linux-kernel - Re: [PATCH v2 08/14] powerpc: Handle KCOV _

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Message-ID: <202507091856.C6510D809A@keescook>
Date: Wed, 9 Jul 2025 18:57:00 -0700
From: Kees Cook <kees@...nel.org>
To: Ritesh Harjani <ritesh.list@...il.com>
Cc: Arnd Bergmann <arnd@...db.de>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Naveen N Rao <naveen@...nel.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linuxppc-dev@...ts.ozlabs.org,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Christoph Hellwig <hch@....de>, Marco Elver <elver@...gle.com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Masahiro Yamada <masahiroy@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas.schier@...ux.dev>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org, kasan-dev@...glegroups.com,
	linux-doc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev, linux-riscv@...ts.infradead.org,
	linux-s390@...r.kernel.org, linux-efi@...r.kernel.org,
	linux-hardening@...r.kernel.org, linux-kbuild@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-kselftest@...r.kernel.org, sparclinux@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: Re: [PATCH v2 08/14] powerpc: Handle KCOV __init vs inline mismatches

On Sat, May 24, 2025 at 04:13:02PM +0530, Ritesh Harjani wrote:
> Kees Cook <kees@...nel.org> writes:
> 
> > When KCOV is enabled all functions get instrumented, unless
> > the __no_sanitize_coverage attribute is used. To prepare for
> > __no_sanitize_coverage being applied to __init functions, we have to
> > handle differences in how GCC's inline optimizations get resolved. For
> > s390 this requires forcing a couple functions to be inline with
> > __always_inline.
> >
> > Signed-off-by: Kees Cook <kees@...nel.org>
> > ---
> > Cc: Madhavan Srinivasan <maddy@...ux.ibm.com>
> > Cc: Michael Ellerman <mpe@...erman.id.au>
> > Cc: Nicholas Piggin <npiggin@...il.com>
> > Cc: Christophe Leroy <christophe.leroy@...roup.eu>
> > Cc: Naveen N Rao <naveen@...nel.org>
> > Cc: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
> > Cc: "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: <linuxppc-dev@...ts.ozlabs.org>
> > ---
> >  arch/powerpc/mm/book3s64/hash_utils.c    | 2 +-
> >  arch/powerpc/mm/book3s64/radix_pgtable.c | 2 +-
> >  2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
> > index 5158aefe4873..93f1e1eb5ea6 100644
> > --- a/arch/powerpc/mm/book3s64/hash_utils.c
> > +++ b/arch/powerpc/mm/book3s64/hash_utils.c
> > @@ -409,7 +409,7 @@ static DEFINE_RAW_SPINLOCK(linear_map_kf_hash_lock);
> >  
> >  static phys_addr_t kfence_pool;
> >  
> > -static inline void hash_kfence_alloc_pool(void)
> > +static __always_inline void hash_kfence_alloc_pool(void)
> >  {
> >  	if (!kfence_early_init_enabled())
> >  		goto err;
> > diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
> > index 9f764bc42b8c..3238e9ed46b5 100644
> > --- a/arch/powerpc/mm/book3s64/radix_pgtable.c
> > +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
> > @@ -363,7 +363,7 @@ static int __meminit create_physical_mapping(unsigned long start,
> >  }
> >  
> >  #ifdef CONFIG_KFENCE
> > -static inline phys_addr_t alloc_kfence_pool(void)
> > +static __always_inline phys_addr_t alloc_kfence_pool(void)
> >  {
> >  	phys_addr_t kfence_pool;
> >  
> 
> I remember seeing a warning msg around .init.text section. Let me dig
> that...
> 
> ... Here it is: https://lore.kernel.org/oe-kbuild-all/202504190552.mnFGs5sj-lkp@intel.com/
> 
> I am not sure why it only complains for hash_debug_pagealloc_alloc_slots().
> I believe there should me more functions to mark with __init here.
> Anyways, here is the patch of what I had in mind.. I am not a compiler expert,
> so please let me know your thoughts on this.

Yeah, this looks good. I'll snag your patch and drop mine. :)

-Kees

-- 
Kees Cook