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Re: [Qemu-devel] [PATCH v12 3/5] linux-user: Add support for translation
From: |
Laurent Vivier |
Subject: |
Re: [Qemu-devel] [PATCH v12 3/5] linux-user: Add support for translation of statx() syscall |
Date: |
Wed, 19 Jun 2019 18:11:49 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 |
Le 19/06/2019 à 16:17, 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 other (more mature) system calls
> (from the same 'stat' family) 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 for hosts
> with glibc older than 2.28 (it is, by design, to be defined in one of
> glibc headers), even though the full statx() functionality may be
> supported in kernel, if the kernel is not older than 4.11. 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 structure statx
> 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, and 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 | 136
> +++++++++++++++++++++++++++++++++++++++++++++-
> linux-user/syscall_defs.h | 37 +++++++++++++
> 2 files changed, 172 insertions(+), 1 deletion(-)
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index d116287..e68a36c 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>
> @@ -316,6 +317,14 @@ _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, },
> @@ -6517,6 +6526,48 @@ 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
> @@ -7095,7 +7146,8 @@ 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) \
> @@ -10173,6 +10225,88 @@ 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
> + if (*((char *)p) == 0) {
> + /*
> + * By file descriptor
> + */
> + if (flags & AT_EMPTY_PATH) {
> + unlock_user(p, arg2, 0);
> + return -TARGET_ENOENT;
> + }
> + ret = get_errno(fstat(dirfd, &st));
> + } else if (*((char *)p) == '/') {
> + /*
> + * By absolute pathname
> + */
> + ret = get_errno(stat(path(p), &st));
> + } else {
> + /*
> + * By pathname relative to the current working directory
> + * (if 'dirfd' is AT_FDCWD) or relative to the directory
> + * referred to by the file descriptor 'dirfd'.
> + */
> + ret = get_errno(fstatat(dirfd, path(p), &st, flags));
> + }
> + unlock_user(p, arg2, 0);
Could you explain why we can't use fstatat() for the two previous cases
"(*((char *)p) == 0)" and "(*((char *)p) == '/')"?
Thanks,
Laurent
[Qemu-devel] [PATCH v12 4/5] linux-user: Add support for strace for statx() syscall, Aleksandar Markovic, 2019/06/19
Re: [Qemu-devel] [PATCH v12 0/5], no-reply, 2019/06/19
Re: [Qemu-devel] [PATCH v12 0/5], no-reply, 2019/06/19