Messages in this thread | | | Date | Tue, 8 May 2007 11:12:43 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] Make bootsector stub 16-bit-only (i386) |
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On Tue, 08 May 2007 04:25:00 -0700 "H. Peter Anvin" <hpa@zytor.com> wrote:
> Andrew Morton wrote: > > >> > >> # Normalize the start address > >> - jmpl $BOOTSEG, $start2 > >> + jmpw $BOOTSEG, $start2 > > > > Sigh, another blow struck in the ongoing struggle between my Vaio and the > > rest of the world. > > > > Stone-cold black-screen lockup immediately upon boot. > > > > Stock FC5 install, config at > > http://userweb.kernel.org/~akpm/config-sony.txt > > Andrew, I'm seriously starting to think there is something fundamentally > wrong with that test setup.
heh. All the other bugs have been real oh-yeah-youre-right bugs. This is the only mystery bug which I recall.
> The bootsect code in question is never executed. AT ALL. The only > raison d'être for it at all is to print an error message if someone > writes the kernel to a raw floppy disk. Nor does it change the > alignment of the header or anything else to that effect -- the assembly > code downstream has an explicit ".org" directive. For what it's worth, > just to make sure I'm not crazy, I just re-tested both booting the > kernel and booting the raw disk image, in simulation and on real > hardware, and it doesn't change anything. I used your configuration > file (yes '' | make oldconfig) minus Bluetooth (which is broken in > current top of Linus) against top of tree Linus + the jmpw patch. I > obviously don't have your Vaio, but I do have my own share of quirky > hardware. FWIW, I netbooted the hardware using pxelinux 3.50-pre7 as > the bootloader.[*] > > I'm not writing this to give you a hard time, far from it. I'm > suggesting that there might be something wrong with that rig that's > giving you false testing failures. I don't particularly care about the > patch itself -- all it does is save 3 bytes which are currently unused > anyway, (although it might help Vivek's work.) However, I'm very > concerned that you might be getting false failures, for obvious reasons. >
I just retested bare 2.6.21 with that patch. Same hang.
Maybe the assembler or linker screwed something up.
Without patch:
(gdb) x/20i _start 0x0 <_start>: ljmpw $0x0,$0x8 0x6 <_start+6>: rolb $0x8c,(%edi) 0x9 <start2+1>: enter $0xd88e,$0x8e 0xd <start2+5>: rorb $0xfb,0x7c00bcd0(%esi) 0x14 <start2+12>: cld 0x15 <start2+13>: mov $0x20ac0031,%esi 0x1a <msg_loop+2>: (bad) 0x1b <msg_loop+3>: je 0x26 <die> 0x1d <msg_loop+5>: mov $0xe,%ah 0x1f <msg_loop+7>: mov $0x10cd0007,%ebx 0x24 <msg_loop+12>: jmp 0x18 <msg_loop> 0x26 <die>: xor %eax,%eax 0x28 <die+2>: int $0x16
With patch:
(gdb) x/20i _start 0x0 <_start>: ljmp $0xc88c,$0x7c00005 0x7 <start2+2>: mov %eax,%ds 0x9 <start2+4>: mov %eax,%es 0xb <start2+6>: mov %eax,%ss 0xd <start2+8>: mov $0xfcfb7c00,%esp 0x12 <start2+13>: mov $0x20ac002e,%esi 0x17 <msg_loop+2>: (bad) 0x18 <msg_loop+3>: je 0x23 <die> 0x1a <msg_loop+5>: mov $0xe,%ah 0x1c <msg_loop+7>: mov $0x10cd0007,%ebx 0x21 <msg_loop+12>: jmp 0x15 <msg_loop>
not sure what's going on there. We seem to have confused gdb. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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