On Wed, Apr 17, 2019 at 01:39:32PM +0300, Jarkko Sakkinen wrote: > From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> > > vDSO functions can now leverage an exception fixup mechanism similar to > kernel exception fixup. For vDSO exception fixup, the initial user is > Intel's Software Guard Extensions (SGX), which will wrap the low-level > transitions to/from the enclave, i.e. EENTER and ERESUME instructions, > in a vDSO function and leverage fixup to intercept exceptions that would > otherwise generate a signal. This allows the vDSO wrapper to return the > fault information directly to its caller, obviating the need for SGX > applications and libraries to juggle signal handlers. > > Attempt to fixup vDSO exceptions immediately prior to populating and > sending signal information. Except for the delivery mechanism, an > exception in a vDSO function should be treated like any other exception > in userspace, e.g. any fault that is successfully handled by the kernel > should not be directly visible to userspace. > > Although it's debatable whether or not all exceptions are of interest to > enclaves, defer to the vDSO fixup to decide whether to do fixup or > generate a signal. Future users of vDSO fixup, if there ever are any, > will undoubtedly have different requirements than SGX enclaves, e.g. the > fixup vs. signal logic can be made function specific if/when necessary. > > Suggested-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx> > Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> > Cc: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> > Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx> > Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> I went through the vDSO changes just to revisit couple of details that I had forgotten. Sean, if you don't mind I'd squash this and prepending patch. Is there any obvious reason why #PF fixup is in its own patch and the rest are collected to the same patch? I would not find it confusing if there was one patch per exception but really don't get this division. /Jarkko
