Re: [PATCH v2 3/4] mm: kmsan: apply __must_check to non-void functions

[Marco Elver <elver@google.com>]

On Thu, 13 Apr 2023 at 15:12, 'Alexander Potapenko' via kasan-dev
<kasan-dev@googlegroups.com> wrote:
>
> Non-void KMSAN hooks may return error codes that indicate that KMSAN
> failed to reflect the changed memory state in the metadata (e.g. it
> could not create the necessary memory mappings). In such cases the
> callers should handle the errors to prevent the tool from using the
> inconsistent metadata in the future.
>
> We mark non-void hooks with __must_check so that error handling is not
> skipped.
>
> Signed-off-by: Alexander Potapenko <glider@google.com>

Reviewed-by: Marco Elver <elver@google.com>

> ---
>  include/linux/kmsan.h | 43 ++++++++++++++++++++++---------------------
>  1 file changed, 22 insertions(+), 21 deletions(-)
>
> diff --git a/include/linux/kmsan.h b/include/linux/kmsan.h
> index 30b17647ce3c7..e0c23a32cdf01 100644
> --- a/include/linux/kmsan.h
> +++ b/include/linux/kmsan.h
> @@ -54,7 +54,8 @@ void __init kmsan_init_runtime(void);
>   * Freed pages are either returned to buddy allocator or held back to be used
>   * as metadata pages.
>   */
> -bool __init kmsan_memblock_free_pages(struct page *page, unsigned int order);
> +bool __init __must_check kmsan_memblock_free_pages(struct page *page,
> +                                                  unsigned int order);
>
>  /**
>   * kmsan_alloc_page() - Notify KMSAN about an alloc_pages() call.
> @@ -137,9 +138,11 @@ void kmsan_kfree_large(const void *ptr);
>   * vmalloc metadata address range. Returns 0 on success, callers must check
>   * for non-zero return value.
>   */
> -int kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,
> -                                  pgprot_t prot, struct page **pages,
> -                                  unsigned int page_shift);
> +int __must_check kmsan_vmap_pages_range_noflush(unsigned long start,
> +                                               unsigned long end,
> +                                               pgprot_t prot,
> +                                               struct page **pages,
> +                                               unsigned int page_shift);
>
>  /**
>   * kmsan_vunmap_kernel_range_noflush() - Notify KMSAN about a vunmap.
> @@ -163,9 +166,9 @@ void kmsan_vunmap_range_noflush(unsigned long start, unsigned long end);
>   * virtual memory. Returns 0 on success, callers must check for non-zero return
>   * value.
>   */
> -int kmsan_ioremap_page_range(unsigned long addr, unsigned long end,
> -                            phys_addr_t phys_addr, pgprot_t prot,
> -                            unsigned int page_shift);
> +int __must_check kmsan_ioremap_page_range(unsigned long addr, unsigned long end,
> +                                         phys_addr_t phys_addr, pgprot_t prot,
> +                                         unsigned int page_shift);
>
>  /**
>   * kmsan_iounmap_page_range() - Notify KMSAN about a iounmap_page_range() call.
> @@ -237,8 +240,8 @@ static inline void kmsan_init_runtime(void)
>  {
>  }
>
> -static inline bool kmsan_memblock_free_pages(struct page *page,
> -                                            unsigned int order)
> +static inline bool __must_check kmsan_memblock_free_pages(struct page *page,
> +                                                         unsigned int order)
>  {
>         return true;
>  }
> @@ -251,10 +254,9 @@ static inline void kmsan_task_exit(struct task_struct *task)
>  {
>  }
>
> -static inline int kmsan_alloc_page(struct page *page, unsigned int order,
> -                                  gfp_t flags)
> +static inline void kmsan_alloc_page(struct page *page, unsigned int order,
> +                                   gfp_t flags)
>  {
> -       return 0;
>  }
>
>  static inline void kmsan_free_page(struct page *page, unsigned int order)
> @@ -283,11 +285,9 @@ static inline void kmsan_kfree_large(const void *ptr)
>  {
>  }
>
> -static inline int kmsan_vmap_pages_range_noflush(unsigned long start,
> -                                                unsigned long end,
> -                                                pgprot_t prot,
> -                                                struct page **pages,
> -                                                unsigned int page_shift)
> +static inline int __must_check kmsan_vmap_pages_range_noflush(
> +       unsigned long start, unsigned long end, pgprot_t prot,
> +       struct page **pages, unsigned int page_shift)
>  {
>         return 0;
>  }
> @@ -297,10 +297,11 @@ static inline void kmsan_vunmap_range_noflush(unsigned long start,
>  {
>  }
>
> -static inline int kmsan_ioremap_page_range(unsigned long start,
> -                                          unsigned long end,
> -                                          phys_addr_t phys_addr, pgprot_t prot,
> -                                          unsigned int page_shift)
> +static inline int __must_check kmsan_ioremap_page_range(unsigned long start,
> +                                                       unsigned long end,
> +                                                       phys_addr_t phys_addr,
> +                                                       pgprot_t prot,
> +                                                       unsigned int page_shift)
>  {
>         return 0;
>  }
> --
> 2.40.0.577.gac1e443424-goog
>
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