Re: [PATCH 00 of 36] x86/paravirt: groundwork for 64-bit Xen support

Jeremy Fitzhardinge
2008-06-26T14:29:18Z

Ingo Molnar wrote:
> * Jeremy Fitzhardinge <jeremy@goop.org> wrote:
>
>
>>> It quickly broke the build in testing:
>>>
>>> include/asm/pgalloc.h: In function ‘paravirt_pgd_free':
>>> include/asm/pgalloc.h:14: error: parameter name omitted
>>> arch/x86/kernel/entry_64.S: In file included from
>>> arch/x86/kernel/traps_64.c:51:include/asm/pgalloc.h: In function
>>> ‘paravirt_pgd_free':
>>> include/asm/pgalloc.h:14: error: parameter name omitted
>>>
>>>
>> No, looks like my fault. The non-PARAVIRT version of
>> paravirt_pgd_free() is:
>>
>> static inline void paravirt_pgd_free(struct mm_struct *mm, pgd_t *) {}
>>
>> but C doesn't like missing parameter names, even if unused.
>>
>> This should fix it:
>>
>
> that fixed the build but now we've got a boot crash with this config:
>
> time.c: Detected 2010.304 MHz processor.
> spurious 8259A interrupt: IRQ7.
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
> IP: [<0000000000000000>]
> PGD 0
> Thread overran stack, or stack corrupted
> Oops: 0010 [1] SMP
> CPU 0
>
> with:
>
> http://redhat.com/~mingo/misc/config-Thu_Jun_26_12_46_46_CEST_2008.bad
>

Blerg, a contextless NULL rip. Have you done any bisection on it?
Could you try again with the same config, but with
"CONFIG_PARAVIRT_DEBUG" enabled as well? That will BUG if it turns out
to be trying to call a NULL paravirt-op

I'll try to repro here anyway.

> i've pushed out the current tip/xen-64bit branch, so that you can see
> how things look like at the moment, but i cannot put it into tip/master
> yet.

Yeah, I was expecting things to break somewhere with this lot :/

Could you add this patch? I don't think it will help this case, but
it's a bugfix.

J

Subject: x86_64: use SWAPGS_UNSAFE_STACK in ia32entry.S

Use SWAPGS_UNSAFE_STACK in ia32entry.S in the places where the active
stack is the usermode stack.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
---
arch/x86/ia32/ia32entry.S | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

===================================================================
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -98,7 +98,7 @@
CFI_SIGNAL_FRAME
CFI_DEF_CFA rsp,0
CFI_REGISTER rsp,rbp
- SWAPGS
+ SWAPGS_UNSAFE_STACK
movq %gs:pda_kernelstack, %rsp
addq $(PDA_STACKOFFSET),%rsp
/*
@@ -210,7 +210,7 @@
CFI_DEF_CFA rsp,PDA_STACKOFFSET
CFI_REGISTER rip,rcx
/*CFI_REGISTER rflags,r11*/
- SWAPGS
+ SWAPGS_UNSAFE_STACK
movl %esp,%r8d
CFI_REGISTER rsp,r8
movq %gs:pda_kernelstack,%rsp