On Thu, Sep 03, 2020 at 10:46:33AM +0100, Boyan Karatotev wrote:
On 02/09/2020 17:48, Dave Martin wrote:
On Fri, Aug 28, 2020 at 02:16:02PM +0100, Boyan Karatotev wrote:
Pointer Authentication (PAuth) is a security feature introduced in ARMv8.3. It introduces instructions to sign addresses and later check for potential corruption using a second modifier value and one of a set of keys. The signature, in the form of the Pointer Authentication Code (PAC), is stored in some of the top unused bits of the virtual address (e.g. [54: 49] if TBID0 is enabled and TnSZ is set to use a 48 bit VA space). A set of controls are present to enable/disable groups of instructions (which use certain keys) for compatibility with libraries that do not utilize the feature. PAuth is used to verify the integrity of return addresses on the stack with less memory than the stack canary.
This patchset adds kselftests to verify the kernel's configuration of the feature and its runtime behaviour. There are 7 tests which verify that:
- an authentication failure leads to a SIGSEGV
- the data/instruction instruction groups are enabled
- the generic instructions are enabled
- all 5 keys are unique for a single thread
- exec() changes all keys to new unique ones
- context switching preserves the 4 data/instruction keys
- context switching preserves the generic keys
The tests have been verified to work on qemu without a working PAUTH Implementation and on ARM's FVP with a full or partial PAuth implementation.
Note: This patchset is only verified for ARMv8.3 and there will be some changes required for ARMv8.6. More details can be found here . Once ARMv8.6 PAuth is merged the first test in this series will required to be updated.
Nit: is it worth running checkpatch over this series?
Although this is not kernel code, there are a number of formatting weirdnesses and surplus blank lines etc. that checkpatch would probably warn about.
I ran it through checkpatch and it came out clean except for some MAINTAINERS warnings. I see that when I add --strict it does complain about multiple blank lines which I can fix for the next version. Are there any other flags I should be running checkpatch with?
Hmmm, probably not. I had thought checkpatch was generally noisier about that kind of thing.
Since the issues were all minor and nobody else objected, I would suggest not to worry about them.