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Re: [Qemu-devel] [PATCH v14 1/5] linux-user: Add support for translation


From: Laurent Vivier
Subject: Re: [Qemu-devel] [PATCH v14 1/5] linux-user: Add support for translation of statx() syscall
Date: Thu, 27 Jun 2019 19:07:03 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0

Le 27/06/2019 à 17:31, Aleksandar Markovic a écrit :
> From: Aleksandar Rikalo <address@hidden>
> 
> Implement support for translation of system call statx().
> 
> The implementation is based on "best effort" approach: if host
> is capable of executing statx(), host statx() is used. If not,
> the implementation includes invoking a more mature system call
> fstatat() on the host side to achieve as close as possible
> functionality.
> 
> Support for statx() in kernel and glibc was, however, introduced
> at different points of time (the difference is more than a year):
> 
>   - kernel: Linux 4.11 (30 April 2017)
>   - glibc: glibc 2.28 (1 Aug 2018)
> 
> In this patch, the availability of statx() support is established
> via __NR_statx (if it is defined, statx() is considered available).
> This coincedes with statx() introduction in kernel.
> 
> However, the structure statx definition may not be available in
> any header for hosts with glibc older than 2.28 (and it is, by
> design, to be defined in one of glibc headers), even though the
> full statx() functionality may be supported in kernel. Hence, a
> structure "target_statx" is defined in this patch, to remove that
> dependency on glibc headers, and to use statx() functionality as
> soon as the host kernel is capable of supporting it. Such statx
> structure definition is used for both target and host structures
> statx (of course, this doesn't mean the endian arrangement is
> the same on target and host - the endian conversion is done in
> all necessary cases).
> 
> Signed-off-by: Aleksandar Rikalo <address@hidden>
> Signed-off-by: Aleksandar Markovic <address@hidden>
> ---
>  linux-user/syscall.c      | 115 
> +++++++++++++++++++++++++++++++++++++++++++++-
>  linux-user/syscall_defs.h |  37 +++++++++++++++
>  2 files changed, 151 insertions(+), 1 deletion(-)
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index b187c12..2001266 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -43,6 +43,7 @@
>  #include <sys/times.h>
>  #include <sys/shm.h>
>  #include <sys/sem.h>
> +#include <sys/stat.h>
>  #include <sys/statfs.h>
>  #include <utime.h>
>  #include <sys/sysinfo.h>
> @@ -315,6 +316,14 @@ _syscall5(int, kcmp, pid_t, pid1, pid_t, pid2, int, type,
>            unsigned long, idx1, unsigned long, idx2)
>  #endif
>  
> +/*
> + * It is assumed that struct statx is architecture independent.
> + */
> +#if defined(TARGET_NR_statx) && defined(__NR_statx)
> +_syscall5(int, statx, int, dirfd, const char *, pathname, int, flags,
> +          unsigned int, mask, struct target_statx *, statxbuf)
> +#endif
> +
>  static bitmask_transtbl fcntl_flags_tbl[] = {
>    { TARGET_O_ACCMODE,   TARGET_O_WRONLY,    O_ACCMODE,   O_WRONLY,    },
>    { TARGET_O_ACCMODE,   TARGET_O_RDWR,      O_ACCMODE,   O_RDWR,      },
> @@ -6467,6 +6476,48 @@ static inline abi_long host_to_target_stat64(void 
> *cpu_env,
>  }
>  #endif
>  
> +#if defined(TARGET_NR_statx) && defined(__NR_statx)
> +static inline abi_long host_to_target_statx(struct target_statx *host_stx,
> +                                            abi_ulong target_addr)
> +{
> +    struct target_statx *target_stx;
> +
> +    if (!lock_user_struct(VERIFY_WRITE, target_stx, target_addr,  0)) {
> +        return -TARGET_EFAULT;
> +    }
> +    memset(target_stx, 0, sizeof(*target_stx));
> +
> +    __put_user(host_stx->stx_mask, &target_stx->stx_mask);
> +    __put_user(host_stx->stx_blksize, &target_stx->stx_blksize);
> +    __put_user(host_stx->stx_attributes, &target_stx->stx_attributes);
> +    __put_user(host_stx->stx_nlink, &target_stx->stx_nlink);
> +    __put_user(host_stx->stx_uid, &target_stx->stx_uid);
> +    __put_user(host_stx->stx_gid, &target_stx->stx_gid);
> +    __put_user(host_stx->stx_mode, &target_stx->stx_mode);
> +    __put_user(host_stx->stx_ino, &target_stx->stx_ino);
> +    __put_user(host_stx->stx_size, &target_stx->stx_size);
> +    __put_user(host_stx->stx_blocks, &target_stx->stx_blocks);
> +    __put_user(host_stx->stx_attributes_mask, 
> &target_stx->stx_attributes_mask);
> +    __put_user(host_stx->stx_atime.tv_sec, &target_stx->stx_atime.tv_sec);
> +    __put_user(host_stx->stx_atime.tv_nsec, &target_stx->stx_atime.tv_nsec);
> +    __put_user(host_stx->stx_btime.tv_sec, &target_stx->stx_atime.tv_sec);
> +    __put_user(host_stx->stx_btime.tv_nsec, &target_stx->stx_atime.tv_nsec);
> +    __put_user(host_stx->stx_ctime.tv_sec, &target_stx->stx_atime.tv_sec);
> +    __put_user(host_stx->stx_ctime.tv_nsec, &target_stx->stx_atime.tv_nsec);
> +    __put_user(host_stx->stx_mtime.tv_sec, &target_stx->stx_atime.tv_sec);
> +    __put_user(host_stx->stx_mtime.tv_nsec, &target_stx->stx_atime.tv_nsec);
> +    __put_user(host_stx->stx_rdev_major, &target_stx->stx_rdev_major);
> +    __put_user(host_stx->stx_rdev_minor, &target_stx->stx_rdev_minor);
> +    __put_user(host_stx->stx_dev_major, &target_stx->stx_dev_major);
> +    __put_user(host_stx->stx_dev_minor, &target_stx->stx_dev_minor);
> +
> +    unlock_user_struct(target_stx, target_addr, 1);
> +
> +    return 0;
> +}
> +#endif
> +
> +
>  /* ??? Using host futex calls even when target atomic operations
>     are not really atomic probably breaks things.  However implementing
>     futexes locally would make futexes shared between multiple processes
> @@ -7045,7 +7096,8 @@ static abi_long do_syscall1(void *cpu_env, int num, 
> abi_long arg1,
>      abi_long ret;
>  #if defined(TARGET_NR_stat) || defined(TARGET_NR_stat64) \
>      || defined(TARGET_NR_lstat) || defined(TARGET_NR_lstat64) \
> -    || defined(TARGET_NR_fstat) || defined(TARGET_NR_fstat64)
> +    || defined(TARGET_NR_fstat) || defined(TARGET_NR_fstat64) \
> +    || defined(TARGET_NR_statx)
>      struct stat st;
>  #endif
>  #if defined(TARGET_NR_statfs) || defined(TARGET_NR_statfs64) \
> @@ -10123,6 +10175,67 @@ static abi_long do_syscall1(void *cpu_env, int num, 
> abi_long arg1,
>              ret = host_to_target_stat64(cpu_env, arg3, &st);
>          return ret;
>  #endif
> +#if defined(TARGET_NR_statx)
> +    case TARGET_NR_statx:
> +        {
> +            struct target_statx *target_stx;
> +            int dirfd = arg1;
> +            int flags = arg3;
> +
> +            p = lock_user_string(arg2);
> +            if (p == NULL) {
> +                return -TARGET_EFAULT;
> +            }
> +#if defined(__NR_statx)
> +            {
> +                /*
> +                 * It is assumed that struct statx is architecture 
> independent.
> +                 */
> +                struct target_statx host_stx;
> +                int mask = arg4;
> +
> +                ret = get_errno(statx(dirfd, p, flags, mask, &host_stx));
> +                if (!is_error(ret)) {
> +                    if (host_to_target_statx(&host_stx, arg5) != 0) {
> +                        unlock_user(p, arg2, 0);
> +                        return -TARGET_EFAULT;
> +                    }
> +                }
> +
> +                if (ret != -TARGET_ENOSYS) {
> +                    unlock_user(p, arg2, 0);
> +                    return ret;
> +                }
> +            }
> +#endif
> +            ret = get_errno(fstatat(dirfd, path(p), &st, flags));
> +            unlock_user(p, arg2, 0);
> +
> +            if (!is_error(ret)) {
> +                if (!lock_user_struct(VERIFY_WRITE, target_stx, arg5, 0)) {
> +                    return -TARGET_EFAULT;
> +                }
> +                memset(target_stx, 0, sizeof(*target_stx));
> +                __put_user(major(st.st_dev), &target_stx->stx_dev_major);
> +                __put_user(minor(st.st_dev), &target_stx->stx_dev_minor);
> +                __put_user(st.st_ino, &target_stx->stx_ino);
> +                __put_user(st.st_mode, &target_stx->stx_mode);
> +                __put_user(st.st_uid, &target_stx->stx_uid);
> +                __put_user(st.st_gid, &target_stx->stx_gid);
> +                __put_user(st.st_nlink, &target_stx->stx_nlink);
> +                __put_user(major(st.st_rdev), &target_stx->stx_rdev_major);
> +                __put_user(minor(st.st_rdev), &target_stx->stx_rdev_minor);
> +                __put_user(st.st_size, &target_stx->stx_size);
> +                __put_user(st.st_blksize, &target_stx->stx_blksize);
> +                __put_user(st.st_blocks, &target_stx->stx_blocks);
> +                __put_user(st.st_atime, &target_stx->stx_atime.tv_sec);
> +                __put_user(st.st_mtime, &target_stx->stx_mtime.tv_sec);
> +                __put_user(st.st_ctime, &target_stx->stx_ctime.tv_sec);
> +                unlock_user_struct(target_stx, arg5, 1);
> +            }
> +        }
> +        return ret;
> +#endif
>  #ifdef TARGET_NR_lchown
>      case TARGET_NR_lchown:
>          if (!(p = lock_user_string(arg1)))
> diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
> index 7f141f6..170c4dd 100644
> --- a/linux-user/syscall_defs.h
> +++ b/linux-user/syscall_defs.h
> @@ -2536,4 +2536,41 @@ struct target_user_cap_data {
>  /* Return size of the log buffer */
>  #define TARGET_SYSLOG_ACTION_SIZE_BUFFER   10
>  
> +struct target_statx_timestamp {
> +   int64_t tv_sec;
> +   uint32_t tv_nsec;
> +   int32_t __reserved;
> +};
> +
> +struct target_statx {
> +   /* 0x00 */
> +   uint32_t stx_mask;       /* What results were written [uncond] */
> +   uint32_t stx_blksize;    /* Preferred general I/O size [uncond] */
> +   uint64_t stx_attributes; /* Flags conveying information about the file */
> +   /* 0x10 */
> +   uint32_t stx_nlink;      /* Number of hard links */
> +   uint32_t stx_uid;        /* User ID of owner */
> +   uint32_t stx_gid;        /* Group ID of owner */
> +   uint16_t stx_mode;       /* File mode */
> +   uint16_t __spare0[1];
> +   /* 0x20 */
> +   uint64_t stx_ino;        /* Inode number */
> +   uint64_t stx_size;       /* File size */
> +   uint64_t stx_blocks;     /* Number of 512-byte blocks allocated */
> +   uint64_t stx_attributes_mask; /* Mask to show what is supported */
> +   /* 0x40 */
> +   struct target_statx_timestamp  stx_atime;  /* Last access time */
> +   struct target_statx_timestamp  stx_btime;  /* File creation time */
> +   struct target_statx_timestamp  stx_ctime;  /* Last attribute change time 
> */
> +   struct target_statx_timestamp  stx_mtime;  /* Last data modification time 
> */
> +   /* 0x80 */
> +   uint32_t stx_rdev_major;   /* Device ID of special file [if bdev/cdev] */
> +   uint32_t stx_rdev_minor;
> +   uint32_t stx_dev_major; /* ID of device containing file [uncond] */
> +   uint32_t stx_dev_minor;
> +   /* 0x90 */
> +   uint64_t __spare2[14];  /* Spare space for future expansion */
> +   /* 0x100 */
> +};
> +
>  #endif
> 

Reviewed-by: Laurent Vivier <address@hidden>



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