Current __virt_to_phys() only print warning messages for non-linear
addresses. It's hard to catch all warnings by those messages. 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()
symbol addresses: kernel warning message
Maybe we should trap all non-linear address translations in the future.
Signed-off-by: Miles Chen <[email protected]>
---
arch/arm64/mm/physaddr.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/arm64/mm/physaddr.c b/arch/arm64/mm/physaddr.c
index 67a9ba9eaa96..f6b935dad19c 100644
--- a/arch/arm64/mm/physaddr.c
+++ b/arch/arm64/mm/physaddr.c
@@ -14,6 +14,11 @@ phys_addr_t __virt_to_phys(unsigned long x)
(void *)x,
(void *)x);
+ /* trap all non-linear and non-symbol addresses */
+ VIRTUAL_BUG_ON(!__is_lm_address(x) &&
+ (x < (unsigned long)KERNEL_START ||
+ x > (unsigned long)KERNEL_END));
+
return __virt_to_phys_nodebug(x);
}
EXPORT_SYMBOL(__virt_to_phys);
--
2.18.0
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?
> 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.
> symbol addresses: kernel warning message
That should already be the case today, since the kernel image is mapped
separately from the linear map, so __is_lm_address(symbol_addr) should
be false.
>
> Maybe we should trap all non-linear address translations in the future.
>
> Signed-off-by: Miles Chen <[email protected]>
> ---
> arch/arm64/mm/physaddr.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/arch/arm64/mm/physaddr.c b/arch/arm64/mm/physaddr.c
> index 67a9ba9eaa96..f6b935dad19c 100644
> --- a/arch/arm64/mm/physaddr.c
> +++ b/arch/arm64/mm/physaddr.c
> @@ -14,6 +14,11 @@ phys_addr_t __virt_to_phys(unsigned long x)
> (void *)x,
> (void *)x);
>
> + /* trap all non-linear and non-symbol addresses */
> + VIRTUAL_BUG_ON(!__is_lm_address(x) &&
> + (x < (unsigned long)KERNEL_START ||
> + x > (unsigned long)KERNEL_END));
The KERNEL_START and KERNEL_END definitions refer to the kernel image,
not the linear map, so it doesn't make any sense to permit those here.
It is *not* valid to call __virt_to_phys() with a symbol address. We
only support those in __virt_to_phys_nodebug() so that broken code has a
chance of stumbling on.
If you want the kernel to die immediately when it hits a warning here,
please set panic_on_warn.
Thanks,
Mark.
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.
Like __phys_addr_symbol() does. __phys_addr_symbol() uses
VIRTUAL_BUG_ON() for non symbol addresses.
>
> > symbol addresses: kernel warning message
>
> That should already be the case today, since the kernel image is mapped
> separately from the linear map, so __is_lm_address(symbol_addr) should
> be false.
>
> >
> > Maybe we should trap all non-linear address translations in the future.
> >
> > Signed-off-by: Miles Chen <[email protected]>
> > ---
> > arch/arm64/mm/physaddr.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/arch/arm64/mm/physaddr.c b/arch/arm64/mm/physaddr.c
> > index 67a9ba9eaa96..f6b935dad19c 100644
> > --- a/arch/arm64/mm/physaddr.c
> > +++ b/arch/arm64/mm/physaddr.c
> > @@ -14,6 +14,11 @@ phys_addr_t __virt_to_phys(unsigned long x)
> > (void *)x,
> > (void *)x);
> >
> > + /* trap all non-linear and non-symbol addresses */
> > + VIRTUAL_BUG_ON(!__is_lm_address(x) &&
> > + (x < (unsigned long)KERNEL_START ||
> > + x > (unsigned long)KERNEL_END));
>
> The KERNEL_START and KERNEL_END definitions refer to the kernel image,
> not the linear map, so it doesn't make any sense to permit those here.
>
> It is *not* valid to call __virt_to_phys() with a symbol address. We
> only support those in __virt_to_phys_nodebug() so that broken code has a
> chance of stumbling on.
>
> If you want the kernel to die immediately when it hits a warning here,
> please set panic_on_warn.
>
> Thanks,
> Mark.
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.
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?
Thanks,
Mark.
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.