On Thu, Oct 24, 2019 at 12:31:24PM +1100, 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...
Maybe this comes from yaboot? https://git.ozlabs.org/?p=yaboot.git%3Ba=blob%3Bf=second/yaboot.c%3Bh=9b66ab...
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 :)
Yeah, I read that from your words, wrong it seems. Sorry. I often used INITRAMFS_SOURCE for kernels for use with SLOF, it's just so convenient.
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".
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
Something like that should work fine. Do it in go-32 and go-64 though? Or is that the wrong spot?
Segher