Subject: [PATCH 3/4] arch, mm: restore dependency of __kernel_map_pages() of DEBUG_PAGEALLOC

From: Mike Rapoport <[email-masked]>
Date: Sun, 25 Oct 2020 12:15:54 +0200

From: Mike Rapoport <[email-masked]>

The design of DEBUG_PAGEALLOC presumes that __kernel_map_pages() must never
fail. With this assumption is wouldn't be safe to allow general usage of
this function.

Moreover, some architectures that implement __kernel_map_pages() have this
function guarded by #ifdef DEBUG_PAGEALLOC and some refuse to map/unmap
pages when page allocation debugging is disabled at runtime.

As all the users of __kernel_map_pages() were converted to use
debug_pagealloc_map_pages() it is safe to make it available only when
DEBUG_PAGEALLOC is set.

Signed-off-by: Mike Rapoport <[email-masked]>
---
 arch/Kconfig                     |  3 +++
 arch/arm64/Kconfig               |  4 +---
 arch/arm64/mm/pageattr.c         |  6 ++++--
 arch/powerpc/Kconfig             |  5 +----
 arch/riscv/Kconfig               |  4 +---
 arch/riscv/include/asm/pgtable.h |  2 --
 arch/riscv/mm/pageattr.c         |  2 ++
 arch/s390/Kconfig                |  4 +---
 arch/sparc/Kconfig               |  4 +---
 arch/x86/Kconfig                 |  4 +---
 arch/x86/mm/pat/set_memory.c     |  2 ++
 include/linux/mm.h               | 10 +++++++---
 12 files changed, 24 insertions(+), 26 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 56b6ccc0e32d..56d4752b6db6 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1028,6 +1028,9 @@ config HAVE_STATIC_CALL_INLINE
 	bool
 	depends on HAVE_STATIC_CALL
 
+config ARCH_SUPPORTS_DEBUG_PAGEALLOC
+	bool
+
 source "kernel/gcov/Kconfig"
 
 source "scripts/gcc-plugins/Kconfig"
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 08fa3a1c50f0..1d4da0843668 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -71,6 +71,7 @@ config ARM64
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS
 	select ARCH_USE_SYM_ANNOTATIONS
+	select ARCH_SUPPORTS_DEBUG_PAGEALLOC
 	select ARCH_SUPPORTS_MEMORY_FAILURE
 	select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK
 	select ARCH_SUPPORTS_ATOMIC_RMW
@@ -1004,9 +1005,6 @@ config HOLES_IN_ZONE
 
 source "kernel/Kconfig.hz"
 
-config ARCH_SUPPORTS_DEBUG_PAGEALLOC
-	def_bool y
-
 config ARCH_SPARSEMEM_ENABLE
 	def_bool y
 	select SPARSEMEM_VMEMMAP_ENABLE
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index 1b94f5b82654..18613d8834db 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -178,13 +178,15 @@ int set_direct_map_default_noflush(struct page *page)
 				   PAGE_SIZE, change_page_range, &data);
 }
 
+#ifdef CONFIG_DEBUG_PAGEALLOC
 void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
-	if (!debug_pagealloc_enabled() && !rodata_full)
+	if (!rodata_full)
 		return;
 
 	set_memory_valid((unsigned long)page_address(page), numpages, enable);
 }
+#endif /* CONFIG_DEBUG_PAGEALLOC */
 
 /*
  * This function is used to determine if a linear map page has been marked as
@@ -204,7 +206,7 @@ bool kernel_page_present(struct page *page)
 	pte_t *ptep;
 	unsigned long addr = (unsigned long)page_address(page);
 
-	if (!debug_pagealloc_enabled() && !rodata_full)
+	if (!rodata_full)
 		return true;
 
 	pgdp = pgd_offset_k(addr);
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index e9f13fe08492..ad8a83f3ddca 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -146,6 +146,7 @@ config PPC
 	select ARCH_MIGHT_HAVE_PC_SERIO
 	select ARCH_OPTIONAL_KERNEL_RWX		if ARCH_HAS_STRICT_KERNEL_RWX
 	select ARCH_SUPPORTS_ATOMIC_RMW
+	select ARCH_SUPPORTS_DEBUG_PAGEALLOC	if PPC32 || PPC_BOOK3S_64
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_CMPXCHG_LOCKREF		if PPC64
 	select ARCH_USE_QUEUED_RWLOCKS		if PPC_QUEUED_SPINLOCKS
@@ -355,10 +356,6 @@ config PPC_OF_PLATFORM_PCI
 	depends on PCI
 	depends on PPC64 # not supported on 32 bits yet
 
-config ARCH_SUPPORTS_DEBUG_PAGEALLOC
-	depends on PPC32 || PPC_BOOK3S_64
-	def_bool y
-
 config ARCH_SUPPORTS_UPROBES
 	def_bool y
 
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index d5e7ca08f22c..c704562ba45e 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -14,6 +14,7 @@ config RISCV
 	def_bool y
 	select ARCH_CLOCKSOURCE_INIT
 	select ARCH_SUPPORTS_ATOMIC_RMW
+	select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
 	select ARCH_HAS_BINFMT_FLAT
 	select ARCH_HAS_DEBUG_VM_PGTABLE
 	select ARCH_HAS_DEBUG_VIRTUAL if MMU
@@ -153,9 +154,6 @@ config ARCH_SELECT_MEMORY_MODEL
 config ARCH_WANT_GENERAL_HUGETLB
 	def_bool y
 
-config ARCH_SUPPORTS_DEBUG_PAGEALLOC
-	def_bool y
-
 config SYS_SUPPORTS_HUGETLBFS
 	depends on MMU
 	def_bool y
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 183f1f4b2ae6..41a72861987c 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -461,8 +461,6 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
 #define VMALLOC_START		0
 #define VMALLOC_END		TASK_SIZE
 
-static inline void __kernel_map_pages(struct page *page, int numpages, int enable) {}
-
 #endif /* !CONFIG_MMU */
 
 #define kern_addr_valid(addr)   (1) /* FIXME */
diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c
index 19fecb362d81..321b09d2e2ea 100644
--- a/arch/riscv/mm/pageattr.c
+++ b/arch/riscv/mm/pageattr.c
@@ -184,6 +184,7 @@ int set_direct_map_default_noflush(struct page *page)
 	return ret;
 }
 
+#ifdef CONFIG_DEBUG_PAGEALLOC
 void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
 	if (!debug_pagealloc_enabled())
@@ -196,3 +197,4 @@ void __kernel_map_pages(struct page *page, int numpages, int enable)
 		__set_memory((unsigned long)page_address(page), numpages,
 			     __pgprot(0), __pgprot(_PAGE_PRESENT));
 }
+#endif
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 34371539a9b9..0a42d457bff4 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -35,9 +35,6 @@ config GENERIC_LOCKBREAK
 config PGSTE
 	def_bool y if KVM
 
-config ARCH_SUPPORTS_DEBUG_PAGEALLOC
-	def_bool y
-
 config AUDIT_ARCH
 	def_bool y
 
@@ -106,6 +103,7 @@ config S390
 	select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE
 	select ARCH_STACKWALK
 	select ARCH_SUPPORTS_ATOMIC_RMW
+	select ARCH_SUPPORTS_DEBUG_PAGEALLOC
 	select ARCH_SUPPORTS_NUMA_BALANCING
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_CMPXCHG_LOCKREF
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index a6ca135442f9..2c729b8d097a 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -88,6 +88,7 @@ config SPARC64
 	select HAVE_C_RECORDMCOUNT
 	select HAVE_ARCH_AUDITSYSCALL
 	select ARCH_SUPPORTS_ATOMIC_RMW
+	select ARCH_SUPPORTS_DEBUG_PAGEALLOC
 	select HAVE_NMI
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select ARCH_USE_QUEUED_RWLOCKS
@@ -148,9 +149,6 @@ config GENERIC_ISA_DMA
 	bool
 	default y if SPARC32
 
-config ARCH_SUPPORTS_DEBUG_PAGEALLOC
-	def_bool y if SPARC64
-
 config PGTABLE_LEVELS
 	default 4 if 64BIT
 	default 3
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f6946b81f74a..0db3fb1da70c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -91,6 +91,7 @@ config X86
 	select ARCH_STACKWALK
 	select ARCH_SUPPORTS_ACPI
 	select ARCH_SUPPORTS_ATOMIC_RMW
+	select ARCH_SUPPORTS_DEBUG_PAGEALLOC
 	select ARCH_SUPPORTS_NUMA_BALANCING	if X86_64
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_QUEUED_RWLOCKS
@@ -329,9 +330,6 @@ config ZONE_DMA32
 config AUDIT_ARCH
 	def_bool y if X86_64
 
-config ARCH_SUPPORTS_DEBUG_PAGEALLOC
-	def_bool y
-
 config KASAN_SHADOW_OFFSET
 	hex
 	depends on KASAN
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 40baa90e74f4..7f248fc45317 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -2194,6 +2194,7 @@ int set_direct_map_default_noflush(struct page *page)
 	return __set_pages_p(page, 1);
 }
 
+#ifdef CONFIG_DEBUG_PAGEALLOC
 void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
 	if (PageHighMem(page))
@@ -2225,6 +2226,7 @@ void __kernel_map_pages(struct page *page, int numpages, int enable)
 
 	arch_flush_lazy_mmu_mode();
 }
+#endif /* CONFIG_DEBUG_PAGEALLOC */
 
 #ifdef CONFIG_HIBERNATION
 bool kernel_page_present(struct page *page)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 14e397f3752c..ab0ef6bd351d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2924,7 +2924,11 @@ static inline bool debug_pagealloc_enabled_static(void)
 	return static_branch_unlikely(&_debug_pagealloc_enabled);
 }
 
-#if defined(CONFIG_DEBUG_PAGEALLOC) || defined(CONFIG_ARCH_HAS_SET_DIRECT_MAP)
+#ifdef CONFIG_DEBUG_PAGEALLOC
+/*
+ * To support DEBUG_PAGEALLOC architecture must ensure that
+ * __kernel_map_pages() never fails
+ */
 extern void __kernel_map_pages(struct page *page, int numpages, int enable);
 
 static inline void debug_pagealloc_map_pages(struct page *page,
@@ -2937,13 +2941,13 @@ static inline void debug_pagealloc_map_pages(struct page *page,
 #ifdef CONFIG_HIBERNATION
 extern bool kernel_page_present(struct page *page);
 #endif	/* CONFIG_HIBERNATION */
-#else	/* CONFIG_DEBUG_PAGEALLOC || CONFIG_ARCH_HAS_SET_DIRECT_MAP */
+#else	/* CONFIG_DEBUG_PAGEALLOC */
 static inline void debug_pagealloc_map_pages(struct page *page,
 					     int numpages, int enable) {}
 #ifdef CONFIG_HIBERNATION
 static inline bool kernel_page_present(struct page *page) { return true; }
 #endif	/* CONFIG_HIBERNATION */
-#endif	/* CONFIG_DEBUG_PAGEALLOC || CONFIG_ARCH_HAS_SET_DIRECT_MAP */
+#endif	/* CONFIG_DEBUG_PAGEALLOC */
 
 #ifdef __HAVE_ARCH_GATE_AREA
 extern struct vm_area_struct *get_gate_vma(struct mm_struct *mm);
-- 
2.28.0