Messages in this thread | | | Subject | Re: [PATCH] arm64: trap illegal translations in __virt_to_phys() | From | Miles Chen <> | Date | Wed, 9 Jan 2019 09:35:17 +0800 |
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On Tue, 2019-01-08 at 12:14 +0000, Mark Rutland wrote: > On Tue, Jan 08, 2019 at 11:24:43AM +0800, Miles Chen wrote: > > On Mon, 2019-01-07 at 15:00 +0000, Mark Rutland wrote: > > > On Mon, Jan 07, 2019 at 07:21:20PM +0800, Miles Chen wrote: > > > > Current __virt_to_phys() only print warning messages for non-linear > > > > addresses. It's hard to catch all warnings by those messages. > > > > > > Why? Are you seeing a large number of warnings somewhere? > > > > Official kernel works fine. I saw some cases in our internal branch and > > we're fixing them. > > > > > > > > > So add a VIRTUAL_BUG_ON() to trap all non-linear and non-symbol > > > > addresses (e.g., stack addresses) > > > > > > > > Tested by pass stack addresses and symbol addresses to __pa(). Result: > > > > stack addresses: kernel BUG() > > > > > > Either: > > > > > > * Stacks are vmap'd, and __is_lm_address(stack_addr) is false. We'll > > > produce a WARNING() today (and return a junk physical address). > > > > > > * Stacks are linear mapped, and cannot be distinguished from other > > > linear mapped addresses. The physical address will be valid. > > > > > > ... so I don't understand why you need to change this. > > > > For the first case: for vmap'd stack, __pa() returns a junk > > physical address and it might be easier to debug this incorrect address > > translation by a BUG() call instead of monitoring the warning log. > > I think that's an argument for upgrading the existing WARN() to a BUG(), > rather than adding a separate VIRTUAL_BUG_ON(). > > However, there are cases where the junk physical address is not used to > perform an access, and the WARN() is more helpful.
got it.
> > You can set panic_on_warn to get an immediate panic() when the WARN() > fires. Is there some reason that approach doesn't work for you?
panic_on_warn works fine. thanks for your comment.
cheers, Miles
> > Thanks, > Mark.
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