Messages in this thread Patch in this message | | | Date | Mon, 21 Jan 2019 22:25:58 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH v2 4/4] arm64: kprobes: Use arch_populate_kprobe_blacklist() |
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On Mon, 21 Jan 2019 12:20:07 +0000 James Morse <james.morse@arm.com> wrote:
> Hello, > > On 15/01/2019 06:25, Masami Hiramatsu wrote: > > Use arch_populate_kprobe_blacklist() instead of > > arch_within_kprobe_blacklist() so that we can see the full > > blacklisted symbols under the debugfs. > > diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c > > index b9e9758b6534..6c066c34c8a4 100644 > > --- a/arch/arm64/kernel/probes/kprobes.c > > +++ b/arch/arm64/kernel/probes/kprobes.c > > @@ -465,26 +465,30 @@ kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr) > > return DBG_HOOK_HANDLED; > > } > > > > -bool arch_within_kprobe_blacklist(unsigned long addr) > > +int __init arch_populate_kprobe_blacklist(void) > > { > > - if ((addr >= (unsigned long)__kprobes_text_start && > > - addr < (unsigned long)__kprobes_text_end) || > > - (addr >= (unsigned long)__entry_text_start && > > - addr < (unsigned long)__entry_text_end) || > > - (addr >= (unsigned long)__idmap_text_start && > > - addr < (unsigned long)__idmap_text_end) || > > > - in_exception_text(addr)) > > You added this one in the previous patch, but it disappears here.
Yes, it is easy to explain how we transcribe from arch_within_kprobe_blacklist() to arch_populate_kprobe_blacklist().
> > > > - return true; > > - > > - if (!is_kernel_in_hyp_mode()) { > > - if ((addr >= (unsigned long)__hyp_text_start && > > - addr < (unsigned long)__hyp_text_end) || > > - (addr >= (unsigned long)__hyp_idmap_text_start && > > - addr < (unsigned long)__hyp_idmap_text_end)) > > - return true; > > - } > > - > > - return false; > > + int ret; > > > > + ret = kprobe_add_area_blacklist((unsigned long)__kprobes_text_start, > > + (unsigned long)__kprobes_text_end); > > + if (ret) > > + return ret; > > Now that we have arch_populate_kprobe_blacklist(), does the arch-code need to > blacklist the kprobes section itself?
Ah, good catch! No, we don't need it here. Sorry I worked on older patch. I'll update it.
> The weak arch_within_kprobe_blacklist() will test it at kprobe-load time, and > populate_kprobe_blacklist() adds it to the list before it calls > arch_populate_kprobe_blacklist(). > > Won't this result in duplicate entries?
yes, so it should not.
> > > > + ret = kprobe_add_area_blacklist((unsigned long)__entry_text_start, > > + (unsigned long)__entry_text_end); > > + if (ret) > > + return ret; > > > + ret = kprobe_add_area_blacklist((unsigned long)__idmap_text_start, > > + (unsigned long)__idmap_text_end); > > > + if (ret || is_kernel_in_hyp_mode()) > > + return ret; > > > Hmmm, I think we have a bug here today.
OK.
> > This is saying we can kprobe KVM when we have VHE, because all of KVMs code runs > at the same exception-level as the kernel. Which is true... > But KVM switches VBAR_EL1, so if we run over one of kprobes BRK instructions, > we're going to hyp-panic, because KVM doesn't handle synchronous exceptions from > EL2. > > The __hyp_text also contains the guest entry/exit code, which we mustn't probe, > even on VHE.
Hmm, I'm not sure when the original code decided this. But it sounds reasonable.
> > I think we should always blacklist the __hyp_text, and KVM should mark its > vhe-only functions with __kprobes. I'll post patches for this.
OK, then I should wait for that, because this series is a kind of improvement. But your's is a bugfix, that should be backported to stable.
Thank you,
> > > Thanks, > > James > > > > + ret = kprobe_add_area_blacklist((unsigned long)__hyp_text_start, > > + (unsigned long)__hyp_text_end); > > + if (ret) > > + return ret; > > + ret = kprobe_add_area_blacklist((unsigned long)__hyp_idmap_text_start, > > + (unsigned long)__hyp_idmap_text_end); > > + return ret; > > } > > > > void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs) > > >
-- Masami Hiramatsu <mhiramat@kernel.org>
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