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Ok so I read the mail from Andy and understand the real problem better: UAI is not context switched and is to be enabled system wide. I don't know what AMD has
by temac 5y ago
Ok so I read the mail from Andy and understand the real problem better: UAI is not context switched and is to be enabled system wide. I don't know what AMD has been smoking.
- saagarjha 5y agoPretty sure this is how it works in ARM as well, except that TBI can be configured per-exception level so it can be turned off in the kernel.
- pm215 5y agoYes. The thing which is controlled per-process (per-thread, really) is the extent to which you can pass a tagged address to a kernel syscall and have it strip the tag and operate on the 'real' address versus handing you a 'bad address' error. The default is 'syscalls (mostly) don't detag addresses'. https://www.kernel.org/doc/html/latest/arm64/tagged-address-abi.html https://www.kernel.org/doc/html/latest/arm64/tagged-address-... has the details. Because TBI is separate for userspace and the kernel you could make it per-process -- just context switch the TBI control bit. But there's no need.