| Message ID | 20180626123154.unjji5glpokedwal@treble (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Herbert Xu |
| Headers | show |
* Josh Poimboeuf <jpoimboe@redhat.com> wrote: > > So that's still incomplete in that doesn't analyze the 32-bit build yet, right? > > We could do INT3s on 64-bit and NOPs on 32-bit. > > Or, possibly even better, we could just keep NOPs everywhere and instead > make objtool smart enough to detect function fallthroughs. That should > be pretty easy, actually. It already does it for C files. > > Something like the below should work, though it's still got a few > issues: > > a) objtool is currently disabled for crypto code because it doesn't > yet understand crypto stack re-alignments (which really needs > fixing anyway); and > > b) it complains about the blank xen hypercalls falling through. Those > aren't actual functions anyway, so we should probably annotate > those somehow so that objtool ignores them anyway. > > I'm a bit swamped at the moment but I can fix those once I get a little > more bandwidth. I at least verified that this patch caught the crypto > missing RETs. Great, I'd be perfectly fine with such an approach. Also, if we have that then we could re-apply Alexey's patch and switch to INT3 (only on 64-bit kernels) without any trouble, because objtool should detect any execution flow bugs before the INT3 could trigger, right? I.e. any INT3 fault would show a combination of *both* an objtool bug and a probable code flow bug - which I suspect would warrant crashing the box ... Thanks, Ingo
On Thu, Jul 05, 2018 at 09:58:15AM +0200, Ingo Molnar wrote: > > * Josh Poimboeuf <jpoimboe@redhat.com> wrote: > > > > So that's still incomplete in that doesn't analyze the 32-bit build yet, right? > > > > We could do INT3s on 64-bit and NOPs on 32-bit. > > > > Or, possibly even better, we could just keep NOPs everywhere and instead > > make objtool smart enough to detect function fallthroughs. That should > > be pretty easy, actually. It already does it for C files. > > > > Something like the below should work, though it's still got a few > > issues: > > > > a) objtool is currently disabled for crypto code because it doesn't > > yet understand crypto stack re-alignments (which really needs > > fixing anyway); and > > > > b) it complains about the blank xen hypercalls falling through. Those > > aren't actual functions anyway, so we should probably annotate > > those somehow so that objtool ignores them anyway. > > > > I'm a bit swamped at the moment but I can fix those once I get a little > > more bandwidth. I at least verified that this patch caught the crypto > > missing RETs. > > Great, I'd be perfectly fine with such an approach. > > Also, if we have that then we could re-apply Alexey's patch and switch to INT3 > (only on 64-bit kernels) without any trouble, because objtool should detect any > execution flow bugs before the INT3 could trigger, right? > > I.e. any INT3 fault would show a combination of *both* an objtool bug and a > probable code flow bug - which I suspect would warrant crashing the box ... Sounds good to me. I can take Alexey's patch and submit a 64-bit version of it, along with the relevant objtool changes (though it may still be a few weeks before I get the chance).
* Josh Poimboeuf <jpoimboe@redhat.com> wrote: > > Great, I'd be perfectly fine with such an approach. > > > > Also, if we have that then we could re-apply Alexey's patch and switch to INT3 > > (only on 64-bit kernels) without any trouble, because objtool should detect any > > execution flow bugs before the INT3 could trigger, right? > > > > I.e. any INT3 fault would show a combination of *both* an objtool bug and a > > probable code flow bug - which I suspect would warrant crashing the box ... > > Sounds good to me. I can take Alexey's patch and submit a 64-bit > version of it, along with the relevant objtool changes (though it may > still be a few weeks before I get the chance). Sounds good to me, thanks! Ingo
diff --git a/arch/x86/crypto/Makefile b/arch/x86/crypto/Makefile index a450ad573dcb..a2c52eec2863 100644 --- a/arch/x86/crypto/Makefile +++ b/arch/x86/crypto/Makefile @@ -3,8 +3,6 @@ # Arch-specific CryptoAPI modules. # -OBJECT_FILES_NON_STANDARD := y - avx_supported := $(call as-instr,vpxor %xmm0$(comma)%xmm0$(comma)%xmm0,yes,no) avx2_supported := $(call as-instr,vpgatherdd %ymm0$(comma)(%eax$(comma)%ymm1\ $(comma)4)$(comma)%ymm2,yes,no) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 2928939b98ec..f740fd828cba 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1798,13 +1798,14 @@ static int validate_branch(struct objtool_file *file, struct instruction *first, while (1) { next_insn = next_insn_same_sec(file, insn); - if (file->c_file && func && insn->func && func != insn->func->pfunc) { + if (func && insn->func && func != insn->func->pfunc) { WARN("%s() falls through to next function %s()", func->name, insn->func->name); return 1; } - func = insn->func ? insn->func->pfunc : NULL; + if (insn->type != INSN_NOP) + func = insn->func ? insn->func->pfunc : NULL; if (func && insn->ignore) { WARN_FUNC("BUG: why am I validating an ignored function?",