On Mon, 2022-11-21 at 09:40 +0200, Mike Rapoport wrote: > On Thu, Nov 17, 2022 at 07:57:59PM +0000, Edgecombe, Rick P wrote: > > On Thu, 2022-11-17 at 12:25 +0000, Schimpe, Christina wrote: > > > > Hmm, we definitely need to be able to set the SSP. Christina, > > > > does > > > > GDB need > > > > anything else? I thought maybe toggling SHSTK_EN? > > > > > > In addition to the SSP, we want to write the CET state. For > > > instance > > > for inferior calls, > > > we want to reset the IBT bits. > > > However, we won't write states that are disallowed by HW. > > > > Sorry, I should have given more background. Peter is saying we > > should > > split the ptrace interface so that shadow stack and IBT are > > separate. > > They would also no longer necessarily mirror the CET_U MSR format. > > Instead the kernel would expose a kernel specific format that has > > the > > needed bits of shadow stack support. And a separate one later for > > IBT. > > > > So the question is what does shadow stack need to support for > > ptrace > > besides SSP? Is it only SSP? The other features are SHSTK_EN and > > WRSS_EN. It might actually be nice to keep how these bits get > > flipped > > more controlled (remove them from ptrace). It looks like CRIU > > didn't > > need them. > > > CRIU reads CET_U with ptrace(PTRACE_GETREGSET, NT_X86_CET). It's done > before the injection of the parasite. The value of SHSTK_EN is used > then to > detect if shadow stack is enabled and to setup victim's shadow stack > for > sigreturn. Hmm, can it read /proc/pid/status? It has some lines like this: x86_Thread_features: shstk wrss x86_Thread_features_locked: shstk wrss
