On Thu, Dec 21, 2006 at 05:32:56AM -0700, Eric W. Biederman wrote:
>
> Take a look at the diff for commit 968de4f02621db35b8ae5239c8cfc6664fb872d8
> of setup.S there are very few candidate instructions.
>
> I suspect with a few minutes of review we should be able to see what the
> assembler is doing wrong and decide if we want to blacklist that assembler
> or work around it's bug.
>
> diff --git a/arch/i386/boot/setup.S b/arch/i386/boot/setup.S
> index 3aec453..9aa8b05 100644
> --- a/arch/i386/boot/setup.S
> +++ b/arch/i386/boot/setup.S
> @@ -588,11 +588,6 @@ rmodeswtch_normal:
> call default_switch
>
> rmodeswtch_end:
> -# we get the code32 start address and modify the below 'jmpi'
> -# (loader may have changed it)
> - movl %cs:code32_start, %eax
> - movl %eax, %cs:code32
> -
> # Now we move the system to its rightful place ... but we check if we have a
> # big-kernel. In that case we *must* not move it ...
> testb $LOADED_HIGH, %cs:loadflags
> @@ -788,11 +783,12 @@ a20_err_msg:
> a20_done:
>
> #endif /* CONFIG_X86_VOYAGER */
> -# set up gdt and idt
> +# set up gdt and idt and 32bit start address
> lidt idt_48 # load idt with 0,0
> xorl %eax, %eax # Compute gdt_base
> movw %ds, %ax # (Convert %ds:gdt to a linear ptr)
> shll $4, %eax
> + addl %eax, code32
> addl $gdt, %eax
> movl %eax, (gdt_48+2)
> lgdt gdt_48 # load gdt with whatever is
> @@ -851,9 +847,26 @@ flush_instr:
> # Manual, Mixing 16-bit and 32-bit code, page 16-6)
>
> .byte 0x66, 0xea # prefix + jmpi-opcode
> -code32: .long 0x1000 # will be set to 0x100000
> - # for big kernels
> +code32: .long startup_32 # will be set to %cs+startup_32
> .word __BOOT_CS
> +.code32
> +startup_32:
> + movl $(__BOOT_DS), %eax
> + movl %eax, %ds
> + movl %eax, %es
> + movl %eax, %fs
> + movl %eax, %gs
> + movl %eax, %ss
> +
> + xorl %eax, %eax
> +1: incl %eax # check that A20 really IS enabled
> + movl %eax, 0x00000000 # loop forever if it isn't
> + cmpl %eax, 0x00100000
> + je 1b
> +
> + # Jump to the 32bit entry point
> + jmpl *(code32_start - start + (DELTA_INITSEG << 4))(%esi)
Hi Eric,
I got a basic query. Why have we introduced this additional jump to
startup_32 in the same file? Won't it work if we stick to old method of
enabling protected mode and then directly taking a jmp to startup_32 in
arch/i386/kernel/head.S. Am I missing something obivious?
Thanks
Vivek
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
