[PATCH v2 21/31] arm64: 32-bit (compat) applications support

On Monday 20 August 2012, Pavel Machek wrote:

quoted

This patch adds support for 32-bit applications. The vectors page is a
binary blob mapped into the application user space at 0xffff0000 (the
AArch64 toolchain does not support compilation of AArch32 code). Full
compatibility with ARMv7 user space is supported. The use of deprecated
ARMv7 functionality (SWP, CP15 barriers) has been disabled by default on
AArch64 kernels and unaligned LDM/STM is not supported.

Please note that only the ARM 32-bit EABI is supported, so no OABI
compatibility.

quoted

+struct compat_statfs {
+     int             f_type;
+     int             f_bsize;
+     int             f_blocks;
+     int             f_bfree;
+     int             f_bavail;
+     int             f_files;
+     int             f_ffree;
+     compat_fsid_t   f_fsid;
+     int             f_namelen;      /* SunOS ignores this field. */

I'm sure it does. But is it good comment?

Good catch. It seems that some of the other compat platforms (x86,
sparc, powerpc) have the same thing. I guess the real solution would
be to introduce an asm-generic/compat.h file that contains a bunch
of those definitions, like

#ifndef compat_timespec
struct compat_timespec {
        compat_time_t   tv_sec;
        s32             tv_nsec;
};
#endif

#ifndef compat_timeval
struct compat_timeval {
        compat_time_t   tv_sec;
        s32             tv_usec;
};
#endif

#ifndef compat_sysctl
struct compat_sysctl {
        unsigned int    name;
        int             nlen;
        unsigned int    oldval;
        unsigned int    oldlenp;
        unsigned int    newval;
        unsigned int    newlen;
        unsigned int    __unused[4];
};
#endif

For the most part, arch/tile should have useful defaults, though not in the
case of struct statfs, because its 32 bit version does not have a statfs syscall
(it only has statfs64).

	Arnd