Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <cover.1605046192.git.andreyknvl@google.com> <619cb0edad35d946c4796976c25bddb5b3eb0c56.1605046192.git.andreyknvl@google.com>
 <CAG_fn=UKSp8shtYujRbM=8ndhLg_Ccdpk9eSfOeb=KpwNi7HBg@mail.gmail.com>
In-Reply-To: <CAG_fn=UKSp8shtYujRbM=8ndhLg_Ccdpk9eSfOeb=KpwNi7HBg@mail.gmail.com>
From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Wed, 11 Nov 2020 19:50:09 +0100
Message-ID: <CAAeHK+zh6tOh91Dg4n4NrJwdPWRaDEtz_Btitg8viQQk7Zm_JQ@mail.gmail.com>
Subject: Re: [PATCH v9 17/44] kasan, arm64: move initialization message
To:     Alexander Potapenko <glider@google.com>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Marco Elver <elver@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        Branislav Rankov <Branislav.Rankov@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Wed, Nov 11, 2020 at 4:04 PM Alexander Potapenko <glider@google.com> wrote:
>
> On Tue, Nov 10, 2020 at 11:11 PM Andrey Konovalov <andreyknvl@google.com> wrote:
> >
> > Software tag-based KASAN mode is fully initialized with kasan_init_tags(),
> > while the generic mode only requires kasan_init(). Move the
> > initialization message for tag-based mode into kasan_init_tags().
> >
> > Also fix pr_fmt() usage for KASAN code: generic.c doesn't need it as it
> > doesn't use any printing functions; tag-based mode should use "kasan:"
> > instead of KBUILD_MODNAME (which stands for file name).
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> > Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> > ---
> > Change-Id: Iddca9764b30ff0fab1922f26ca9d4f39b6f22673
> > ---
> >  arch/arm64/include/asm/kasan.h |  9 +++------
> >  arch/arm64/mm/kasan_init.c     | 13 +++++--------
> >  mm/kasan/generic.c             |  2 --
> >  mm/kasan/sw_tags.c             |  4 +++-
> >  4 files changed, 11 insertions(+), 17 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/kasan.h b/arch/arm64/include/asm/kasan.h
> > index f7ea70d02cab..0aaf9044cd6a 100644
> > --- a/arch/arm64/include/asm/kasan.h
> > +++ b/arch/arm64/include/asm/kasan.h
> > @@ -12,14 +12,10 @@
> >  #define arch_kasan_reset_tag(addr)     __tag_reset(addr)
> >  #define arch_kasan_get_tag(addr)       __tag_get(addr)
> >
> > -#ifdef CONFIG_KASAN
> > -void kasan_init(void);
> > -#else
> > -static inline void kasan_init(void) { }
> > -#endif
> > -
> >  #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
> >
> > +void kasan_init(void);
> > +
> >  /*
> >   * KASAN_SHADOW_START: beginning of the kernel virtual addresses.
> >   * KASAN_SHADOW_END: KASAN_SHADOW_START + 1/N of kernel virtual addresses,
> > @@ -43,6 +39,7 @@ void kasan_copy_shadow(pgd_t *pgdir);
> >  asmlinkage void kasan_early_init(void);
> >
> >  #else
> > +static inline void kasan_init(void) { }
> >  static inline void kasan_copy_shadow(pgd_t *pgdir) { }
> >  #endif
> >
> > diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> > index 5172799f831f..e35ce04beed1 100644
> > --- a/arch/arm64/mm/kasan_init.c
> > +++ b/arch/arm64/mm/kasan_init.c
> > @@ -278,17 +278,14 @@ static void __init kasan_init_depth(void)
> >         init_task.kasan_depth = 0;
> >  }
> >
> > -#else /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS) */
> > -
> > -static inline void __init kasan_init_shadow(void) { }
> > -
> > -static inline void __init kasan_init_depth(void) { }
> > -
> > -#endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
> > -
> >  void __init kasan_init(void)
> >  {
> >         kasan_init_shadow();
> >         kasan_init_depth();
> > +#if defined(CONFIG_KASAN_GENERIC)
> > +       /* CONFIG_KASAN_SW_TAGS also requires kasan_init_tags(). */
> >         pr_info("KernelAddressSanitizer initialized\n");
> > +#endif
> >  }
>
> Cannot we have a single kasan_init() function that will call
> tool-specific initialization functions and print the message at the
> end?

Unfortunately no. For different modes we need different functions that
are called in different places in the kernel. E.g. for generic KASAN
we only need kasan_init() to setup shadow pages; for SW tags we also
need kasan_init_sw_tags() which initializes per-cpu state and
finilizes initialization process.