Hi, On Thu, 31 Jul 2025, Deepak Gupta wrote:
[ ... ] > vDSO related Opens (in the flux) > ================================= > > I am listing these opens for laying out plan and what to expect in future > patch sets. And of course for the sake of discussion. > [ ... ] > How many vDSOs > --------------- > Shadow stack instructions are carved out of zimop (may be operations) and if > CPU > doesn't implement zimop, they're illegal instructions. Kernel could be > running on > a CPU which may or may not implement zimop. And thus kernel will have to > carry 2 > different vDSOs and expose the appropriate one depending on whether CPU > implements > zimop or not. If we merge this series without this, then when CFI is enabled in the Kconfig, we'll wind up with a non-portable kernel that won't run on older hardware. We go to great lengths to enable kernel binary portability across the presence or absence of other RISC-V extensions, and I think these CFI extensions should be no different. So before considering this for merging, I'd like to see at least an attempt to implement the dual-vDSO approach (or something equivalent) where the same kernel binary with CFI enabled can run on both pre-Zimop and post-Zimop hardware, with the existing userspaces that are common today. thanks Deepak, - Paul
