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    Subject[RFC PATCH 5/5] mm: introduce MADV_DOEXEC
    Date
    madvise MADV_DOEXEC preserves a memory range across exec.  Initially
    only supported for non-executable, non-stack, anonymous memory.
    MADV_DONTEXEC reverts the effect of a previous MADV_DOXEXEC call and
    undoes the preservation of the range. After a successful exec call,
    the behavior of all ranges reverts to MADV_DONTEXEC.

    Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
    Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.com>
    ---
    include/uapi/asm-generic/mman-common.h | 3 +++
    mm/madvise.c | 25 +++++++++++++++++++++++++
    2 files changed, 28 insertions(+)

    diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h
    index f94f65d429be..7c5f616b28f7 100644
    --- a/include/uapi/asm-generic/mman-common.h
    +++ b/include/uapi/asm-generic/mman-common.h
    @@ -72,6 +72,9 @@
    #define MADV_COLD 20 /* deactivate these pages */
    #define MADV_PAGEOUT 21 /* reclaim these pages */

    +#define MADV_DOEXEC 22 /* do inherit across exec */
    +#define MADV_DONTEXEC 23 /* don't inherit across exec */
    +
    /* compatibility flags */
    #define MAP_FILE 0

    diff --git a/mm/madvise.c b/mm/madvise.c
    index dd1d43cf026d..b447fa748649 100644
    --- a/mm/madvise.c
    +++ b/mm/madvise.c
    @@ -103,6 +103,26 @@ static long madvise_behavior(struct vm_area_struct *vma,
    case MADV_KEEPONFORK:
    new_flags &= ~VM_WIPEONFORK;
    break;
    + case MADV_DOEXEC:
    + /*
    + * MADV_DOEXEC is only supported on private, non-executable,
    + * non-stack anonymous memory and if the VM_EXEC_KEEP flag
    + * is available.
    + */
    + if (!VM_EXEC_KEEP || vma->vm_file || vma->vm_flags & (VM_EXEC|VM_SHARED|VM_STACK)) {
    + error = -EINVAL;
    + goto out;
    + }
    + new_flags |= (new_flags & ~VM_MAYEXEC) | VM_EXEC_KEEP;
    + break;
    + case MADV_DONTEXEC:
    + if (!VM_EXEC_KEEP) {
    + error = -EINVAL;
    + goto out;
    + }
    + if (new_flags & VM_EXEC_KEEP)
    + new_flags |= (new_flags & ~VM_EXEC_KEEP) | VM_MAYEXEC;
    + break;
    case MADV_DONTDUMP:
    new_flags |= VM_DONTDUMP;
    break;
    @@ -983,6 +1003,8 @@ static int madvise_inject_error(int behavior,
    case MADV_SOFT_OFFLINE:
    case MADV_HWPOISON:
    #endif
    + case MADV_DOEXEC:
    + case MADV_DONTEXEC:
    return true;

    default:
    @@ -1037,6 +1059,9 @@ static int madvise_inject_error(int behavior,
    * MADV_DONTDUMP - the application wants to prevent pages in the given range
    * from being included in its core dump.
    * MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump.
    + * MADV_DOEXEC - On exec, preserve and duplicate this area in the new process
    + * if the new process allows it.
    + * MADV_DONTEXEC - Undo the effect of MADV_DOEXEC.
    *
    * return values:
    * zero - success
    --
    1.8.3.1
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