linux-kernel - [PATCH] x86/mm/kaiser: avoid 32-bit/PAE build warning

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Date:   Wed,  6 Dec 2017 15:15:41 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     x86@...nel.org
Cc:     Arnd Bergmann <arnd@...db.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] x86/mm/kaiser: avoid 32-bit/PAE build warning

The new kaiser_add_mapping() function is provided globally and
called from x86 code that can be used in configurations without
KAISER but with 64-bit page flags, in particular _PAGE_NX, which
uses bit 63, leading to a compiler warning:

arch/x86/kernel/ldt.c: In function 'alloc_ldt_struct':
arch/x86/include/asm/pgtable_types.h:183:24: error: conversion from 'long long unsigned int' to 'long unsigned int' changes value from '9223372036854776163' to '355' [-Werror=overflow]
 #define __PAGE_KERNEL  (__PAGE_KERNEL_EXEC | _PAGE_NX)
                        ^
arch/x86/kernel/ldt.c:104:6: note: in expansion of macro '__PAGE_KERNEL'
      __PAGE_KERNEL | _PAGE_GLOBAL);
arch/x86/kernel/ldt.c: In function 'alloc_ldt_struct':
arch/x86/include/asm/pgtable_types.h:183:24: error: conversion from 'long long unsigned int' to 'long unsigned int' changes value from '9223372036854776163' to '355' [-Werror=overflow]
 #define __PAGE_KERNEL  (__PAGE_KERNEL_EXEC | _PAGE_NX)
                        ^
arch/x86/kernel/ldt.c:104:6: note: in expansion of macro '__PAGE_KERNEL'
      __PAGE_KERNEL | _PAGE_GLOBAL);

This changes the type to u64 in the architecture-independent dummy,
and to pteval_t in the x86 specific portion that is used when KAISER
is enabled, ensuring that the flags can always fit. Unfortunately,
pteval_t is not provided by most other architectures, so we are
a little bit inconsistent here.

Fixes: efd9d1a6b30b ("x86/mm/kaiser: Unmap kernel mappings from userspace page tables, core patch")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
I only started building linux-next again today, so this probably
got noticed by others already, and it's possible someone had a better
fix for it. If so, please just ignore my version.
---
 arch/x86/include/asm/kaiser.h | 2 +-
 arch/x86/mm/kaiser.c          | 6 +++---
 include/linux/kaiser.h        | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/kaiser.h b/arch/x86/include/asm/kaiser.h
index 7c636cd25d65..5fcb9f81e615 100644
--- a/arch/x86/include/asm/kaiser.h
+++ b/arch/x86/include/asm/kaiser.h
@@ -31,7 +31,7 @@
  *  table.
  */
 extern int kaiser_add_mapping(unsigned long addr, unsigned long size,
-			      unsigned long flags);
+			      pteval_t flags);
 
 /**
  *  kaiser_add_mapping_cpu_entry - map the cpu entry area
diff --git a/arch/x86/mm/kaiser.c b/arch/x86/mm/kaiser.c
index 0ff502fa655b..2e2d340edbf0 100644
--- a/arch/x86/mm/kaiser.c
+++ b/arch/x86/mm/kaiser.c
@@ -261,7 +261,7 @@ static pte_t *kaiser_shadow_pagetable_walk(unsigned long address,
  * table pages.
  */
 int kaiser_add_user_map(const void *__start_addr, unsigned long size,
-			unsigned long flags)
+			pteval_t flags)
 {
 	unsigned long start_addr = (unsigned long)__start_addr;
 	unsigned long address = start_addr & PAGE_MASK;
@@ -312,7 +312,7 @@ int kaiser_add_user_map(const void *__start_addr, unsigned long size,
 
 int kaiser_add_user_map_ptrs(const void *__start_addr,
 			     const void *__end_addr,
-			     unsigned long flags)
+			     pteval_t flags)
 {
 	return kaiser_add_user_map(__start_addr,
 				   __end_addr - __start_addr,
@@ -470,7 +470,7 @@ static int __init kaiser_boottime_control(void)
 subsys_initcall(kaiser_boottime_control);
 
 int kaiser_add_mapping(unsigned long addr, unsigned long size,
-		       unsigned long flags)
+		       pteval_t flags)
 {
 	return kaiser_add_user_map((const void *)addr, size, flags);
 }
diff --git a/include/linux/kaiser.h b/include/linux/kaiser.h
index 77db4230a0dd..795fccf76849 100644
--- a/include/linux/kaiser.h
+++ b/include/linux/kaiser.h
@@ -20,7 +20,7 @@ static inline void kaiser_remove_mapping(unsigned long start, unsigned long size
 }
 
 static inline int kaiser_add_mapping(unsigned long addr, unsigned long size,
-				     unsigned long flags)
+				     u64 flags)
 {
 	return 0;
 }
-- 
2.9.0