Bernhard Walle wrote:
> Hi Jay,
>
> while testing the fix for my last problem, I found another issue. I
> think the attached patch is the right fix for it, can you please review
> the patch and add it to your patch series in next release?
>
>
> Regards,
> Bernhard
>
Thanks Bernhard, Applied.
- jay
===================================================================================
This patch fixes following problem:
When panic() in user context, for example by
# modprobe crasher call_panic
then KDB crashed in kdba_getpc() once because regs was not checked for being
NULL:
Entering kdb (current=0xffff880036c747c0, pid 4420) on processor 1
Oops: <NULL>
BUG: unable to handle kernel NULL pointer dereference at
0000000000000080
IP: [<ffffffff80415ee2>] kdba_getpc+0x0/0x8
PGD 379f4067 PUD 39997067 PMD 0
Oops: 0000 [1] SMP
last sysfs file: /sys/devices/pci0000:00/0000:00:1c.5/0000:06:00.0/irq
kdb: Debugger re-entered on cpu 1, new reason = 5
Not executing a kdb command
No longjmp available for recovery
Cannot recover, allowing event to proceed
Even if that has ieen fixed, then kdba_dumpregs() crashed because
the return value of kdba_getpc() was assumed to be non-NULL.
This patch simply ports the error handling from its 32 bit counterpart
implementation. After applying that fix, the test mentioned above succeeds:
Entering kdb (current=0xffff8800355fc480, pid 7564) on processor 1
Oops: <NULL>
due to oops @ 0x0
kdba_dumpregs: pt_regs not available, use bt* or pid to select a
different task
[1]kdb>
Signed-off-by: Bernhard Walle <[EMAIL PROTECTED]>
---
arch/x86/kdb/kdbasupport_64.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
--- a/arch/x86/kdb/kdbasupport_64.c
+++ b/arch/x86/kdb/kdbasupport_64.c
@@ -500,6 +500,11 @@ kdba_dumpregs(struct pt_regs *regs,
struct kdbregs *rlp;
kdb_machreg_t contents;
+ if (!regs) {
+ kdb_printf("%s: pt_regs not available, use bt* or pid
to select a
different task\n", __FUNCTION__);
+ return KDB_BADREG;
+ }
+
for (i=0, rlp=kdbreglist; i<nkdbreglist; i++,rlp++) {
kdb_printf("%8s = ", rlp->reg_name);
kdba_getregcontents(rlp->reg_name, regs, &contents);
@@ -553,7 +558,7 @@ EXPORT_SYMBOL(kdba_dumpregs);
kdb_machreg_t
kdba_getpc(struct pt_regs *regs)
{
- return regs->ip;
+ return regs ? regs->ip : 0;
}
int
---------------------------
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