Re: [Qemu-devel] [PATCH] Implement fstatat64() syscall

["Kirill A. Shutemov" <kirill@shutemov.name>]

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On Fri, Sep 19, 2008 at 05:09:18PM +0300, Riku Voipio wrote:
> On Thu, Sep 18, 2008 at 06:07:03PM +0300, Kirill A. Shutemov wrote:
> > Move transformation of struct stat64 into the separate function and
> > implement fstatat64() using it.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
> > ---
> >  linux-user/syscall.c |  141 +++++++++++++++++++++++++++++--------------------
> >  1 files changed, 83 insertions(+), 58 deletions(-)
> > 
> > diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> > index 88b44b8..ac7e7d9 100644
> > --- a/linux-user/syscall.c
> > +++ b/linux-user/syscall.c
> > @@ -156,6 +156,7 @@ static type name (type1 arg1,type2 arg2,type3 arg3,type4 arg4,type5 arg5,	\
> >  #define __NR_sys_faccessat __NR_faccessat
> >  #define __NR_sys_fchmodat __NR_fchmodat
> >  #define __NR_sys_fchownat __NR_fchownat
> > +#define __NR_sys_fstatat64 __NR_fstatat64
> >  #define __NR_sys_getcwd1 __NR_getcwd
> >  #define __NR_sys_getdents __NR_getdents
> >  #define __NR_sys_getdents64 __NR_getdents64
> > @@ -200,6 +201,10 @@ _syscall4(int,sys_fchmodat,int,dirfd,const char *,pathname,
> >  _syscall5(int,sys_fchownat,int,dirfd,const char *,pathname,
> >            uid_t,owner,gid_t,group,int,flags)
> >  #endif
> > +#if defined(TARGET_NR_fstatat64) && defined(__NR_fstatat64)
> > +_syscall4(int,sys_fstatat64,int,dirfd,const char *,pathname,
> > +         struct stat *,buf,int,flags)
> > +#endif
> >  _syscall2(int,sys_getcwd1,char *,buf,size_t,size)
> >  #if TARGET_ABI_BITS == 32
> >  _syscall3(int, sys_getdents, uint, fd, struct dirent *, dirp, uint, count);
> > @@ -3149,6 +3154,67 @@ static inline abi_long host_to_target_timespec(abi_ulong target_addr,
> >      return 0;
> >  }
> >  
> > +#ifdef TARGET_NR_stat64
> > +static inline abi_long host_to_target_stat64(void *cpu_env,
> > +					     abi_ulong target_addr,
> > +					     struct stat *host_st)
> > +{
> > +#ifdef TARGET_ARM
> > +	if (((CPUARMState *)cpu_env)->eabi) {
> > +		struct target_eabi_stat64 *target_st;
> > +
> > +		if (!lock_user_struct(VERIFY_WRITE, target_st, target_addr, 0))
> > +			return -TARGET_EFAULT;
> > +		memset(target_st, 0, sizeof(struct target_eabi_stat64));
> > +		__put_user(host_st->st_dev, &target_st->st_dev);
> > +		__put_user(host_st->st_ino, &target_st->st_ino);
> > +#ifdef TARGET_STAT64_HAS_BROKEN_ST_INO
> > +		__put_user(host_st->st_ino, &target_st->__st_ino);
> > +#endif
> > +		__put_user(host_st->st_mode, &target_st->st_mode);
> > +		__put_user(host_st->st_nlink, &target_st->st_nlink);
> > +		__put_user(host_st->st_uid, &target_st->st_uid);
> > +		__put_user(host_st->st_gid, &target_st->st_gid);
> > +		__put_user(host_st->st_rdev, &target_st->st_rdev);
> > +		__put_user(host_st->st_size, &target_st->st_size);
> > +		__put_user(host_st->st_blksize, &target_st->st_blksize);
> > +		__put_user(host_st->st_blocks, &target_st->st_blocks);
> > +		__put_user(host_st->st_atime, &target_st->target_st_atime);
> > +		__put_user(host_st->st_mtime, &target_st->target_st_mtime);
> > +		__put_user(host_st->st_ctime, &target_st->target_st_ctime);
> > +		unlock_user_struct(target_st, target_addr, 1);
> > +	} else
> > +#endif
> > +	{
> > +		struct target_stat64 *target_st;
> > +
> > +		if (!lock_user_struct(VERIFY_WRITE, target_st, target_addr, 0))
> > +			return -TARGET_EFAULT;
> > +		memset(target_st, 0, sizeof(struct target_stat64));
> > +		__put_user(host_st->st_dev, &target_st->st_dev);
> > +		__put_user(host_st->st_ino, &target_st->st_ino);
> > +#ifdef TARGET_STAT64_HAS_BROKEN_ST_INO
> > +		__put_user(host_st->st_ino, &target_st->__st_ino);
> > +#endif
> > +		__put_user(host_st->st_mode, &target_st->st_mode);
> > +		__put_user(host_st->st_nlink, &target_st->st_nlink);
> > +		__put_user(host_st->st_uid, &target_st->st_uid);
> > +		__put_user(host_st->st_gid, &target_st->st_gid);
> > +		__put_user(host_st->st_rdev, &target_st->st_rdev);
> > +		/* XXX: better use of kernel struct */
> > +		__put_user(host_st->st_size, &target_st->st_size);
> > +		__put_user(host_st->st_blksize, &target_st->st_blksize);
> > +		__put_user(host_st->st_blocks, &target_st->st_blocks);
> > +		__put_user(host_st->st_atime, &target_st->target_st_atime);
> > +		__put_user(host_st->st_mtime, &target_st->target_st_mtime);
> > +		__put_user(host_st->st_ctime, &target_st->target_st_ctime);
> > +		unlock_user_struct(target_st, target_addr, 1);
> > +	}
> > +
> > +	return 0;
> > +}
> > +#endif
> 
> This is suboptimal - we same code (list of __put_user()) twice. We
> should have smaller if/else in the beginning of the function that sets
> target_st.

Pay attention that struct in 'if' and in 'else' is different. There is no
way to make it pretty(without dirty preprocessing hacks).

-- 
Regards,  Kirill A. Shutemov
 + Belarus, Minsk
 + ALT Linux Team, http://www.altlinux.com/

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