Messages in this thread | | | Date | Wed, 29 Nov 2006 20:53:41 -0800 | From | Jun Sun <> | Subject | Re: failed 'ljmp' in linear addressing mode |
| |
On Tue, Nov 28, 2006 at 05:40:56PM -0800, Jun Sun wrote: > > Can you elaborate more why this last ljmp will fail? I thought at this point > the paging is turned off, and 0x1000-0000 would simply mean a physical > address - which is a valid physical address in RAM, btw. > <snip>
I finally got it working, even though I don't understand at all. :)
I realized that after paging mode is turned off, 0x1000-0000 is actually at the same flag 4G code segment as caller code. So I tried to just "call" and that worked.
Here is the excerpt of the related code in case someone else needs to do the same:
In arch/i386/kernel/machine_kexec.c:
extern void do_os_switching(void); void os_switch(void) { void (*foo)(void);
/* absolutely no irq */ local_irq_disable();
/* create identity mapping */ foo=virt_to_phys(do_os_switching); identity_map_page((unsigned long)foo);
/* jump to the real address */ load_segments(); set_gdt(phys_to_virt(0),0); set_idt(phys_to_virt(0),0); foo(); }
In arch/i386/kernel/acpi/wakeup.S:
.align 4096 ENTRY(do_os_switching) /* JSUN, 0x11 was the boot up value for cr0. */ movl $0x11, %eax movl %eax, %cr0
/* clear cr4 */ movl $0, %eax movl %eax, %cr4
/* clear cr3, flush TLB */ movl $0, %eax movl %eax, %cr3
movl $0x10000000,%eax call *%eax
I have a second Linux kernel loaded at 0x1000-0000. Now the only matter remaining is to figure out why the tsc timer stopped working ... :)
Cheers.
Jun - 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/
| |