[v2,08/14] powerpc: Handle KCOV __init vs inline mismatches

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@kernel.org>
---
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Naveen N Rao <naveen@kernel.org>
Cc: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: <linuxppc-dev@lists.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(-)

On Thu, 2025-05-22 at 21:39 -0700, Kees Cook wrote:
> 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

I assume you mean powerpc here, though I'm sure my employer is happy
that you're at least confusing us with IBM's other architecture :)

On May 22, 2025 10:24:30 PM PDT, Andrew Donnellan <ajd@linux.ibm.com> wrote:
>On Thu, 2025-05-22 at 21:39 -0700, Kees Cook wrote:
>> 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
>
>I assume you mean powerpc here, though I'm sure my employer is happy
>that you're at least confusing us with IBM's other architecture :)

Whoops! Yes. Paste-o on my part. The rest of the sentence was updated correctly though. :)

Kees Cook <kees@kernel.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@kernel.org>
> ---
> Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
> Cc: Naveen N Rao <naveen@kernel.org>
> Cc: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: <linuxppc-dev@lists.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.

-ritesh