[RFC PATCH 1/5] adds the procfs facilities
Nadia Derbey
Nadia.Derbey at bull.net
Mon Jul 7 22:25:18 PDT 2008
Serge E. Hallyn wrote:
> Quoting Nadia.Derbey at bull.net (Nadia.Derbey at bull.net):
>
>>[PATCH 01/05]
>>
>>This patch adds the procfs facility needed to feed some data for the
>>next syscall to be called.
>>
>>The effect of issuing
>>echo "LONG<Y> <XX>" > /proc/self/task/<tid>/next_syscall_data
>>is that <XX> will be stored in a new field of the task structure
>>(next_syscall_data). This field, in turn will be taken as the data to feed
>>next syscall that supports the feature.
>>
>><Y> is the number of values provided on the line.
>>For the sake of simplicity it is now fixed to 1, but this can be extended as
>>needed, in the future.
>>
>>This is particularly useful when restarting an application, as we need
>>sometimes the syscalls to have a non-default behavior.
>>
>>Signed-off-by: Nadia Derbey <Nadia.Derbey at bull.net>
>>
>>---
>> fs/exec.c | 6 +
>> fs/proc/base.c | 75 ++++++++++++++++++
>> include/linux/next_syscall_data.h | 35 ++++++++
>> include/linux/sched.h | 6 +
>> kernel/Makefile | 3
>> kernel/exit.c | 4 +
>> kernel/fork.c | 2
>> kernel/next_syscall_data.c | 151 ++++++++++++++++++++++++++++++++++++++
>> 8 files changed, 281 insertions(+), 1 deletion(-)
>>
>>Index: linux-2.6.26-rc5-mm3/include/linux/sched.h
>>===================================================================
>>--- linux-2.6.26-rc5-mm3.orig/include/linux/sched.h 2008-06-25 17:10:38.000000000 +0200
>>+++ linux-2.6.26-rc5-mm3/include/linux/sched.h 2008-06-27 14:18:56.000000000 +0200
>>@@ -87,6 +87,7 @@ struct sched_param {
>> #include <linux/task_io_accounting.h>
>> #include <linux/kobject.h>
>> #include <linux/latencytop.h>
>>+#include <linux/next_syscall_data.h>
>>
>> #include <asm/processor.h>
>>
>>@@ -1312,6 +1313,11 @@ struct task_struct {
>> int latency_record_count;
>> struct latency_record latency_record[LT_SAVECOUNT];
>> #endif
>>+ /*
>>+ * If non-NULL indicates that next operation will be forced, e.g.
>>+ * that next object to be created will have a predefined id.
>>+ */
>>+ struct next_syscall_data *nsd;
>> };
>>
>> /*
>>Index: linux-2.6.26-rc5-mm3/include/linux/next_syscall_data.h
>>===================================================================
>>--- /dev/null 1970-01-01 00:00:00.000000000 +0000
>>+++ linux-2.6.26-rc5-mm3/include/linux/next_syscall_data.h 2008-07-01 10:25:48.000000000 +0200
>>@@ -0,0 +1,35 @@
>>+/*
>>+ * include/linux/next_syscall_data.h
>>+ *
>>+ * Definitions to support fixed data for next syscall to be called. The
>>+ * following is supported today:
>>+ * . object creation with a predefined id.
>>+ *
>>+ */
>>+
>>+#ifndef _LINUX_NEXT_SYSCALL_DATA_H
>>+#define _LINUX_NEXT_SYSCALL_DATA_H
>>+
>>+#define NDATA 1
>>+
>>+/*
>>+ * If this structure is pointed to by a task_struct, next syscall to be called
>>+ * by the task will have a non-default behavior.
>>+ * For example, it can be used to pre-set the id of the object to be created
>>+ * by next syscall.
>>+ */
>>+struct next_syscall_data {
>>+ int ndata;
>>+ long data[NDATA];
>>+};
>>+
>>+extern ssize_t get_next_syscall_data(struct task_struct *, char *, size_t);
>>+extern int set_next_syscall_data(struct task_struct *, char *);
>>+extern int reset_next_syscall_data(struct task_struct *);
>>+
>>+static inline void exit_next_syscall_data(struct task_struct *tsk)
>>+{
>>+ reset_next_syscall_data(tsk);
>>+}
>>+
>>+#endif /* _LINUX_NEXT_SYSCALL_DATA_H */
>>Index: linux-2.6.26-rc5-mm3/fs/proc/base.c
>>===================================================================
>>--- linux-2.6.26-rc5-mm3.orig/fs/proc/base.c 2008-06-25 17:11:04.000000000 +0200
>>+++ linux-2.6.26-rc5-mm3/fs/proc/base.c 2008-07-01 09:09:30.000000000 +0200
>>@@ -1158,6 +1158,76 @@ static const struct file_operations proc
>> };
>> #endif
>>
>>+static ssize_t next_syscall_data_read(struct file *file, char __user *buf,
>>+ size_t count, loff_t *ppos)
>>+{
>>+ struct task_struct *task;
>>+ char *page;
>>+ ssize_t length;
>>+
>>+ task = get_proc_task(file->f_path.dentry->d_inode);
>>+ if (!task)
>>+ return -ESRCH;
>>+
>>+ if (count >= PAGE_SIZE)
>>+ count = PAGE_SIZE - 1;
>>+
>>+ length = -ENOMEM;
>>+ page = (char *) __get_free_page(GFP_TEMPORARY);
>>+ if (!page)
>>+ goto out;
>>+
>>+ length = get_next_syscall_data(task, (char *) page, count);
>>+ if (length >= 0)
>>+ length = simple_read_from_buffer(buf, count, ppos,
>>+ (char *)page, length);
>>+ free_page((unsigned long) page);
>>+
>>+out:
>>+ put_task_struct(task);
>>+ return length;
>>+}
>>+
>>+static ssize_t next_syscall_data_write(struct file *file,
>>+ const char __user *buf,
>>+ size_t count, loff_t *ppos)
>>+{
>>+ struct inode *inode = file->f_path.dentry->d_inode;
>>+ char *page;
>>+ ssize_t length;
>>+
>>+ if (pid_task(proc_pid(inode), PIDTYPE_PID) != current)
>>+ return -EPERM;
>>+
>>+ if (count >= PAGE_SIZE)
>>+ count = PAGE_SIZE - 1;
>>+
>>+ if (*ppos != 0) {
>>+ /* No partial writes. */
>>+ return -EINVAL;
>>+ }
>>+ page = (char *)__get_free_page(GFP_TEMPORARY);
>>+ if (!page)
>>+ return -ENOMEM;
>>+ length = -EFAULT;
>>+ if (copy_from_user(page, buf, count))
>>+ goto out_free_page;
>>+
>>+ page[count] = '\0';
>>+
>>+ length = set_next_syscall_data(current, page);
>>+ if (!length)
>>+ length = count;
>>+
>>+out_free_page:
>>+ free_page((unsigned long) page);
>>+ return length;
>>+}
>>+
>>+static const struct file_operations proc_next_syscall_data_operations = {
>>+ .read = next_syscall_data_read,
>>+ .write = next_syscall_data_write,
>>+};
>>
>> #ifdef CONFIG_SCHED_DEBUG
>> /*
>>@@ -2853,6 +2923,11 @@ static const struct pid_entry tid_base_s
>> #ifdef CONFIG_TASK_IO_ACCOUNTING
>> INF("io", S_IRUGO, tid_io_accounting),
>> #endif
>>+ /*
>>+ * NOTE that this file is not added into tgid_base_stuff[] since it
>>+ * has to be specified on a per-thread basis.
>>+ */
>>+ REG("next_syscall_data", S_IRUGO|S_IWUSR, next_syscall_data),
>> };
>>
>> static int proc_tid_base_readdir(struct file * filp,
>>Index: linux-2.6.26-rc5-mm3/kernel/Makefile
>>===================================================================
>>--- linux-2.6.26-rc5-mm3.orig/kernel/Makefile 2008-06-25 17:10:41.000000000 +0200
>>+++ linux-2.6.26-rc5-mm3/kernel/Makefile 2008-06-27 09:03:01.000000000 +0200
>>@@ -9,7 +9,8 @@ obj-y = sched.o fork.o exec_domain.o
>> rcupdate.o extable.o params.o posix-timers.o \
>> kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
>> hrtimer.o rwsem.o nsproxy.o srcu.o semaphore.o \
>>- notifier.o ksysfs.o pm_qos_params.o sched_clock.o
>>+ notifier.o ksysfs.o pm_qos_params.o sched_clock.o \
>>+ next_syscall_data.o
>>
>> CFLAGS_REMOVE_sched.o = -pg -mno-spe
>>
>>Index: linux-2.6.26-rc5-mm3/kernel/next_syscall_data.c
>>===================================================================
>>--- /dev/null 1970-01-01 00:00:00.000000000 +0000
>>+++ linux-2.6.26-rc5-mm3/kernel/next_syscall_data.c 2008-07-01 10:39:43.000000000 +0200
>>@@ -0,0 +1,151 @@
>>+/*
>>+ * linux/kernel/next_syscall_data.c
>>+ *
>>+ *
>>+ * Provide the get_next_syscall_data() / set_next_syscall_data() routines
>>+ * (called from fs/proc/base.c).
>>+ * They allow to specify some particular data for the next syscall to be
>>+ * called.
>>+ * E.g. they can be used to specify the id for the next resource to be
>>+ * allocated, instead of letting the allocator set it for us.
>>+ */
>>+
>>+#include <linux/sched.h>
>>+#include <linux/ctype.h>
>>+
>>+
>>+
>>+ssize_t get_next_syscall_data(struct task_struct *task, char *buffer,
>>+ size_t size)
>>+{
>>+ struct next_syscall_data *nsd;
>>+ char *bufptr = buffer;
>>+ ssize_t rc, count = 0;
>>+ int i;
>>+
>>+ nsd = task->nsd;
>>+ if (!nsd || !nsd->ndata)
>>+ return snprintf(buffer, size, "UNSET\n");
>>+
>>+ count = snprintf(bufptr, size, "LONG%d ", nsd->ndata);
>>+
>>+ for (i = 0; i < nsd->ndata - 1; i++) {
>>+ rc = snprintf(&bufptr[count], size - count, "%ld ",
>>+ nsd->data[i]);
>>+ if (rc >= size - count)
>>+ return -ENOMEM;
>>+ count += rc;
>>+ }
>>+
>>+ rc = snprintf(&bufptr[count], size - count, "%ld\n", nsd->data[i]);
>>+ if (rc >= size - count)
>>+ return -ENOMEM;
>>+ count += rc;
>>+
>>+ return count;
>>+}
>>+
>>+static int fill_next_syscall_data(struct task_struct *task, int ndata,
>>+ char *buffer)
>>+{
>>+ char *token, *buff = buffer;
>>+ char *end;
>>+ struct next_syscall_data *nsd = task->nsd;
>>+ int i;
>>+
>>+ if (!nsd) {
>>+ nsd = kmalloc(sizeof(*nsd), GFP_KERNEL);
>>+ if (!nsd)
>>+ return -ENOMEM;
>>+ task->nsd = nsd;
>>+ }
>>+
>>+ nsd->ndata = ndata;
>>+
>>+ i = 0;
>>+ while ((token = strsep(&buff, " ")) != NULL && i < ndata) {
>>+ long data;
>>+
>>+ if (!*token)
>>+ goto out_free;
>>+ data = simple_strtol(token, &end, 0);
>>+ if (end == token || (*end && !isspace(*end)))
>>+ goto out_free;
>>+ nsd->data[i] = data;
>>+ i++;
>>+ }
>>+
>>+ if (i != ndata)
>>+ goto out_free;
>>+
>>+ return 0;
>>+
>>+out_free:
>>+ kfree(nsd);
>
Serge,
Thanks for reviewing this so fast!
>
> Shouldn't you also reset task->nsd to NULL here? :-)
Oh yes!
>
>
>>+ return -EINVAL;
>>+}
>>+
>>+/*
>>+ * Parses a line with the following format:
>>+ * <x> <id0> ... <idx-1>
>>+ * Currently, only x=1 is accepted.
>>+ * Any trailing character on the line is skipped.
>>+ */
>>+static int do_set_next_syscall_data(struct task_struct *task, char *nb,
>>+ char *buffer)
>>+{
>>+ int ndata;
>>+ char *end;
>>+
>>+ ndata = simple_strtol(nb, &end, 0);
>>+ if (*end)
>>+ return -EINVAL;
>>+
>>+ if (ndata > NDATA)
>>+ return -EINVAL;
>>+
>>+ return fill_next_syscall_data(task, ndata, buffer);
>>+}
>>+
>>+int reset_next_syscall_data(struct task_struct *task)
>
>
> Why have this return an int? It always returns 0, and callers ignore
> the return value.
>
You're right, will change it to a void.
>
>>+{
>>+ struct next_syscall_data *nsd;
>>+
>>+ nsd = task->nsd;
>>+ if (!nsd)
>>+ return 0;
>>+
>>+ task->nsd = NULL;
>>+ kfree(nsd);
>>+ return 0;
>>+}
>>+
>>+#define LONG_STR "LONG"
>>+#define RESET_STR "RESET"
>>+
>>+/*
>>+ * Parses a line written to /proc/self/task/<my_tid>/next_syscall_data.
>>+ * this line has the following format:
>>+ * LONG<x> id --> a sequence of id(s) is specified
>>+ * currently, only x=1 is accepted
>>+ */
>>+int set_next_syscall_data(struct task_struct *task, char *buffer)
>>+{
>>+ char *token, *out = buffer;
>>+ size_t sz;
>>+
>>+ if (!out)
>>+ return -EINVAL;
>>+
>>+ token = strsep(&out, " ");
>>+
>>+ sz = strlen(LONG_STR);
>>+
>>+ if (!strncmp(token, LONG_STR, sz))
>>+ return do_set_next_syscall_data(task, token + sz, out);
>>+
>>+ if (!strncmp(token, RESET_STR, strlen(RESET_STR)))
>>+ return reset_next_syscall_data(task);
>>+
>>+ return -EINVAL;
>>+}
>>Index: linux-2.6.26-rc5-mm3/kernel/fork.c
>>===================================================================
>>--- linux-2.6.26-rc5-mm3.orig/kernel/fork.c 2008-06-25 17:10:41.000000000 +0200
>>+++ linux-2.6.26-rc5-mm3/kernel/fork.c 2008-07-01 10:25:46.000000000 +0200
>>@@ -1077,6 +1077,8 @@ static struct task_struct *copy_process(
>> p->blocked_on = NULL; /* not blocked yet */
>> #endif
>>
>>+ p->nsd = NULL; /* no next syscall data is the default */
>>+
>> /* Perform scheduler related setup. Assign this task to a CPU. */
>> sched_fork(p, clone_flags);
>>
>>Index: linux-2.6.26-rc5-mm3/fs/exec.c
>>===================================================================
>>--- linux-2.6.26-rc5-mm3.orig/fs/exec.c 2008-06-25 17:11:05.000000000 +0200
>>+++ linux-2.6.26-rc5-mm3/fs/exec.c 2008-06-27 14:53:08.000000000 +0200
>>@@ -1014,6 +1014,12 @@ int flush_old_exec(struct linux_binprm *
>> flush_signal_handlers(current, 0);
>> flush_old_files(current->files);
>>
>>+ /*
>>+ * the next syscall data is not inherited across execve()
>>+ */
>>+ if (unlikely(current->nsd))
>>+ reset_next_syscall_data(current);
>>+
>> return 0;
>>
>> out:
>>Index: linux-2.6.26-rc5-mm3/kernel/exit.c
>>===================================================================
>>--- linux-2.6.26-rc5-mm3.orig/kernel/exit.c 2008-06-25 17:10:41.000000000 +0200
>>+++ linux-2.6.26-rc5-mm3/kernel/exit.c 2008-06-27 14:57:55.000000000 +0200
>>@@ -1069,6 +1069,10 @@ NORET_TYPE void do_exit(long code)
>>
>> proc_exit_connector(tsk);
>> exit_notify(tsk, group_dead);
>>+
>>+ if (unlikely(tsk->nsd))
>>+ exit_next_syscall_data(tsk);
>>+
>> #ifdef CONFIG_NUMA
>> mpol_put(tsk->mempolicy);
>> tsk->mempolicy = NULL;
>>
>>--
>
>
>
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