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  • 32-bit on 64-bit

    From Paul Edwards@21:1/5 to All on Wed Aug 16 07:35:27 2023
    I have had success in getting Win64 executables to
    run under UEFI with a relatively small amount of
    "glue" to switch formats.

    And I decided to see if I could get Win32 executables
    to run instead of Win64, using different - more
    complicated - "glue".

    Here is a simple call to puts, but written in assembler
    (so I need a C compiler to generate assembler that
    looks like this - a separate exercise):

    https://sourceforge.net/p/pdos/gitcode/ci/master/tree/pdpclib/msdemo32.asm

    So this is dependent on msvcrt.dll, and then this loader code:

    https://sourceforge.net/p/pdos/gitcode/ci/master/tree/bios/exeload.c

    (search for w32puts) will put in the stubs for the win32
    executable, and the puts stub can be found here:

    https://sourceforge.net/p/pdos/gitcode/ci/master/tree/generic/w32hack.asm

    So anyway, with this in place, it means I can write a 32-bit
    windows executable that works on anything from win 95
    to win 11, and it also runs on an appropriate 64-bit UEFI-based
    system (basically just UCX64 from http://pdos.org). Note that
    this is running 32-bit code in long mode.

    There will be issues for something like printf, where I don't
    know how many parameters there are, so I will just assume
    a maximum of 4 or something like that.

    Any thoughts/improvements?

    Thanks. Paul.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Paul Edwards@21:1/5 to All on Wed Aug 16 09:03:26 2023
    Note that I tested the win64 on real hardware previously,
    but I only just tested the win32 on real hardware now
    and it failed. I'll need to find out why tomorrow.

    Note that it worked on qemu.

    BFN. Paul.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Paul Edwards@21:1/5 to All on Wed Aug 16 10:24:32 2023
    Ok, so my bootx64.efi contains a 1 in the upper 32 bits
    of addresses, ie it has been loaded above the 4 GiB
    mark (on real hardware).

    I'm not sure how to get around that issue.

    I could arrange for the high 32 bits of the return address
    to be copied onto the stack and then do a ret instead of
    a jmp, but that wouldn't work on a 32-bit system.

    BFN. Paul.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Paul Edwards@21:1/5 to Paul Edwards on Wed Aug 16 11:59:55 2023
    On Wednesday, August 16, 2023 at 10:40:29 PM UTC+8, Paul Edwards wrote:

    There will be issues for something like printf, where I don't
    know how many parameters there are, so I will just assume
    a maximum of 4 or something like that.

    I thought of a possible solution for this.

    I can make it mandatory to call getmainargs, and have a
    fudged argc - if argc is greater than x'80000000' then it
    means that it is running under a 64-bit environment, and
    argv is also fudged, and is a struct, and has a pointer to
    a global variable that contains the number of parameters
    to any variable-argument function.

    So, when the global exists, the value gets populated.

    Otherwise, it's a standard win32 environment that works
    without assistance.

    BFN. Paul.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Paul Edwards@21:1/5 to Paul Edwards on Wed Aug 16 11:39:51 2023
    On Thursday, August 17, 2023 at 1:27:20 AM UTC+8, Paul Edwards wrote:

    Ok, so my bootx64.efi contains a 1 in the upper 32 bits
    of addresses, ie it has been loaded above the 4 GiB
    mark (on real hardware).

    I'm not sure how to get around that issue.

    Switching linker to pdld has a low base address, and that
    was sufficient for real hardware to work (plus another bug
    fix was needed).

    All code has been committed, and there is a w32hack.zip
    available in the UCX64 section of http://pdos.org if you
    want an image to burn to USB stick.

    So we're back to working code, just after code review
    or whatever.

    BFN. Paul.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)