OSDev.org

• 1. Compile test.c into test.exe:
  • let say, it will have default base (4Mb),
  • code section and entry point at (4Mb+4k),
  • data section at (4Mb+8k), and bss section (4Mb+12k)
• 2. Your utility should take text.exe as input and produce test.bin
• 3. Somehow set new target address by changing 4 bytes inside test.bin (specific offset?) to (2Mb)
• 4. Use modified test.bin to create floppy image with GRUB that will load test.bin to some address (64k)
• 5. Test it under QEMU or VMware:
  • your init code should copy and rebase
  • original code section to (2Mb+4k),
  • data section to (2Mb+8k), clear bss, and
  • jump to the proper entry point at (2Mb+4k).

• Your source code must be ISC licensed similarly to other contests on this forum
• All entries must be posted to this thread with source code and compile instructions attached (no links)
• You can use GRUB only to load boot binary, set up initial stack, and get control in 32-bit protected mode
• You cannot utilize any advanced GRUB functionality or additional modules (compression, ELF handling, etc...)
• Accepted are C, C++, and x86 assembler sources compilable with tcc, gcc, gasm, fasm, nasm, or msvs/cl/masm
• Prizes will be awarded via PayPal in USD within two weeks of contest closing date (i.e. entry submission deadline)

• Entries are accepted starting May 1, 2010 00:00:01 UTC
• For entry to qualify resulting boot binaries must be less or equal to the original executable size.
• There are three separate $25 prizes:
• First entry that successfully boots PE executable (generated by one of compilers) gets $25
• First entry that successfully boots ELF executable (generated by one of compilers) gets $25
• First entry that successfully handles both PE and ELF executables and all compilers (tcc,gcc,msvc) gets remaining $25
• Deadline for the first part of the contest is May 31, 2010 23:59:59 UTC

• Your utility needs to build upon the best solution from the Part I and create a compressed boot binaries for each test case
• There will be three test executables: ~12k (public), ~64k (hidden), ~256k (public) ;; (size, gzipped size, and md5s will be public)
• Each executable will be compressible by ~2 times using gzip and will contain similar proportion of code, globals, and text messages.
• Init code should decompress original code, perform base relocations and jump to the executable entry address
• In order to qualify first entry must produce binaries at least 1024 bytes less than ones produced by the uncompressed winning entry from the Part I
• Each subsequent entry must improve total compressed size by at least 1024 bytes and no binary should be larger than best result of the previously qualified entry
• Example:
  • First entry: 9k, 51k, 180k (total=240k) -> quilifies.
  • Second entry: 11k, 49k, 160k (total=220k) -> nop
  • Third entry: 9k, 49k, 142k (total=200k) -> quilifies.
  • Fourth entry: 8k, 42k, 140k (total=190k) -> quilifies.
• Last Qualified entry on the contest closing date wins $60 prize!
• There will be a extra $40 prize if winning entry uses decompressor code attached below.

Gigasoft wrote:As I understand it, this is obviously not meant for random PE or ELF files taken out of the blue (which it would be useless to convert). The PE or ELF files will be linked with /FIXED:NO or /DLL (for PE using the Microsoft Linker) or whatever options ELF linkers use to specify that they should output a relocatable executable. In PE files, this is accomplished by inlucding a base relocation data directory. In ELF files, a standard relocation table is used with all entries having a symbol index of 0.

int x=42;
int _start(void)
{
 return x;
}

gcc -nostdlib -shared test.c -o test.elf

cl /nologo /c test.c
link /nologo /NODEFAULTLIB /SUBSYSTEM:CONSOLE  /FIXED:NO /ENTRY:_start test.obj

Owen wrote:Really, I don't see the point. Linker scripts aren't hard, and kernels generally make some assumptions about the region they are loaded into anyway.

Owen wrote:Hmm? It looks like my linker dislikes your proposal - namely, it enforces strict W^X.

pinged wrote:Shouldn't you be using -fPIC?

int foo(char*p) { return 42; }
char *p="Hello World";
int (*fooPtr)(char*)=&foo;

int _start(void)
{
  return (*fooPtr)(p);
}

gcc -nostdlib -fPIC test1.c -o test1.elf
objdump -rxds test1.elf

Contest: make 32-bit PEs & ELFs easy bootable & relocateable

Combuster wrote:

Contest: make 32-bit PEs & ELFs easy bootable & relocateable

Emphasis mine. I think this experiment has failed. It is just as easy to add -T link.ld to all the mess you already have to supply to gcc/ld instead of adding yet another step in the process - especially when the former has been tried and supported for like the past decade.

Combuster wrote:So, you're writing out a contest in order to get a desgin specifically for you?

Combuster wrote:... it is generally a bad idea to use a random compiler for OS development ...