February 2007 - OpenBIOS - mail.coreboot.org

Sun OBP bugs in 1.0RC1
by Peter March 16, 2007

March 16, 2007

I've been trying to get old versions of SunOS to load under qemu. In doing so, I've encountered a number of bugs in OBP. I'm not always certain of the best fix, but I can at least provide a quick hack that will get people farther along. 1) Error message: "kmem_alloc failed, nbytes 680" Bug: obp_dumb_memalloc is a bit too dumb. It needs to pick an address if passed a null address. (According to the comment in the allocator in OpenSolaris prom_alloc.c (see <http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/psm/promif/ie…>), "If virthint is zero, a suitable virt is chosen.") Quick fix: If passed a null address, start doling out addresses at 10MB and increment by size. Shortcomings: The quick fix ignores the issue of free() and doesn't remove memory from the virtual-memory/available node. After the quick fix, the boot gets farther, leading us to: 2) Error message: "Unhandled Exception 0x00000080" Bug: Trap 0 (entry 0x80 in the table, i.e. syscall_trap_4x) is undefined. This is because the SunOS bootloader installs the trap by writing code in the trap table, but the trap table is in the .text section of OpenBIOS. Thus the trap 0 handler simply jumps to "bug". Quick fix: Move the trap table to the .data section. Insert a "b entry; nop; nop; nop;" before "bug:". Shortcomings: Requires the extra "b entry" code. Allows the only VM copy of the trap table to be permanently changed. OpenBIOS should copy the read-only trap table to read-write memory (and update %tbr) upon reset/entry. 3) #2 above actually exposes another bug. The write to the read-only trap table does not cause an access violation -- instead, it silently fails. The "std" instruction at 0x403e6c in the bootloader has no effect. Bug: Uncertain. It could be a systemic bug in qemu, but it appears that the VM's MMU believes that the page is writable. That means that the VM's MMU is not having the access protection flags set for pages mapped to ROM. It thinks everything is rwx. Fix?: The VM's MMU should have the access protection flags properly set for each ROM section. This should probably be done within OpenBIOS. E.g., .text should be r-x, .data should probably be rwx, etc. This is the one fix I'm really not sure how to implement. Any suggestions? This may be a problem that only affects this bootloader, so fixing #2 above may be all that's strictly necessary. But I'm not positive that this bug doesn't have other ill effects I haven't found yet. At any rate, fixing #2 gets us still further, to: 4) Error messages: "obp_devopen(sd(0,0,0):d) = 0xffd8e270 obp_inst2pkg(fd 0xffd8e270) = 0xffd57f44 obp_getprop(0xffd57f44, device_type) (not found)" Bug: The OpenBIOS "interpose" implementation is not transparent to non-interposition-aware code (in violation of the interposition spec). The inst2pkg call in this sequence returns the phandle for /packages/misc-files, instead of the proper phandle. Quick fix: Comment out the "interpose disk-label" lines in ob_sd_open. Shortcomings: It disables disk-label. The correct fix is to fix the underlying problem with interposition, but I'm not sure exactly what it is. Could someone help? Fixing #4 gets us quite a bit further, until: 5) Error message: "Unhandled Exception 0x00000009 PC = 0xf0138b20 NPC = 0xf0138b24 Stopping execution" Bug: The instruction is trying to read from 0xfd020000+4, which is an invalid address. This address isn't mapped by OBP by default on Sun hardware, so the bootloader must be trying to (a) map this address and failing silently or (b) skipping the mapping for some reason. The instruction is hard-coded to look at this absolute address. Fix: Unknown. This may be another instance of writes silently failing, hence my interest in #3 above. It could also be a side-effect of the quick fix for #4. I'm happy to work further on these fixes and put them into patch form. Could someone point me to how I'd do that?

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x86 ISA binding for open firmware
by (अमेय) Ameya ( पाळंदे) Palande March 15, 2007

March 15, 2007

Hi, I am not able to locate x86 open firmware isa specific supplements. Can any one give me information about this ? I want information about client execution environment on x86. Thank you. Regards, Ameya.

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problem in running ofclient
by (अमेय) Ameya ( पाळंदे) Palande March 15, 2007

March 15, 2007

Hi, I am trying to run ofclient on x86. I started openbios from GRUB. But its not working, I can't see Hello World message. :( Can any one tell me how openbios passes client_interface_handler to client program ? Thank you, Regards, Ameya.

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RAM codes.
by Feng, Libo March 8, 2007

March 8, 2007

I am studying the LinuxBios project. I have a question about the RAM code: from Makefile, it seems that LinuxBios could load codes from FLASH to RAM twice, first for linuxbios_ram, second for so-called payload. My understanding is correct or not. However, also from Makefile, it seems that linuxbios is dependent on LINUXBIOS_RAM_ROM, but doesn't include it. The below is abstracted from a Makefile: linuxbios: crt0.o $(INIT-OBJECTS) $(LINUXBIOS_APC) $(LINUXBIOS_RAM_ROM) ldscript.ld $(CC) -nostdlib -nostartfiles -static -o $@ -T ldscript.ld crt0.o $(INIT-OBJECTS) $(CROSS_COMPILE)nm -n linuxbios | sort > linuxbios.map. So, there is no action on LINUXBIOS_RAM_ROM. Does it mean linuxbios_ram is not very important. Even without it, the system is also ok? Feng Libo

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Re: [OpenBIOS] Sun OBP bugs in 1.0RC1
by Blue Swirl Feb. 17, 2007

Feb. 17, 2007

>2) Error message: "Unhandled Exception 0x00000080" > >Bug: Trap 0 (entry 0x80 in the table, i.e. syscall_trap_4x) is >undefined. This is because the SunOS bootloader installs the trap by >writing code in the trap table, but the trap table is in the .text >section of OpenBIOS. Thus the trap 0 handler simply jumps to "bug". Okay, can you try if this patch helps? _________________________________________________________________ Express yourself instantly with MSN Messenger! Download today it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/

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