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Message-Id: <20130116123502.70af6b85.akpm@linux-foundation.org>
Date: Wed, 16 Jan 2013 12:35:02 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Andrey Vagin <avagin@...nvz.org>
Cc: linux-kernel@...r.kernel.org, criu@...nvz.org,
linux-fsdevel@...r.kernel.org, linux-api@...r.kernel.org,
Alexander Viro <viro@...iv.linux.org.uk>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
David Howells <dhowells@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Oleg Nesterov <oleg@...hat.com>,
Michael Kerrisk <mtk.manpages@...il.com>,
Pavel Emelyanov <xemul@...allels.com>,
Cyrill Gorcunov <gorcunov@...nvz.org>,
Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [PATCH 2/3] signalfd: add ability to return siginfo in a raw
format (v2)
On Mon, 14 Jan 2013 20:53:54 +0400
Andrey Vagin <avagin@...nvz.org> 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.
>
> ...
>
> --- a/fs/signalfd.c
> +++ b/fs/signalfd.c
> @@ -30,6 +30,7 @@
> #include <linux/signalfd.h>
> #include <linux/syscalls.h>
> #include <linux/proc_fs.h>
> +#include <linux/compat.h>
>
> void signalfd_cleanup(struct sighand_struct *sighand)
> {
> @@ -74,6 +75,38 @@ static unsigned int signalfd_poll(struct file *file, poll_table *wait)
> }
>
> /*
> + * Copy a whole siginfo into users spaces.
"userspace"
> + * The main idea of this format is that it should be enough
> + * for restoring siginfo back into the kernel.
> + */
> +static int signalfd_copy_raw_info(struct signalfd_siginfo __user *siginfo,
> + siginfo_t *kinfo)
> +{
> + siginfo_t *uinfo = (siginfo_t *) siginfo;
Should be
siginfo_t __user *uinfo = (siginfo_t __user *)siginfo;
> + int err;
> +
> + BUILD_BUG_ON(sizeof(siginfo_t) != sizeof(struct signalfd_siginfo));
> +
> + err = __clear_user(uinfo, sizeof(*uinfo));
>
> +#ifdef CONFIG_COMPAT
> + if (unlikely(is_compat_task())) {
> + compat_siginfo_t *compat_uinfo = (compat_siginfo_t *) siginfo;
> +
> + err |= copy_siginfo_to_user32(compat_uinfo, kinfo);
> + err |= put_user(kinfo->si_code, &compat_uinfo->si_code);
> +
> + return err ? -EFAULT: sizeof(*compat_uinfo);
> + }
> +#endif
> +
> + err |= copy_siginfo_to_user(uinfo, kinfo);
> + err |= put_user(kinfo->si_code, &uinfo->si_code);
> +
> + return err ? -EFAULT: sizeof(*uinfo);
> +}
> +
> +/*
> * Copied from copy_siginfo_to_user() in kernel/signal.c
> */
> static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
>
> ...
>
> --- a/include/uapi/linux/signalfd.h
> +++ b/include/uapi/linux/signalfd.h
> @@ -15,6 +15,7 @@
> /* Flags for signalfd4. */
> #define SFD_CLOEXEC O_CLOEXEC
> #define SFD_NONBLOCK O_NONBLOCK
> +#define SFD_RAW O_DIRECT
>
> struct signalfd_siginfo {
> __u32 ssi_signo;
As SFD_RAW is being added to the kernel API we should document it.
Please keep Michael cc'ed and work with him on getting the manpages
updated.
I usually ask that checkpoint-restart specific code be wrapped in
#ifdef CONFIG_CHECKPOINT_RESTORE, mainly so we can identify it all
if/when your project fails and we decide to remove the feature ;) But
as this patch extends the user API I think it simplifies life if we
make the extension permanent. Perhaps this is a bad idea, as
permanently adding this extension to the API makes it harder to ever
remove the c/r feature.
Proposed fixups. Please review and test this and check that sparse is
happy with it.
From: Andrew Morton <akpm@...ux-foundation.org>
Subject: signalfd-add-ability-to-return-siginfo-in-a-raw-format-v2-fix
fix __user annotations, tidy comments and code layout
Cc: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: Andrey Vagin <avagin@...nvz.org>
Cc: Cyrill Gorcunov <gorcunov@...nvz.org>
Cc: David Howells <dhowells@...hat.com>
Cc: Michael Kerrisk <mtk.manpages@...il.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Pavel Emelyanov <xemul@...allels.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---
fs/signalfd.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff -puN fs/signalfd.c~signalfd-add-ability-to-return-siginfo-in-a-raw-format-v2-fix fs/signalfd.c
--- a/fs/signalfd.c~signalfd-add-ability-to-return-siginfo-in-a-raw-format-v2-fix
+++ a/fs/signalfd.c
@@ -75,14 +75,14 @@ static unsigned int signalfd_poll(struct
}
/*
- * Copy a whole siginfo into users spaces.
+ * Copy a whole siginfo into userspace.
* The main idea of this format is that it should be enough
* for restoring siginfo back into the kernel.
*/
static int signalfd_copy_raw_info(struct signalfd_siginfo __user *siginfo,
siginfo_t *kinfo)
{
- siginfo_t *uinfo = (siginfo_t *) siginfo;
+ siginfo_t __user *uinfo = (siginfo_t __user *)siginfo;
int err;
BUILD_BUG_ON(sizeof(siginfo_t) != sizeof(struct signalfd_siginfo));
@@ -91,19 +91,20 @@ static int signalfd_copy_raw_info(struct
#ifdef CONFIG_COMPAT
if (unlikely(is_compat_task())) {
- compat_siginfo_t *compat_uinfo = (compat_siginfo_t *) siginfo;
+ compat_siginfo_t __user *compat_uinfo;
+ compat_uinfo = (compat_siginfo_t __user *)siginfo;
err |= copy_siginfo_to_user32(compat_uinfo, kinfo);
err |= put_user(kinfo->si_code, &compat_uinfo->si_code);
- return err ? -EFAULT: sizeof(*compat_uinfo);
+ return err ? -EFAULT : sizeof(*compat_uinfo);
}
#endif
err |= copy_siginfo_to_user(uinfo, kinfo);
err |= put_user(kinfo->si_code, &uinfo->si_code);
- return err ? -EFAULT: sizeof(*uinfo);
+ return err ? -EFAULT : sizeof(*uinfo);
}
/*
_
--
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