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Date:   Thu, 13 Apr 2023 15:12:22 +0200
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Message-ID: <20230413131223.4135168-3-glider@google.com>
Subject: [PATCH v2 3/4] mm: kmsan: apply __must_check to non-void functions
From:   Alexander Potapenko <glider@google.com>
To:     glider@google.com
Cc:     urezki@gmail.com, hch@infradead.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, akpm@linux-foundation.org, elver@google.com,
        dvyukov@google.com, kasan-dev@googlegroups.com
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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>
---
 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