README.md

Add CRC checksum and version information to ELF and binary files

Embedded programmers often face the task to insert a checksum into binaries after linking. A bootloader can then verify the checksum before allowing a firmware update or running the program.

add_version_info is a small python script that can insert version control information and checksums into ELF or binary firmware images.

Usage

The tool will search for two 16 byte markers in the firmware image and fill in a structure with the current git or subversion id, a checksum, and build time information. The checksum is forged, so that running a CRC32 check over the entire image will yield the requested checksum.

Example

version.h

#include <stdint.h>

#define VCS_INFO_START "VCSINFO2_START->"
#define VCS_INFO_END   "<---VCSINFO2_END"

struct version_info {
    char        vcs_info_start[16];

    // set by add-version-info.py
    //
    uint32_t    image_crc;
    uint32_t    image_start;
    uint32_t    image_size;

    char        vcs_id[32];
    char        build_user[16];
    char        build_host[16];
    char        build_date[16];
    char        build_time[16];

    // set at compile-time
    //
    char        product_name[32];
    int         major;
    int         minor;
    int         patch;

    char        vcs_info_end[16];
};

extern volatile const struct version_info  version_info;

void print_version_info(int verbose);

version.c

#include "version.h"

volatile const struct version_info version_info = {
    .vcs_info_start = VCS_INFO_START,
    .product_name   = "add_version_info example",
    .major          = 1,
    .minor          = 2,
    .patch          = 3,
    .vcs_info_end   = VCS_INFO_END
};

void print_version_info(const struct version_info *v)
{
    printf(
        "%s v%d.%d.%d %s %s %s\n"
        "  Compiled %s %s by %s on %s\n"
        v->product_name,
        v->major, v->minor, v->patch,
        v->vcs_id,
        v->build_date, v->build_time,
        v->build_date, v->build_time,
        v->build_user, v->build_host
    );
}

void main(void)
{
    print_version_info(&version_info);
}

Makefile rule

# Link: create ELF output file from object files
#
$(TARGET).elf: $(OBJECTS)
	@echo
	@echo Linking: $@
	$(CC) $(OBJECTS) $(LDFLAGS) --output $(basename $@).tmp

	@echo
	@echo Post-processing: $@
	add-version-info.py -v $(basename $@).tmp $@