From 6b3478bb8b5718d86cb04f41043a8e0cce4df24c Mon Sep 17 00:00:00 2001

From: "plai@redhat.com" <plai@redhat.com>

Date: Tue, 20 Aug 2019 16:12:49 +0100

Subject: [PATCH 02/11] mmap-alloc: unfold qemu_ram_mmap()

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RH-Author: plai@redhat.com

Message-id: <1566317571-5697-3-git-send-email-plai@redhat.com>

Patchwork-id: 90083

O-Subject: [RHEL8.2 qemu-kvm PATCH 2/4] mmap-alloc: unfold qemu_ram_mmap()

Bugzilla: 1539282

RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>

RH-Acked-by: Pankaj Gupta <pagupta@redhat.com>

RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>

From: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>

Unfold parts of qemu_ram_mmap() for the sake of understanding, moving

declarations to the top, and keeping architecture-specifics in the

ifdef-else blocks.  No changes in the function behaviour.

Give ptr and ptr1 meaningful names:

  ptr  -> guardptr : pointer to the PROT_NONE guard region

  ptr1 -> ptr      : pointer to the mapped memory returned to caller

Signed-off-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>

Reviewed-by: Greg Kurz <groug@kaod.org>

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

(cherry picked from commit 2044c3e7116eeac0449dcb4a4130cc8f8b9310da)

Signed-off-by: Paul Lai <plai@redhat.com>

Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>

---

 util/mmap-alloc.c | 53 ++++++++++++++++++++++++++++++++++-------------------

 1 file changed, 34 insertions(+), 19 deletions(-)

diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c

index 55d1890..b29fcee 100644

--- a/util/mmap-alloc.c

+++ b/util/mmap-alloc.c

@@ -79,11 +79,19 @@ void *qemu_ram_mmap(int fd,

                     bool shared,

                     bool is_pmem)

 {

+    int flags;

+    int guardfd;

+    size_t offset;

+    size_t total;

+    void *guardptr;

+    void *ptr;

+

     /*

      * Note: this always allocates at least one extra page of virtual address

      * space, even if size is already aligned.

      */

-    size_t total = size + align;

+    total = size + align;

+

 #if defined(__powerpc64__) && defined(__linux__)

     /* On ppc64 mappings in the same segment (aka slice) must share the same

      * page size. Since we will be re-allocating part of this segment

@@ -93,16 +101,22 @@ void *qemu_ram_mmap(int fd,

      * We do this unless we are using the system page size, in which case

      * anonymous memory is OK.

      */

-    int anonfd = fd == -1 || qemu_fd_getpagesize(fd) == getpagesize() ? -1 : fd;

-    int flags = anonfd == -1 ? MAP_ANONYMOUS : MAP_NORESERVE;

-    void *ptr = mmap(0, total, PROT_NONE, flags | MAP_PRIVATE, anonfd, 0);

+    flags = MAP_PRIVATE;

+    if (fd == -1 || qemu_fd_getpagesize(fd) == getpagesize()) {

+        guardfd = -1;

+        flags |= MAP_ANONYMOUS;

+    } else {

+        guardfd = fd;

+        flags |= MAP_NORESERVE;

+    }

 #else

-    void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);

+    guardfd = -1;

+    flags = MAP_PRIVATE | MAP_ANONYMOUS;

 #endif

-    size_t offset;

-    void *ptr1;

-    if (ptr == MAP_FAILED) {

+    guardptr = mmap(0, total, PROT_NONE, flags, guardfd, 0);

+

+    if (guardptr == MAP_FAILED) {

         return MAP_FAILED;

     }

@@ -110,19 +124,20 @@ void *qemu_ram_mmap(int fd,

     /* Always align to host page size */

     assert(align >= getpagesize());

-    offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;

-    ptr1 = mmap(ptr + offset, size, PROT_READ | PROT_WRITE,

-                MAP_FIXED |

-                (fd == -1 ? MAP_ANONYMOUS : 0) |

-                (shared ? MAP_SHARED : MAP_PRIVATE),

-                fd, 0);

-    if (ptr1 == MAP_FAILED) {

-        munmap(ptr, total);

+    flags = MAP_FIXED;

+    flags |= fd == -1 ? MAP_ANONYMOUS : 0;

+    flags |= shared ? MAP_SHARED : MAP_PRIVATE;

+    offset = QEMU_ALIGN_UP((uintptr_t)guardptr, align) - (uintptr_t)guardptr;

+

+    ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE, flags, fd, 0);

+

+    if (ptr == MAP_FAILED) {

+        munmap(guardptr, total);

         return MAP_FAILED;

     }

     if (offset > 0) {

-        munmap(ptr, offset);

+        munmap(guardptr, offset);

     }

     /*

@@ -131,10 +146,10 @@ void *qemu_ram_mmap(int fd,

      */

     total -= offset;

     if (total > size + getpagesize()) {

-        munmap(ptr1 + size + getpagesize(), total - size - getpagesize());

+        munmap(ptr + size + getpagesize(), total - size - getpagesize());

     }

-    return ptr1;

+    return ptr;

 }

 void qemu_ram_munmap(void *ptr, size_t size)

-- 

1.8.3.1