glibc

[CTho9305]

how can I tell which parts are actually in use, or what my programs might need? I'm trying to get by with the kernel alone, and set init= my program

will ltrace do it? but that would take a while before all the code in some of my programs actually runs...

 

[Nothinman]

Compile your program statically, it'll be bigger but will be a lot easier than pulling apart glibc.

 

[Bremen]

Removing parts of glibc would run havoc with any program linked to it. Essentially you'd need to recompile everything every time you made a change (at least thats the way I understand how dynamic linking works). So if you needed to put something back into glibc for a program you're compiling it would force you to recompile everything. Static linking may not save as much space, but it will keep you sane.

 

[Nothinman]

Part of the reason for using dynamic linking is so that when a library changes you don't need to recompile all the programs that use it, so as long as he had some implementation of every function glibc implements (even if they all just had return 0; in them) they would run, although maybe not correctly.

 

[CTho9305]

<< Compile your program statically, it'll be bigger but will be a lot easier than pulling apart glibc. >>



i dont have the source code. if I did, i would have done that, or looked at what it calls

 

[CTho9305]

hmmm... does this mean it is statically compiled? "Linux (x86) (console version 0.99, new build against glibc2.0)"
the program

 

[CTho9305]

I ltraced it and got a huge file after a couple minutes (350 meg)... cut it to the first 8 bytes of each line, sorted, and got the following calls:
_IO_put __errno __fxsta __libc_ __xstat calloc close fclose fflush fgets fileno flock fopen free fscanf ftell fwrite getcwd getenv getprio gettime localti lseek malloc memcmp memcpy memmove memset open opendir pthread read readdir realloc setenv setprio sigacti sigadds sigempt signal srandom strlen system time tzset tzset write

how do I find where these are?

 

[Nothinman]

Type 'ldd programname' and you'll get a list of libraries it uses like:

ldd /bin/ls
librt.so.1 => /lib/librt.so.1 (0x4001d000)
libc.so.6 => /lib/libc.so.6 (0x4002e000)
libpthread.so.0 => /lib/libpthread.so.0 (0x4014c000)
/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)

 

[CTho9305]

thanks