Adding CRC32 to ELF

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Adding CRC32 to ELF

Vincent van Beveren
Hello everyone,

I'm setting up a new build targeting an embedded platform (LM32) and
trying to integrate a CRC32 into the resulting ELF. I have previously
done this using plain Makefiles with the following steps (pseudo code):

target.elf: <obj-files>
    link <obj-files> --symbol CRC_VALUE=0 intermediate.elf
    objcopy --binary intermediate.elf intermediate.bin
    link <obj-files> --symbol CRC_VALUE=`crc32 intermediate.bin` target.elf
    rm intermediate.bin

Now I would like to achieve the same thing with CMake. I'm using
add_executable with multiple targets. The end of my CMakeLists.txt looks
like this, where F_GEN contains generic source files and F__* source
files specific for that variant of the build:

# [...defining of cross compiler, and source files, some compile flags,
etc...]
# Educate the linker
add_link_options(
     -nostartfiles
     -nodefaultlibs
     -nostdlib
     -Wl,--gc-sections
     -T ${CMAKE_SOURCE_DIR}/${P_SRC}/romram.ld
     -Wl,--defsym=CRC_VALUE=0
     -Wl,--defsym=_start=0
     )

# DOM v2 target
add_executable( clb_v2_dom.elf ${F_GEN} ${F__DOM} )
target_compile_definitions(clb_v2_dom.elf PUBLIC -DDOM -DCLBV2 )

# BASE v2 target
add_executable( clb_v2_base.elf ${F_GEN} ${F__BASE} )
# TODO migrate define 'DUBASE' -> 'BASE'
target_compile_definitions(clb_v2_base.elf PUBLIC -DDUBASE -DBASE -DCLBV2)

# Golden v2 target
add_executable( clb_v2_golden.elf ${F_GEN} ${F__GLD} )
target_compile_definitions( clb_v2_golden.elf PUBLIC -DGOLDEN -DCLBV2 )

==

As you can see CRC_VALUE is now simply defined 0 for every target. Which
works well for compiling but during runtime poses a problem to the ROM
verification procedure. What would a 'proper' way be of adding a CRC to
an ELF file be using CMake, and be different for each target. Any help
is welcome!

Kind regards,
Vincent



--
National Institute for Subatomic Physics Nikhef
Department of Computer Technology
Science Park 105
1098 XG AMSTERDAM

tel.  : +31 (0)20 592 2032
e-mail: [hidden email]
site  : http://www.nikhef.nl/~vincentb

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Re: Adding CRC32 to ELF

Eric Noulard


Le lun. 7 oct. 2019 à 14:41, Vincent van Beveren <[hidden email]> a écrit :
Hello everyone,

I'm setting up a new build targeting an embedded platform (LM32) and
trying to integrate a CRC32 into the resulting ELF. I have previously
done this using plain Makefiles with the following steps (pseudo code):

target.elf: <obj-files>
    link <obj-files> --symbol CRC_VALUE=0 intermediate.elf
    objcopy --binary intermediate.elf intermediate.bin
    link <obj-files> --symbol CRC_VALUE=`crc32 intermediate.bin` target.elf
    rm intermediate.bin

Now I would like to achieve the same thing with CMake. I'm using
add_executable with multiple targets. The end of my CMakeLists.txt looks
like this, where F_GEN contains generic source files and F__* source
files specific for that variant of the build:

# [...defining of cross compiler, and source files, some compile flags,
etc...]
# Educate the linker
add_link_options(
     -nostartfiles
     -nodefaultlibs
     -nostdlib
     -Wl,--gc-sections
     -T ${CMAKE_SOURCE_DIR}/${P_SRC}/romram.ld
     -Wl,--defsym=CRC_VALUE=0
     -Wl,--defsym=_start=0
     )

# DOM v2 target
add_executable( clb_v2_dom.elf ${F_GEN} ${F__DOM} )
target_compile_definitions(clb_v2_dom.elf PUBLIC -DDOM -DCLBV2 )

# BASE v2 target
add_executable( clb_v2_base.elf ${F_GEN} ${F__BASE} )
# TODO migrate define 'DUBASE' -> 'BASE'
target_compile_definitions(clb_v2_base.elf PUBLIC -DDUBASE -DBASE -DCLBV2)

# Golden v2 target
add_executable( clb_v2_golden.elf ${F_GEN} ${F__GLD} )
target_compile_definitions( clb_v2_golden.elf PUBLIC -DGOLDEN -DCLBV2 )

==

As you can see CRC_VALUE is now simply defined 0 for every target. Which
works well for compiling but during runtime poses a problem to the ROM
verification procedure. What would a 'proper' way be of adding a CRC to
an ELF file be using CMake, and be different for each target. Any help
is welcome!

I would try to add a set of custom command as POST_BUILD event.

add_custom_command(TARGET clb_v2_base.elf POST_BUILD
                                   COMMAND crc32 $<TARGET_FILE:clb_v2_base.elf> > $<TARGET_FILE:clb_v2_base.elf>.crc32
                                   COMMAND ${CMAKE_C_COMPILER} --symbol $<TARGET_FILE:clb_v2_base.elf>.crc32  $<TARGET_FILE:clb_v2_base.elf>
                                  )

I don't know if the linker can read the computed crc32 from the previously generated file but you get the idea.
Moreover if you want to easily collect objects used for linking a target you may need to use an intermediate
OBJECT library in order to be able to retrieve $<TARGET_OBJECTS:objlib>
i.e. replace: 
add_executable( clb_v2_dom.elf ${F_GEN} ${F__DOM} )

by
add_library(clb_v2_dom.objs OBJECT ${F_GEN} ${F__DOM})
add_executable(clb_v2_dom.elf  $<TARGET_OBJECTS:clb_v2_dom.objs>)

and then:

add_custom_command(TARGET clb_v2_dom.elf POST_BUILD
                                   COMMAND crc32 $<TARGET_FILE:clb_v2_dom.elf> > $<TARGET_FILE:clb_v2_dom.elf>.crc32
                                   COMMAND ${CMAKE_C_COMPILER} $<TARGET_OBJECTS:clb_v2_dom.objs> --symbol $<TARGET_FILE:clb_v2_dom.elf>.crc32  $<TARGET_FILE:clb_v2_dom.elf>
                                  )

If this looks ok to you I would then write my own

lm32_add_executable that would wraps this up in order to be called as:

lm32_add_executable(EXECUTABLE clb_v2_dom.elf
                                 SOURCES ${F_GEN} ${F__DOM})




Kind regards,
Vincent



--
National Institute for Subatomic Physics Nikhef
Department of Computer Technology
Science Park 105
1098 XG AMSTERDAM

tel.  : +31 (0)20 592 2032
e-mail: [hidden email]
site  : http://www.nikhef.nl/~vincentb

--

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Eric

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Re: Adding CRC32 to ELF

Vincent van Beveren

Hi Eric,

Thanks for your prompt reply.

I have been able to follow your steps up until the item, so thanks!

 COMMAND ${CMAKE_C_COMPILER} $<TARGET_OBJECTS:clb_v2_dom.objs> --symbol $<TARGET_FILE:clb_v2_dom.elf>.crc32  $<TARGET_FILE:clb_v2_dom.elf>

I ran into two challenges:
- The argument '$<TARGET_FILE:clb_v2_dom.elf>.crc32' should be the actual content of the file, and not the file itself, i.e. the calculated CRC value.  How to do this?
- As far as I can see, non of the previously defined linker flags are added to this command. Of course I can do this, but it would mean I need to define things twice.

Cheers,
Vincent

On 7-10-2019 at 15:55 wrote Eric Noulard:


Le lun. 7 oct. 2019 à 14:41, Vincent van Beveren <[hidden email]> a écrit :
Hello everyone,

I'm setting up a new build targeting an embedded platform (LM32) and
trying to integrate a CRC32 into the resulting ELF. I have previously
done this using plain Makefiles with the following steps (pseudo code):

target.elf: <obj-files>
    link <obj-files> --symbol CRC_VALUE=0 intermediate.elf
    objcopy --binary intermediate.elf intermediate.bin
    link <obj-files> --symbol CRC_VALUE=`crc32 intermediate.bin` target.elf
    rm intermediate.bin

Now I would like to achieve the same thing with CMake. I'm using
add_executable with multiple targets. The end of my CMakeLists.txt looks
like this, where F_GEN contains generic source files and F__* source
files specific for that variant of the build:

# [...defining of cross compiler, and source files, some compile flags,
etc...]
# Educate the linker
add_link_options(
     -nostartfiles
     -nodefaultlibs
     -nostdlib
     -Wl,--gc-sections
     -T ${CMAKE_SOURCE_DIR}/${P_SRC}/romram.ld
     -Wl,--defsym=CRC_VALUE=0
     -Wl,--defsym=_start=0
     )

# DOM v2 target
add_executable( clb_v2_dom.elf ${F_GEN} ${F__DOM} )
target_compile_definitions(clb_v2_dom.elf PUBLIC -DDOM -DCLBV2 )

# BASE v2 target
add_executable( clb_v2_base.elf ${F_GEN} ${F__BASE} )
# TODO migrate define 'DUBASE' -> 'BASE'
target_compile_definitions(clb_v2_base.elf PUBLIC -DDUBASE -DBASE -DCLBV2)

# Golden v2 target
add_executable( clb_v2_golden.elf ${F_GEN} ${F__GLD} )
target_compile_definitions( clb_v2_golden.elf PUBLIC -DGOLDEN -DCLBV2 )

==

As you can see CRC_VALUE is now simply defined 0 for every target. Which
works well for compiling but during runtime poses a problem to the ROM
verification procedure. What would a 'proper' way be of adding a CRC to
an ELF file be using CMake, and be different for each target. Any help
is welcome!

I would try to add a set of custom command as POST_BUILD event.

add_custom_command(TARGET clb_v2_base.elf POST_BUILD
                                   COMMAND crc32 $<TARGET_FILE:clb_v2_base.elf> > $<TARGET_FILE:clb_v2_base.elf>.crc32
                                   COMMAND ${CMAKE_C_COMPILER} --symbol $<TARGET_FILE:clb_v2_base.elf>.crc32  $<TARGET_FILE:clb_v2_base.elf>
                                  )

I don't know if the linker can read the computed crc32 from the previously generated file but you get the idea.
Moreover if you want to easily collect objects used for linking a target you may need to use an intermediate
OBJECT library in order to be able to retrieve $<TARGET_OBJECTS:objlib>
i.e. replace: 
add_executable( clb_v2_dom.elf ${F_GEN} ${F__DOM} )

by
add_library(clb_v2_dom.objs OBJECT ${F_GEN} ${F__DOM})
add_executable(clb_v2_dom.elf  $<TARGET_OBJECTS:clb_v2_dom.objs>)

and then:

add_custom_command(TARGET clb_v2_dom.elf POST_BUILD
                                   COMMAND crc32 $<TARGET_FILE:clb_v2_dom.elf> > $<TARGET_FILE:clb_v2_dom.elf>.crc32
                                   COMMAND ${CMAKE_C_COMPILER} $<TARGET_OBJECTS:clb_v2_dom.objs> --symbol $<TARGET_FILE:clb_v2_dom.elf>.crc32  $<TARGET_FILE:clb_v2_dom.elf>
                                  )

If this looks ok to you I would then write my own

lm32_add_executable that would wraps this up in order to be called as:

lm32_add_executable(EXECUTABLE clb_v2_dom.elf
                                 SOURCES ${F_GEN} ${F__DOM})




Kind regards,
Vincent



--
National Institute for Subatomic Physics Nikhef
Department of Computer Technology
Science Park 105
1098 XG AMSTERDAM

tel.  : +31 (0)20 592 2032
e-mail: [hidden email]
site  : http://www.nikhef.nl/~vincentb

--

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Kitware offers various services to support the CMake community. For more information on each offering, please visit:

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--
Eric
-- 
National Institute for Subatomic Physics Nikhef
Department of Computer Technology
Science Park 105
1098 XG AMSTERDAM

tel.  : +31 (0)20 592 2032
e-mail: [hidden email]
site  : http://www.nikhef.nl/~vincentb

--

Powered by www.kitware.com

Please keep messages on-topic and check the CMake FAQ at: http://www.cmake.org/Wiki/CMake_FAQ

Kitware offers various services to support the CMake community. For more information on each offering, please visit:

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