Re: [PATCH 2/5] asm-generic: move MAP_* flags from mman-common.h to mman.h

From: Lorenzo Stoakes
Date: Wed Oct 09 2024 - 10:26:40 EST

On Wed, Sep 25, 2024 at 09:06:12PM +0000, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> powerpc and sparc include asm-generic/mman-common.h to get the MAP_* flags
> 0x008000 through 0x4000000, but those flags are all different on alpha,
> mips, parisc and xtensa.
>
> Add duplicate definitions for these along with the MAP_* flags for 0x100
> through 0x4000 that are already different on powerpc and sparc, as a
> preparation for actually sharing mman-common.h with all architectures.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
> arch/powerpc/include/uapi/asm/mman.h | 16 ++++++++++++++++
> arch/sparc/include/uapi/asm/mman.h | 15 +++++++++++++++
> include/uapi/asm-generic/mman-common.h | 16 ----------------
> include/uapi/asm-generic/mman.h | 21 +++++++++++++++++++++
> include/uapi/linux/mman.h | 5 +++++
> 5 files changed, 57 insertions(+), 16 deletions(-)
>
> diff --git a/arch/powerpc/include/uapi/asm/mman.h b/arch/powerpc/include/uapi/asm/mman.h
> index c0c737215b00..d57b347c37fe 100644
> --- a/arch/powerpc/include/uapi/asm/mman.h
> +++ b/arch/powerpc/include/uapi/asm/mman.h
> @@ -13,6 +13,11 @@
>
> #define PROT_SAO 0x10 /* Strong Access Ordering */
>
> +/* 0x01 - 0x03 are defined in linux/mman.h */
> +#define MAP_TYPE 0x0f /* Mask for type of mapping */
> +#define MAP_FIXED 0x10 /* Interpret addr exactly */
> +#define MAP_ANONYMOUS 0x20 /* don't use a file */
> +
> #define MAP_RENAME MAP_ANONYMOUS /* In SunOS terminology */
> #define MAP_NORESERVE 0x40 /* don't reserve swap pages */
> #define MAP_LOCKED 0x80
> @@ -21,6 +26,17 @@
> #define MAP_DENYWRITE 0x0800 /* ETXTBSY */
> #define MAP_EXECUTABLE 0x1000 /* mark it as an executable */
>
> +#define MAP_POPULATE 0x008000 /* populate (prefault) pagetables */
> +#define MAP_NONBLOCK 0x010000 /* do not block on IO */
> +#define MAP_STACK 0x020000 /* give out an address that is best suited for process/thread stacks */
> +#define MAP_HUGETLB 0x040000 /* create a huge page mapping */
> +#define MAP_SYNC 0x080000 /* perform synchronous page faults for the mapping */
> +#define MAP_FIXED_NOREPLACE 0x100000 /* MAP_FIXED which doesn't unmap underlying mapping */
> +
> +#define MAP_UNINITIALIZED 0x4000000 /* For anonymous mmap, memory could be
> + * uninitialized */
> +
> +
>
> #define MCL_CURRENT 0x2000 /* lock all currently mapped pages */
> #define MCL_FUTURE 0x4000 /* lock all additions to address space */
> diff --git a/arch/sparc/include/uapi/asm/mman.h b/arch/sparc/include/uapi/asm/mman.h
> index cec9f4109687..afb86698cdb1 100644
> --- a/arch/sparc/include/uapi/asm/mman.h
> +++ b/arch/sparc/include/uapi/asm/mman.h
> @@ -8,6 +8,11 @@
>
> #define PROT_ADI 0x10 /* ADI enabled */
>
> +/* 0x01 - 0x03 are defined in linux/mman.h */
> +#define MAP_TYPE 0x0f /* Mask for type of mapping */
> +#define MAP_FIXED 0x10 /* Interpret addr exactly */
> +#define MAP_ANONYMOUS 0x20 /* don't use a file */
> +
> #define MAP_RENAME MAP_ANONYMOUS /* In SunOS terminology */
> #define MAP_NORESERVE 0x40 /* don't reserve swap pages */
> #define MAP_INHERIT 0x80 /* SunOS doesn't do this, but... */
> @@ -18,6 +23,16 @@
> #define MAP_DENYWRITE 0x0800 /* ETXTBSY */
> #define MAP_EXECUTABLE 0x1000 /* mark it as an executable */
>
> +#define MAP_POPULATE 0x008000 /* populate (prefault) pagetables */
> +#define MAP_NONBLOCK 0x010000 /* do not block on IO */
> +#define MAP_STACK 0x020000 /* give out an address that is best suited for process/thread stacks */
> +#define MAP_HUGETLB 0x040000 /* create a huge page mapping */
> +#define MAP_SYNC 0x080000 /* perform synchronous page faults for the mapping */
> +#define MAP_FIXED_NOREPLACE 0x100000 /* MAP_FIXED which doesn't unmap underlying mapping */
> +
> +#define MAP_UNINITIALIZED 0x4000000 /* For anonymous mmap, memory could be
> + * uninitialized */
> +
> #define MCL_CURRENT 0x2000 /* lock all currently mapped pages */
> #define MCL_FUTURE 0x4000 /* lock all additions to address space */
> #define MCL_ONFAULT 0x8000 /* lock all pages that are faulted in */
> diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h
> index 792ad5599d9c..8d66d2dabaa8 100644
> --- a/include/uapi/asm-generic/mman-common.h
> +++ b/include/uapi/asm-generic/mman-common.h
> @@ -17,22 +17,6 @@
> #define PROT_GROWSDOWN 0x01000000 /* mprotect flag: extend change to start of growsdown vma */
> #define PROT_GROWSUP 0x02000000 /* mprotect flag: extend change to end of growsup vma */
>
> -/* 0x01 - 0x03 are defined in linux/mman.h */
> -#define MAP_TYPE 0x0f /* Mask for type of mapping */
> -#define MAP_FIXED 0x10 /* Interpret addr exactly */
> -#define MAP_ANONYMOUS 0x20 /* don't use a file */
> -

Hm, maybe I'm missing something, but why are we duplicating these?

> -/* 0x0100 - 0x4000 flags are defined in asm-generic/mman.h */
> -#define MAP_POPULATE 0x008000 /* populate (prefault) pagetables */
> -#define MAP_NONBLOCK 0x010000 /* do not block on IO */
> -#define MAP_STACK 0x020000 /* give out an address that is best suited for process/thread stacks */
> -#define MAP_HUGETLB 0x040000 /* create a huge page mapping */
> -#define MAP_SYNC 0x080000 /* perform synchronous page faults for the mapping */
> -#define MAP_FIXED_NOREPLACE 0x100000 /* MAP_FIXED which doesn't unmap underlying mapping */
> -
> -#define MAP_UNINITIALIZED 0x4000000 /* For anonymous mmap, memory could be
> - * uninitialized */
> -
> /*
> * Flags for mlock
> */
> diff --git a/include/uapi/asm-generic/mman.h b/include/uapi/asm-generic/mman.h
> index 57e8195d0b53..f26f9b4c03e1 100644
> --- a/include/uapi/asm-generic/mman.h
> +++ b/include/uapi/asm-generic/mman.h
> @@ -4,12 +4,33 @@
>
> #include <asm-generic/mman-common.h>
>
> +/*
> + * 0x01 - 0x03 are defined in linux/mman.h
> + * 0x04 - 0x200000 are architecture specific
> + * 0x200000 - 0x2000000 are available for common assignments in linux/mman.h
> + * 0x4000000 - 0x80000000 are used for hugepage encodings
> + */
> +#define MAP_TYPE 0x0f /* Mask for type of mapping */
> +#define MAP_FIXED 0x10 /* Interpret addr exactly */
> +#define MAP_ANONYMOUS 0x20 /* don't use a file */
> +
> #define MAP_GROWSDOWN 0x0100 /* stack-like segment */
> #define MAP_DENYWRITE 0x0800 /* ETXTBSY */
> #define MAP_EXECUTABLE 0x1000 /* mark it as an executable */
> #define MAP_LOCKED 0x2000 /* pages are locked */
> #define MAP_NORESERVE 0x4000 /* don't check for reservations */
>
> +#define MAP_POPULATE 0x008000 /* populate (prefault) pagetables */
> +#define MAP_NONBLOCK 0x010000 /* do not block on IO */
> +#define MAP_STACK 0x020000 /* give out an address that is best suited for process/thread stacks */
> +#define MAP_HUGETLB 0x040000 /* create a huge page mapping */
> +#define MAP_SYNC 0x080000 /* perform synchronous page faults for the mapping */
> +#define MAP_FIXED_NOREPLACE 0x100000 /* MAP_FIXED which doesn't unmap underlying mapping */
> +
> +#define MAP_UNINITIALIZED 0x4000000 /* For anonymous mmap, memory could be
> + * uninitialized */
> +
> +
> /*
> * Bits [26:31] are reserved, see asm-generic/hugetlb_encode.h
> * for MAP_HUGETLB usage
> diff --git a/include/uapi/linux/mman.h b/include/uapi/linux/mman.h
> index e89d00528f2f..b70cb06dd7ef 100644
> --- a/include/uapi/linux/mman.h
> +++ b/include/uapi/linux/mman.h
> @@ -18,6 +18,11 @@
> #define MAP_PRIVATE 0x02 /* Changes are private */
> #define MAP_SHARED_VALIDATE 0x03 /* share + validate extension flags */
> #define MAP_DROPPABLE 0x08 /* Zero memory under memory pressure. */
> +/*
> + * 0x10 through 0x200000 are used for architecture specific definitions
> + * in asm/mman.h, numbers 0x400000 through 0x2000000 are currently
> + * available on all architectures.
> + */

Nice to add this documentation!

>
> /*
> * Huge page size encoding when MAP_HUGETLB is specified, and a huge page
> --
> 2.39.2
>