On Thu, Jun 13, 2019 at 02:23:43PM +0100, Dave P Martin wrote:
On Thu, Jun 13, 2019 at 01:28:21PM +0100, Catalin Marinas wrote:
On Thu, Jun 13, 2019 at 12:37:32PM +0100, Dave P Martin wrote:
On Thu, Jun 13, 2019 at 11:15:34AM +0100, Vincenzo Frascino wrote:
On 12/06/2019 16:35, Catalin Marinas wrote:
On Wed, Jun 12, 2019 at 03:21:10PM +0100, Vincenzo Frascino wrote:
- PR_GET_TAGGED_ADDR_CTRL: can be used to check the status of the Tagged
Address ABI.[...]
Is there a canonical way to detect whether this whole API/ABI is available? (i.e., try to call this prctl / check for an HWCAP bit, etc.)
The canonical way is a prctl() call. HWCAP doesn't make sense since it's not a hardware feature. If you really want a different way of detecting this (which I don't think it's worth), we can reinstate the AT_FLAGS bit.
Sure, I think this probably makes sense -- I'm still getting my around which parts of the design are directly related to MTE and which aren't.
I was a bit concerned about the interaction between PR_SET_TAGGED_ADDR_CTRL and the sysctl: the caller might conclude that this API is unavailable when actually tagged addresses are stuck on.
I'm not sure whether this matters, but it's a bit weird.
One option would be to change the semantics, so that the sysctl just forbids turning tagging from off to on. Alternatively, we could return a different error code to distinguish this case.
This is the intention, just to forbid turning tagging on. We could return -EPERM instead, though my original intent was to simply pretend that the prctl does not exist like in an older kernel version.