On 12/28, Andrey Vagin wrote:
>
> signalfd should be called with the flag SFD_RAW for that.
>
> signalfd_siginfo is not full for siginfo with a negative si_code.
> copy_siginfo_to_user() is copied a full siginfo to user-space, if
> si_code is negative. signalfd_copyinfo() doesn't do that and can't be
> expanded, because it has not compatible format with siginfo_t.
>
> Another problem is that a constant __SI_* is removed from si_code.
> It's not a problem for usual applications, because they expect
> a defined type of siginfo (internal logic).
> When we want to dump pending signals, we can't predict a type of
> siginfo, so we should get it from kernel.
>
> The main idea of the raw format is that it should be enough for
> restoring exactly the same siginfo for the current process.
>
> This functionality is required for checkpointing pending signals.
And this should be used along with pread().
I won't argue, but perhaps we should simply postulate that pread()
always dumps siginfo in raw format and avoid the new flag?
> @@ -272,20 +311,35 @@ SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *,
> user_mask,
> signotset(&sigmask);
>
> if (ufd == -1) {
> + struct file *file;
> ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
> if (!ctx)
> return -ENOMEM;
>
> ctx->sigmask = sigmask;
>
> + ufd = get_unused_fd_flags(flags);
> + if (ufd < 0) {
> + kfree(ctx);
> + goto out;
> + }
> +
> /*
> * When we call this, the initialization must be complete, since
> * anon_inode_getfd() will install the fd.
> */
> - ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
> + file = anon_inode_getfile("[signalfd]", &signalfd_fops, ctx,
> O_RDWR | (flags & (O_CLOEXEC |
> O_NONBLOCK)));
> - if (ufd < 0)
> + if (IS_ERR(file)) {
> + put_unused_fd(ufd);
> + ufd = PTR_ERR(file);
> kfree(ctx);
> + goto out;
> + }
> +
> + file->f_flags |= flags & SFD_RAW;
> +
> + fd_install(ufd, file);
And this is needed because we want to set more bits in f_flags/f_mode.
I am wondering if we can change anon_inode_getfd/getfile somehow so
that the user can pass more flags...
Or. Currently fops->open() is never used if this file_operations is used
by anon_inode_get*. So perhaps we can change anon_inode_getfile() to call
fops->open() if it is not zero before return?
OK, this is almost off-topic, please ignore.
Oleg.
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