On 24/10/2019 12:31, Alexey Kardashevskiy wrote: > > > On 23/10/2019 22:21, Segher Boessenkool wrote: >> On Wed, Oct 23, 2019 at 12:36:35PM +1100, Oliver O'Halloran wrote: >>> When booting under OF the zImage expects the initrd address and size to be >>> passed to it using registers r3 and r4. SLOF (guest firmware used by QEMU) >>> currently doesn't do this so the zImage is not aware of the initrd >>> location. This can result in initrd corruption either though the zImage >>> extracting the vmlinux over the initrd, or by the vmlinux overwriting the >>> initrd when relocating itself. >>> >>> QEMU does put the linux,initrd-start and linux,initrd-end properties into >>> the devicetree to vmlinux to find the initrd. We can work around the SLOF >>> bug by also looking those properties in the zImage. >> >> This is not a bug. What boot protocol requires passing the initrd start >> and size in GPR3, GPR4? > > So far I was unable to identify it... > >> The CHRP binding (what SLOF implements) requires passing two zeroes here. >> And ePAPR requires passing the address of a device tree and a zero, plus >> something in GPR6 to allow distinguishing what it does. >> >> As Alexey says, initramfs works just fine, so please use that? initrd was >> deprecated when this code was written already. > > I did not say about anything working fine :) > > In my case I was using a new QEMU which does full FDT on client-arch-support and that thing would put the original > linux,initrd-start/end to the FDT even though the initrd was unpacked and the properties were changes in SLOF. With that > fixed, this is an alternative fix for SLOF but I am not pushing it out as I have no idea about the bindings and this > also breaks "vmlinux". ah no, that works for vmlinux as well. Hm. > > > diff --git a/slof/fs/client.fs b/slof/fs/client.fs > index 8a7f6ac4326d..138177e4c2a3 100644 > --- a/slof/fs/client.fs > +++ b/slof/fs/client.fs > @@ -45,6 +45,17 @@ VARIABLE client-callback \ Address of client's callback function > >r ciregs >r7 ! ciregs >r6 ! client-entry-point @ ciregs >r5 ! > \ Initialise client-stack-pointer > cistack ciregs >r1 ! > + > + s" linux,initrd-end" get-chosen IF decode-int -rot 2drop ELSE 0 THEN > + s" linux,initrd-start" get-chosen IF decode-int -rot 2drop ELSE 0 THEN > + 2dup - dup IF > + ciregs >r4 ! > + ciregs >r3 ! > + drop > + ELSE > + 3drop > + THEN > + > > -- Alexey
