[PATCH 13/17] Add set_alias_ function and x86 implementation

[Rick Edgecombe]

This adds two new functions set_alias_default_noflush and set_alias_nv_noflush
for setting the alias mapping for the page to its default valid permissions
and to an invalid state that cannot be cached in a TLB, respectively. These
functions to not flush the TLB.

Note, __kernel_map_pages does something similar but flushes the TLB and doesn't
reset the permission bits to default on all architectures.

There is also an ARCH config ARCH_HAS_SET_ALIAS for specifying whether these
have an actual implementation or a default empty one.

Cc: Dave Hansen <dave.hansen at linux.intel.com>
Cc: Andy Lutomirski <luto at kernel.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe at intel.com>
---
 arch/Kconfig                      |  4 ++++
 arch/x86/Kconfig                  |  1 +
 arch/x86/include/asm/set_memory.h |  3 +++
 arch/x86/mm/pageattr.c            | 14 +++++++++++---
 include/linux/set_memory.h        | 10 ++++++++++
 5 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 4cfb6de48f79..4ef9db190f2d 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -249,6 +249,10 @@ config ARCH_HAS_FORTIFY_SOURCE
 config ARCH_HAS_SET_MEMORY
 	bool
 
+# Select if arch has all set_alias_nv/default() functions
+config ARCH_HAS_SET_ALIAS
+	bool
+
 # Select if arch init_task must go in the __init_task_data section
 config ARCH_TASK_STRUCT_ON_STACK
        bool
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 15af091611e2..14ad28769256 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -66,6 +66,7 @@ config X86
 	select ARCH_HAS_UACCESS_FLUSHCACHE	if X86_64
 	select ARCH_HAS_UACCESS_MCSAFE		if X86_64 && X86_MCE
 	select ARCH_HAS_SET_MEMORY
+	select ARCH_HAS_SET_ALIAS
 	select ARCH_HAS_STRICT_KERNEL_RWX
 	select ARCH_HAS_STRICT_MODULE_RWX
 	select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
diff --git a/arch/x86/include/asm/set_memory.h b/arch/x86/include/asm/set_memory.h
index 07a25753e85c..2ef4e4222df1 100644
--- a/arch/x86/include/asm/set_memory.h
+++ b/arch/x86/include/asm/set_memory.h
@@ -85,6 +85,9 @@ int set_pages_nx(struct page *page, int numpages);
 int set_pages_ro(struct page *page, int numpages);
 int set_pages_rw(struct page *page, int numpages);
 
+int set_alias_nv_noflush(struct page *page);
+int set_alias_default_noflush(struct page *page);
+
 extern int kernel_set_to_readonly;
 void set_kernel_text_rw(void);
 void set_kernel_text_ro(void);
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 4f8972311a77..3a51915a1410 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -2209,8 +2209,6 @@ int set_pages_rw(struct page *page, int numpages)
 	return set_memory_rw(addr, numpages);
 }
 
-#ifdef CONFIG_DEBUG_PAGEALLOC
-
 static int __set_pages_p(struct page *page, int numpages)
 {
 	unsigned long tempaddr = (unsigned long) page_address(page);
@@ -2249,6 +2247,17 @@ static int __set_pages_np(struct page *page, int numpages)
 	return __change_page_attr_set_clr(&cpa, 0);
 }
 
+int set_alias_nv_noflush(struct page *page)
+{
+	return __set_pages_np(page, 1);
+}
+
+int set_alias_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))
@@ -2282,7 +2291,6 @@ void __kernel_map_pages(struct page *page, int numpages, int enable)
 }
 
 #ifdef CONFIG_HIBERNATION
-
 bool kernel_page_present(struct page *page)
 {
 	unsigned int level;
diff --git a/include/linux/set_memory.h b/include/linux/set_memory.h
index 2a986d282a97..d19481ac6a8f 100644
--- a/include/linux/set_memory.h
+++ b/include/linux/set_memory.h
@@ -10,6 +10,16 @@
 
 #ifdef CONFIG_ARCH_HAS_SET_MEMORY
 #include <asm/set_memory.h>
+#ifndef CONFIG_ARCH_HAS_SET_ALIAS
+static inline int set_alias_nv_noflush(struct page *page)
+{
+	return 0;
+}
+static inline int set_alias_default_noflush(struct page *page)
+{
+	return 0;
+}
+#endif
 #else
 static inline int set_memory_ro(unsigned long addr, int numpages) { return 0; }
 static inline int set_memory_rw(unsigned long addr, int numpages) { return 0; }
-- 
2.17.1