[Qemu-devel] [PATCH] linux-user: use libc wrapper instead of direct mremap syscall

[Qemu-devel] [PATCH] linux-user: use libc wrapper instead of direct mremap syscall

[Felix Janda]

This commit essentially reverts commit
3af72a4d98dca033492102603734cbc63cd2694a, which has replaced
five-argument calls to mremap() by direct mremap syscalls for
compatibility with glibc older than version 2.4.

The direct syscall was buggy for 64bit targets on 32bit hosts
because of the default integer type promotions. Since glibc-2.4
is now a decade old, we can remove this workaround.

Signed-off-by: Felix Janda <felix.janda@posteo.de>
---
 linux-user/mmap.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index c4371d9..ffd099d 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -17,8 +17,6 @@
  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
  */
 #include "qemu/osdep.h"
-#include <linux/mman.h>
-#include <linux/unistd.h>
 
 #include "qemu.h"
 #include "qemu-common.h"
@@ -681,10 +679,8 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
     mmap_lock();
 
     if (flags & MREMAP_FIXED) {
-        host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
-                                     old_size, new_size,
-                                     flags,
-                                     g2h(new_addr));
+        host_addr = mremap(g2h(old_addr), old_size, new_size,
+                           flags, g2h(new_addr));
 
         if (reserved_va && host_addr != MAP_FAILED) {
             /* If new and old addresses overlap then the above mremap will
@@ -700,10 +696,8 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
             errno = ENOMEM;
             host_addr = MAP_FAILED;
         } else {
-            host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
-                                         old_size, new_size,
-                                         flags | MREMAP_FIXED,
-                                         g2h(mmap_start));
+            host_addr = mremap(g2h(old_addr), old_size, new_size,
+                               flags | MREMAP_FIXED, g2h(mmap_start));
             if (reserved_va) {
                 mmap_reserve(old_addr, old_size);
             }
-- 
2.7.3

Re: [Qemu-devel] [PATCH] linux-user: use libc wrapper instead of direct mremap syscall

[Peter Maydell]

On 30 September 2016 at 16:39, Felix Janda <felix.janda@posteo.de> wrote:
> This commit essentially reverts commit
> 3af72a4d98dca033492102603734cbc63cd2694a, which has replaced
> five-argument calls to mremap() by direct mremap syscalls for
> compatibility with glibc older than version 2.4.
>
> The direct syscall was buggy for 64bit targets on 32bit hosts
> because of the default integer type promotions. Since glibc-2.4
> is now a decade old, we can remove this workaround.
>
> Signed-off-by: Felix Janda <felix.janda@posteo.de>


Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM

Re: [Qemu-devel] [PATCH] linux-user: use libc wrapper instead of direct mremap syscall

[Riku Voipio]

On Fri, Sep 30, 2016 at 07:35:45PM -0700, Peter Maydell wrote:
> On 30 September 2016 at 16:39, Felix Janda <felix.janda@posteo.de> wrote:
> > This commit essentially reverts commit
> > 3af72a4d98dca033492102603734cbc63cd2694a, which has replaced
> > five-argument calls to mremap() by direct mremap syscalls for
> > compatibility with glibc older than version 2.4.
> >
> > The direct syscall was buggy for 64bit targets on 32bit hosts
> > because of the default integer type promotions. Since glibc-2.4
> > is now a decade old, we can remove this workaround.
> >
> > Signed-off-by: Felix Janda <felix.janda@posteo.de>
> 
> 
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

Applied to linux-user, thanks

Re: [Qemu-devel] [PATCH] linux-user: use libc wrapper instead of direct mremap syscall

[Riku Voipio]

On Fri, Sep 30, 2016 at 07:39:27PM -0400, Felix Janda wrote:
> This commit essentially reverts commit
> 3af72a4d98dca033492102603734cbc63cd2694a, which has replaced
> five-argument calls to mremap() by direct mremap syscalls for
> compatibility with glibc older than version 2.4.
> 
> The direct syscall was buggy for 64bit targets on 32bit hosts
> because of the default integer type promotions. Since glibc-2.4
> is now a decade old, we can remove this workaround.

Applied this and the <poll.h> patch to linux-user

Thanks,
Riku
 
> Signed-off-by: Felix Janda <felix.janda@posteo.de>
> ---
>  linux-user/mmap.c | 14 ++++----------
>  1 file changed, 4 insertions(+), 10 deletions(-)
> 
> diff --git a/linux-user/mmap.c b/linux-user/mmap.c
> index c4371d9..ffd099d 100644
> --- a/linux-user/mmap.c
> +++ b/linux-user/mmap.c
> @@ -17,8 +17,6 @@
>   *  along with this program; if not, see <http://www.gnu.org/licenses/>.
>   */
>  #include "qemu/osdep.h"
> -#include <linux/mman.h>
> -#include <linux/unistd.h>
>  
>  #include "qemu.h"
>  #include "qemu-common.h"
> @@ -681,10 +679,8 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
>      mmap_lock();
>  
>      if (flags & MREMAP_FIXED) {
> -        host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
> -                                     old_size, new_size,
> -                                     flags,
> -                                     g2h(new_addr));
> +        host_addr = mremap(g2h(old_addr), old_size, new_size,
> +                           flags, g2h(new_addr));
>  
>          if (reserved_va && host_addr != MAP_FAILED) {
>              /* If new and old addresses overlap then the above mremap will
> @@ -700,10 +696,8 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
>              errno = ENOMEM;
>              host_addr = MAP_FAILED;
>          } else {
> -            host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
> -                                         old_size, new_size,
> -                                         flags | MREMAP_FIXED,
> -                                         g2h(mmap_start));
> +            host_addr = mremap(g2h(old_addr), old_size, new_size,
> +                               flags | MREMAP_FIXED, g2h(mmap_start));
>              if (reserved_va) {
>                  mmap_reserve(old_addr, old_size);
>              }
> -- 
> 2.7.3
> 
>