Hello Hugo,
Is this issue specific to the receive ioctl?
Because what you are describing applies to any user-kernel ioctl-based
interface, when you compile the user-space as 32-bit, which the kernel
space has been compiled as 64-bit. For that purpose, I believe, there
exists the "compat_ioctl" callback. It's implementation should do
"thunking", i.e., treat the user-space structure as if it were
compiled for 32-bit, and unpack it properly.
Today, however, btrfs supplies the same callback both for
"unlocked_ioctl" and "compat_ioctl". So we should see the same problem
with all ioctls, if I am not missing anything.
Thanks,
Alex.
On Mon, Jan 6, 2014 at 10:50 AM, Hugo Mills <h...@carfax.org.uk> wrote:
> On Sun, Jan 05, 2014 at 06:26:11PM +0000, Hugo Mills wrote:
>> On Sun, Jan 05, 2014 at 05:55:27PM +0000, Hugo Mills wrote:
>> > The structure for BTRFS_SET_RECEIVED_IOCTL packs differently on 32-bit
>> > and 64-bit systems. This means that it is impossible to use btrfs
>> > receive on a system with a 64-bit kernel and 32-bit userspace, because
>> > the structure size (and hence the ioctl number) is different.
>> >
>> > This patch adds a compatibility structure and ioctl to deal with the
>> > above case.
>>
>> Oops, forgot to mention -- this has been compile tested, but not
>> actually run yet. The machine in question is several miles away and is
>> a production machine (it's my work desktop, and I can't afford much
>> downtime on it).
>
> ... And it doesn't even compile properly, now I come to build a
> .deb. I'm still interested in comments about the general approach, but
> the specific patch is a load of balls.
>
> Hugo.
>
>> Hugo.
>>
>> > Signed-off-by: Hugo Mills <h...@carfax.org.uk>
>> > ---
>> > fs/btrfs/ioctl.c | 95
>> > +++++++++++++++++++++++++++++++++++++++++++++++++++-----
>> > 1 file changed, 87 insertions(+), 8 deletions(-)
>> >
>> > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
>> > index 21da576..e186439 100644
>> > --- a/fs/btrfs/ioctl.c
>> > +++ b/fs/btrfs/ioctl.c
>> > @@ -57,6 +57,32 @@
>> > #include "send.h"
>> > #include "dev-replace.h"
>> >
>> > +#ifdef CONFIG_64BIT
>> > +/* If we have a 32-bit userspace and 64-bit kernel, then the UAPI
>> > + * structures are incorrect, as the timespec structure from userspace
>> > + * is 4 bytes too small. We define these alternatives here to teach
>> > + * the kernel about the 32-bit struct packing.
>> > + */
>> > +struct btrfs_ioctl_timespec {
>> > + __u64 sec;
>> > + __u32 nsec;
>> > +} ((__packed__));
>> > +
>> > +struct btrfs_ioctl_received_subvol_args {
>> > + char uuid[BTRFS_UUID_SIZE]; /* in */
>> > + __u64 stransid; /* in */
>> > + __u64 rtransid; /* out */
>> > + struct btrfs_ioctl_timespec stime; /* in */
>> > + struct btrfs_ioctl_timespec rtime; /* out */
>> > + __u64 flags; /* in */
>> > + __u64 reserved[16]; /* in */
>> > +} ((__packed__));
>> > +#endif
>> > +
>> > +#define BTRFS_IOC_SET_RECEIVED_SUBVOL_32 _IOWR(BTRFS_IOCTL_MAGIC, 37, \
>> > + struct btrfs_ioctl_received_subvol_args_32)
>> > +
>> > +
>> > static int btrfs_clone(struct inode *src, struct inode *inode,
>> > u64 off, u64 olen, u64 olen_aligned, u64 destoff);
>> >
>> > @@ -4313,10 +4339,69 @@ static long btrfs_ioctl_quota_rescan_wait(struct
>> > file *file, void __user *arg)
>> > return btrfs_qgroup_wait_for_completion(root->fs_info);
>> > }
>> >
>> > +#ifdef CONFIG_64BIT
>> > +static long btrfs_ioctl_set_received_subvol_32(struct file *file,
>> > + void __user *arg)
>> > +{
>> > + struct btrfs_ioctl_received_subvol_args_32 *args32 = NULL;
>> > + struct btrfs_ioctl_received_subvol_args *args64 = NULL;
>> > + int ret = 0;
>> > +
>> > + args32 = memdup_user(arg, sizeof(*args32));
>> > + if (IS_ERR(args32)) {
>> > + ret = PTR_ERR(args32);
>> > + args32 = NULL;
>> > + goto out;
>> > + }
>> > +
>> > + args64 = malloc(sizeof(*args64));
>> > + if (IS_ERR(args64)) {
>> > + ret = PTR_ERR(args64);
>> > + args64 = NULL;
>> > + goto out;
>> > + }
>> > +
>> > + memcpy(args64->uuid, args32->uuid, BTRFS_UUID_SIZE);
>> > + args64->stransid = args32->stransid;
>> > + args64->rtransid = args32->rtransid;
>> > + args64->stime.sec = args32->stime.sec;
>> > + args64->stime.nsec = args32->stime.nsec;
>> > + args64->rtime.sec = args32->rtime.sec;
>> > + args64->rtime.nsec = args32->rtime.nsec;
>> > + args64->flags = args32->flags;
>> > +
>> > + ret = _btrfs_ioctl_set_received_subvol(file, args64);
>> > +
>> > +out:
>> > + kfree(args32);
>> > + kfree(args64);
>> > + return ret;
>> > +}
>> > +#endif
>> > +
>> > static long btrfs_ioctl_set_received_subvol(struct file *file,
>> > void __user *arg)
>> > {
>> > struct btrfs_ioctl_received_subvol_args *sa = NULL;
>> > + int ret = 0;
>> > +
>> > + sa = memdup_user(arg, sizeof(*sa));
>> > + if (IS_ERR(sa)) {
>> > + ret = PTR_ERR(sa);
>> > + sa = NULL;
>> > + goto out;
>> > + }
>> > +
>> > + ret = _btrfs_ioctl_set_received_subvol(file, sa);
>> > +
>> > +out:
>> > + kfree(sa);
>> > + return ret;
>> > +}
>> > +
>> > +static long _btrfs_ioctl_set_received_subvol(struct file *file,
>> > + struct
>> > btrfs_ioctl_received_subvol_args *sa)
>> > +{
>> > struct inode *inode = file_inode(file);
>> > struct btrfs_root *root = BTRFS_I(inode)->root;
>> > struct btrfs_root_item *root_item = &root->root_item;
>> > @@ -4346,13 +4431,6 @@ static long btrfs_ioctl_set_received_subvol(struct
>> > file *file,
>> > goto out;
>> > }
>> >
>> > - sa = memdup_user(arg, sizeof(*sa));
>> > - if (IS_ERR(sa)) {
>> > - ret = PTR_ERR(sa);
>> > - sa = NULL;
>> > - goto out;
>> > - }
>> > -
>> > /*
>> > * 1 - root item
>> > * 2 - uuid items (received uuid + subvol uuid)
>> > @@ -4411,7 +4489,6 @@ static long btrfs_ioctl_set_received_subvol(struct
>> > file *file,
>> > ret = -EFAULT;
>> >
>> > out:
>> > - kfree(sa);
>> > up_write(&root->fs_info->subvol_sem);
>> > mnt_drop_write_file(file);
>> > return ret;
>> > @@ -4572,6 +4649,8 @@ long btrfs_ioctl(struct file *file, unsigned int
>> > return btrfs_ioctl_balance_progress(root, argp);
>> > case BTRFS_IOC_SET_RECEIVED_SUBVOL:
>> > return btrfs_ioctl_set_received_subvol(file, argp);
>> > + case BTRFS_IOC_SET_RECEIVED_SUBVOL_32:
>> > + return btrfs_ioctl_set_received_subvol_32(file, argp);
>> > case BTRFS_IOC_SEND:
>> > return btrfs_ioctl_send(file, argp);
>> > case BTRFS_IOC_GET_DEV_STATS:
>>
>
> --
> === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
> PGP key: 65E74AC0 from wwwkeys.eu.pgp.net or http://www.carfax.org.uk
> --- Nothing right in my left brain. Nothing left in ---
> my right brain.
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