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   Sexy Moon (moon@shitposter.club)'s status on Wednesday, 18-Oct-2023 19:43:03 JST Sexy Moon
   So on x86 you can bootstrap your kernel by using bios interrupt 13h to read the disk in a generic way. it doesn't appear there's a way to do that in 64-bit mode?
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     Sexy Moon (moon@shitposter.club)'s status on Wednesday, 18-Oct-2023 19:44:44 JST Sexy Moon

     in reply to
     Looks like you have to use EFI function for that.
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     ロミンちゃん (romin@shitposter.club)'s status on Wednesday, 18-Oct-2023 19:46:38 JST ロミンちゃん

     in reply to
     @Moon what are you doing
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     Sexy Moon (moon@shitposter.club)'s status on Wednesday, 18-Oct-2023 19:49:27 JST Sexy Moon

     in reply to

     • ロミンちゃん
     @romin I found assembler code to boot an x64 machine directly in to 64-bit mode but it doesn't have BIOS so you can't use int13h to load a kernel from disk so I was trying to figure out how to do that. and it looks like you have to create an EFI application basically to access the disk, there doesn't seem to be a way around it.
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     Sexy Moon (moon@shitposter.club)'s status on Wednesday, 18-Oct-2023 19:50:10 JST Sexy Moon

     in reply to

     • ロミンちゃん
     @romin I just wanted to know if you can load an x64 machine directly into 64-bit mode
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     ロミンちゃん (romin@shitposter.club)'s status on Wednesday, 18-Oct-2023 19:52:43 JST ロミンちゃん

     in reply to
     @Moon doesn't x86_64 predate EFI? How did they do it before?
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     Sexy Moon (moon@shitposter.club)'s status on Wednesday, 18-Oct-2023 19:54:19 JST Sexy Moon

     in reply to

     • ロミンちゃん
     @romin I found alleged code for booting it but no clear answer on how you access hardware after that other than "you have to enumerate the PCI bus and know how to communicate with it"
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     :afire: palingenetic man :afire: (anonaccount@poa.st)'s status on Wednesday, 18-Oct-2023 19:56:01 JST :afire: palingenetic man :afire:

     in reply to
     @Moon The approach for Protected Mode and above in OS programming is to write your own drivers interfacing with and enumerating devices directly through ports, which means that you will have to read the specifications and allow an unspecified but like large amount of exceptions. I would just customize Linux if I were in you.
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     Sexy Moon (moon@shitposter.club)'s status on Wednesday, 18-Oct-2023 19:56:02 JST Sexy Moon

     in reply to

     • :afire: palingenetic man :afire:
     @anonaccount no problem, I'm just trying to understand what would be the smallest code that boots directly into 64-bit and can then load a kernel from disk.
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     ロミンちゃん (romin@shitposter.club)'s status on Wednesday, 18-Oct-2023 19:56:19 JST ロミンちゃん

     in reply to
     @Moon
     >you have to enumerate the PCI bus and know how to communicate with it
     uhh no thank you
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     ロミンちゃん (romin@shitposter.club)'s status on Wednesday, 18-Oct-2023 19:57:46 JST ロミンちゃん

     in reply to

     • :afire: palingenetic man :afire:
     @Moon @anonaccount just use systemd-boot (yes I know) and sew your own efi executable
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     Sexy Moon (moon@shitposter.club)'s status on Wednesday, 18-Oct-2023 19:59:41 JST Sexy Moon

     in reply to

     • :afire: palingenetic man :afire:
     • ロミンちゃん
     @romin @anonaccount I have actually made a simple EFI application already but I wondered how EFI boots or if that question even makes sense. Coreboot seems conceptually so much better than EFI.
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     :afire: palingenetic man :afire: (anonaccount@poa.st)'s status on Wednesday, 18-Oct-2023 20:12:49 JST :afire: palingenetic man :afire:

     in reply to
     @Moon Are you familiar with POSIX-UEFI? It provides a simple "fopen" function to open a file, couple it with the umpteeth ELF / Mach-O loader taken from a security blog or GitHub and call it a done job.
     wiki.osdev.org/POSIX-UEFI
     
     Also, I must warn you that EFI does provide in-built support only for the FAT32 filesystem.
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     翠星石 (suiseiseki@freesoftwareextremist.com)'s status on Wednesday, 18-Oct-2023 22:26:18 JST 翠星石

     in reply to
     @Moon On AMD64 CPU's you cannot load directly into 64 bit mode - they used to boot in 16 bit mode, with certain instructions required to boot into 32 bit and then finally 64 bit mode - although reading down it seems that 16 bit more was finally removed on the newest computers.
     
     Most proprietary BIOS's seem to be programmed for 16 bit or 32 bit mode even though that doesn't make that much sense.
     
     You pretty much want to look into coreboot (specifically the GNUboot version), as it runs the 6(?) required instructions to get into 64 bit mode and then does everything in 64 bit and has drivers for southbridges, framebuffer, keyboards etc and then you can get it to boot GNU Grub.
     
     Grub can load kernels directly in 64 bit mode without using the cancer known as UEFI, so it's time to reeeeeaaaaadddd theeeeeee soooouuurce.
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     翠星石 (suiseiseki@freesoftwareextremist.com)'s status on Wednesday, 18-Oct-2023 22:38:34 JST 翠星石

     in reply to

     • 翠星石
     @Moon Well there it is; https://git.savannah.gnu.org/cgit/grub.git/tree/grub-core/commands/boot.c
     https://git.savannah.gnu.org/cgit/grub.git/tree/grub-core/loader/linux.c
     
     So that's one way to boot from 16 bit mode to 32 bit mode huh?: https://git.savannah.gnu.org/cgit/grub.git/tree/grub-core/boot/i386/pc/boot.S
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