[PATCH v18 62/80] c/r: checkpoint and restore (shared) task's sighand_struct

Oren Laadan
2009-09-24T00:41:40Z

This patch adds the checkpointing and restart of signal handling
state - 'struct sighand_struct'. Since the contents of this state
only affect userspace, no input validation is required.

Add _NSIG to kernel constants saved/tested with image header.

Number of signals (_NSIG) is arch-dependent, but is within __KERNEL__
and not visibile to userspace compile. Therefore, define per arch
CKPT_ARCH_NSIG in <asm/checkpoint_hdr.h>.

Changelog[v1]:
- Rename headerless struct ckpt_hdr_* to struct ckpt_*

Signed-off-by: Oren Laadan <orenl@cs.columbia.edu>
---
arch/s390/include/asm/checkpoint_hdr.h | 8 ++
arch/x86/include/asm/checkpoint_hdr.h | 8 ++
checkpoint/Makefile | 3 +-
checkpoint/checkpoint.c | 2 +
checkpoint/objhash.c | 26 +++++
checkpoint/process.c | 19 ++++
checkpoint/restart.c | 3 +
checkpoint/signal.c | 163 ++++++++++++++++++++++++++++++++
include/linux/checkpoint.h | 9 ++-
include/linux/checkpoint_hdr.h | 22 +++++
10 files changed, 261 insertions(+), 2 deletions(-)
create mode 100644 checkpoint/signal.c

diff --git a/arch/s390/include/asm/checkpoint_hdr.h b/arch/s390/include/asm/checkpoint_hdr.h
index ad9449e..1976355 100644
--- a/arch/s390/include/asm/checkpoint_hdr.h
+++ b/arch/s390/include/asm/checkpoint_hdr.h
@@ -82,6 +82,14 @@ struct ckpt_hdr_mm_context {
unsigned long asce_limit;
};

+#define CKPT_ARCH_NSIG 64
+#ifdef __KERNEL__
+#include <asm/signal.h>
+#if CKPT_ARCH_NSIG != _SIGCONTEXT_NSIG
+#error CKPT_ARCH_NSIG size is wrong (asm/sigcontext.h and asm/checkpoint_hdr.h)
+#endif
+#endif
+
struct ckpt_hdr_header_arch {
struct ckpt_hdr h;
};
diff --git a/arch/x86/include/asm/checkpoint_hdr.h b/arch/x86/include/asm/checkpoint_hdr.h
index 0e756b0..1228d1b 100644
--- a/arch/x86/include/asm/checkpoint_hdr.h
+++ b/arch/x86/include/asm/checkpoint_hdr.h
@@ -48,6 +48,14 @@ enum {
CKPT_HDR_MM_CONTEXT_LDT,
};

+#define CKPT_ARCH_NSIG 64
+#ifdef __KERNEL__
+#include <asm/signal.h>
+#if CKPT_ARCH_NSIG != _NSIG
+#error CKPT_ARCH_NSIG size is wrong per asm/signal.h and asm/checkpoint_hdr.h
+#endif
+#endif
+
struct ckpt_hdr_header_arch {
struct ckpt_hdr h;
/* FIXME: add HAVE_HWFP */
diff --git a/checkpoint/Makefile b/checkpoint/Makefile
index bb2c0ca..f8a55df 100644
--- a/checkpoint/Makefile
+++ b/checkpoint/Makefile
@@ -10,4 +10,5 @@ obj-$(CONFIG_CHECKPOINT) += \
process.o \
namespace.o \
files.o \
- memory.o
+ memory.o \
+ signal.o
diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c
index 27eec5c..3460c03 100644
--- a/checkpoint/checkpoint.c
+++ b/checkpoint/checkpoint.c
@@ -288,6 +288,8 @@ static void fill_kernel_const(struct ckpt_const *h)
h->task_comm_len = sizeof(tsk->comm);
/* mm */
h->mm_saved_auxv_len = sizeof(mm->saved_auxv);
+ /* signal */
+ h->signal_nsig = _NSIG;
/* uts */
h->uts_sysname_len = sizeof(uts->sysname);
h->uts_nodename_len = sizeof(uts->nodename);
diff --git a/checkpoint/objhash.c b/checkpoint/objhash.c
index f8a3210..b4034dc 100644
--- a/checkpoint/objhash.c
+++ b/checkpoint/objhash.c
@@ -125,6 +125,22 @@ static int obj_mm_users(void *ptr)
return atomic_read(&((struct mm_struct *) ptr)->mm_users);
}

+static int obj_sighand_grab(void *ptr)
+{
+ atomic_inc(&((struct sighand_struct *) ptr)->count);
+ return 0;
+}
+
+static void obj_sighand_drop(void *ptr, int lastref)
+{
+ __cleanup_sighand((struct sighand_struct *) ptr);
+}
+
+static int obj_sighand_users(void *ptr)
+{
+ return atomic_read(&((struct sighand_struct *) ptr)->count);
+}
+
static int obj_ns_grab(void *ptr)
{
get_nsproxy((struct nsproxy *) ptr);
@@ -263,6 +279,16 @@ static struct ckpt_obj_ops ckpt_obj_ops[] = {
.checkpoint = checkpoint_mm,
.restore = restore_mm,
},
+ /* sighand object */
+ {
+ .obj_name = "SIGHAND",
+ .obj_type = CKPT_OBJ_SIGHAND,
+ .ref_drop = obj_sighand_drop,
+ .ref_grab = obj_sighand_grab,
+ .ref_users = obj_sighand_users,
+ .checkpoint = checkpoint_sighand,
+ .restore = restore_sighand,
+ },
/* ns object */
{
.obj_name = "NSPROXY",
diff --git a/checkpoint/process.c b/checkpoint/process.c
index 1e79f73..56f33dd 100644
--- a/checkpoint/process.c
+++ b/checkpoint/process.c
@@ -181,6 +181,7 @@ static int checkpoint_task_objs(struct ckpt_ctx *ctx, struct task_struct *t)
struct ckpt_hdr_task_objs *h;
int files_objref;
int mm_objref;
+ int sighand_objref;
int ret;

/*
@@ -214,11 +215,19 @@ static int checkpoint_task_objs(struct ckpt_ctx *ctx, struct task_struct *t)
return mm_objref;
}

+ sighand_objref = checkpoint_obj_sighand(ctx, t);
+ ckpt_debug("sighand: objref %d\n", sighand_objref);
+ if (sighand_objref < 0) {
+ ckpt_write_err(ctx, "TE", "sighand_struct", sighand_objref);
+ return sighand_objref;
+ }
+
h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_TASK_OBJS);
if (!h)
return -ENOMEM;
h->files_objref = files_objref;
h->mm_objref = mm_objref;
+ h->sighand_objref = sighand_objref;
ret = ckpt_write_obj(ctx, &h->h);
ckpt_hdr_put(ctx, h);

@@ -382,6 +391,9 @@ int ckpt_collect_task(struct ckpt_ctx *ctx, struct task_struct *t)
if (ret < 0)
return ret;
ret = ckpt_collect_mm(ctx, t);
+ if (ret < 0)
+ return ret;
+ ret = ckpt_collect_sighand(ctx, t);

return ret;
}
@@ -529,10 +541,17 @@ static int restore_task_objs(struct ckpt_ctx *ctx)

ret = restore_obj_file_table(ctx, h->files_objref);
ckpt_debug("file_table: ret %d (%p)\n", ret, current->files);
+ if (ret < 0)
+ goto out;

ret = restore_obj_mm(ctx, h->mm_objref);
ckpt_debug("mm: ret %d (%p)\n", ret, current->mm);
+ if (ret < 0)
+ goto out;

+ ret = restore_obj_sighand(ctx, h->sighand_objref);
+ ckpt_debug("sighand: ret %d (%p)\n", ret, current->sighand);
+ out:
ckpt_hdr_put(ctx, h);
return ret;
}
diff --git a/checkpoint/restart.c b/checkpoint/restart.c
index 53a759a..73c4e72 100644
--- a/checkpoint/restart.c
+++ b/checkpoint/restart.c
@@ -383,6 +383,9 @@ static int check_kernel_const(struct ckpt_const *h)
/* mm */
if (h->mm_saved_auxv_len != sizeof(mm->saved_auxv))
return -EINVAL;
+ /* signal */
+ if (h->signal_nsig != _NSIG)
+ return -EINVAL;
/* uts */
if (h->uts_sysname_len != sizeof(uts->sysname))
return -EINVAL;
diff --git a/checkpoint/signal.c b/checkpoint/signal.c
new file mode 100644
index 0000000..1aadadd
--- /dev/null
+++ b/checkpoint/signal.c
@@ -0,0 +1,163 @@
+/*
+ * Checkpoint task signals
+ *
+ * Copyright (C) 2009 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+/* default debug level for output */
+#define CKPT_DFLAG CKPT_DSYS
+
+#include <linux/sched.h>
+#include <linux/signal.h>
+#include <linux/errno.h>
+#include <linux/checkpoint.h>
+#include <linux/checkpoint_hdr.h>
+
+static inline void fill_sigset(struct ckpt_sigset *h, sigset_t *sigset)
+{
+ memcpy(&h->sigset, sigset, sizeof(*sigset));
+}
+
+static inline void load_sigset(sigset_t *sigset, struct ckpt_sigset *h)
+{
+ memcpy(sigset, &h->sigset, sizeof(*sigset));
+}
+
+/***********************************************************************
+ * sighand checkpoint/collect/restart
+ */
+
+static int do_checkpoint_sighand(struct ckpt_ctx *ctx,
+ struct sighand_struct *sighand)
+{
+ struct ckpt_hdr_sighand *h;
+ struct ckpt_sigaction *hh;
+ struct sigaction *sa;
+ int i, ret;
+
+ h = ckpt_hdr_get_type(ctx, _NSIG * sizeof(*hh) + sizeof(*h),
+ CKPT_HDR_SIGHAND);
+ if (!h)
+ return -ENOMEM;
+
+ hh = h->action;
+ spin_lock_irq(&sighand->siglock);
+ for (i = 0; i < _NSIG; i++) {
+ sa = &sighand->action[i].sa;
+ hh[i]._sa_handler = (unsigned long) sa->sa_handler;
+ hh[i].sa_flags = sa->sa_flags;
+ hh[i].sa_restorer = (unsigned long) sa->sa_restorer;
+ fill_sigset(&hh[i].sa_mask, &sa->sa_mask);
+ }
+ spin_unlock_irq(&sighand->siglock);
+
+ ret = ckpt_write_obj(ctx, &h->h);
+ ckpt_hdr_put(ctx, h);
+
+ return ret;
+}
+
+int checkpoint_sighand(struct ckpt_ctx *ctx, void *ptr)
+{
+ return do_checkpoint_sighand(ctx, (struct sighand_struct *) ptr);
+}
+
+int checkpoint_obj_sighand(struct ckpt_ctx *ctx, struct task_struct *t)
+{
+ struct sighand_struct *sighand;
+ int objref;
+
+ read_lock(&tasklist_lock);
+ sighand = rcu_dereference(t->sighand);
+ atomic_inc(&sighand->count);
+ read_unlock(&tasklist_lock);
+
+ objref = checkpoint_obj(ctx, sighand, CKPT_OBJ_SIGHAND);
+ __cleanup_sighand(sighand);
+
+ return objref;
+}
+
+int ckpt_collect_sighand(struct ckpt_ctx *ctx, struct task_struct *t)
+{
+ struct sighand_struct *sighand;
+ int ret;
+
+ read_lock(&tasklist_lock);
+ sighand = rcu_dereference(t->sighand);
+ atomic_inc(&sighand->count);
+ read_unlock(&tasklist_lock);
+
+ ret = ckpt_obj_collect(ctx, sighand, CKPT_OBJ_SIGHAND);
+ __cleanup_sighand(sighand);
+
+ return ret;
+}
+
+static struct sighand_struct *do_restore_sighand(struct ckpt_ctx *ctx)
+{
+ struct ckpt_hdr_sighand *h;
+ struct ckpt_sigaction *hh;
+ struct sighand_struct *sighand;
+ struct sigaction *sa;
+ int i;
+
+ h = ckpt_read_obj_type(ctx, _NSIG * sizeof(*hh) + sizeof(*h),
+ CKPT_HDR_SIGHAND);
+ if (IS_ERR(h))
+ return ERR_PTR(PTR_ERR(h));
+
+ sighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
+ if (!sighand) {
+ sighand = ERR_PTR(-ENOMEM);
+ goto out;
+ }
+ atomic_set(&sighand->count, 1);
+
+ hh = h->action;
+ for (i = 0; i < _NSIG; i++) {
+ sa = &sighand->action[i].sa;
+ sa->sa_handler = (void *) (unsigned long) hh[i]._sa_handler;
+ sa->sa_flags = hh[i].sa_flags;
+ sa->sa_restorer = (void *) (unsigned long) hh[i].sa_restorer;
+ load_sigset(&sa->sa_mask, &hh[i].sa_mask);
+ }
+ out:
+ ckpt_hdr_put(ctx, h);
+ return sighand;
+}
+
+void *restore_sighand(struct ckpt_ctx *ctx)
+{
+ return (void *) do_restore_sighand(ctx);
+}
+
+int restore_obj_sighand(struct ckpt_ctx *ctx, int sighand_objref)
+{
+ struct sighand_struct *sighand;
+ struct sighand_struct *old_sighand;
+
+ sighand = ckpt_obj_fetch(ctx, sighand_objref, CKPT_OBJ_SIGHAND);
+ if (IS_ERR(sighand))
+ return PTR_ERR(sighand);
+
+ if (sighand == current->sighand)
+ return 0;
+
+ atomic_inc(&sighand->count);
+
+ /* manipulate tsk->sighand with tasklist lock write-held */
+ write_lock_irq(&tasklist_lock);
+ old_sighand = rcu_dereference(current->sighand);
+ spin_lock(&old_sighand->siglock);
+ rcu_assign_pointer(current->sighand, sighand);
+ spin_unlock(&old_sighand->siglock);
+ write_unlock_irq(&tasklist_lock);
+ __cleanup_sighand(old_sighand);
+
+ return 0;
+}
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 3dbf188..c0e549e 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -245,6 +245,14 @@ extern int restore_memory_contents(struct ckpt_ctx *ctx, struct inode *inode);
VM_RESERVED | VM_NORESERVE | VM_HUGETLB | VM_NONLINEAR | \
VM_MAPPED_COPY | VM_INSERTPAGE | VM_MIXEDMAP | VM_SAO)

+/* signals */
+extern int checkpoint_obj_sighand(struct ckpt_ctx *ctx, struct task_struct *t);
+extern int restore_obj_sighand(struct ckpt_ctx *ctx, int sighand_objref);
+
+extern int ckpt_collect_sighand(struct ckpt_ctx *ctx, struct task_struct *t);
+extern int checkpoint_sighand(struct ckpt_ctx *ctx, void *ptr);
+extern void *restore_sighand(struct ckpt_ctx *ctx);
+
static inline int ckpt_validate_errno(int errno)
{
return (errno >= 0) && (errno < MAX_ERRNO);
@@ -277,7 +285,6 @@ static inline int ckpt_validate_errno(int errno)
memcpy(LIVE, SAVE, count * sizeof(*SAVE)); \
} while (0)

-
/* debugging flags */
#define CKPT_DBASE 0x1 /* anything */
#define CKPT_DSYS 0x2 /* generic (system) */
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index ca24112..3d3a105 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -87,6 +87,8 @@ enum {
CKPT_HDR_IPC_MSG_MSG,
CKPT_HDR_IPC_SEM,

+ CKPT_HDR_SIGHAND = 601,
+
CKPT_HDR_TAIL = 9001,

CKPT_HDR_ERROR = 9999,
@@ -113,6 +115,7 @@ enum obj_type {
CKPT_OBJ_FILE_TABLE,
CKPT_OBJ_FILE,
CKPT_OBJ_MM,
+ CKPT_OBJ_SIGHAND,
CKPT_OBJ_NS,
CKPT_OBJ_UTS_NS,
CKPT_OBJ_IPC_NS,
@@ -129,6 +132,8 @@ struct ckpt_const {
__u16 task_comm_len;
/* mm */
__u16 mm_saved_auxv_len;
+ /* signal */
+ __u16 signal_nsig;
/* uts */
__u16 uts_sysname_len;
__u16 uts_nodename_len;
@@ -299,6 +304,7 @@ struct ckpt_hdr_task_objs {

__s32 files_objref;
__s32 mm_objref;
+ __s32 sighand_objref;
} __attribute__((aligned(8)));

/* restart blocks */
@@ -414,6 +420,22 @@ struct ckpt_hdr_pgarr {
__u64 nr_pages; /* number of pages to saved */
} __attribute__((aligned(8)));

+/* signals */
+struct ckpt_sigset {
+ __u8 sigset[CKPT_ARCH_NSIG / 8];
+} __attribute__((aligned(8)));
+
+struct ckpt_sigaction {
+ __u64 _sa_handler;
+ __u64 sa_flags;
+ __u64 sa_restorer;
+ struct ckpt_sigset sa_mask;
+} __attribute__((aligned(8)));
+
+struct ckpt_hdr_sighand {
+ struct ckpt_hdr h;
+ struct ckpt_sigaction action[0];
+} __attribute__((aligned(8)));

/* ipc commons */
struct ckpt_hdr_ipcns {
--
1.6.0.4