ARM: Permission fault

[xmm15]

Hi,

I am running qemu1.6 with the realview-pb-8 "machine" (cortex-A8). When attempting to read from the serial port I get a permission fault. I am trying to read at 0x10009018.

That address is identity mapped with a small page.
My L1 page table descriptor is assigned to domain 1 (client)
the L2 small page descriptor is set with flags 0x021.
I am attempting to read this value from a privileged level.

If I set bit 8 (TEX2) in the descriptor, I dont get the fault. But I don't understand why.
Also, setting the Xn bit in the small page descriptor also generates an abort.

I know it's a long shot, but I hope someone has an answer. I'd appreciate any suggestions as to where to look.
When setting the domain to "manager" everything is fine. When leaving it at Client but using AP=011, I still get the abort. Could it be a bug in quemu?

[Roman]

Sorry, I can't help you, because I am not an ARM programmer, but I have a question, why do you use such an old version of QEMU?

[xmm15]

Because I can.

[Lionel]

Because I can.

And yet you have expressed yourself that it might be a qemu bug? Please, update QEMU, and recheck the ARMARM and cortexA8 documentation. You have read the documentation, right? I'll admit I know nothing myself.

[iansjack]

Because I can.

Because you can live with possible bugs?

Don't drive a horse and cart and then complain how slow it is.

[xmm15]

Wow! Where does that flamming come from?

I am politely asking a question and you guys get shoked? Could you please point me to where the complaining is in my question?

Lionel: I did not express that it might be a bug, I asked to know if it was a bug that someone might know something about. You did read my post right?
IansJack: Yes I can live with possible bugs, that is why I am asking if that bug is one of them. Are you telling me there are no bugs in the latest release?

I simply asked if maybe it could be a bug that someone is aware of. If you are not aware of such a bug, then its no big deal, I'll figure it out.

I actually just did. It was because I was overwriting some bits in the system control register. So making sure that the register is still ok fixed it.
So I am not acusing qemu of anything, nor was I complaining. I was simply asking a question. I'm sorry if I have offended anyone. I thought this forum was for enthousiasts that had fun developping software and helping out a fellow developer.

[iansjack]

If you suspect a bug in a tool you are using an obvious first line of attack is to try a newer version of the tool to see if the behaviour persists. i would have thought this was a fairly obvious problem-solving procedure.

Using an older version of a tool "because I can" doesn't seem particularly sensible to me if you suspect that there may be a problem with that tool. Getting upset when people try to help you by pointing that out seems a little childish.

I'm glad you solved your problem.

[xmm15]

Before upgrading my software, I thought I'd ask if it is a known bug to avoid upgrading the software for no good reason. If it ain't broke, then don't fix it. I'm happy to see that it is not a bug, so lucky for me, I do not need to upgrade a software that is running perfectly fine.

I don't think it is a bad thing to ask for help on a forum, because forums are made just for that.

[iansjack]

I don't think it is a bad thing to ask for help on a forum, because forums are made just for that.

I quite agree with you (though I don't think that forums are just for problem solving).

It can be a little off-putting when people try to help by making suggestions and are met with hostility from the OP. Suggestions are not meant to be taken personally.

Anyway, enough. You have discovered your error and we are all happy.