Am Dienstag, 4. September 2018, 04:11:07 CEST schrieb Haibo Xu (Arm Technology China): > Hi Richard, > > What do you mean by done it in the core? moving macro definition to > include/uapi/linux/ptrace.h? > The patch is strictly follow x86's sematic on PTRACE_SYSEMU/SINGLESTEP > support.
Well, the feature itself is not really architecture specific. Just because x86 does it in arch/x86, it does not mean that this is the best way. I guess this is also what Will tried to say. If we can, we should implement PTRACE_SYSEMU in the core ptrace code and not per architecture. > > > I wonder what Haibo Xu want to do with PTRACE_SYSEMU on arm64. > > > Are you porting UML or gvisor to arm64? > > > > That's a good question. Haibo? > > The story is we are working on a container runtime(Google Gvisor) support on > ARM64 platform, > and the Gvisor depend on Linux kernel PTRACE_SYSEMU/SINGLESTEP support. Gvisor also supports a kvm backend which should be *much* faster than PTRACE_SYSEMU. Otherwise gvisor suffers from the same performance drawbacks as UML does. Pagefaults via SIGSEGV/mmap, syscall gate via ptrace(). Did you check, is PTRACE_SYSEMU really the way to go for gvisor? Last time I checked the KVM backend looked promising but still WIP, though. I also wonder whether PTRACE_SYSEMU is really the only missing bit to support gvisor on arm64. Did you check how to work around VIPT/VIVT caching issues? UML (and gvisor in this context) have lots of implicit x86 dependencies. Thanks, //richard
