Re: "Boot this kernel once" functionality? (amd64)
On Sep 24, 9:14am, Reinoud Zandijk wrote: } Subject: Re: "Boot this kernel once" functionality? (amd64) } On Wed, Sep 16, 2020 at 12:09:43PM +0200, Martin Husemann wrote: } > On Wed, Sep 16, 2020 at 12:05:26PM +0200, Anthony Mallet wrote: } > > I was also wondering if it would be possible to pass arguments to the } > > primary or secondary bootloader via reboot(2) and the boothowto } > > flags. But this doesn't seem doable. Right? } > } > This works fine on e.g. sparc*; I can do: shutdown -b netbsd.t -r now } > } > and it will pass "netbsd.t" as boot argument to the firmware, which passes } > it on to the bootloader and then it boots /netbsd.t once. } } In shutdown(8) I read that the arguments are passed to reboot(8) and that is } mentioned in kloader(4) so I guess its using that mechanism. } } As for amd64, it would be great if I could boot a kernel once. It could } simplify testing out a new kernel. Not that a few lines of boot.cfg can't do } that but still. } } > I don't know if there is enough of a persistent environment for UEFI boots } > (I would guess there is), and probably no easy way for BIOS boot. } } I could imagine some BIOS/UEFI wiping all DRAM on reboot for security reasons. UEFI has the concept of persistent variable storage (key/value store). See Section 8.2 "Variable Services" of the UEFI spec. }-- End of excerpt from Reinoud Zandijk
re: "Boot this kernel once" functionality? (amd64)
Reinoud Zandijk writes: > On Wed, Sep 16, 2020 at 12:09:43PM +0200, Martin Husemann wrote: > > On Wed, Sep 16, 2020 at 12:05:26PM +0200, Anthony Mallet wrote: > > > I was also wondering if it would be possible to pass arguments to the > > > primary or secondary bootloader via reboot(2) and the boothowto > > > flags. But this doesn't seem doable. Right? > > > > This works fine on e.g. sparc*; I can do: shutdown -b netbsd.t -r now > > > > and it will pass "netbsd.t" as boot argument to the firmware, which passes > > it on to the bootloader and then it boots /netbsd.t once. > > In shutdown(8) I read that the arguments are passed to reboot(8) and that is > mentioned in kloader(4) so I guess its using that mechanism. this does not use kloader(4), which appeared in netbsd 1.6. the "pass boot args to loader" appeared in netbsd 1.3, and it is implemented on sparc* by asking the firmware to reboot with these arguments instead of the default. it very much relies upon this firmware feature. .mrg.
Re: "Boot this kernel once" functionality? (amd64)
On Wed, Sep 16, 2020 at 12:09:43PM +0200, Martin Husemann wrote: > On Wed, Sep 16, 2020 at 12:05:26PM +0200, Anthony Mallet wrote: > > I was also wondering if it would be possible to pass arguments to the > > primary or secondary bootloader via reboot(2) and the boothowto > > flags. But this doesn't seem doable. Right? > > This works fine on e.g. sparc*; I can do: shutdown -b netbsd.t -r now > > and it will pass "netbsd.t" as boot argument to the firmware, which passes > it on to the bootloader and then it boots /netbsd.t once. In shutdown(8) I read that the arguments are passed to reboot(8) and that is mentioned in kloader(4) so I guess its using that mechanism. As for amd64, it would be great if I could boot a kernel once. It could simplify testing out a new kernel. Not that a few lines of boot.cfg can't do that but still. > I don't know if there is enough of a persistent environment for UEFI boots > (I would guess there is), and probably no easy way for BIOS boot. I could imagine some BIOS/UEFI wiping all DRAM on reboot for security reasons. Reinoud
Re: "Boot this kernel once" functionality? (amd64)
[I noticed that for some reason I was not subscribed anymore to tech-kern, so I'm manually pasting some replies read from the mail-index web :/] Mouse wrote: > kexec stuff? I've occasionally wondered why more ports don't implement > it. Valery Ushakov wrote: > As der Mouse mentioned upthread, kloader(4) would seem like a > promising candidate to implement this. > Of course that doesn't suit your immediate needs... I was not aware of kloader(4), thanks! I don't need an urgent solution, so this looks actually very promising. I will try to read more about this and get familiar with the code. In the meantime, if you (Mouse) come up with something to test or just draft ideas, I'd be happy to help.
Re: "Boot this kernel once" functionality? (amd64)
On Wed, Sep 16, 2020 at 12:20:57 +0200, Anthony Mallet wrote: > On Wednesday 16 Sep 2020, at 12:09, Martin Husemann wrote: > > This works fine on e.g. sparc*; I can do: shutdown -b netbsd.t -r > > now > > > > No state is modified on any disks, very convenient. > > Right, not changing any state seems safer! > > > I don't know if there is enough of a persistent environment for UEFI > > boots (I would guess there is), and probably no easy way for BIOS > > boot. > > The machine in question is not UEFI, so I would be more interested in > a pure BIOS solution. As der Mouse mentioned upthread, kloader(4) would seem like a promising candidate to implement this. It doesn't support x86 currently, but existing kloader_machdep.c files are minuscule - the non-boilerplate code is essentially just one function that is essentially a bit more than a fancy memcpy. The realy interesting question is if NetBSD on a given platform leaves the machine in a state that a newly booted kernel expects the machine to be in. The hpc* ports that support kloader do not expect anything much from the initial state of the machine. Of course that doesn't suit your immediate needs... -uwe
Re: "Boot this kernel once" functionality? (amd64)
>> I was wondering how easy that would be to add a "boot once" feature > FWIW: the Amiga port had a /dev/reload in its very early days, where > you could cp a kernel too, which would then be bootet. I'm not sure > this is easy to make on a PC platform. kexec stuff? I've occasionally wondered why more ports don't implement it. I ran into it on...hpcmips, maybe. Something that had WinCE in ROM and used it as a booter, I think, though those memories are pretty fuzzy by now. Certainly would speed up many reboots. I may have a look at it; I was recently reading early boot code and I don't recall anything that would make it difficult. /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTMLmo...@rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B
Re: "Boot this kernel once" functionality? (amd64)
On Wed, 16 Sep 2020, Anthony Mallet wrote: I was wondering how easy that would be to add a "boot once" feature to FWIW: the Amiga port had a /dev/reload in its very early days, where you could cp a kernel too, which would then be bootet. I'm not sure this is easy to make on a PC platform. - Hubert
Re: "Boot this kernel once" functionality? (amd64)
On Wednesday 16 Sep 2020, at 12:09, Martin Husemann wrote: > This works fine on e.g. sparc*; I can do: shutdown -b netbsd.t -r > now > > No state is modified on any disks, very convenient. Right, not changing any state seems safer! > I don't know if there is enough of a persistent environment for UEFI > boots (I would guess there is), and probably no easy way for BIOS > boot. The machine in question is not UEFI, so I would be more interested in a pure BIOS solution.
Re: "Boot this kernel once" functionality? (amd64)
On Wed, Sep 16, 2020 at 12:05:26PM +0200, Anthony Mallet wrote: > I was also wondering if it would be possible to pass arguments to the > primary or secondary bootloader via reboot(2) and the boothowto > flags. But this doesn't seem doable. Right? This works fine on e.g. sparc*; I can do: shutdown -b netbsd.t -r now and it will pass "netbsd.t" as boot argument to the firmware, which passes it on to the bootloader and then it boots /netbsd.t once. No state is modified on any disks, very convenient. I don't know if there is enough of a persistent environment for UEFI boots (I would guess there is), and probably no easy way for BIOS boot. Martin
