can we add personal information in elf file?

[Brian Dessent]

vichy wrote:

> I have a script which can build my source code as ELF daily, but I want to
> add my personal information in elf file, such that I can not only identify
> the file by date but also by the information I added.
> I have seen the format of elf, but there seems have no space to put
> user-defined information in ELF header.
> If someone has the same experience or knows where we can put user-defined
> information in elf, please let me know.

There's no need to invent any special header fields, just use a named
section marked noload.  The compiler already does something like this
with .comment to identify the version and options used etc.

$ echo 'int main() { puts ("Hello world"); }' | gcc -x c - -c -o hello.o

$ echo "this is my special data" >mydata

$ objcopy --add-section .mydata=mydata \
          --set-section-flags .mydata=noload,readonly hello.o hello2.o

$ gcc hello2.o -o hello

$ ./hello
Hello world

$ objdump -sj .mydata hello

hello:     file format elf32-i386

Contents of section .mydata:
 0000 74686973 20697320 6d792073 70656369  this is my speci
 0010 616c2064 6174610a                    al data.        

Brian