output from what you're seeing?

Thanks,
Peter

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Peter Tyser]

On Tue, 2010-06-15 at 14:05 -0500, Timur Tabi wrote:
> Timur Tabi wrote:
> > Peter Tyser wrote:
> >> Previously, standalone applications were compiled with gcc flags that 
> >> produced relocatable executables on the PowerPC architecture (eg with the
> >> -mrelocatable and -fPIC flags).  There's no reason for these applications
> >> to be fully relocatable at this time since no relocation fixups are
> >> performed on standalone applications.
> > 
> > This didn't work for me.  The entry point for my application in 401b4.
> 
> So if I comment-out the ifeq, like this:
> 
> #ifeq ($(ARCH),powerpc)
> CFLAGS := $(filter-out $(RELFLAGS),$(CFLAGS))
> #endif

Was commenting out the 'ifeq' above necessary?  It shouldn't be, so my
first question would be why it was needed.

Best,
Peter

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Timur Tabi]

Peter Tyser wrote:
> Was commenting out the 'ifeq' above necessary?  It shouldn't be, so my
> first question would be why it was needed.

Probably because I was using an older U-Boot.  When I switch to the latest
code, it compiles fine.

However, my entry point is not at 40000:

$ nm -n examples/standalone/flash_wp
00040000 t command_exit
000400c4 t is_locked
00040184 T flash_wp
000403d0 T dummy

'flash_wp' should be at 40000.  command_exit and is_locked are two functions
in my code.  command_exit, however, is not the first function, it's the third.

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Wolfgang Denk]

From: Peter Tyser <ptyser@xes-inc.com>

Previously, standalone applications were compiled with gcc flags that
produced relocatable executables on the PowerPC architecture (eg with
the -mrelocatable and -fPIC flags).  There's no reason for these
applications to be fully relocatable at this time since no relocation
fixups are performed on standalone applications.

Additionally, removing the gcc relocation flags results in the entry
point of applications residing at the base of the image.  When
a standalone application was relocatable, the entry point was generally
located at an offset into the image which was confusing and prone to
errors.

This change moves the entry point of PowerPC standalone applications
from 0x40004 (usually) to 0x40000.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
Signed-off-by: Wolfgang Denk <wd@denx.de>
---

It seems we need to cleanup a few more make variables (+AFLAGS, CPPFLAGS)

 examples/standalone/Makefile |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/examples/standalone/Makefile b/examples/standalone/Makefile
index 6ea3b93..5f1f800 100644
--- a/examples/standalone/Makefile
+++ b/examples/standalone/Makefile
@@ -72,6 +72,16 @@ gcclibdir := $(shell dirname `$(CC) -print-libgcc-file-name`)
 
 CPPFLAGS += -I..
 
+# For PowerPC there's no need to compile standalone applications as a
+# relocatable executable.  The relocation data is not needed, and
+# also causes the entry point of the standalone application to be
+# inconsistent.
+ifeq ($(ARCH),powerpc)
+AFLAGS := $(filter-out $(RELFLAGS),$(AFLAGS))
+CFLAGS := $(filter-out $(RELFLAGS),$(CFLAGS))
+CPPFLAGS := $(filter-out $(RELFLAGS),$(CPPFLAGS))
+endif
+
 all:	$(obj).depend $(OBJS) $(LIB) $(SREC) $(BIN) $(ELF)
 
 #########################################################################
-- 
1.7.0.1

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Peter Tyser]

On Tue, 2010-06-15 at 14:45 -0500, Timur Tabi wrote:
> Peter Tyser wrote:
> > Was commenting out the 'ifeq' above necessary?  It shouldn't be, so my
> > first question would be why it was needed.
> 
> Probably because I was using an older U-Boot.  When I switch to the latest
> code, it compiles fine.
> 
> However, my entry point is not at 40000:
> 
> $ nm -n examples/standalone/flash_wp
> 00040000 t command_exit
> 000400c4 t is_locked
> 00040184 T flash_wp
> 000403d0 T dummy
> 
> 'flash_wp' should be at 40000.  command_exit and is_locked are two functions
> in my code.  command_exit, however, is not the first function, it's the third.

I think by default its not possible to guarantee function order in gcc's
output if a file contains multiple functions.  We could create a basic
linker script...  I think we could also do it with some gcc/ld-foo like:

--- a/examples/standalone/Makefile
+++ b/examples/standalone/Makefile
@@ -78,6 +78,7 @@ CPPFLAGS += -I..
 # inconsistent.
 ifeq ($(ARCH),powerpc)
 CFLAGS := $(filter-out $(RELFLAGS),$(CFLAGS))
+CFLAGS += -fno-toplevel-reorder
 endif
 
 all:   $(obj).depend $(OBJS) $(LIB) $(SREC) $(BIN) $(ELF)
@@ -88,7 +89,7 @@ $(LIB):       $(obj).depend $(LIBOBJS)
 
 $(ELF):
 $(obj)%:       $(obj)%.o $(LIB)
-               $(LD) -g -Ttext $(STANDALONE_LOAD_ADDR) \
+               $(LD) -g -Ttext $(STANDALONE_LOAD_ADDR) -sort-common \
                        -o $@ -e $(SYM_PREFIX)$(notdir $(<:.o=)) $< $(LIB) \
                        -L$(gcclibdir) -lgcc
 
Could you try the above change with your flash_wp test case?  Or make
the flash_wp app public?  It should put the first function@the base
of the image in theory.

Best,
Peter

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Wolfgang Denk]

Dear Peter Tyser,

In message <1276632905.32134.1535.camel@petert> you wrote:
>
> I think by default its not possible to guarantee function order in gcc's
> output if a file contains multiple functions.  We could create a basic

Correct. If you check for example the "timer" example program (build
for some 8xx system, say TQM860L) you can see that it's sufficient to
have a forward declaration for a static function before the real code
that the C compiler will place the code for this function in front,
whichis probably not what you want here.

> linker script...  I think we could also do it with some gcc/ld-foo like:
> 
> --- a/examples/standalone/Makefile
> +++ b/examples/standalone/Makefile
> @@ -78,6 +78,7 @@ CPPFLAGS += -I..
>  # inconsistent.
>  ifeq ($(ARCH),powerpc)
>  CFLAGS := $(filter-out $(RELFLAGS),$(CFLAGS))
> +CFLAGS += -fno-toplevel-reorder
>  endif

This alone is sufficient to "fix" for example the aforementioned
"timer" example program.

Without:

	...
	00040428 T strcmp
	000400e8 T timer
	00040000 t timer_handler
	00040318 T tstc
	00040398 T udelay
	...

With:

	...
	00040428 T strcmp
	00040000 T timer
	000402b8 t timer_handler
	00040318 T tstc
	00040398 T udelay
	...

>  all:   $(obj).depend $(OBJS) $(LIB) $(SREC) $(BIN) $(ELF)
> @@ -88,7 +89,7 @@ $(LIB):       $(obj).depend $(LIBOBJS)
>  
>  $(ELF):
>  $(obj)%:       $(obj)%.o $(LIB)
> -               $(LD) -g -Ttext $(STANDALONE_LOAD_ADDR) \
> +               $(LD) -g -Ttext $(STANDALONE_LOAD_ADDR) -sort-common \
>                         -o $@ -e $(SYM_PREFIX)$(notdir $(<:.o=)) $< $(LIB) \
>                         -L$(gcclibdir) -lgcc

I'm not sure if this is needed.

> Could you try the above change with your flash_wp test case?  Or make
> the flash_wp app public?  It should put the first function at the base
> of the image in theory.

I think the "timer" code is sufficient to show the problem, and that
your fix helps.  If Timur confirms it's working for his secret code
too we should apply this.

Thanks a lot!

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Is a computer language with goto's totally Wirth-less?

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Peter Tyser]

<snip>

> >  all:   $(obj).depend $(OBJS) $(LIB) $(SREC) $(BIN) $(ELF)
> > @@ -88,7 +89,7 @@ $(LIB):       $(obj).depend $(LIBOBJS)
> >  
> >  $(ELF):
> >  $(obj)%:       $(obj)%.o $(LIB)
> > -               $(LD) -g -Ttext $(STANDALONE_LOAD_ADDR) \
> > +               $(LD) -g -Ttext $(STANDALONE_LOAD_ADDR) -sort-common \
> >                         -o $@ -e $(SYM_PREFIX)$(notdir $(<:.o=)) $< $(LIB) \
> >                         -L$(gcclibdir) -lgcc
> 
> I'm not sure if this is needed.

Agreed, in fact, I'm not sure why I even put that in there in the first
place after re-reading ld's man page:)

> > Could you try the above change with your flash_wp test case?  Or make
> > the flash_wp app public?  It should put the first function at the base
> > of the image in theory.
> 
> I think the "timer" code is sufficient to show the problem, and that
> your fix helps.  If Timur confirms it's working for his secret code
> too we should apply this.

Do you want this rolled into the first patch, or sent as a follow-up?

Best,
Peter

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Timur Tabi]

Wolfgang Denk wrote:
> I think the "timer" code is sufficient to show the problem, and that
> your fix helps.  If Timur confirms it's working for his secret code
> too we should apply this.

Doing this at the top of my source file:

	static int __flash_wp(int argc, char *argv[]);

	int flash_wp(int argc, char *argv[])
	{
	        return __flash_wp(argc, argv);
	}

and then adding this line:

	CFLAGS += -fno-toplevel-reorder

was all I needed to get my entry point to appear at 40000 without needing to
define any more forward references or caring about the order of the
functions in the file.

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Wolfgang Denk]

Dear Peter,

In message <1276634341.32134.1541.camel@petert> you wrote:
> 
> > I think the "timer" code is sufficient to show the problem, and that
> > your fix helps.  If Timur confirms it's working for his secret code
> > too we should apply this.
> 
> Do you want this rolled into the first patch, or sent as a follow-up?

Please roll it into one patch.  Thanks!

Best regards,

Wolfgang Denk

--
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
It is easier to change the specification to fit the program than vice
versa.

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Wolfgang Denk]

Dear Timur Tabi,

In message <4C17E4F2.70309@freescale.com> you wrote:
> 
> Doing this at the top of my source file:
> 
> 	static int __flash_wp(int argc, char *argv[]);
> 
> 	int flash_wp(int argc, char *argv[])
> 	{
> 	        return __flash_wp(argc, argv);
> 	}
> 
> and then adding this line:
> 
> 	CFLAGS += -fno-toplevel-reorder
> 
> was all I needed to get my entry point to appear at 40000 without needing to
> define any more forward references or caring about the order of the
> functions in the file.

I think the "static int __flash_wp()" thing is not even needed
assuming that flash_wp() is the first function in your file.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
The use of anthropomorphic terminology when  dealing  with  computing
systems is a symptom of professional immaturity.   -- Edsger Dijkstra

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Timur Tabi]

Wolfgang Denk wrote:
> I think the "static int __flash_wp()" thing is not even needed
> assuming that flash_wp() is the first function in your file.

That's the thing -- I don't want flash_wp() to be the first function in my
file.  I would then need a forward reference to all the other functions in
my file, and I hate doing that.

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Wolfgang Denk]

Dear Timur Tabi,

In message <4C17EA8D.9080606@freescale.com> you wrote:
> Wolfgang Denk wrote:
> > I think the "static int __flash_wp()" thing is not even needed
> > assuming that flash_wp() is the first function in your file.
> 
> That's the thing -- I don't want flash_wp() to be the first function in my
> file.  I would then need a forward reference to all the other functions in
> my file, and I hate doing that.

OK - but then please don't claim that such a construct was necessary.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
You can fool some of the people all of the time, and You can fool all
of the people some of the time, but You can't fool mom.

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Peter Tyser]

On Tue, 2010-06-15 at 22:51 +0200, Wolfgang Denk wrote:
> Dear Peter,
> 
> In message <1276634341.32134.1541.camel@petert> you wrote:
> > 
> > > I think the "timer" code is sufficient to show the problem, and that
> > > your fix helps.  If Timur confirms it's working for his secret code
> > > too we should apply this.
> > 
> > Do you want this rolled into the first patch, or sent as a follow-up?
> 
> Please roll it into one patch.  Thanks!

It looks like the -fno-toplevel-reorder flag is only available in gcc >=
4.2 (http://gcc.gnu.org/gcc-4.2/changes.html released May 2007).  So, do
we add support to U-Boot to conditionally check for the gcc version like
Linux to know when to use -fno-toplevel-reorder?  Or do we use a linker
script that would support more versions of gcc at the cost of more
complexity?

Best,
Peter

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Timur Tabi]

On Tue, Jun 15, 2010 at 10:37 PM, Peter Tyser <ptyser@xes-inc.com> wrote:

> It looks like the -fno-toplevel-reorder flag is only available in gcc >=
> 4.2 (http://gcc.gnu.org/gcc-4.2/changes.html released May 2007). ?So, do
> we add support to U-Boot to conditionally check for the gcc version like
> Linux to know when to use -fno-toplevel-reorder? ?Or do we use a linker
> script that would support more versions of gcc at the cost of more
> complexity?

What happens if you use the flag on earlier versions of gcc?  If the
flag is just silently ignored, then maybe it's not such a big deal to
always include it, and just add a comment saying that it only works on
gcc 4.2 or higher?

-- 
Timur Tabi
Linux kernel developer at Freescale

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Wolfgang Denk]

Dear Timur Tabi,

In message <AANLkTild0OSohtPUQpqwsrZSAxPtCqnb_C2S0WTvIh1a@mail.gmail.com> you wrote:
> 
> > we add support to U-Boot to conditionally check for the gcc version like
> > Linux to know when to use -fno-toplevel-reorder? =A0Or do we use a linker
> > script that would support more versions of gcc at the cost of more
> > complexity?
> 
> What happens if you use the flag on earlier versions of gcc?  If the
> flag is just silently ignored, then maybe it's not such a big deal to
> always include it, and just add a comment saying that it only works on
> gcc 4.2 or higher?

It raises an error.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
If I can have honesty, it's easier to overlook mistakes.
	-- Kirk, "Space Seed", stardate 3141.9

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Wolfgang Denk]

In message <1276631305-30648-1-git-send-email-wd@denx.de> you wrote:
> From: Peter Tyser <ptyser@xes-inc.com>
> 
> Previously, standalone applications were compiled with gcc flags that
> produced relocatable executables on the PowerPC architecture (eg with
> the -mrelocatable and -fPIC flags).  There's no reason for these
> applications to be fully relocatable at this time since no relocation
> fixups are performed on standalone applications.
> 
> Additionally, removing the gcc relocation flags results in the entry
> point of applications residing at the base of the image.  When
> a standalone application was relocatable, the entry point was generally
> located at an offset into the image which was confusing and prone to
> errors.
> 
> This change moves the entry point of PowerPC standalone applications
> from 0x40004 (usually) to 0x40000.
> 
> Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
> Signed-off-by: Wolfgang Denk <wd@denx.de>
> ---
> 
> It seems we need to cleanup a few more make variables (+AFLAGS, CPPFLAGS)
> 
>  examples/standalone/Makefile |   10 ++++++++++
>  1 files changed, 10 insertions(+), 0 deletions(-)

Applied to "next".

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Totally illogical, there was no chance.
	-- Spock, "The Galileo Seven", stardate 2822.3

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Wolfgang Denk]

Dear Timur Tabi,

In message <20100616145133.BBDE7D81C69@gemini.denx.de> I wrote:
> 
> > > we add support to U-Boot to conditionally check for the gcc version like
> > > Linux to know when to use -fno-toplevel-reorder? =A0Or do we use a linker
> > > script that would support more versions of gcc at the cost of more
> > > complexity?
> > 
> > What happens if you use the flag on earlier versions of gcc?  If the
> > flag is just silently ignored, then maybe it's not such a big deal to
> > always include it, and just add a comment saying that it only works on
> > gcc 4.2 or higher?
> 
> It raises an error.

AFAICT you did not reply to this, and the problem is still unsolved.

Do you still have this on your list?

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
"Pardon me for breathing, which I never do anyway so I don't know why
I bother to say it, oh God, I'm so depressed. Here's another of those
self-satisfied doors. Life! Don't talk to me about life."
                                        - Marvin the Paranoid Android

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Timur Tabi]

On Fri, Sep 10, 2010 at 2:49 PM, Wolfgang Denk <wd@denx.de> wrote:

> AFAICT you did not reply to this, and the problem is still unsolved.
>
> Do you still have this on your list?

Sorry, I'm confused.  What exactly do you want me to do?  Since you
applied Peter's patch, the problem has gone away for me.

-- 
Timur Tabi
Linux kernel developer at Freescale

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Peter Tyser]

On Fri, 2010-09-10 at 14:53 -0500, Timur Tabi wrote:
> On Fri, Sep 10, 2010 at 2:49 PM, Wolfgang Denk <wd@denx.de> wrote:
> 
> > AFAICT you did not reply to this, and the problem is still unsolved.
> >
> > Do you still have this on your list?
> 
> Sorry, I'm confused.  What exactly do you want me to do?  Since you
> applied Peter's patch, the problem has gone away for me.

Wolfgang applied the "examples/standalone: Remove relocation compile
flags for PowerPC" patch.  That patch should remove the few bytes of
relocation cruft that bumped up the first function address by a few
bytes in standalone images.

However, I think there's still the issue that if there are multiple
functions in a standalone application there's no guarantee the entry
point function will be at the base of the image.  eg if the app were:

int helper_func() {
	code()...
}

int entry_point() {
	// application entry point
}

The entry point wouldn't be at the base of the image, it'd be offset by
the size of helper_func(), and it would jump around depending on
compiler version, flags, etc.

My last question on the issue was:
It looks like the -fno-toplevel-reorder flag is only available in gcc >=
4.2 (http://gcc.gnu.org/gcc-4.2/changes.html released May 2007).  So, do
we add support to U-Boot to conditionally check for the gcc version like
Linux to know when to use -fno-toplevel-reorder?  Or do we use a linker
script that would support more versions of gcc at the cost of more
complexity?

I never heard back about the preferred method.  I'd personally lean
towards checking for compiler version and using the gcc version check +
-fno-toplevel-reorder.

Best,
Peter

[U-Boot] [PATCH] examples/standalone: Remove relocation compile flags for PowerPC

[Wolfgang Denk]

Dear Peter Tyser,

In message <1284149249.26713.2926.camel@petert> you wrote:
>
> > Sorry, I'm confused.  What exactly do you want me to do?  Since you
> > applied Peter's patch, the problem has gone away for me.
> 
> However, I think there's still the issue that if there are multiple
> functions in a standalone application there's no guarantee the entry
> point function will be at the base of the image.  eg if the app were:

That's my understanding as well.

> My last question on the issue was:
> It looks like the -fno-toplevel-reorder flag is only available in gcc >=
> 4.2 (http://gcc.gnu.org/gcc-4.2/changes.html released May 2007).  So, do
> we add support to U-Boot to conditionally check for the gcc version like
> Linux to know when to use -fno-toplevel-reorder?  Or do we use a linker
> script that would support more versions of gcc at the cost of more
> complexity?
> 
> I never heard back about the preferred method.  I'd personally lean
> towards checking for compiler version and using the gcc version check +
> -fno-toplevel-reorder.

Given the fact that GCC 4.2 is already pretty old I also tend to add a
gcc version check with -fno-toplevel-reorder instead of increasing the
complexity of the linker scripts.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
You can observe a lot just by watching.                  - Yogi Berra

[U-Boot] [PATCH] examples/standalone: Use gcc's -fno-toplevel-reorder

[Peter Tyser]

Using -fno-toplevel-reorder causes gcc to not reorder functions.  This
ensures that an application's entry point will be the first function in
the application's source file.

This change, along with commit 620bbba524fbaa26971a5004793010b169824f1b
should cause a standalone application's entry point to be at the base of
the compiled binary.  Previously, the entry point could change depending
on gcc version and flags.

Note -fno-toplevel-reorder is only available in gcc version 4.2 or
greater.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
---
I didn't have a version of gcc < 4.2.  The change is pretty trivial so
it should work, but it'd be appreciated if someone with an old toolchain
installed could give the patch a shot.

 examples/standalone/Makefile |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/examples/standalone/Makefile b/examples/standalone/Makefile
index 5f1f800..c2dd514 100644
--- a/examples/standalone/Makefile
+++ b/examples/standalone/Makefile
@@ -82,6 +82,11 @@ CFLAGS := $(filter-out $(RELFLAGS),$(CFLAGS))
 CPPFLAGS := $(filter-out $(RELFLAGS),$(CPPFLAGS))
 endif
 
+# We don't want gcc reordering functions if possible.  This ensures that an
+# application's entry point will be the first function in the application's
+# source file.
+CFLAGS += $(call cc-option,-fno-toplevel-reorder)
+
 all:	$(obj).depend $(OBJS) $(LIB) $(SREC) $(BIN) $(ELF)
 
 #########################################################################
-- 
1.7.1.13.gcfb88

[U-Boot] [PATCH] examples/standalone: Use gcc's -fno-toplevel-reorder

[Andrew Dyer]

On Sun, Sep 12, 2010 at 17:38, Peter Tyser <ptyser@xes-inc.com> wrote:
> Using -fno-toplevel-reorder causes gcc to not reorder functions. ?This
> ensures that an application's entry point will be the first function in
> the application's source file.
>
> This change, along with commit 620bbba524fbaa26971a5004793010b169824f1b
> should cause a standalone application's entry point to be at the base of
> the compiled binary. ?Previously, the entry point could change depending
> on gcc version and flags.
>
> Note -fno-toplevel-reorder is only available in gcc version 4.2 or
> greater.
>
> Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
> ---
> I didn't have a version of gcc < 4.2. ?The change is pretty trivial so
> it should work, but it'd be appreciated if someone with an old toolchain
> installed could give the patch a shot.
>

Since I was writing a standalone test program today, I manually tested
against an older u-boot and arm gcc 4.4.1.  Worked fine.  You can add
my tested-by if you feel that's sufficient.

I wonder if this is the right way to fix this.  It seems a bit subtle.
 I thought of two other possible workarounds - have the Makefile use
mkimage as part of the output so the entry point is embedded in the
mkimage file, or redo the programs to have a main() as entry and write
a crt0.S equivalent and have the entry location for that fixed in a
linker file.

[U-Boot] [PATCH] examples/standalone: Use gcc's -fno-toplevel-reorder

[Peter Tyser]

Hi Andrew,

On Sun, 2010-09-12 at 21:00 -0500, Andrew Dyer wrote:
> On Sun, Sep 12, 2010 at 17:38, Peter Tyser <ptyser@xes-inc.com> wrote:
> > Using -fno-toplevel-reorder causes gcc to not reorder functions.  This
> > ensures that an application's entry point will be the first function in
> > the application's source file.
> >
> > This change, along with commit 620bbba524fbaa26971a5004793010b169824f1b
> > should cause a standalone application's entry point to be at the base of
> > the compiled binary.  Previously, the entry point could change depending
> > on gcc version and flags.
> >
> > Note -fno-toplevel-reorder is only available in gcc version 4.2 or
> > greater.
> >
> > Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
> > ---
> > I didn't have a version of gcc < 4.2.  The change is pretty trivial so
> > it should work, but it'd be appreciated if someone with an old toolchain
> > installed could give the patch a shot.
> >
> 
> Since I was writing a standalone test program today, I manually tested
> against an older u-boot and arm gcc 4.4.1.  Worked fine.  You can add
> my tested-by if you feel that's sufficient.
> I wonder if this is the right way to fix this.  It seems a bit subtle.
>  I thought of two other possible workarounds - have the Makefile use
> mkimage as part of the output so the entry point is embedded in the
> mkimage file, or redo the programs to have a main() as entry and write
> a crt0.S equivalent and have the entry location for that fixed in a
> linker file.

Thanks for testing.  I agree this isn't the most elegant solution, but
its one big advantage is simplicity in my mind.  Creating/maintaining a
crt0.S and/or link script for each CPU architecture seems like overkill
for a simple (deprecated?) application interface to me.  I was under the
impression the preferred application interface going forward was the one
enabled by CONFIG_API in examples/api.  It uses the crt0 solution, but
only supports ppc and arm right now.

Using a uImage format for apps seems like a fine solution too.  Do
others have a preference?

I agree we should be using main() as the entry point either way.  I'll
add that to the TODO list.  If we did go with -fno-toplevel-reorder I
could add the following to each application to make it clear what's
going on:
/* Define main() protoype first to ensure its the first function in the image */
int main(int argc, char * const argv[]);

Best,
Peter

[U-Boot] [PATCH] examples/standalone: Use gcc's -fno-toplevel-reorder

[Detlev Zundel]

Hi Peter,

> I agree we should be using main() as the entry point either way.  I'll
> add that to the TODO list.  If we did go with -fno-toplevel-reorder I
> could add the following to each application to make it clear what's
> going on:
> /* Define main() protoype first to ensure its the first function in the image */

     when linked with -fno-toplevel-reorder

> int main(int argc, char * const argv[]);

This would be appreciated.

Cheers
  Detlev

-- 
SWYM XYZ (Sympathize with your machinery).  [..] In fact it is often
called a no-op, because it performs no operation.  It does, however,
keep the machine running smoothly, just as real-world swimming helps
to keep programmers healthy.             -- Donald Knuth, Fascicle 1
--
DENX Software Engineering GmbH,      MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich,  Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-40 Fax: (+49)-8142-66989-80 Email: dzu at denx.de

[U-Boot] [PATCH] examples/standalone: Use gcc's -fno-toplevel-reorder

[Wolfgang Denk]

Dear Peter Tyser,

In message <1284331129-12911-1-git-send-email-ptyser@xes-inc.com> you wrote:
> Using -fno-toplevel-reorder causes gcc to not reorder functions.  This
> ensures that an application's entry point will be the first function in
> the application's source file.
> 
> This change, along with commit 620bbba524fbaa26971a5004793010b169824f1b
> should cause a standalone application's entry point to be at the base of
> the compiled binary.  Previously, the entry point could change depending
> on gcc version and flags.
> 
> Note -fno-toplevel-reorder is only available in gcc version 4.2 or
> greater.
> 
> Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
> ---
> I didn't have a version of gcc < 4.2.  The change is pretty trivial so
> it should work, but it'd be appreciated if someone with an old toolchain
> installed could give the patch a shot.
> 
>  examples/standalone/Makefile |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)

Applied, thanks.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
It is a good thing for an uneducated man to read books of quotations.
                        - Sir Winston Churchill _My Early Life_ ch. 9