[CMake] 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



-- 
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Department of Computer Technology
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tel.  : +31 (0)20 592 2032
e-mail: v.van.beveren at nikhef.nl
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