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Date: Wed, 13 Feb 2013 19:16:35 +0400
From: Andrey Vagin <avagin@...nvz.org>
To: linux-kernel@...r.kernel.org
Cc: criu@...nvz.org, linux-api@...r.kernel.org,
Andrey Vagin <avagin@...nvz.org>,
Roland McGrath <roland@...hat.com>,
Oleg Nesterov <oleg@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
David Howells <dhowells@...hat.com>,
Dave Jones <davej@...hat.com>,
"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
Pavel Emelyanov <xemul@...allels.com>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH] ptrace: add ability to retrieve signals without removing them from a queue
This patch adds a new ptrace request PTRACE_PEEKSIGINFO.
This request is used to retrieve information about a signal with the
specified sequence number. A siginfo_t structure is copied from the child
to location data in the parent.
The low 16 bits of addr contains a sequence number of signal in a queue.
All other bits of addr is used for flags. Currently here is only one
flag PTRACE_PEEK_SHARED for dumping signals from process-wide shared
queue. If this flag is not set, a signal is read from a per-thread
queue. A result siginfo contains a kernel part of si_code which usually
striped, but it's required for queuing the same siginfo back during
restore of pending signals.
If a signal with the specified sequence number doesn't exist, ptrace
returns ENOENT.
This functionality is required for checkpointing pending signals.
The prototype of this code was developed by Oleg Nesterov.
Cc: Roland McGrath <roland@...hat.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc: David Howells <dhowells@...hat.com>
Cc: Dave Jones <davej@...hat.com>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
Cc: Pavel Emelyanov <xemul@...allels.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Andrey Vagin <avagin@...nvz.org>
---
include/uapi/linux/ptrace.h | 9 +++++++
kernel/ptrace.c | 64 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 73 insertions(+)
diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
index 022ab18..5d851d5 100644
--- a/include/uapi/linux/ptrace.h
+++ b/include/uapi/linux/ptrace.h
@@ -52,6 +52,15 @@
#define PTRACE_INTERRUPT 0x4207
#define PTRACE_LISTEN 0x4208
+#define PTRACE_PEEKSIGINFO 0x4209
+
+/*
+ * The lower 16 bits of addr is a sequence number of a signal.
+ * All other bits can be used for flags.
+ */
+#define PTRACE_PEEKSIGINFO_FLAGS_MASK (~0UL << 16)
+#define PTRACE_PEEK_SHARED (1UL << 31)
+
/* Wait extended result codes for the above trace options. */
#define PTRACE_EVENT_FORK 1
#define PTRACE_EVENT_VFORK 2
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 1599157..27fd31a 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -579,6 +579,40 @@ static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
return error;
}
+#ifdef CONFIG_CHECKPOINT_RESTORE
+static int ptrace_peek_siginfo(struct task_struct *child,
+ unsigned long addr, siginfo_t *siginfo)
+{
+ struct sigpending *pending;
+ struct sigqueue *q;
+ unsigned long flags;
+ unsigned int nr;
+ int ret = -ENOENT;
+
+ nr = addr & ~PTRACE_PEEKSIGINFO_FLAGS_MASK;
+ flags = addr & PTRACE_PEEKSIGINFO_FLAGS_MASK;
+
+ if (flags & PTRACE_PEEK_SHARED)
+ pending = &child->signal->shared_pending;
+ else
+ pending = &child->pending;
+
+ if (flags & ~PTRACE_PEEK_SHARED)
+ return -EINVAL; /* unknown flags */
+
+ spin_lock_irq(&child->sighand->siglock);
+ list_for_each_entry(q, &pending->list, list) {
+ if (!nr--) {
+ copy_siginfo(siginfo, &q->info);
+ ret = 0;
+ break;
+ }
+ }
+ spin_unlock_irq(&child->sighand->siglock);
+
+ return ret;
+}
+#endif
#ifdef PTRACE_SINGLESTEP
#define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)
@@ -703,6 +737,21 @@ int ptrace_request(struct task_struct *child, long request,
ret = put_user(child->ptrace_message, datalp);
break;
+#ifdef CONFIG_CHECKPOINT_RESTORE
+ case PTRACE_PEEKSIGINFO:
+ {
+ siginfo_t __user *uinfo = (siginfo_t __user *) data;
+
+ ret = ptrace_peek_siginfo(child, addr, &siginfo);
+
+ if (!ret)
+ ret = copy_siginfo_to_user(uinfo, &siginfo);
+ if (!ret)
+ ret = __put_user(siginfo.si_code, &uinfo->si_code);
+ break;
+ }
+#endif
+
case PTRACE_GETSIGINFO:
ret = ptrace_getsiginfo(child, &siginfo);
if (!ret)
@@ -959,6 +1008,21 @@ int compat_ptrace_request(struct task_struct *child, compat_long_t request,
ret = put_user((compat_ulong_t) child->ptrace_message, datap);
break;
+#ifdef CONFIG_CHECKPOINT_RESTORE
+ case PTRACE_PEEKSIGINFO:
+ {
+ compat_siginfo_t __user *uinfo = compat_ptr(data);
+
+ ret = ptrace_peek_siginfo(child, addr, &siginfo);
+
+ if (!ret)
+ ret = copy_siginfo_to_user32(uinfo, &siginfo);
+ if (!ret)
+ ret = __put_user(siginfo.si_code, &uinfo->si_code);
+ break;
+ }
+#endif
+
case PTRACE_GETSIGINFO:
ret = ptrace_getsiginfo(child, &siginfo);
if (!ret)
--
1.7.11.7
--
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