19.10.2016 18:32, Matthew Whitehead пишет: > Lennart, > I think I found the problem. I don't know what kernel.img does, but I'm > guessing it is an essential part of grub2, loading after the 1st and 2nd > stage loaders? I disassembled the binary using 'objdump -D -b binary -m i386 > kernel.img' and found several cases both of rdtsc and cpuid. Both of these > instructions do not exist on first generation 80486 cpus. Here they are, and > I've attached the full disassembly output. > > 53a0: 85 c0 test %eax,%eax > 53a2: 74 6f je 0x5413 > 53a4: b8 01 00 00 00 mov $0x1,%eax > 53a9: 0f a2 cpuid > 53ab: 80 e2 10 and $0x10,%dl > 53ae: 74 63 je 0x5413 > 53b0: 31 c0 xor %eax,%eax > 53b2: 0f a2 cpuid > 53b4: 0f 31 rdtsc > 53b6: a3 48 67 01 00 mov %eax,0x16748 > 53bb: 89 15 4c 67 01 00 mov %edx,0x1674c > 53c1: 31 c0 xor %eax,%eax > 53c3: 0f a2 cpuid > 53c5: 0f 31 rdtsc > 53c7: 89 c6 mov %eax,%esi > 53c9: b8 ff ff 00 00 mov $0xffff,%eax > 53ce: 89 d7 mov %edx,%edi > 53d0: e8 83 00 00 00 call 0x5458 > 53d5: 31 c0 xor %eax,%eax > 53d7: 0f a2 cpuid > 53d9: 0f 31 rdtsc > 53db: 89 45 e0 mov %eax,-0x20(%ebp) > 53de: 8b 4d e0 mov -0x20(%ebp),%ecx > ... > 5439: 31 c0 xor %eax,%eax > 543b: 0f a2 cpuid > 543d: 0f 31 rdtsc > 543f: 8b 0d 50 67 01 00 mov 0x16750,%ecx > 5445: 6a 00 push $0x0 > 5447: e8 8f dc ff ff call 0x30db > > How can we adjust the makefiles to include -march=i486 or something similar? >
This code is likely grub_cpu_is_tsc_supported() (see include/grub/i386/tsc.h) which *is* protected by grub_cpu_is_cpuid_supported(). Can you test if this function yields wrong result in your case (just compile it separately)? > - Matthew > > > > _______________________________________________ > Grub-devel mailing list > Grub-devel@gnu.org > https://lists.gnu.org/mailman/listinfo/grub-devel > _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
