Messages in this thread | | | Date | Tue, 7 Apr 2020 20:13:25 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 4/4] x86,module: Detect CRn and DRn manipulation |
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On Tue, Apr 07, 2020 at 10:01:04AM -0700, Kees Cook wrote: > On Tue, Apr 07, 2020 at 01:02:40PM +0200, Peter Zijlstra wrote: > > Since we now have infrastructure to analyze module text, disallow > > modules that write to CRn and DRn registers. > > > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > > --- > > arch/x86/kernel/module.c | 21 +++++++++++++++++++++ > > 1 file changed, 21 insertions(+) > > > > --- a/arch/x86/kernel/module.c > > +++ b/arch/x86/kernel/module.c > > @@ -266,6 +266,22 @@ static bool insn_is_vmx(struct insn *ins > > return false; > > } > > > > +static bool insn_is_mov_CRn(struct insn *insn) > > +{ > > + if (insn->opcode.bytes[0] == 0x0f && insn->opcode.bytes[1] == 0x22) > > + return true; > > I always cringe at numeric literals. Would it be overkill to add defines > for these (and the others that have comments next to them in 3/4)? It > makes stuff easier to grep, etc. (e.g. we have register names in > arch/x86/include/asm/asm.h, do we need instruction names somewhere else? > I assume objtool has a bunch of this too...)
objtool does not, have a peek at tools/objtool/arch/x86/decode.c
I'm not sure what the best way is here, the x86 opcode map is a disaster. Even the mnemonic doesn't help us here, as that's just MOV :/
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