Messages in this thread | | | Date | Wed, 3 Mar 2021 14:08:36 +0530 | From | "Naveen N. Rao" <> | Subject | Re: [PATCH v3] powerpc/uprobes: Validation for prefixed instruction |
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On 2021/03/04 10:35AM, Ravi Bangoria wrote: > As per ISA 3.1, prefixed instruction should not cross 64-byte > boundary. So don't allow Uprobe on such prefixed instruction. > > 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 that probe > is on the 64-byte unaligned 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. > > Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com> > --- > v2: https://lore.kernel.org/r/20210204104703.273429-1-ravi.bangoria@linux.ibm.com > v2->v3: > - Drop restriction for Uprobe on suffix of prefixed instruction. > It needs lot of code change including generic code but what > we get in return is not worth it. > > arch/powerpc/kernel/uprobes.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/arch/powerpc/kernel/uprobes.c b/arch/powerpc/kernel/uprobes.c > index e8a63713e655..c400971ebe70 100644 > --- a/arch/powerpc/kernel/uprobes.c > +++ b/arch/powerpc/kernel/uprobes.c > @@ -41,6 +41,14 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, > if (addr & 0x03) > return -EINVAL; > > + if (!IS_ENABLED(CONFIG_PPC64) || !cpu_has_feature(CPU_FTR_ARCH_31)) > + return 0;
Sorry, I missed this last time, but I think we can drop the above checks. ppc_inst_prefixed() already factors in the dependency on CONFIG_PPC64, and I don't think we need to confirm if we're running on a ISA V3.1 for the below check.
With that: Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> + > + if (ppc_inst_prefixed(auprobe->insn) && (addr & 0x3F) == 0x3C) { > + pr_info_ratelimited("Cannot register a uprobe on 64 byte unaligned prefixed instruction\n"); > + return -EINVAL; > + } > +
- Naveen
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