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    Subject[PATCH 4.19 475/639] x86/pgtable/32: Fix LOWMEM_PAGES constant
    Date
    From: Arnd Bergmann <arnd@arndb.de>

    [ Upstream commit 26515699863d68058e290e18e83f444925920be5 ]

    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
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 b3ec519e39827..71e1df8601765 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 */
    --
    2.20.1


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