[Qemu-devel] sparc mmu bug(and fix) seen with NetBSD

[Qemu-devel] sparc mmu bug(and fix) seen with NetBSD

[Cliff Wright]

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When using QEMU 0.9.1 for sparc emulation on i386 booting NetBSD 4.0 miniroot.fs a bug with the MMU is seen. A fault type is mis-aligned with
the fault status register. This is seen by NetBSD with a copy on write
that causes a write fault, with no fault type in the register, NetBSD just
returns to the faulting instruction, causing an infinite loop.
Below is a patch to the 0.9.1 source, however I see the same problem
in the subversion source.



-- 
Cliff Wright <cliff@snipe444.org>

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--- helper.c.orig	2008-01-06 11:38:45.000000000 -0800
+++ helper.c	2008-06-24 10:23:00.000000000 -0700
@@ -197,7 +197,7 @@
     }
     /* check access */
     access_perms = (pde & PTE_ACCESS_MASK) >> PTE_ACCESS_SHIFT;
-    error_code = access_table[*access_index][access_perms];
+    error_code = access_table[*access_index][access_perms] << 2;
     if (error_code && !((env->mmuregs[0] & MMU_NF) && is_user))
         return error_code;
 

Re: [Qemu-devel] sparc mmu bug(and fix) seen with NetBSD

[Blue Swirl]

On 6/24/08, Cliff Wright <cliff@snipe444.org> wrote:
> When using QEMU 0.9.1 for sparc emulation on i386 booting NetBSD 4.0 miniroot.fs a bug with the MMU is seen. A fault type is mis-aligned with
>  the fault status register. This is seen by NetBSD with a copy on write
>  that causes a write fault, with no fault type in the register, NetBSD just
>  returns to the faulting instruction, causing an infinite loop.
>  Below is a patch to the 0.9.1 source, however I see the same problem
>  in the subversion source.

Thank you very much! I'll commit a similar patch ASAP.

It looks like next problem is the keyboard, I can't write to the
installer prompt.