[CMake] Adding CRC32 to ELF
Vincent van Beveren
v.van.beveren at nikhef.nl
Mon Oct 7 11:09:32 EDT 2019
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
> <v.van.beveren at nikhef.nl <mailto:v.van.beveren at nikhef.nl>> 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.
> https://cmake.org/cmake/help/v3.15/command/add_custom_command.html#build-events
>
> 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>
> see:
> https://cmake.org/cmake/help/latest/command/add_library.html#object-libraries
> 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: v.van.beveren at nikhef.nl <mailto:v.van.beveren at nikhef.nl>
> site : http://www.nikhef.nl/~vincentb
>
> --
>
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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: v.van.beveren at nikhef.nl
site : http://www.nikhef.nl/~vincentb
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