Michael Ellerman <m...@ellerman.id.au> writes: > Hi Daniel, > > Great work thanks for getting this going. >
> Have you tried running with KVM? > > I'm wondering if we should be excluding some of the KVM code that runs in > real mode, eg: > > arch/powerpc/kvm/book3s_hv_rm_mmu.c > arch/powerpc/kvm/book3s_hv_rm_xics.c > > And maybe some other bits. > > Also the early setup code, a/p/k/setup*.c might be dicey. My philosphy was just to copy the GCOV excludes, although you're right that perhaps we want to be more aggressive in excluding here given that the UBSAN handlers print a bunch of stuff. I'm happy to respin with further exclusions - they're really easy to add. > In all of the above it's probably OK unless you actually hit a warning at the > wrong point, so testing will probably not find problems. Although I guess we > could add some deliberatly incorrect code at certain points and check we > survive the warning. Yep. I'll run a kvm guest on an instrumented kernel and let you know what happens! > > Is there an easy way to spot the calls to UBSAN in the generated code? Yes - because of the handler functions, they're *really* easy to spot. Here's some assembly for GregorianDay(): c00000000002924c: 6d 26 7e 48 bl c00000000080b8b8 <__ubsan_handle_mul_overflow+0x8> c000000000029250: 00 00 00 60 nop c000000000029254: 38 fe ff 4b b c00000000002908c <GregorianDay+0xdc> c000000000029258: 8c ff 62 3c addis r3,r2,-116 c00000000002925c: 01 00 a0 38 li r5,1 c000000000029260: 78 db 64 7f mr r4,r27 c000000000029264: 50 9c 63 38 addi r3,r3,-25520 c000000000029268: 41 26 7e 48 bl c00000000080b8a8 <__ubsan_handle_sub_overflow+0x8> c00000000002926c: 00 00 00 60 nop c000000000029270: 44 fe ff 4b b c0000000000290b4 <GregorianDay+0x104> c000000000029274: 8c ff 62 3c addis r3,r2,-116 c000000000029278: 78 d3 45 7f mr r5,r26 c00000000002927c: e0 9c 63 38 addi r3,r3,-25376 c000000000029280: 19 26 7e 48 bl c00000000080b898 <__ubsan_handle_add_overflow+0x8> c000000000029284: 00 00 00 60 nop c000000000029288: 94 fe ff 4b b c00000000002911c <GregorianDay+0x16c> c00000000002928c: 8c ff 62 3c addis r3,r2,-116 c000000000029290: 78 f3 c4 7f mr r4,r30 c000000000029294: 68 9c 63 38 addi r3,r3,-25496 c000000000029298: b1 21 7e 48 bl c00000000080b448 <__ubsan_handle_out_of_bounds+0x8> c00000000002929c: 00 00 00 60 nop c0000000000292a0: 20 fe ff 4b b c0000000000290c0 <GregorianDay+0x110> c0000000000292a4: 14 4a 24 7d add r9,r4,r9 c0000000000292a8: 40 48 a4 7f cmpld cr7,r4,r9 c0000000000292ac: 2c fe fd 41 bgt+ cr7,c0000000000290d8 <GregorianDay+0x128> You can see that there are lots of calls to __ubsan_handle_blah_blah inserted. Regards, Daniel > > cheers > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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