Problem with Boot entry's on UEFI motherboard.

Discussion in 'BIOS Mods' started by nononsence, Oct 26, 2011.

  1. nononsence

    nononsence MDL Addicted

    Aug 18, 2009
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    Has anyone else had problems installing an OS other than Windows on an UEFI motherboard, I think I caught
    MSI filtering the boot entry's to only allow "Windows Boot Manager" to be displayed on my motherboard.
    see my thread on the MSI forum.

    http://forum-en.msi.com/index.php?topic=153411.msg1134733#msg1134733
     
  2. crappy44

    crappy44 MDL Novice

    Apr 22, 2011
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    Hey,

    what happens if you add a new boot entry via the bcfg command from the shell2.0?

    like:

    bcfg boot add 0 fs0:\EFI\someloader.efi "My new boot option"
     
  3. nononsence

    nononsence MDL Addicted

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    BCDedit /enum firmware , shows that it exists but when I reboot the boot entry is not there. I may try to patch it but I'll end up bricking this board.
     
  4. nononsence

    nononsence MDL Addicted

    Aug 18, 2009
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    I think this is the what we have too look forward to, if you want to boot another OS you will need to have Windows installed
    and use windows boot manager to do it. I haven't sat down and really analyzed the code yet but clearly it is looping through
    the boot entry's looking for "Windows Boot Manager" then doing something with the boot order. also it looks like a compile
    time option, if r8d is set to 1 the unpleasantness happens if it is set to 2 then the unpleasantness does not happen.
     
  5. crappy44

    crappy44 MDL Novice

    Apr 22, 2011
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    That sounds more like a bug from msi. Iwould write to the support or get another board. Personally I use rEFIt to choose which OS to boot.
     
  6. nononsence

    nononsence MDL Addicted

    Aug 18, 2009
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    even if it is just a bug, I want to know why "Windows Boot Manager" if being searched for in the boot entries
    it could be that the code is making sure that "Windows Boot Manager" is the default boot entry when no
    other valid boot entry's are found and is inadvertently dropping the other entry's.

    also no response from MSI tech support, if I RMA it I would receive another board with the same problem.
     
  7. crappy44

    crappy44 MDL Novice

    Apr 22, 2011
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    That is also hardcoded in my firmware just like Efi Internal Shell. If found it will use that string in the boot options menu. It's part of the auto detection in case that you clear nvram.
     
  8. nononsence

    nononsence MDL Addicted

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    that would make sense but when I delete the entry it does not reappear.
     
  9. nononsence

    nononsence MDL Addicted

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    and when I change the description of the bootmgr entry from "Windows Boot Manager" to "Win"
    the boot entry disappears from the list of entry's
     
  10. nononsence

    nononsence MDL Addicted

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    #10 nononsence, Oct 26, 2011
    Last edited: Oct 26, 2011
    (OP)
    and for my final test if I install the grub2 bootloader with the description of "Windows Boot Manager" I can now boot Linux
    WTF MSI???

    [​IMG]

    Uploaded with ImageShack.us
     
  11. crappy44

    crappy44 MDL Novice

    Apr 22, 2011
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    On my firmware it reappears on next boot. msi at its best again :p
     
  12. nononsence

    nononsence MDL Addicted

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    #12 nononsence, Oct 28, 2011
    Last edited by a moderator: Apr 20, 2017
    (OP)
    I took some time to analyze the code, and there is no doubt about it it delete's any entry that does not have the label of "Windows Boot Manager"
    first it does a string compare to "Windows Boot Manager" the result is returned on rax, if rax is 0 then the function exits, else is sets up and calls
    RuntimeServices->SetVariable with the attributes set to 0 and the size set to 0 which will delete the boot entry. I have also found an unused
    function that which look's more like the boot entry function in my Asus board. code exists in the bios to do the job right but is unused why?

    I have no choice but to conclude that this code was developed passed code review and made it to production on purpose.

    Code:
    sub_180000758proc near; CODE XREF: sub_1800007F0+33p
    ; sub_18000083C+45p
    
    var_38= qwordptr -38h
    var_28= byte ptr -28h
    arg_0= qwordptr  8
    
    mov[rsp+arg_0], rbx
    pushrdi
    subrsp, 50h
    movrbx, rdx
    movrdi, rcx
    cmpr8d, 1
    jnzshort loc_1800007D9
    movrcx, [rbx+18h]
    leardx, aWindowsBootMan ; "WindowsBoot Manager"
    movr8d, 14h
    callStrCmp
    testrax, rax
    jzshort Exit
    moveax, 0FFFFh
    cmp[rbx+40h], ax
    jzshort loc_1800007CC
    movzxr8d, word ptr [rbx+40h]
    leardx, aBoot04x; "Boot%04X"
    learcx, [rsp+58h+var_28]
    callsub_180002960
    movrax, cs:RunTimeServices
    and[rsp+58h+var_38], 0
    leardx, unk_180035DF8 ; GUID
    learcx, [rsp+58h+var_28]
    xorr9d, r9d; Size = 0
    xorr8d, r8d; Attributes = 0
    callqword ptr [rax+58h] ; RuntimeServices->SetVariable
    
    loc_1800007CC:; CODE XREF: sub_180000758+3Aj
    movrdx, rbx
    movrcx, rdi
    callsub_18000E7A8
    jmpshort Exit
    ; ---------------------------------------------------------------------------
    
    loc_1800007D9:; CODE XREF: sub_180000758+14j
    cmpr8d, 2
    jnzshort Exit
    anddword ptr [rdx+10h], 0FFFFFFFEh
    
    Exit:; CODE XREF: sub_180000758+2Fj
    ; sub_180000758+7Fj ...
    movrbx, [rsp+58h+arg_0]
    addrsp, 50h
    poprdi
    retn
    sub_180000758endp
    
     
  13. crappy44

    crappy44 MDL Novice

    Apr 22, 2011
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    #13 crappy44, Oct 29, 2011
    Last edited: Oct 29, 2011
    What about patching sub_180000758 or replace the 2 calls to it with calls to the right code? Or compile rEFIt and add it as Windows Boot Manager and choose which OS to boot from its gui. rEFIt does a search on the EFI Partition for all kind of efi bootloader. grub, win, etc...

    btw does your mobo support the driver-XXXX variable to load additional drivers?