[U-Boot] [RFC] ARM: Toolchain configuration for Cortex A8 based OMAP3?

[ksi at koi8.net]

On Sat, 23 Aug 2008, Dirk Behme wrote:

> Woodruff, Richard wrote:
>> Hi Dirk,
>>
>>> Relevant parts of OMAP3 patch we talk about here (most probably
>>> reformated cause of copy & paste to mailtool, so just for discussion.
>>> Final patches will be sent by git-send-mail). Note the -lgcc_eh which
>>> seems to be CodeSourcery specific, and the -march=armv7a in config.mk.
>>>
>>> diff -uprN uboot_clean/Makefile uboot_beagle/Makefile
>>> --- uboot_clean/Makefile      2008-08-22 19:57:05.000000000 +0200
>>> +++ uboot_beagle/Makefile     2008-08-22 19:53:52.000000000 +0200
>>> @@ -141,7 +141,7 @@ ifeq ($(ARCH),ppc)
>>>  CROSS_COMPILE = ppc_8xx-
>>>  endif
>>>  ifeq ($(ARCH),arm)
>>> -CROSS_COMPILE = arm-linux-
>>> +CROSS_COMPILE = arm-none-linux-gnueabi-
>>
>> CROSS_COMPILE can always be set as an environment variable.  It is
> only for convenience.  CodeSourcy from my vantage point is common enough
> it would nice to see it the default.  In the end it doesn't matter.
>>
>>>  endif
>>>  ifeq ($(ARCH),i386)
>>>  CROSS_COMPILE = i386-linux-
>>> @@ -253,7 +253,7 @@ LIBBOARD = board/$(BOARDDIR)/lib$(BOARD)
>>>  LIBBOARD := $(addprefix $(obj),$(LIBBOARD))
>>>
>>>  # Add GCC lib
>>> -PLATFORM_LIBS += -L $(shell dirname `$(CC) $(CFLAGS)
>>> -print-libgcc-file-name`) -lgcc
>>> +PLATFORM_LIBS += -L $(shell dirname `$(CC) $(CFLAGS)
>>> -print-libgcc-file-name`) -lgcc -lgcc_eh
>>
>> What is being gained by changing platform libs part?  Every now and
> then I update my local omap3 u-boot and I've not had to change that to
> get it working with codesourcy tool chains.  It might be I've not hit
> the issue yet.
>
> Did check regarding -lgcc_eh: Used CodeSourcery tool chain and
> compiled (linked) with and without -lgcc_eh. The resulting binaries
> are identical and no link issues. Seems we can remove -lgcc_eh then. I
> just wonder now why it is there and what it is (was?) good for?

AFAIK, you can safely remove it. I don't know how CodeSourcery build their
toolchains but when I do mine I remove it from glibc and then there is no
libgcc_eh at all. The trick is glibc headers are required to build first
stage cross-gcc and cross gcc is required to build glibc. And glibc in turn
is required to build gcc :) It might be easier to do it with previous
versions installed but I usually build toolchains as RPM packages assuming
no previous toolchain is installed. And it is build in buildroot with all
the system stuff going into sysroot.

The build process is multi-stage -- first just provisional glibc headers are
built, then they are used to build limited first stage cross-gcc, then this
gcc is used to build full-blown glibc that gets installed in sysroot
overwriting those provisional headers, then this newly built glibc is used
to build the full cross-gcc.

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