On Wed, Nov 16, 2022 at 10:38:19PM +0000, Edgecombe, Rick P wrote: > On Wed, 2022-11-16 at 11:18 +0100, Peter Zijlstra wrote: > > > > > > > > Should you write a 64bit value even if the task receiving a > > > > signal is > > > > 32bit ? > > > > > > 32 bit support was also dropped. > > > > How? Task could start life as 64bit, frob LDT to set up 32bit code > > segment and jump into it and start doing 32bit syscalls, then what? > > > > AFAICT those 32bit syscalls will end up doing SA_IA32_ABI sigframes. > > Hmm, good point. This series used to support normal 32 bit apps via > ia32 emulation which would have handled this. But I removed it (blocked > in the enabling logic) because it didn't seem like it would get enough > use to justify the extra code. That doesn't block this scenario here > though. > > Pardon the possibly naive question, but is this 32/64 bit mixing > something any normal, shstk-desiring, applications would actually do? O > r more that they could do? It is not something common, but it is something that things like Wine do IIRC, and it would be a real shame if Wine could not use shadow stacks or something, right ;-) But more to the point; since the kernel cannot forbit this scenario (aside from taking away the LDT entirely) it is something that needs handling.
