[Qemu-devel] [PATCH v4 0/2] trivial changes on util/mmap-alloc

[Qemu-devel] [PATCH v4 0/2] trivial changes on util/mmap-alloc

[Cao jin]

Cao jin (2):
  util/mmap-alloc: check parameter before using
  util/mmap-alloc: refactor a little bit for readability

 util/mmap-alloc.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

-- 
2.1.0

[Qemu-devel] [PATCH v4 1/2] util/mmap-alloc: check parameter before using

[Cao jin]

Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
---
 util/mmap-alloc.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
index 5a85aa3..d713a72 100644
--- a/util/mmap-alloc.c
+++ b/util/mmap-alloc.c
@@ -12,6 +12,7 @@
 
 #include "qemu/osdep.h"
 #include "qemu/mmap-alloc.h"
+#include "qemu/host-utils.h"
 
 #define HUGETLBFS_MAGIC       0x958458f6
 
@@ -61,18 +62,18 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
 #else
     void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
 #endif
-    size_t offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;
+    size_t offset;
     void *ptr1;
 
     if (ptr == MAP_FAILED) {
         return MAP_FAILED;
     }
 
-    /* Make sure align is a power of 2 */
-    assert(!(align & (align - 1)));
+    assert(is_power_of_2(align));
     /* 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) |
-- 
2.1.0

[Qemu-devel] [PATCH v4 2/2] util/mmap-alloc: refactor a little bit for readability

[Cao jin]

1st mmap returns *ptr* which aligns to host page size,

    |             size + align               |
    ------------------------------------------
 ptr

input param *align* could be 1M, or 2M, or host page size. After
QEMU_ALIGN_UP, offset will >= 0

2nd mmap use flag MAP_FIXED, then it return ptr+offset, or else fail.
If it success, then we will have something like:

    | offset |          size             |
    --------------------------------------
 ptr      ptr1

*ptr1* is what we really want to return, it equals ptr+offset.

Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
---
 util/mmap-alloc.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

This one may be controversial, take it or not as you will:)

diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
index d713a72..2f55f5e 100644
--- a/util/mmap-alloc.c
+++ b/util/mmap-alloc.c
@@ -84,22 +84,20 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
         return MAP_FAILED;
     }
 
-    ptr += offset;
-    total -= offset;
-
     if (offset > 0) {
-        munmap(ptr - offset, offset);
+        munmap(ptr, offset);
     }
 
     /*
      * Leave a single PROT_NONE page allocated after the RAM block, to serve as
      * a guard page guarding against potential buffer overflows.
      */
+    total -= offset;
     if (total > size + getpagesize()) {
-        munmap(ptr + size + getpagesize(), total - size - getpagesize());
+        munmap(ptr1 + size + getpagesize(), total - size - getpagesize());
     }
 
-    return ptr;
+    return ptr1;
 }
 
 void qemu_ram_munmap(void *ptr, size_t size)
-- 
2.1.0

Re: [Qemu-devel] [PATCH v4 1/2] util/mmap-alloc: check parameter before using

[Thomas Huth]

On 02.11.2016 14:44, Cao jin wrote:
> Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
> ---
>  util/mmap-alloc.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
> index 5a85aa3..d713a72 100644
> --- a/util/mmap-alloc.c
> +++ b/util/mmap-alloc.c
> @@ -12,6 +12,7 @@
>  
>  #include "qemu/osdep.h"
>  #include "qemu/mmap-alloc.h"
> +#include "qemu/host-utils.h"
>  
>  #define HUGETLBFS_MAGIC       0x958458f6
>  
> @@ -61,18 +62,18 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
>  #else
>      void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
>  #endif
> -    size_t offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;
> +    size_t offset;
>      void *ptr1;
>  
>      if (ptr == MAP_FAILED) {
>          return MAP_FAILED;
>      }
>  
> -    /* Make sure align is a power of 2 */
> -    assert(!(align & (align - 1)));
> +    assert(is_power_of_2(align));
>      /* 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) |
> 

Reviewed-by: Thomas Huth <thuth@redhat.com>

Re: [Qemu-devel] [PATCH v4 1/2] util/mmap-alloc: check parameter before using

[Cao jin]

ping

On 11/02/2016 09:44 PM, Cao jin wrote:
> Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
> ---
>  util/mmap-alloc.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
> index 5a85aa3..d713a72 100644
> --- a/util/mmap-alloc.c
> +++ b/util/mmap-alloc.c
> @@ -12,6 +12,7 @@
>  
>  #include "qemu/osdep.h"
>  #include "qemu/mmap-alloc.h"
> +#include "qemu/host-utils.h"
>  
>  #define HUGETLBFS_MAGIC       0x958458f6
>  
> @@ -61,18 +62,18 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
>  #else
>      void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
>  #endif
> -    size_t offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;
> +    size_t offset;
>      void *ptr1;
>  
>      if (ptr == MAP_FAILED) {
>          return MAP_FAILED;
>      }
>  
> -    /* Make sure align is a power of 2 */
> -    assert(!(align & (align - 1)));
> +    assert(is_power_of_2(align));
>      /* 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) |
> 

-- 
Sincerely,
Cao jin

Re: [Qemu-devel] [PATCH v4 0/2] trivial changes on util/mmap-alloc

[Michael Tokarev]

02.11.2016 16:44, Cao jin wrote:
> Cao jin (2):
>   util/mmap-alloc: check parameter before using
>   util/mmap-alloc: refactor a little bit for readability
> 
>  util/mmap-alloc.c | 17 ++++++++---------
>  1 file changed, 8 insertions(+), 9 deletions(-)

Applied (finally) to -trivial, thank you very much!

/mjt