Hello,
my research group is working on lightweight operating systems for
many-core processors. We are looking for a full system simulator that
supports debugging of x86-64 code and processor state. Qemu does not
tell much about the cpu state and the Bochs debugger has problems with
addresses in the high 64bit kernel-space. Hence, gem5 is very
interesting for us.
Unfortunately, we are not able to boot our kernel ELF images at the
moment. I applied the x86 32bit multiboot patches from
https://bitbucket.org/chrism333/gem5-patches/src/ and adapted the gem5
configuration successfully. Now gem5 tries to load the ELF image via
sim/system.cc, which ends up in ElfObject::loadSections and does fancy
things with virtual addresses and hard-coded section names.
The ELF loader is surely doing the correct thing to load 64bit
user-space applications. But during the multiboot startup it should
really just load all LOAD segments to the requested physical addresses
and leave everything else alone -- especially virtual addresses.
Assuming that I am able to implement such a simplified ELF loader for
kernel images, what is a good way to integrate it into the existing
infrastructure? Is it mandatory to derive the class MultibootX86System
(in arch/x86/multiboot/system.hh) from the class System (in sim/system.hh)?
Best regards,
Randolf Rotta
For reference, our kernel ELF image looks like this:
objdump -fph boot32.elf
boot32.elf: file format elf32-i386
architecture: i386, flags 0x00000012:
EXEC_P, HAS_SYMS
start address 0x00200058
Program Header:
LOAD off 0x00000078 vaddr 0x00200000 paddr 0x00200000 align 2**3
filesz 0x000003ed memsz 0x00206000 flags rwx
LOAD off 0x00000480 vaddr 0x81000000 paddr 0x00800000 align 2**6
filesz 0x0000da90 memsz 0x00401000 flags rwx
Sections:
Idx Name Size VMA LMA File off Algn
0 .init 000003ed 00200000 00200000 00000078 2**3
CONTENTS, ALLOC, LOAD, READONLY, CODE
1 .initbss 00205000 00201000 00201000 00000465 2**0
ALLOC
2 .text 00009256 81000000 00800000 00000480 2**1
CONTENTS, ALLOC, LOAD, READONLY, CODE
3 .rodata 00000c4d 81009280 00809280 00009700 2**6
CONTENTS, ALLOC, LOAD, READONLY, DATA
4 .eh_frame 00003bb8 81009ed0 00809ed0 0000a350 2**3
CONTENTS, ALLOC, LOAD, READONLY, DATA
5 .init_array 00000008 8100da88 0080da88 0000df08 2**3
CONTENTS, ALLOC, LOAD, DATA
6 .bss 003f3540 8100dac0 0080dac0 0000df10 2**6
ALLOC
_______________________________________________
gem5-dev mailing list
[email protected]
http://m5sim.org/mailman/listinfo/gem5-dev
