Messages in this thread |  | | Subject | Re: [PATCH v2] powerpc/uprobes: Validation for prefixed instruction | From | Ravi Bangoria <> | Date | Mon, 8 Feb 2021 16:38:08 +0530 |
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On 2/4/21 6:45 PM, Naveen N. Rao wrote: > On 2021/02/04 04:19PM, Ravi Bangoria wrote: >> >> >> On 2/4/21 4:17 PM, Ravi Bangoria wrote: >>> Don't allow Uprobe on 2nd word of a prefixed instruction. As per >>> ISA 3.1, prefixed instruction should not cross 64-byte boundary. >>> So don't allow Uprobe on such prefixed instruction as well. >>> >>> There are two ways probed instruction is changed in mapped pages. >>> First, when Uprobe is activated, it searches for all the relevant >>> pages and replace instruction in them. In this case, if we notice >>> that probe is on the 2nd word of prefixed instruction, error out >>> directly. Second, when Uprobe is already active and user maps a >>> relevant page via mmap(), instruction is replaced via mmap() code >>> path. But because Uprobe is invalid, entire mmap() operation can >>> not be stopped. In this case just print an error and continue. >> >> @mpe, >> >> arch_uprobe_analyze_insn() can return early if >> cpu_has_feature(CPU_FTR_ARCH_31) is not set. But that will >> miss out a rare scenario of user running binary with prefixed >> instruction on p10 predecessors. Please let me know if I >> should add cpu_has_feature(CPU_FTR_ARCH_31) or not. > > The check you are adding is very specific to prefixed instructions, so > it makes sense to add a cpu feature check for v3.1. > > On older processors, those are invalid instructions like any other. The > instruction emulation infrastructure will refuse to emulate it and the > instruction will be single stepped.
Sure will add it.
Ravi
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