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The other downside I see is that it rules out booting other operating systems (at least right now). Other than linux itself (and maybe freebsd?) you can't kexec

The other downside I see is that it rules out booting other operating systems (at least right now). Other than linux itself (and maybe freebsd?) you can't kexec from a running linux kernel to another OS.

jacobush 8y ago
But why couldn't you?
nickik 8y ago
You actually can.
- bubblethink 8y ago
  How does one boot windows from a running linux kernel ?
  - Iolaum 8y ago
    I don't know the details but I recall that using linux as a bootloader was a potential threat the ChromeOS people wanted to block with some patches to the Linux kernel that tied it somehow to secure boot that the kernel maintainers (Linus himself commented on the issue as it was controversial) rejected at the form the patches had at the time. Here's a post, with some technical details, from one of the developers that were involved in the issue: https://mjg59.dreamwidth.org/50577.html https://mjg59.dreamwidth.org/50577.html
    - pjc50 8y ago
      I think there are two things being conflated here: - the "shim" bootloader: https://wiki.ubuntu.com/UEFI/SecureBoot/Testing#Shim_bootloader_signed_with_Microsoft_key https://wiki.ubuntu.com/UEFI/SecureBoot/Testing#Shim_bootloa... - it's important that this can't be used to boot a Windows that thinks it's secure but isn't. - the "lockdown" patches you refer to. The goal of those is to maintain the attestation that the running kernel code is the code that was loaded through a signature chain. If you can modify the kernel at runtime, obviously the attestation has to be invalid. I don't think it's impossible to boot Windows from Linux, but doing so should result in Windows detecting that it's in insecure/unsigned mode.
e12e 8y ago
Not sure if this is current, but apparently you can kexec to grub4dos, an on to windows (i assume this won't work for W10 with secure boot enabled, though): http://reboot.pro/topic/7223-how-to-boot-directly-into-windows-from-kexecgrub4dos/ http://reboot.pro/topic/7223-how-to-boot-directly-into-windo...

jacobush 8y ago

But why couldn't you?

nickik 8y ago

You actually can.

bubblethink 8y ago
How does one boot windows from a running linux kernel ?
- Iolaum 8y ago
  I don't know the details but I recall that using linux as a bootloader was a potential threat the ChromeOS people wanted to block with some patches to the Linux kernel that tied it somehow to secure boot that the kernel maintainers (Linus himself commented on the issue as it was controversial) rejected at the form the patches had at the time. Here's a post, with some technical details, from one of the developers that were involved in the issue: https://mjg59.dreamwidth.org/50577.html https://mjg59.dreamwidth.org/50577.html
  - pjc50 8y ago
    I think there are two things being conflated here: - the "shim" bootloader: https://wiki.ubuntu.com/UEFI/SecureBoot/Testing#Shim_bootloader_signed_with_Microsoft_key https://wiki.ubuntu.com/UEFI/SecureBoot/Testing#Shim_bootloa... - it's important that this can't be used to boot a Windows that thinks it's secure but isn't. - the "lockdown" patches you refer to. The goal of those is to maintain the attestation that the running kernel code is the code that was loaded through a signature chain. If you can modify the kernel at runtime, obviously the attestation has to be invalid. I don't think it's impossible to boot Windows from Linux, but doing so should result in Windows detecting that it's in insecure/unsigned mode.

e12e 8y ago

Not sure if this is current, but apparently you can kexec to grub4dos, an on to windows (i assume this won't work for W10 with secure boot enabled, though): http://reboot.pro/topic/7223-how-to-boot-directly-into-windows-from-kexecgrub4dos/ http://reboot.pro/topic/7223-how-to-boot-directly-into-windo...