Patchwork Add Prefer_MAP_32BIT_EXEC for Silvermont

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Submitter H.J. Lu
Date Dec. 11, 2015, 7:26 p.m.
Message ID <CAMe9rOqhK+Ws=DQZh5N8_QbDkmtcv9wx5Jo_8exO9yBmwYxf-A@mail.gmail.com>
Download mbox | patch
Permalink /patch/9988/
State New
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Comments

H.J. Lu - Dec. 11, 2015, 7:26 p.m.
On Fri, Dec 11, 2015 at 9:02 AM, Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
>
> On 11-12-2015 14:40, H.J. Lu wrote:
>> On Fri, Dec 11, 2015 at 8:23 AM, Adhemerval Zanella
>> <adhemerval.zanella@linaro.org> wrote:
>>>
>>>
>>> On 11-12-2015 13:59, H.J. Lu wrote:
>>>> On Fri, Dec 11, 2015 at 7:39 AM, Joseph Myers <joseph@codesourcery.com> wrote:
>>>>>> On Fri, 11 Dec 2015, H.J. Lu wrote:
>>>>>>
>>>>>>>> +++ b/sysdeps/unix/sysv/linux/x86_64/64/mmap.c
>>>>>>>> @@ -0,0 +1,49 @@
>>>>>>>> +/* Copyright (C) 2015 Free Software Foundation, Inc.
>>>>>>
>>>>>> All new files should have a descriptive first line before the copyright
>>>>>> notice.
>>>>>>
>>>> Here is the updated patch.
>>>
>>>>
>>>> diff --git a/sysdeps/unix/sysv/linux/x86_64/64/mmap.c b/sysdeps/unix/sysv/linux/x86_64/64/mmap.c
>>>> new file mode 100644
>>>> index 0000000..c34f633
>>>> --- /dev/null
>>>> +++ b/sysdeps/unix/sysv/linux/x86_64/64/mmap.c
>>>
>>>> +
>>>> +__ptr_t
>>>> +__mmap (__ptr_t addr, size_t len, int prot, int flags, int fd, off_t offset)
>>>> +{
>>>> +  /* If the Prefer_MAP_32BIT_EXEC bit is set, try to map executable pages
>>>> +     with MAP_32BIT first.  */
>>>> +  if (addr == NULL
>>>> +      && (prot & PROT_EXEC) != 0
>>>> +      && HAS_ARCH_FEATURE (Prefer_MAP_32BIT_EXEC))
>>>> +    {
>>>> +      addr = (__ptr_t) INLINE_SYSCALL (mmap, 6, addr, len, prot,
>>>> +                                    flags | MAP_32BIT,
>>>> +                                    fd, offset);
>>>> +      if (addr != MAP_FAILED)
>>>> +     return addr;
>>>> +    }
>>>> +  return (__ptr_t) INLINE_SYSCALL (mmap, 6, addr, len, prot, flags,
>>>> +                                fd, offset);
>>>> +}
>>>> +
>>>
>>> I would advise not add another syscall variant implementation, but rather
>>> work on make a generic implementation with adjustments made by each platform.
>>> Something like
>>>
>>> __ptr_t
>>> __mmap (__ptr_t addr, size_t len, int prot, int flags, int fd, off_t offset)
>>> {
>>>   flags = MMAP_ARCH_FLAGS (flags);
>>>   return (__ptr_t) INLINE_SYSCALL( mmap, 6, addr, len, prot, flags, fd,  offset);
>>> }
>>>
>>> And then define MMAP_ARCH_FLAG for x86 to add the MAP_32BIT when required.
>>>
>>
>> This won't work here since we fallback to the default mmap when
>> MAP_32BIT fails.
>
> So just change the MMAP_ARCH_FLAGS hook to something like:
>
>  __ptr_t ret = __mmap_arch (addr, len, prot, flags, fd, offset));
>  if (ret != MAP_FAILED)
>    ret = INLINE_SYSCALL (mmap, 6, addr, len, prot, flags, fd, offset);
>  return ret
>
> The default value for __mmap_arch could be a constant value so compiler
> could remove the the comparison if it is the case.

How about this?

Patch

diff --git a/sysdeps/unix/sysv/linux/wordsize-64/mmap.c b/sysdeps/unix/sysv/linux/wordsize-64/mmap.c
new file mode 100644
index 0000000..e098976
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/wordsize-64/mmap.c
@@ -0,0 +1,40 @@ 
+/* Linux mmap system call.  64-bit version.
+   Copyright (C) 2015 Free Software Foundation, Inc.
+
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <errno.h>
+#include <sysdep.h>
+
+/* An architecture may override this.  */
+#ifndef MMAP_PREPARE
+# define MMAP_PREPARE(addr, len, prot, flags, fd, offset)
+#endif
+
+__ptr_t
+__mmap (__ptr_t addr, size_t len, int prot, int flags, int fd, off_t offset)
+{
+  MMAP_PREPARE (addr, len, prot, flags, fd, offset);
+  return (__ptr_t) INLINE_SYSCALL (mmap, 6, addr, len, prot, flags,
+				   fd, offset);
+}
+
+weak_alias (__mmap, mmap)
+weak_alias (__mmap, mmap64)
+weak_alias (__mmap, __mmap64)
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/mmap.c b/sysdeps/unix/sysv/linux/x86_64/64/mmap.c
new file mode 100644
index 0000000..031316c
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86_64/64/mmap.c
@@ -0,0 +1,37 @@ 
+/* Linux mmap system call.  x86-64 version.
+   Copyright (C) 2015 Free Software Foundation, Inc.
+
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <ldsodefs.h>
+
+/* If the Prefer_MAP_32BIT_EXEC bit is set, try to map executable pages
+   with MAP_32BIT first.  */
+#define MMAP_PREPARE(addr, len, prot, flags, fd, offset)		\
+  if ((addr) == NULL							\
+      && ((prot) & PROT_EXEC) != 0					\
+      && HAS_ARCH_FEATURE (Prefer_MAP_32BIT_EXEC))			\
+    {									\
+      __ptr_t ret = (__ptr_t) INLINE_SYSCALL (mmap, 6, (addr), (len),	\
+					      (prot),			\
+					      (flags) | MAP_32BIT,	\
+					      (fd), (offset));		\
+      if (ret != MAP_FAILED)						\
+	return ret;							\
+    }
+
+#include <sysdeps/unix/sysv/linux/wordsize-64/mmap.c>