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* [PATCH] x86: fix LOWMEM_PAGES constant
@ 2019-07-10 13:04 ` Arnd Bergmann
  0 siblings, 0 replies; 3+ messages in thread
From: Arnd Bergmann @ 2019-07-10 13:04 UTC (permalink / raw)
  To: Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86
  Cc: Arnd Bergmann, Boris Ostrovsky, Andy Lutomirski, Brian Gerst,
	Denys Vlasenko, H. Peter Anvin, Josh Poimboeuf, Linus Torvalds,
	Peter Zijlstra, matt, xen-devel, Ingo Molnar, Joerg Roedel,
	linux-kernel, clang-built-linux

clang points out that the computation of LOWMEM_PAGES causes
a signed integer overflow on 32-bit x86:

arch/x86/kernel/head32.c:83:20: error: signed shift result (0x100000000) requires 34 bits to represent, but 'int' only has 32 bits [-Werror,-Wshift-overflow]
                (PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT);
                                 ^~~~~~~~~~~~
arch/x86/include/asm/pgtable_32.h:109:27: note: expanded from macro 'LOWMEM_PAGES'
 #define LOWMEM_PAGES ((((2<<31) - __PAGE_OFFSET) >> PAGE_SHIFT))
                         ~^ ~~
arch/x86/include/asm/pgtable_32.h:98:34: note: expanded from macro 'PAGE_TABLE_SIZE'
 #define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD)

Use the _ULL() macro to make it a 64-bit constant.

Fixes: 1e620f9b23e5 ("x86/boot/32: Convert the 32-bit pgtable setup code from assembly to C")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/x86/include/asm/pgtable_32.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/pgtable_32.h b/arch/x86/include/asm/pgtable_32.h
index 4fe9e7fc74d3..c78da8eda8f2 100644
--- a/arch/x86/include/asm/pgtable_32.h
+++ b/arch/x86/include/asm/pgtable_32.h
@@ -106,6 +106,6 @@ do {						\
  * with only a host target support using a 32-bit type for internal
  * representation.
  */
-#define LOWMEM_PAGES ((((2<<31) - __PAGE_OFFSET) >> PAGE_SHIFT))
+#define LOWMEM_PAGES ((((_ULL(2)<<31) - __PAGE_OFFSET) >> PAGE_SHIFT))
 
 #endif /* _ASM_X86_PGTABLE_32_H */
-- 
2.20.0


^ permalink raw reply related	[flat|nested] 3+ messages in thread
* [Xen-devel] [PATCH] x86: fix LOWMEM_PAGES constant
@ 2019-07-10 13:04 ` Arnd Bergmann
  0 siblings, 0 replies; 3+ messages in thread
From: Arnd Bergmann @ 2019-07-10 13:04 UTC (permalink / raw)
  To: Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86
  Cc: Joerg Roedel, Denys Vlasenko, Arnd Bergmann, clang-built-linux,
	Peter Zijlstra, Brian Gerst, Josh Poimboeuf, linux-kernel, matt,
	Andy Lutomirski, H. Peter Anvin, xen-devel, Boris Ostrovsky,
	Linus Torvalds, Ingo Molnar

clang points out that the computation of LOWMEM_PAGES causes
a signed integer overflow on 32-bit x86:

arch/x86/kernel/head32.c:83:20: error: signed shift result (0x100000000) requires 34 bits to represent, but 'int' only has 32 bits [-Werror,-Wshift-overflow]
                (PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT);
                                 ^~~~~~~~~~~~
arch/x86/include/asm/pgtable_32.h:109:27: note: expanded from macro 'LOWMEM_PAGES'
 #define LOWMEM_PAGES ((((2<<31) - __PAGE_OFFSET) >> PAGE_SHIFT))
                         ~^ ~~
arch/x86/include/asm/pgtable_32.h:98:34: note: expanded from macro 'PAGE_TABLE_SIZE'
 #define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD)

Use the _ULL() macro to make it a 64-bit constant.

Fixes: 1e620f9b23e5 ("x86/boot/32: Convert the 32-bit pgtable setup code from assembly to C")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/x86/include/asm/pgtable_32.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/pgtable_32.h b/arch/x86/include/asm/pgtable_32.h
index 4fe9e7fc74d3..c78da8eda8f2 100644
--- a/arch/x86/include/asm/pgtable_32.h
+++ b/arch/x86/include/asm/pgtable_32.h
@@ -106,6 +106,6 @@ do {						\
  * with only a host target support using a 32-bit type for internal
  * representation.
  */
-#define LOWMEM_PAGES ((((2<<31) - __PAGE_OFFSET) >> PAGE_SHIFT))
+#define LOWMEM_PAGES ((((_ULL(2)<<31) - __PAGE_OFFSET) >> PAGE_SHIFT))
 
 #endif /* _ASM_X86_PGTABLE_32_H */
-- 
2.20.0


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^ permalink raw reply related	[flat|nested] 3+ messages in thread
* [tip:x86/urgent] x86/pgtable/32: Fix LOWMEM_PAGES constant
  2019-07-10 13:04 ` [Xen-devel] " Arnd Bergmann
  (?)
@ 2019-07-10 15:25 ` tip-bot for Arnd Bergmann
  -1 siblings, 0 replies; 3+ messages in thread
From: tip-bot for Arnd Bergmann @ 2019-07-10 15:25 UTC (permalink / raw)
  To: linux-tip-commits; +Cc: linux-kernel, arnd, tglx, hpa, mingo

Commit-ID:  26515699863d68058e290e18e83f444925920be5
Gitweb:     https://git.kernel.org/tip/26515699863d68058e290e18e83f444925920be5
Author:     Arnd Bergmann <arnd@arndb.de>
AuthorDate: Wed, 10 Jul 2019 15:04:55 +0200
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Wed, 10 Jul 2019 17:19:58 +0200

x86/pgtable/32: Fix LOWMEM_PAGES constant

clang points out that the computation of LOWMEM_PAGES causes a signed
integer overflow on 32-bit x86:

arch/x86/kernel/head32.c:83:20: error: signed shift result (0x100000000) requires 34 bits to represent, but 'int' only has 32 bits [-Werror,-Wshift-overflow]
                (PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT);
                                 ^~~~~~~~~~~~
arch/x86/include/asm/pgtable_32.h:109:27: note: expanded from macro 'LOWMEM_PAGES'
 #define LOWMEM_PAGES ((((2<<31) - __PAGE_OFFSET) >> PAGE_SHIFT))
                         ~^ ~~
arch/x86/include/asm/pgtable_32.h:98:34: note: expanded from macro 'PAGE_TABLE_SIZE'
 #define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD)

Use the _ULL() macro to make it a 64-bit constant.

Fixes: 1e620f9b23e5 ("x86/boot/32: Convert the 32-bit pgtable setup code from assembly to C")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190710130522.1802800-1-arnd@arndb.de

---
 arch/x86/include/asm/pgtable_32.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/pgtable_32.h b/arch/x86/include/asm/pgtable_32.h
index 4fe9e7fc74d3..c78da8eda8f2 100644
--- a/arch/x86/include/asm/pgtable_32.h
+++ b/arch/x86/include/asm/pgtable_32.h
@@ -106,6 +106,6 @@ do {						\
  * with only a host target support using a 32-bit type for internal
  * representation.
  */
-#define LOWMEM_PAGES ((((2<<31) - __PAGE_OFFSET) >> PAGE_SHIFT))
+#define LOWMEM_PAGES ((((_ULL(2)<<31) - __PAGE_OFFSET) >> PAGE_SHIFT))
 
 #endif /* _ASM_X86_PGTABLE_32_H */

^ permalink raw reply related	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2019-07-10 15:25 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-07-10 13:04 [PATCH] x86: fix LOWMEM_PAGES constant Arnd Bergmann
2019-07-10 13:04 ` [Xen-devel] " Arnd Bergmann
2019-07-10 15:25 ` [tip:x86/urgent] x86/pgtable/32: Fix " tip-bot for Arnd Bergmann

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