Re: [PATCH 20/25] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it

[Zhangjian (Bamvor)]

Hi, Arnd

On 2016/5/10 16:36, Arnd Bergmann wrote:
> On Tuesday 10 May 2016 15:42:07 Zhangjian wrote:
> > On 2016/5/6 20:37, Yury Norov wrote:
> > > On Fri, May 06, 2016 at 08:16:48PM +0800, Zhangjian (Bamvor) wrote:
> > >
> > > AFAIR, here we don't shift offset, as it's 64-bit both in user-
> > > and kernel-space,
> > In your ilp32-2.22 branch, you wrapper mmap to mmap2 in which type of
> > offset is off_t. And off_t is 32bit in ilp32, correct?
> > "sysdeps/unix/sysv/linux/aarch64/ilp32/mmap64.c"
> > /* mmap is provided by mmap as they are the same. */
> > void *__mmap (void *__addr, size_t __len, int __prot,
> >                        int __flags, int __fd, __off_t __offset)
> > {
> >      void *result;
> >      result = (void *)
> >        INLINE_SYSCALL (mmap2, 6, __addr,
> >                        __len, __prot, __flags, __fd, __offset);
> >      return result;
> > }
>
> __off_t should be 'long long' on new architectures, and map
> to __kernel_loff_t.
>
> Can you see how it is defined?
For kernel part, in "include/uapi/asm-generic/posix_types.h":
    #ifndef __kernel_long_t
    typedef long            __kernel_long_t;
    typedef unsigned long   __kernel_ulong_t;
    #endif
    typedef __kernel_long_t __kernel_off_t;
in "include/linux/types.h":
    typedef __kernel_off_t          off_t;

"include/uapi/asm-generic/posix_types.h" is uapi, we could not check
"ARCH_32BIT_OFF_T" here. Besides, the `__kernel_long_t` is long which
mean it is 32bit in ILP32. should we define something like x32?
    ```
    diff --git a/arch/arm64/include/uapi/asm/posix_types.h b/arch/arm64/include/uapi/asm/posix_types.h
    index 7985ff6..9baa8d3 100644
    --- a/arch/arm64/include/uapi/asm/posix_types.h
    +++ b/arch/arm64/include/uapi/asm/posix_types.h
    @@ -5,6 +5,9 @@ typedef unsigned short __kernel_old_uid_t;
     typedef unsigned short __kernel_old_gid_t;
      #define __kernel_old_uid_t __kernel_old_uid_t

     +typedef long long __kernel_long_t;
     +typedef unsigned long long __kernel_ulong_t;
     +
      #include <asm-generic/posix_types.h>

      #endif /*  __ASM_POSIX_TYPES_H */u
    ```
After this definition, the following kernel types is 64bit in ILP32:
    typedef __kernel_long_t         __kernel_suseconds_t;
    typedef __kernel_long_t __kernel_ssize_t;
    typedef __kernel_long_t __kernel_ptrdiff_t;
    typedef __kernel_long_t __kernel_off_t;
    typedef __kernel_long_t __kernel_time_t;
    typedef __kernel_long_t __kernel_clock_t;
    typedef __kernel_ulong_t __kernel_ino_t;
    typedef __kernel_ulong_t __kernel_size_t;

But it is not a generic way to define off_t to 64bit if
ARCH_32BIT_OFF_T is not defined. How about this one? We need to
define `__kernel_off_t` on all the old 32bit architecture like
arm:
```
diff --git a/arch/arm/include/uapi/asm/posix_types.h b/arch/arm/include/uapi/asm/posix_types.h
index d2de9cb..f9d065c 100644
--- a/arch/arm/include/uapi/asm/posix_types.h
+++ b/arch/arm/include/uapi/asm/posix_types.h
@@ -32,6 +32,9 @@ typedef unsigned short                __kernel_gid_t;
 typedef unsigned short         __kernel_old_dev_t;
 #define __kernel_old_dev_t __kernel_old_dev_t

+typedef __kernel_long_t        __kernel_off_t;
+#define __kernel_off_t
+
 #include <asm-generic/posix_types.h>

 #endif
```
And We could change the generic posix_types.h a little bit:
```
diff --git a/include/uapi/asm-generic/posix_types.h b/include/uapi/asm-generic/posix_types.h
index fe74fcc..7bbaf04 100644
--- a/include/uapi/asm-generic/posix_types.h
+++ b/include/uapi/asm-generic/posix_types.h
@@ -80,10 +80,13 @@ typedef struct {
 } __kernel_fsid_t;
 #endif

+#ifndef __kernel_off_t
+typedef long long __kernel_off_t;
+#endif
+
 /*
  * anything below here should be completely generic
  */
-typedef __kernel_long_t        __kernel_off_t;
 typedef long long      __kernel_loff_t;
 typedef __kernel_long_t        __kernel_time_t;
 typedef __kernel_long_t        __kernel_clock_t;
```

On the other hand, glibc define it own off_t in "bits/types.h":
    __STD_TYPE __OFF_T_TYPE __off_t;        /* Type of file sizes and offsets.  */
    __STD_TYPE __OFF64_T_TYPE __off64_t;    /* Type of file sizes and offsets (LFS).  */

in "sysdeps/unix/sysv/linux/aarch64/bits/typesizes.h":
    #define __OFF_T_TYPE            __SLONGWORD_TYPE
    #define __OFF64_T_TYPE          __SQUAD_TYPE

If we define off_t as 64bit in glibc:
    #define __OFF_T_TYPE           __SQUAD_TYPE

Should We need to align all the off_t syscall to 64bit syscall in
kernel?

Regards

Bamvor


> 	Arnd