Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64

From	Alexander Potapenko <glider@google.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64
Date	2016-06-14 19:20 +0200
Message-ID	<rK0am-7OM-25@gated-at.bofh.it> (permalink)
References	<rJZQZ-7rp-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Hi all,

On Tue, Jun 14, 2016 at 6:57 PM, Alexander Potapenko <glider@google.com> wrote:
> Add ARCH_HAS_KCOV to ARM64 config. To avoid crashes, disable
> instrumentation of the following files:
>
> arch/arm64/boot/*
> arch/arm64/kvm/hyp/*
>
> Signed-off-by: Alexander Potapenko <glider@google.com>
> ---
> v2: - disable instrumentation of arch/arm64/{boot,kvm/hyp}
>     - enable instrumentation of arch/arm64/lib/delay.c
> ---
>  arch/arm64/Kconfig          | 1 +
>  arch/arm64/boot/Makefile    | 4 ++++
>  arch/arm64/kvm/hyp/Makefile | 4 ++++
>  3 files changed, 9 insertions(+)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 5a0a691..eb0b0a0 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -7,6 +7,7 @@ config ARM64
>         select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
>         select ARCH_HAS_ELF_RANDOMIZE
>         select ARCH_HAS_GCOV_PROFILE_ALL
> +       select ARCH_HAS_KCOV
>         select ARCH_HAS_SG_CHAIN
>         select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>         select ARCH_USE_CMPXCHG_LOCKREF
> diff --git a/arch/arm64/boot/Makefile b/arch/arm64/boot/Makefile
> index 305c552..74cec89 100644
> --- a/arch/arm64/boot/Makefile
> +++ b/arch/arm64/boot/Makefile
> @@ -14,6 +14,10 @@
>  # Based on the ia64 boot/Makefile.
>  #
>
> +# Avoid potential boot-time problems with kcov instrumentation. We are mostly
> +# interested in syscall coverage, so boot code is not interesting anyway.
> +KCOV_INSTRUMENT                := n
> +
>  targets := Image Image.gz
>
>  $(obj)/Image: vmlinux FORCE
> diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile
> index 778d0ef..0c85feb 100644
> --- a/arch/arm64/kvm/hyp/Makefile
> +++ b/arch/arm64/kvm/hyp/Makefile
> @@ -17,6 +17,10 @@ obj-$(CONFIG_KVM_ARM_HOST) += tlb.o
>  obj-$(CONFIG_KVM_ARM_HOST) += hyp-entry.o
>  obj-$(CONFIG_KVM_ARM_HOST) += s2-setup.o
>
> +# KVM code is run at a different exception code with a different map, so
> +# compiler instrumentation that inserts callbacks or checks into the code may
> +# cause crashes. Just disable it.
>  GCOV_PROFILE   := n
>  KASAN_SANITIZE := n
>  UBSAN_SANITIZE := n
> +KCOV_INSTRUMENT        := n
> --
> 2.8.0.rc3.226.g39d4020
>
Following the previous patch discussion, I have dropped the delay.c
exception, which isn't strictly required for kcov to function.
We can decide what to do with it later.
Instead I've added rules to avoid instrumentation of arch/arm64/boot
and arch/arm64/kvm


-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Matthew Scott Sucherman, Paul Terence Manicle
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg

Thread

[PATCH v2] arm64: allow building with kcov coverage on ARM64 Alexander Potapenko <glider@google.com> - 2016-06-14 19:00 +0200
  Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Alexander Potapenko <glider@google.com> - 2016-06-14 19:20 +0200
  Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Mark Rutland <mark.rutland@arm.com> - 2016-06-14 20:00 +0200
    Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Alexander Potapenko <glider@google.com> - 2016-06-14 20:20 +0200
      Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Mark Rutland <mark.rutland@arm.com> - 2016-06-15 11:30 +0200
        Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Mark Rutland <mark.rutland@arm.com> - 2016-06-15 13:50 +0200
          Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Alexander Potapenko <glider@google.com> - 2016-06-15 14:00 +0200
            Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Mark Rutland <mark.rutland@arm.com> - 2016-06-15 16:30 +0200
              Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Dmitry Vyukov <dvyukov@google.com> - 2016-06-15 16:40 +0200
                Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Mark Rutland <mark.rutland@arm.com> - 2016-06-15 17:10 +0200
                Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Dmitry Vyukov <dvyukov@google.com> - 2016-06-15 17:30 +0200
              Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 James Morse <james.morse@arm.com> - 2016-06-16 12:50 +0200
                Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Alexander Potapenko <glider@google.com> - 2016-06-16 17:30 +0200
                Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Mark Rutland <mark.rutland@arm.com> - 2016-06-16 17:50 +0200
                Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Catalin Marinas <catalin.marinas@arm.com> - 2016-06-16 18:30 +0200
                Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Catalin Marinas <catalin.marinas@arm.com> - 2016-06-16 18:40 +0200
                Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Alexander Potapenko <glider@google.com> - 2016-06-16 18:40 +0200
                Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 James Morse <james.morse@arm.com> - 2016-06-16 18:40 +0200
                Re: [PATCH v2] arm64: allow building with kcov coverage on ARM64 Mark Rutland <mark.rutland@arm.com> - 2016-06-16 18:40 +0200

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