On Wednesday 11 May 2016 19:16:44 Zhangjian wrote:

Hi,

On 2016/5/11 18:12, Zhangjian (Bamvor) wrote:

quoted

Hi, Arnd

On 2016/5/11 16:09, Arnd Bergmann wrote:
 > On Wednesday 11 May 2016 10:04:16 Zhangjian wrote:
 >>> I don't remember. It's probably not important whether we have the shift
 >>> in there, as long as it's independent of the actual kernel page size and
 >>> user space and kernel agree on the calling conventions.
 >> Well. I am ok with where to shift the pages size because we get the same
 >> result. I was just thinking if we should get rid of the name of mmap2 in our
 >> ILP32 porting. Actually, it is mmap but we name it as mmap2. User may confused
 >> if they do not know the implementations.
 >
 > That is a good point: If the implementation matches the mmap() behavior rather than
 > mmap2(), we should rename the macro by doing
 >
 > #undef __NR_mmap2
 > #define __NR_mmap 222
 >
 > in the uapi/asm/unistd.h file for ilp32 mode.
Do you mean define the following things in kernel:

diff --git a/arch/arm64/include/uapi/asm/unistd.h b/arch/arm64/include/uapi/asm/unistd.h
index 1caadc2..3f79640 100644
--- a/arch/arm64/include/uapi/asm/unistd.h
+++ b/arch/arm64/include/uapi/asm/unistd.h
@@ -14,3 +14,9 @@
   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
   */
  #include <asm-generic/unistd.h>
+
+#ifdef __ILP32__
+#undef __NR_mmap2
+#define __NR_mmap 222
+#endif /* #ifdef __ILP32__ */
+

Then glibc could call mmap instead of mmap2.
I could not try it now. Because after change off_t to 64bit in glibc, stat
is fail. I may need to revert the stat relative patch.

After revert stat relative patch in glibc, mmap01-mmap14 success. But mmap16
success with segfault. I will investigate it later.

There is pointer and size_t in mmap, so, IIUC, we need to clear the top halves
of register by using COMPAT_SYSCALL_WRAP6.

Correct, good catch!

And after check the function in
arch/s390/kernel/compat_linux.c, I feel that we need to do the same thing for
pread64 and pwrite64.

But I got following error when I try to add
COMPAT_SYSCALL_WRAP4(pread64, unsigned int, fd, char __user *, buf,
size_t, count, loff_t, pos);
COMPAT_SYSCALL_WRAP4(pwrite64, unsigned int, fd, const char __user *, buf,
size_t, count, loff_t, pos);

Hmm, that is indeed tricky. I think COMPAT_SYSCALL_WRAP4 rightfully
refuses the loff_t argument here, as the common case is that this is
not possible.

Can you open-code this using a COMPAT_SYSCALL4 definition similar to what
arch/tile has, but without the merging of the two halves of the argument?

	Arnd