Hello, On 22/01/2019 03:11, Masami Hiramatsu wrote: > On Mon, 21 Jan 2019 17:04:01 +0000 > James Morse <james.morse@xxxxxxx> wrote: >> On systems with VHE the kernel and KVM's world-switch code run at the >> same exception level. Code that is only used on a VHE system does not >> need to be annotated as __hyp_text as it can reside anywhere in the >> kernel text. >> >> __hyp_text was also used to prevent kprobes from patching breakpoint >> instructions into this region, as this code runs at a different >> exception level. While this is no longer true with VHE, KVM still >> switches VBAR_EL1, meaning a kprobe's breakpoint executed in the >> world-switch code will cause a hyp-panic. >> Annotate the VHE world-switch functions that aren't marked >> __hyp_text as __kprobes. >> --- >> This has been an issue since the VHE/non-VHE world-switch paths were >> split. Before then the code was common, and covered by __hyp_text, which >> is always blacklisted by a subsequent patch. > > Thank you very much for fixing it! > > BTW, would you mind if I ask you using NOKPROBE_SYMBOL() macro instead of > __kprobes attribute? __kprobes moves the function into __kprobe_text > forcibly, OTOH, NOKPROBE_SYMBOL() has no such side-effect. Aha, yes. __kprobes moves the function to a special section, whereas the macro spits out the address of the function into the blacklist section, which is processed via init_kprobes(). I used __kprobes as its in keeping with __hyp_text, but this is clearly better as it doesn't restrict the layout of the code. (and it solves the hibernate/kexec problems as those would otherwise need to be in two sections!) For my own education, when should __kprobes be used? Is it legacy? Thanks! James _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
