[Buildroot] Bare metal toolchain support?

[Buildroot] Bare metal toolchain support?

[Alvaro Gamez]

Hi,

Is buildroot able to build a baremetal toolchain?

Specifically, I'm trying to build a small bootloader for the microblaze
architecture. Xilinx provides an SDK, and I wonder if I can build one like
this using buildroot, so I can keep all my code and workflow centralized
under buildroot.

$ mb-gcc -v
Using built-in specs.
COLLECT_GCC=mb-gcc
COLLECT_LTO_WRAPPER=/opt/Xilinx/SDK/2016.2/gnu/microblaze/lin/bin/../libexec/gcc/microblaze-xilinx-elf/5.2.0/lto-wrapper
Target: microblaze-xilinx-elf
Configured with:
/proj/sdk/gnu/microblaze/builds/HEAD/nightly/2016_06_03/rdi_scripts/../build/lin/ctng_bld/target_build/src/gcc-custom/configure
--build=i686-build_pc-linux-gnu --host=i686-build_pc-linux-gnu
--target=microblaze-xilinx-elf
--prefix=/proj/sdk/gnu/microblaze/builds/HEAD/nightly/2016_06_03/rdi_scripts/../build/lin/ctng_output
--with-local-prefix=/proj/sdk/gnu/microblaze/builds/HEAD/nightly/2016_06_03/rdi_scripts/../build/lin/ctng_output/microblaze-xilinx-elf/sysroot
--disable-libmudflap
--with-sysroot=/proj/sdk/gnu/microblaze/builds/HEAD/nightly/2016_06_03/rdi_scripts/../build/lin/ctng_output/microblaze-xilinx-elf/sysroot
--with-newlib --enable-threads=no --disable-shared
--with-pkgversion='crosstool-NG 1.20.0' --disable-__cxa_atexit
--with-gmp=/proj/sdk/gnu/microblaze/builds/HEAD/nightly/2016_06_03/rdi_scripts/../build/lin/ctng_bld/target_build/microblaze-xilinx-elf/buildtools
--with-mpfr=/proj/sdk/gnu/microblaze/builds/HEAD/nightly/2016_06_03/rdi_scripts/../build/lin/ctng_bld/target_build/microblaze-xilinx-elf/buildtools
--with-mpc=/proj/sdk/gnu/microblaze/builds/HEAD/nightly/2016_06_03/rdi_scripts/../build/lin/ctng_bld/target_build/microblaze-xilinx-elf/buildtools
--with-ppl=no --with-isl=no --with-cloog=no --with-libelf=no --disable-lto
--enable-target-optspace --without-long-double-128 --disable-libgomp
--disable-libmudflap --disable-nls --disable-libstdcxx-pch
--enable-languages=c,c++
Thread model: single
gcc version 5.2.0 (crosstool-NG 1.20.0)


Best regards

-- 
?lvaro G?mez Machado
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[Buildroot] Bare metal toolchain support?

[Thomas Petazzoni]

Hello,

On Wed, 23 Nov 2016 10:49:10 +0100, Alvaro Gamez wrote:

> Is buildroot able to build a baremetal toolchain?

No, but this is generally not needed. A Linux-capable toolchain is
capable of building userspace applications, but also the Linux kernel
and bootloaders like Barebox, U-Boot, etc (which you could build with
bare metal toolchains).

> Specifically, I'm trying to build a small bootloader for the microblaze
> architecture. Xilinx provides an SDK, and I wonder if I can build one like
> this using buildroot, so I can keep all my code and workflow centralized
> under buildroot.

Have you tried building this small bootloader with the Buildroot
toolchain?

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

[Buildroot] Bare metal toolchain support?

[Alvaro Gamez]

Hi, Thomas

2016-11-23 11:35 GMT+01:00 Thomas Petazzoni <
thomas.petazzoni@free-electrons.com>:

> No, but this is generally not needed. A Linux-capable toolchain is
> capable of building userspace applications, but also the Linux kernel
> and bootloaders like Barebox, U-Boot, etc (which you could build with
> bare metal toolchains).
>
> > Specifically, I'm trying to build a small bootloader for the microblaze
> > architecture. Xilinx provides an SDK, and I wonder if I can build one
> like
> > this using buildroot, so I can keep all my code and workflow centralized
> > under buildroot.
>
> Have you tried building this small bootloader with the Buildroot
> toolchain?
>
>
Xilinx provides a very simple bootloader, which depends on what they call a
BSP for my platform,
so first of all, I have to compile this BSP, which provides drivers for
xilinx's IP cores. I'm having
only partial success, as drivers code compiles without an issue, but I'm
reaching a point that seems
to be related to the toolchain.

My guess is once this is solved, the BSP will build and the bootloader as
well, as it only uses functions
from these drivers.

output/host/usr/bin/microblazeel-linux-gcc  -O2 -c -mcpu=v9.6
-mlittle-endian -mno-xl-soft-div -mno-xl-soft-mul -mxl-barrel-shift
-mxl-multiply-high -mxl-pattern-compare  -g -I./. -I../../../include
xil_exception.c microblaze_sleep.c fcntl.c xil_testio.c xil_io.c
xil_printf.c outbyte.c microblaze_interrupt_handler.c pvr.c
microblaze_exception_handler.c inbyte.c xil_cache.c xil_misc_psreset_api.c
print.c xplatform_info.c xil_testmem.c _exit.c errno.c
microblaze_interrupts_g.c xil_assert.c xil_testcache.c
microblaze_update_dcache.S microblaze_disable_dcache.S
microblaze_invalidate_dcache_range.S microblaze_flush_dcache.S
microblaze_invalidate_icache.S microblaze_invalidate_cache_ext_range.S
microblaze_flush_cache_ext_range.S microblaze_scrub.S
microblaze_enable_dcache.S microblaze_disable_icache.S
microblaze_disable_interrupts.S microblaze_invalidate_dcache.S
microblaze_flush_cache_ext.S microblaze_invalidate_cache_ext.S
microblaze_flush_dcache_range.S microblaze_disable_exceptions.S
microblaze_init_icache_range.S hw_exception_handler.S
microblaze_enable_icache.S microblaze_enable_interrupts.S
microblaze_update_icache.S microblaze_init_dcache_range.S
microblaze_invalidate_icache_range.S microblaze_enable_exceptions.S
errno.c:6:19: fatal error: reent.h: No such file or directory
 #include <reent.h>

This reent.h header doesn't exist in the toolchain built by buildroot, but
it exists on Xilinx's:

/opt/Xilinx/SDK/2016.2/gnu/microblaze/lin/microblaze-xilinx-elf/include/include/reent.h
/opt/Xilinx/SDK/2016.2/gnu/microblaze/lin/microblaze-xilinx-elf/include/include/sys/reent.h
/opt/Xilinx/SDK/2016.2/gnu/microblaze/lin/microblaze-xilinx-elf/include/reent.h
/opt/Xilinx/SDK/2016.2/gnu/microblaze/lin/microblaze-xilinx-elf/include/sys/reent.h
/opt/Xilinx/SDK/2016.2/gnu/microblaze/lin/microblaze-xilinx-elf/sysroot/usr/include/reent.h
/opt/Xilinx/SDK/2016.2/gnu/microblaze/lin/microblaze-xilinx-elf/sysroot/usr/include/sys/reent.h

Best regards

-- 
?lvaro G?mez Machado
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[Buildroot] Bare metal toolchain support?

[Thomas Petazzoni]

Hello,

On Wed, 23 Nov 2016 12:20:35 +0100, Alvaro Gamez wrote:

> errno.c:6:19: fatal error: reent.h: No such file or directory
>  #include <reent.h>
> 
> This reent.h header doesn't exist in the toolchain built by buildroot, but
> it exists on Xilinx's:

reent.h is a newlib-specific header, which indeed will only exist on
bare-metal toolchains that use newlib. However, it's surprising that
bootloader code includes reent.h: this file defines the reentrant
variant of a number of system-level functions (close, stat, etc.). Which
doesn't make a lot of sense in a bootloader.

Perhaps it is not really used? I guess, you'll have to hack things
a bit to get them to build.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

[Buildroot] Bare metal toolchain support?

[Alvaro Gamez]

2016-11-23 13:06 GMT+01:00 Thomas Petazzoni <
thomas.petazzoni@free-electrons.com>:

> Perhaps it is not really used? I guess, you'll have to hack things
> a bit to get them to build.
>

Just to see how far the compilation would go, I removed errno.c from the
codebase
(a little drastic solution, but as you say, no one will use errno on this
thingy) and I got the
full BSP to compile. Hooray!


Now, I'm trying to compile the bootloader itself. It has complained about
function putnum()
(which prints a number through a serial port), that also seems to live only
on Xilinx' toolchain.
Maybe it's also a newlib thing.

I've also removed calls to that function and the final error is this one:


/home/agamez/mb-bootloader/scripts/..//test/output/host/usr/bin/microblazeel-linux-gcc
-Wl,-T -Wl,../src/lscript.ld -L../../bootloader_bsp/microblaze_0/lib
-mlittle-endian -mxl-barrel-shift -mxl-pattern-compare -mno-xl-soft-div
-mcpu=v9.6 -mno-xl-soft-mul -mxl-multiply-high -Wl,--no-relax -o
"bootloader.elf"  ./src/bootloader.o ./src/platform.o ./src/srec.o
-Wl,--start-group,-lxil,-lgcc,-lc,--end-group -Wl,--start-group,-lxilisf,-
lxil,-lgcc,-lc,--end-group
/home/agamez/mb-bootloader/test/output/host/usr/
microblazeel-buildroot-linux-gnu/sysroot/usr/lib/crt1.o: In function
`_start':
(.text+0x30): undefined reference to `__libc_csu_init'
/home/agamez/mb-bootloader/test/output/host/usr/
microblazeel-buildroot-linux-gnu/sysroot/usr/lib/crt1.o: In function
`_start':
(.text+0x38): undefined reference to `__libc_csu_fini'
/home/agamez/mb-bootloader/test/output/host/usr/
microblazeel-buildroot-linux-gnu/sysroot/usr/lib/crt1.o: In function
`_start':
(.text+0x40): undefined reference to `__libc_start_main'
/home/agamez/mb-bootloader/test/output/host/usr/lib/gcc/
microblazeel-buildroot-linux-gnu/4.9.3/../../../../
microblazeel-buildroot-linux-gnu/bin/ld: xilisf_read.o: unknown relocation
type 30
/home/agamez/mb-bootloader/test/output/host/usr/lib/gcc/
microblazeel-buildroot-linux-gnu/4.9.3/../../../../
microblazeel-buildroot-linux-gnu/bin/ld: xilisf_read.o: unknown relocation
type 30
/home/agamez/mb-bootloader/test/output/host/usr/lib/gcc/
microblazeel-buildroot-linux-gnu/4.9.3/../../../../
microblazeel-buildroot-linux-gnu/bin/ld: xilisf_read.o: unknown relocation
type 30
/home/agamez/mb-bootloader/test/output/host/usr/lib/gcc/
microblazeel-buildroot-linux-gnu/4.9.3/../../../../
microblazeel-buildroot-linux-gnu/bin/ld: xilisf_read.o: unknown relocation
type 30
/home/agamez/mb-bootloader/test/output/host/usr/lib/gcc/
microblazeel-buildroot-linux-gnu/4.9.3/../../../../
microblazeel-buildroot-linux-gnu/bin/ld: xilisf_read.o: unknown relocation
type 30
/home/agamez/mb-bootloader/test/output/host/usr/lib/gcc/
microblazeel-buildroot-linux-gnu/4.9.3/../../../../
microblazeel-buildroot-linux-gnu/bin/ld: final link failed: Bad value
collect2: error: ld returned 1 exit status
makefile:36: recipe for target 'bootloader.elf' failed
make: *** [bootloader.elf] Error 1


xilisf_read.c file is part of the BSP, it is a library to read data from an
SPI flash,
from which I want to load the OS, so this time I can't hack around it
anymore,
as I need this to work.

Also, the bootloader trying to compile against crt1.o (and not finding
entries)
shouldn't be worrying too?

I can provide lscript.ld if it's helpful, but I don't think so. This is
above my knowledge, though.

Thanks, best regards!




-- 
?lvaro G?mez Machado
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[Buildroot] Bare metal toolchain support?

[Alvaro Gamez]

2016-11-23 13:16 GMT+01:00 Alvaro Gamez <alvaro.gamez@hazent.com>:

> /home/agamez/mb-bootloader/test/output/host/usr/lib/gcc/micr
> oblazeel-buildroot-linux-gnu/4.9.3/../../../../microblazeel-buildroot-linux-gnu/bin/ld:
> xilisf_read.o: unknown relocation type 30
>

Comparing the output of readelf over xilisf_read.o as compiled by
Xilinx toolchain and with buildroot's toolchain.

Under Xilinx':
00000000  0000001e R_MICROBLAZE_32_NONE              c

Under buildroots':
00000000  0000001e unrecognized: 1e                 c

I've searched for the R_MICROBLAZE_32_NONE string and there's only this
thing on google:
http://git.yoctoproject.org/cgit/cgit.cgi/meta-xilinx/plain/recipes-microblaze/gdb/files/0014-LOCAL-Fixup-debug_loc-sections-after-linker-relaxati.patch

So, I can understand that Xilinx may have patched something but the
question is:
how come buildroot's toolchain is generating a relocation entry with value
30 (1e),
when this relocation number doesn't exist on buildroot's toolchain?
I've grepped for both 30 and 1e around the codebase of the BSP and there's
no
reference to this value.

This looks like black magic to me...

Best regards!



-- 
?lvaro G?mez Machado
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[Buildroot] Bare metal toolchain support?

[Alvaro Gamez]

Hi!


2016-11-23 15:49 GMT+01:00 Alvaro Gamez <alvaro.gamez@hazent.com>:

> Under Xilinx':
> 00000000  0000001e R_MICROBLAZE_32_NONE              c
>
> Under buildroots':
> 00000000  0000001e unrecognized: 1e                 c
>

I've made some progress on this. There was something wrong on my setup
that made it use some toolchain apps from Xilinx but some others from
buildroot,
so it's even a miracle it reached that far. Once solved lots of environment
variables
and the like, there remains just this one error on compilation:

/home/sslayer/Proyectos/ART/ESA/DRVM-software.git/DRVM/output/host/usr/bin/microblazeel-linux-gcc
-Wl,-T -Wl,lscript.ld -L../bsp/lib -mlittle-endian -mxl-barrel-shift
-mxl-pattern-compare -mno-xl-soft-div -mcpu=v9.6 -mno-xl-soft-mul
-mxl-multiply-high -Wl,--no-relax -o "bootloader.elf" bootloader.o
platform.o srec.o  -Wl,--start-group,-lxil,-lgcc,-lc,--end-group
-Wl,--start-group,-lxilisf,-lxil,-lgcc,-lc,--end-group
/home/sslayer/Proyectos/ART/ESA/DRVM-software.git/DRVM/output/host/usr/microblazeel-buildroot-linux-gnu/sysroot/usr/lib/libc_nonshared.a(elf-init.oS):
In function `__libc_csu_init':
(.text+0x44): undefined reference to `__init_array_start'
/home/sslayer/Proyectos/ART/ESA/DRVM-software.git/DRVM/output/host/usr/microblazeel-buildroot-linux-gnu/sysroot/usr/lib/libc_nonshared.a(elf-init.oS):
In function `__libc_csu_init':
(.text+0x4c): undefined reference to `__init_array_end'
collect2: error: ld returned 1 exit status
Makefile:32: recipe for target 'bootloader.elf' failed
make: *** [bootloader.elf] Error 1


So... back to square oneI guess. I don't know what to do with this now.


Best regards


-- 
?lvaro G?mez Machado
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[Buildroot] Bare metal toolchain support?

[Arnout Vandecappelle]

On 23-11-16 17:44, Alvaro Gamez wrote:
> Hi!
> 
> 
> 2016-11-23 15:49 GMT+01:00 Alvaro Gamez <alvaro.gamez@hazent.com
> <mailto:alvaro.gamez@hazent.com>>:
> 
>     Under Xilinx':
>     00000000  0000001e R_MICROBLAZE_32_NONE              c
> 
>     Under buildroots':
>     00000000  0000001e unrecognized: 1e                 c
> 
> 
> I've made some progress on this. There was something wrong on my setup
> that made it use some toolchain apps from Xilinx but some others from buildroot,
> so it's even a miracle it reached that far. Once solved lots of environment
> variables
> and the like, there remains just this one error on compilation:
> 
> /home/sslayer/Proyectos/ART/ESA/DRVM-software.git/DRVM/output/host/usr/bin/microblazeel-linux-gcc
> -Wl,-T -Wl,lscript.ld -L../bsp/lib -mlittle-endian -mxl-barrel-shift
> -mxl-pattern-compare -mno-xl-soft-div -mcpu=v9.6 -mno-xl-soft-mul
> -mxl-multiply-high -Wl,--no-relax -o "bootloader.elf" bootloader.o platform.o
> srec.o  -Wl,--start-group,-lxil,-lgcc,-lc,--end-group
> -Wl,--start-group,-lxilisf,-lxil,-lgcc,-lc,--end-group
> /home/sslayer/Proyectos/ART/ESA/DRVM-software.git/DRVM/output/host/usr/microblazeel-buildroot-linux-gnu/sysroot/usr/lib/libc_nonshared.a(elf-init.oS):
> In function `__libc_csu_init':
> (.text+0x44): undefined reference to `__init_array_start'
> /home/sslayer/Proyectos/ART/ESA/DRVM-software.git/DRVM/output/host/usr/microblazeel-buildroot-linux-gnu/sysroot/usr/lib/libc_nonshared.a(elf-init.oS):
> In function `__libc_csu_init':
> (.text+0x4c): undefined reference to `__init_array_end'
> collect2: error: ld returned 1 exit status
> Makefile:32: recipe for target 'bootloader.elf' failed
> make: *** [bootloader.elf] Error 1
> 
> 
> So... back to square oneI guess. I don't know what to do with this now.

 I haven't followed this in detail, but is there any reason why
CC="$(TARGET_CC) -ffreestanding" doesn't work?

 Regards,
 Arnout

-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

[Buildroot] Bare metal toolchain support?

[Alvaro Gamez]

2016-11-24 21:41 GMT+01:00 Arnout Vandecappelle <arnout@mind.be>:

>  I haven't followed this in detail, but is there any reason why
> CC="$(TARGET_CC) -ffreestanding" doesn't work?
>

Hi Arnout,

In the end I've managed to get this thing to build and it's working now on
the platform.

The reason why that won't work with this codebase is because the BSP over
which the
bootloader is built requires some newlib files. Specifically, it requires
the set of crt*.S files,
which seem to have been semi-split from newlib into libgloss.

I've copied files from here and patched crtinit.S to add __init and __fini
sections

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;a=tree;f=libgloss/
microblaze;h=d713445523e8a7cd84cc3e4dadf12d06a8a3daa6;hb=HEAD

I also found this document
https://forums.xilinx.com/xlnx/attachments/xlnx/zaps/
13261/1/(Guidance%20Note)%20Zynq%20-%20Using%20a%20Custom%20BareMetal%20GCC%
20Toolchain%20in%20XSDK%20(Cross%20GCC)%20r05.docx
<https://forums.xilinx.com/xlnx/attachments/xlnx/zaps/13261/1/%28Guidance%20Note%29%20Zynq%20-%20Using%20a%20Custom%20BareMetal%20GCC%20Toolchain%20in%20XSDK%20%28Cross%20GCC%29%20r05.docx>

which helped me create a Xilinx.spec file to pass over to gcc

In the end it's been an almost 18 hours journey that has been fruitful:
I've learned
lots of things I didn't know and I've managed to do what I needed: bulding
standalone
applications for microblaze using buildroot.

However, I don't know if I can generalize this work to improve buildroot
and make this
available for anyone. Should newlib exist as a package for buildroot? Maybe
only libgloss?
I don't mind working on this, but I'd need some guidance, as I don't have
everything clear
yet. What could be a nice starting point?

I see on the list there was a patch from March "toolchain: add support for
the newlib library"
but as far as I know it hasn't been comitted. Maybe improving that patch to
fix the issues
it had could be the first step.

Best regards!

-- 
?lvaro G?mez Machado
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[Buildroot] Bare metal toolchain support?

[Arnout Vandecappelle]

On 25-11-16 08:54, Alvaro Gamez wrote:
> However, I don't know if I can generalize this work to improve buildroot and
> make this
> available for anyone. Should newlib exist as a package for buildroot? Maybe only
> libgloss?

 It never hurts to throw patches on the list so they are stored for posterity.
The worst that can happen is that we don't apply them.

> I don't mind working on this, but I'd need some guidance, as I don't have
> everything clear
> yet. What could be a nice starting point?
> 
> I see on the list there was a patch from March "toolchain: add support for the
> newlib library"
> but as far as I know it hasn't been comitted. Maybe improving that patch to fix
> the issues
> it had could be the first step.

 I gave a few comments on them, but please note this remark I made in response
to Chris's patch:

>>  I've checked with other core developers and there is not a lot of enthusiasm to 
>> include this (as witnessed by the long delay in reviewing this patch). So you'd 
>> need to be very active in pushing this to make it feasible.

 Regards,
 Arnout


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF