lkml.org 
[lkml]   [2008]   [Feb]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [rft] s2ram wakeup moves to .c, could fix few machines
    On Fri 2008-02-08 13:02:57, H. Peter Anvin wrote:
    > Pavel Machek wrote:
    >> On Fri 2008-02-08 17:23:15, Rafael J. Wysocki wrote:
    >>> On Friday, 8 of February 2008, Pavel Machek wrote:
    >>>> Hi!
    >>> Hi,
    >>>
    >>>>>> I really need the entry point to be at offset 0, so that I can get
    >>>>>> pointers to my data. I could not figure out how to do it any other
    >>>>>> way. And if 0 is taken, I thought I'd put header at the end.
    >>>>>>
    >>>>> Why not just put the structure at 0, and put pointers in the structure
    >>>>> to everything else you need?
    >>>> segments:offsets rear its ugly head here. I need %ds to point to my
    >>>> data, and the way to do it is copy it from %cs; that needs start to be
    >>>> at 0.
    >>> Hm, why exactly is that necessay?
    >>
    >> It is not _neccessary_. Try to come up with another method that gets
    >> relocations right. I could not :-(.
    >>
    >> (Actually, putting table at the offset 0 and short jump at beggining
    >> of the table would probably do the trick. But that still keeps code at
    >> offset 0 :-).
    >
    > Why not just put a pointer to the start of the code in the table, and make
    > an indirect call to it?

    Indirect call from where?

    BIOS jumps to address you provide.

    > Where is this code?

    arch/x86/kernel/acpi/realmode/wakeup.S

    BIOS jumps to wakeup_code. With CS=something, IP=0. If wakeup code is
    at other address than zero, I'll not be able to easily address data
    below it.
    Pavel

    .globl wakeup_header
    wakeup_header:
    ...
    realmode_flags: .long 0
    signature: .long 0x51ee1111
    ...
    .text
    .globl _start
    .code16
    wakeup_code:
    _start:
    cli
    cld

    /* Set up segments */
    movw %cs,%ax
    movw %ax,%ds
    movw %ax,%es
    movw %ax,%ss

    ...
    /* Check header signature... */
    movl signature, %eax
    cmpl $0x51ee1111, %eax
    jne bogus_real_magic



    Pavel
    --
    (english) http://www.livejournal.com/~pavelmachek
    (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


    \
     
     \ /
      Last update: 2008-02-08 22:11    [W:0.023 / U:0.528 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site