Messages in this thread | | | Date | Thu, 27 Jul 2023 09:40:07 +0900 | From | Masami Hiramatsu (Google) <> | Subject | Re: [PATCH v2 2/2] x86/kprobes: Prohibit probing on compiler generated CFI checking code |
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On Wed, 26 Jul 2023 11:29:17 +0200 Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, Jul 26, 2023 at 12:23:17PM +0900, Masami Hiramatsu wrote: > > On Tue, 11 Jul 2023 10:50:58 +0900 > > "Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote: > > > > > From: Masami Hiramatsu (Google) <mhiramat@kernel.org> > > > > > > Prohibit probing on the compiler generated CFI typeid checking code > > > because it is used for decoding typeid when CFI error happens. > > > > > > The compiler generates the following instruction sequence for indirect > > > call checks on x86; > > > > > > movl -<id>, %r10d ; 6 bytes > > > addl -4(%reg), %r10d ; 4 bytes > > > je .Ltmp1 ; 2 bytes > > > ud2 ; <- regs->ip > > > > > > And handle_cfi_failure() decodes these instructions (movl and addl) > > > for the typeid and the target address. Thus if we put a kprobe on > > > those instructions, the decode will fail and report a wrong typeid > > > and target address. > > > > > > > > > > Hi Peter, > > > > Can I pick this to probes/fixes branch ? > > I'll stick them in tip/x86/core, that ok?
Yes, since it is for CFI change.
Thank you,
-- Masami Hiramatsu (Google) <mhiramat@kernel.org>
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