Question about certain GNU tools (objdump,ld,nm,strip)

[Faw]

I have downloaded the sample operating systems from OSD (http://my.execpc.com/~geezer/osd/) and I have some questions:

The make file for OSD3 (one of the simple demo kernels) has the following:

krnl.x: $(OBJS) $(LDSCRIPT)   $(MAKEDEP)
$(LD) -o$@ $(OBJS)
objdump --source $@ >krnl.lst
nm --line-numbers $@ | sort >krnl.sym
strip $@

What the purpose if the objdump, and nm line? I guess it is to save some debug information into krnl.lst and krnl.sym, right? Could I eliminate the 'objdump','nm' and 'strip' command and call LD with the '--strip-all' argument?

[Tim]

Yes, and yes.

[Faw]

Ok, LD can do the 'strip' command with the --strip-all flag. Is there flag (or flags) in LD that would let me do the same as the 'objdump' and 'nm' commands?

[Solar]

ld is a linker, and as such its purpose isn't to produce any debugging output. So no, you can't do objdump using ld - or there wouldn't be an objdump, right?



This makefile does two things: Create debug output (using objdump and nm) and linking the object files (using ld).

The 'strip' at the end is not strictly necessary because ld has a 'stip-all' option, and you can leave out the debug steps ('objdump' and 'nm'). Actually, if you run 'ld' with strip-all, there won't be any debug information left in the binary for objdump and/or nm to process, so calling them would be rather pointless.

Does that help?

[Faw]

Thanks, it sort of helps...

I ask because I'm trying to use Borland C++BuilderX for OS Development and I have to configure it so it uses the LD linker and NASM. Originally it comes with Borland and MingW toolsets. Since C++BuilderX Personal Edition is free (and fairly decent) I wanted to use it.

[Pype.Clicker]

Ok, LD can do the 'strip' command with the --strip-all flag. Is there flag (or flags) in LD that would let me do the same as the 'objdump' and 'nm' commands?

i dunno exactly what "nm" and "objdump" does with those arguments, but you can get the "map" of your built file using -Map <filename> flag in LD.

It will show, among other things, the "LinkerScript and Memory Map"

Code: Select all

Linker script and memory map

                0x0000000000000074                . = SIZEOF_HEADERS
.text           0x0000000000000000    0x1c4e0
                0x0000000000002000                . = 0x2000
 *fill*         0x0000000000000000 0x100002000 00
 *(.text)
 .text          0x0000000000002000      0x104 bin/kernel.o
                0x00000000000020fc                farJmp
                0x00000000000020e0                enablePaging
                0x00000000000020f4                farCall
                0x0000000000002000                start
 *fill*         0x0000000000002104        0xc 00
 .text          0x0000000000002110      0x200 bin/config.o
                0x0000000000002232                _prepare
                0x00000000000022eb                setBreakPoints

However, do not expect line numbers or static function names here ...