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Daniel, Thanks for the hint, I looked at the 1M binary and noticed that the beginning of the file had the code but at the end was some "stuff". I then exectued "objdump -D t1" and saw at the "stuff" is an ".eh_frame", not sure what that is and I need to find out but by changing the objcopy command to: objcopy -R .note -R .comment -R .eh_frame -S -O binary t1 t1.bin The resulting file is 48 bytes and is exactly the data from <main> seen in the objdump. Quite nice that standard objdump and objcopy work with the elf64-x86-64 files! Thanks, Wink Ps: Take care of your RSI. -----Original Message----- From: Daniel Kegel [mailto:dkegel@google.com] Sent: Monday, February 16, 2004 10:36 AM To: wink saville Cc: crossgcc@sources.redhat.com Subject: Re: X86_64 cross compiler and generating binaries wink saville wrote: > I'm looking to create a simple kernel for the Amd64 and want to make a > boot loader to start with. I have followed the instructions provided > here, > http://www.nondot.org/sabre/os/files/Booting/CompilingBinaryFilesUsing > ACompiler.pdf. > > I created a small program, t1.c ... > > When I compile this using a cross compiler created using Kegel's > crosstool > (http://kegel.com/crosstool/) using the following: > > gcc -c -o t1.o t1.c > ld -Ttext 0x0 -e main -o t1 t1.o > objcopy -R .note -R .comment -S -O binary t1 t1.bin > > The result is: > > t1.o 1256 bytes > t1 1049835 bytes > t1.bin 1048680 bytes > > When I compile it with gcc 3.3.2 (Debian) using the same options... > The result is: > > t1.o 699 bytes > t1 4791 bytes > t1.bin 51 bytes > > Sooooo, the 1M file is a mite big, any ideas what I'm doing wrong? I suspect the default load address of x86_64's abi is higher than the one in x86's abi. Thus there are about a million zeroes at the start of the t1.bin compiled for x86_64. I couldn't find where it says this in http://www.x86-64.org/documentation/abi.pdf but I bet that's it. Running hexdump on both t1's verifies this. The start address for x86 seems to be 0x1000 or so, and for x86 it's 0x100000. - Dan ------ Want more information? See the CrossGCC FAQ, http://www.objsw.com/CrossGCC/ Want to unsubscribe? Send a note to crossgcc-unsubscribe@sources.redhat.com
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