[linux.git] / mm / util.c

#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/compiler.h>
#include <linux/export.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/security.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/mman.h>
#include <linux/hugetlb.h>
#include <linux/vmalloc.h>

#include <asm/uaccess.h>

#include "internal.h"

/**
 * kstrdup - allocate space for and copy an existing string
 * @s: the string to duplicate
 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
 */
char *kstrdup(const char *s, gfp_t gfp)
{
	size_t len;
	char *buf;

	if (!s)
		return NULL;

	len = strlen(s) + 1;
	buf = kmalloc_track_caller(len, gfp);
	if (buf)
		memcpy(buf, s, len);
	return buf;
}
EXPORT_SYMBOL(kstrdup);

/**
 * kstrndup - allocate space for and copy an existing string
 * @s: the string to duplicate
 * @max: read at most @max chars from @s
 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
 */
char *kstrndup(const char *s, size_t max, gfp_t gfp)
{
	size_t len;
	char *buf;

	if (!s)
		return NULL;

	len = strnlen(s, max);
	buf = kmalloc_track_caller(len+1, gfp);
	if (buf) {
		memcpy(buf, s, len);
		buf[len] = '\0';
	}
	return buf;
}
EXPORT_SYMBOL(kstrndup);

/**
 * kmemdup - duplicate region of memory
 *
 * @src: memory region to duplicate
 * @len: memory region length
 * @gfp: GFP mask to use
 */
void *kmemdup(const void *src, size_t len, gfp_t gfp)
{
	void *p;

	p = kmalloc_track_caller(len, gfp);
	if (p)
		memcpy(p, src, len);
	return p;
}
EXPORT_SYMBOL(kmemdup);

/**
 * memdup_user - duplicate memory region from user space
 *
 * @src: source address in user space
 * @len: number of bytes to copy
 *
 * Returns an ERR_PTR() on failure.
 */
void *memdup_user(const void __user *src, size_t len)
{
	void *p;

	/*
	 * Always use GFP_KERNEL, since copy_from_user() can sleep and
	 * cause pagefault, which makes it pointless to use GFP_NOFS
	 * or GFP_ATOMIC.
	 */
	p = kmalloc_track_caller(len, GFP_KERNEL);
	if (!p)
		return ERR_PTR(-ENOMEM);

	if (copy_from_user(p, src, len)) {
		kfree(p);
		return ERR_PTR(-EFAULT);
	}

	return p;
}
EXPORT_SYMBOL(memdup_user);

/*
 * strndup_user - duplicate an existing string from user space
 * @s: The string to duplicate
 * @n: Maximum number of bytes to copy, including the trailing NUL.
 */
char *strndup_user(const char __user *s, long n)
{
	char *p;
	long length;

	length = strnlen_user(s, n);

	if (!length)
		return ERR_PTR(-EFAULT);

	if (length > n)
		return ERR_PTR(-EINVAL);

	p = memdup_user(s, length);

	if (IS_ERR(p))
		return p;

	p[length - 1] = '\0';

	return p;
}
EXPORT_SYMBOL(strndup_user);

void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
		struct vm_area_struct *prev, struct rb_node *rb_parent)
{
	struct vm_area_struct *next;

	vma->vm_prev = prev;
	if (prev) {
		next = prev->vm_next;
		prev->vm_next = vma;
	} else {
		mm->mmap = vma;
		if (rb_parent)
			next = rb_entry(rb_parent,
					struct vm_area_struct, vm_rb);
		else
			next = NULL;
	}
	vma->vm_next = next;
	if (next)
		next->vm_prev = vma;
}

/* Check if the vma is being used as a stack by this task */
static int vm_is_stack_for_task(struct task_struct *t,
				struct vm_area_struct *vma)
{
	return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
}

/*
 * Check if the vma is being used as a stack.
 * If is_group is non-zero, check in the entire thread group or else
 * just check in the current task. Returns the task_struct of the task
 * that the vma is stack for. Must be called under rcu_read_lock().
 */
struct task_struct *task_of_stack(struct task_struct *task,
				struct vm_area_struct *vma, bool in_group)
{
	if (vm_is_stack_for_task(task, vma))
		return task;

	if (in_group) {
		struct task_struct *t;

		for_each_thread(task, t) {
			if (vm_is_stack_for_task(t, vma))
				return t;
		}
	}

	return NULL;
}

#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
void arch_pick_mmap_layout(struct mm_struct *mm)
{
	mm->mmap_base = TASK_UNMAPPED_BASE;
	mm->get_unmapped_area = arch_get_unmapped_area;
}
#endif

/*
 * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
 * back to the regular GUP.
 * If the architecture not support this function, simply return with no
 * page pinned
 */
int __weak __get_user_pages_fast(unsigned long start,
				 int nr_pages, int write, struct page **pages)
{
	return 0;
}
EXPORT_SYMBOL_GPL(__get_user_pages_fast);

/**
 * get_user_pages_fast() - pin user pages in memory
 * @start:	starting user address
 * @nr_pages:	number of pages from start to pin
 * @write:	whether pages will be written to
 * @pages:	array that receives pointers to the pages pinned.
 *		Should be at least nr_pages long.
 *
 * Returns number of pages pinned. This may be fewer than the number
 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 * were pinned, returns -errno.
 *
 * get_user_pages_fast provides equivalent functionality to get_user_pages,
 * operating on current and current->mm, with force=0 and vma=NULL. However
 * unlike get_user_pages, it must be called without mmap_sem held.
 *
 * get_user_pages_fast may take mmap_sem and page table locks, so no
 * assumptions can be made about lack of locking. get_user_pages_fast is to be
 * implemented in a way that is advantageous (vs get_user_pages()) when the
 * user memory area is already faulted in and present in ptes. However if the
 * pages have to be faulted in, it may turn out to be slightly slower so
 * callers need to carefully consider what to use. On many architectures,
 * get_user_pages_fast simply falls back to get_user_pages.
 */
int __weak get_user_pages_fast(unsigned long start,
				int nr_pages, int write, struct page **pages)
{
	struct mm_struct *mm = current->mm;
	int ret;

	down_read(&mm->mmap_sem);
	ret = get_user_pages(current, mm, start, nr_pages,
					write, 0, pages, NULL);
	up_read(&mm->mmap_sem);

	return ret;
}
EXPORT_SYMBOL_GPL(get_user_pages_fast);

unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
	unsigned long len, unsigned long prot,
	unsigned long flag, unsigned long pgoff)
{
	unsigned long ret;
	struct mm_struct *mm = current->mm;
	unsigned long populate;

	ret = security_mmap_file(file, prot, flag);
	if (!ret) {
		down_write(&mm->mmap_sem);
		ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
				    &populate);
		up_write(&mm->mmap_sem);
		if (populate)
			mm_populate(ret, populate);
	}
	return ret;
}

unsigned long vm_mmap(struct file *file, unsigned long addr,
	unsigned long len, unsigned long prot,
	unsigned long flag, unsigned long offset)
{
	if (unlikely(offset + PAGE_ALIGN(len) < offset))
		return -EINVAL;
	if (unlikely(offset & ~PAGE_MASK))
		return -EINVAL;

	return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
}
EXPORT_SYMBOL(vm_mmap);

void kvfree(const void *addr)
{
	if (is_vmalloc_addr(addr))
		vfree(addr);
	else
		kfree(addr);
}
EXPORT_SYMBOL(kvfree);

struct address_space *page_mapping(struct page *page)
{
	struct address_space *mapping = page->mapping;

	/* This happens if someone calls flush_dcache_page on slab page */
	if (unlikely(PageSlab(page)))
		return NULL;

	if (unlikely(PageSwapCache(page))) {
		swp_entry_t entry;

		entry.val = page_private(page);
		mapping = swap_address_space(entry);
	} else if ((unsigned long)mapping & PAGE_MAPPING_ANON)
		mapping = NULL;
	return mapping;
}

int overcommit_ratio_handler(struct ctl_table *table, int write,
			     void __user *buffer, size_t *lenp,
			     loff_t *ppos)
{
	int ret;

	ret = proc_dointvec(table, write, buffer, lenp, ppos);
	if (ret == 0 && write)
		sysctl_overcommit_kbytes = 0;
	return ret;
}

int overcommit_kbytes_handler(struct ctl_table *table, int write,
			     void __user *buffer, size_t *lenp,
			     loff_t *ppos)
{
	int ret;

	ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
	if (ret == 0 && write)
		sysctl_overcommit_ratio = 0;
	return ret;
}

/*
 * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
 */
unsigned long vm_commit_limit(void)
{
	unsigned long allowed;

	if (sysctl_overcommit_kbytes)
		allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
	else
		allowed = ((totalram_pages - hugetlb_total_pages())
			   * sysctl_overcommit_ratio / 100);
	allowed += total_swap_pages;

	return allowed;
}

/**
 * get_cmdline() - copy the cmdline value to a buffer.
 * @task:     the task whose cmdline value to copy.
 * @buffer:   the buffer to copy to.
 * @buflen:   the length of the buffer. Larger cmdline values are truncated
 *            to this length.
 * Returns the size of the cmdline field copied. Note that the copy does
 * not guarantee an ending NULL byte.
 */
int get_cmdline(struct task_struct *task, char *buffer, int buflen)
{
	int res = 0;
	unsigned int len;
	struct mm_struct *mm = get_task_mm(task);
	if (!mm)
		goto out;
	if (!mm->arg_end)
		goto out_mm;	/* Shh! No looking before we're done */

	len = mm->arg_end - mm->arg_start;

	if (len > buflen)
		len = buflen;

	res = access_process_vm(task, mm->arg_start, buffer, len, 0);

	/*
	 * If the nul at the end of args has been overwritten, then
	 * assume application is using setproctitle(3).
	 */
	if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
		len = strnlen(buffer, res);
		if (len < res) {
			res = len;
		} else {
			len = mm->env_end - mm->env_start;
			if (len > buflen - res)
				len = buflen - res;
			res += access_process_vm(task, mm->env_start,
						 buffer+res, len, 0);
			res = strnlen(buffer, res);
		}
	}
out_mm:
	mmput(mm);
out:
	return res;
}
Commit	Line	Data
16d69265	1	#include <linux/mm.h>
30992c97 MM	2	#include <linux/slab.h>
30992c97 MM	3	#include <linux/string.h>
3b32123d	4	#include <linux/compiler.h>
b95f1b31	5	#include <linux/export.h>
96840aa0	6	#include <linux/err.h>
3b8f14b4	7	#include <linux/sched.h>
eb36c587	8	#include <linux/security.h>
9800339b	9	#include <linux/swap.h>
33806f06	10	#include <linux/swapops.h>
00619bcc JM	11	#include <linux/mman.h>
00619bcc JM	12	#include <linux/hugetlb.h>
39f1f78d	13	#include <linux/vmalloc.h>
00619bcc	14
96840aa0	15	#include <asm/uaccess.h>
30992c97	16
6038def0 NK	17	#include "internal.h"
6038def0 NK	18
30992c97	19	/**
30992c97	20	* kstrdup - allocate space for and copy an existing string
30992c97 MM	21	* @s: the string to duplicate
	22	* @gfp: the GFP mask used in the kmalloc() call when allocating memory
	23	*/
	24	char kstrdup(const char s, gfp_t gfp)
	25	{
	26	size_t len;
	27	char *buf;
	28
	29	if (!s)
	30	return NULL;
	31
	32	len = strlen(s) + 1;
1d2c8eea	33	buf = kmalloc_track_caller(len, gfp);
30992c97 MM	34	if (buf)
	35	memcpy(buf, s, len);
	36	return buf;
	37	}
	38	EXPORT_SYMBOL(kstrdup);
96840aa0	39
1e66df3e JF	40	/**
	41	* kstrndup - allocate space for and copy an existing string
	42	* @s: the string to duplicate
	43	* @max: read at most @max chars from @s
	44	* @gfp: the GFP mask used in the kmalloc() call when allocating memory
	45	*/
	46	char kstrndup(const char s, size_t max, gfp_t gfp)
	47	{
	48	size_t len;
	49	char *buf;
	50
	51	if (!s)
	52	return NULL;
	53
	54	len = strnlen(s, max);
	55	buf = kmalloc_track_caller(len+1, gfp);
	56	if (buf) {
	57	memcpy(buf, s, len);
	58	buf[len] = '\0';
	59	}
	60	return buf;
	61	}
	62	EXPORT_SYMBOL(kstrndup);
	63
1a2f67b4 AD	64	/**
	65	* kmemdup - duplicate region of memory
	66	*
	67	* @src: memory region to duplicate
	68	* @len: memory region length
	69	* @gfp: GFP mask to use
	70	*/
	71	void kmemdup(const void src, size_t len, gfp_t gfp)
	72	{
	73	void *p;
	74
1d2c8eea	75	p = kmalloc_track_caller(len, gfp);
1a2f67b4 AD	76	if (p)
	77	memcpy(p, src, len);
	78	return p;
	79	}
	80	EXPORT_SYMBOL(kmemdup);
	81
610a77e0 LZ	82	/**
	83	* memdup_user - duplicate memory region from user space
	84	*
	85	* @src: source address in user space
	86	* @len: number of bytes to copy
	87	*
	88	* Returns an ERR_PTR() on failure.
	89	*/
	90	void memdup_user(const void __user src, size_t len)
	91	{
	92	void *p;
	93
	94	/*
	95	* Always use GFP_KERNEL, since copy_from_user() can sleep and
	96	* cause pagefault, which makes it pointless to use GFP_NOFS
	97	* or GFP_ATOMIC.
	98	*/
	99	p = kmalloc_track_caller(len, GFP_KERNEL);
	100	if (!p)
	101	return ERR_PTR(-ENOMEM);
	102
	103	if (copy_from_user(p, src, len)) {
	104	kfree(p);
	105	return ERR_PTR(-EFAULT);
	106	}
	107
	108	return p;
	109	}
	110	EXPORT_SYMBOL(memdup_user);
	111
96840aa0 DA	112	/*
96840aa0 DA	113	* strndup_user - duplicate an existing string from user space
96840aa0 DA	114	* @s: The string to duplicate
	115	* @n: Maximum number of bytes to copy, including the trailing NUL.
	116	*/
	117	char strndup_user(const char __user s, long n)
	118	{
	119	char *p;
	120	long length;
	121
	122	length = strnlen_user(s, n);
	123
	124	if (!length)
	125	return ERR_PTR(-EFAULT);
	126
	127	if (length > n)
	128	return ERR_PTR(-EINVAL);
	129
90d74045	130	p = memdup_user(s, length);
96840aa0	131
90d74045 JL	132	if (IS_ERR(p))
90d74045 JL	133	return p;
96840aa0 DA	134
	135	p[length - 1] = '\0';
	136
	137	return p;
	138	}
	139	EXPORT_SYMBOL(strndup_user);
16d69265	140
6038def0 NK	141	void __vma_link_list(struct mm_struct mm, struct vm_area_struct vma,
	142	struct vm_area_struct prev, struct rb_node rb_parent)
	143	{
	144	struct vm_area_struct *next;
	145
	146	vma->vm_prev = prev;
	147	if (prev) {
	148	next = prev->vm_next;
	149	prev->vm_next = vma;
	150	} else {
	151	mm->mmap = vma;
	152	if (rb_parent)
	153	next = rb_entry(rb_parent,
	154	struct vm_area_struct, vm_rb);
	155	else
	156	next = NULL;
	157	}
	158	vma->vm_next = next;
	159	if (next)
	160	next->vm_prev = vma;
	161	}
	162
b7643757 SP	163	/* Check if the vma is being used as a stack by this task */
	164	static int vm_is_stack_for_task(struct task_struct *t,
	165	struct vm_area_struct *vma)
	166	{
	167	return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
	168	}
	169
	170	/*
	171	* Check if the vma is being used as a stack.
	172	* If is_group is non-zero, check in the entire thread group or else
58cb6548 ON	173	* just check in the current task. Returns the task_struct of the task
58cb6548 ON	174	* that the vma is stack for. Must be called under rcu_read_lock().
b7643757	175	*/
58cb6548 ON	176	struct task_struct task_of_stack(struct task_struct task,
58cb6548 ON	177	struct vm_area_struct *vma, bool in_group)
b7643757	178	{
b7643757	179	if (vm_is_stack_for_task(task, vma))
58cb6548	180	return task;
b7643757 SP	181
	182	if (in_group) {
	183	struct task_struct *t;
b7643757	184
4449a51a	185	for_each_thread(task, t) {
58cb6548 ON	186	if (vm_is_stack_for_task(t, vma))
58cb6548 ON	187	return t;
4449a51a	188	}
b7643757 SP	189	}
b7643757 SP	190
58cb6548	191	return NULL;
b7643757 SP	192	}
b7643757 SP	193
efc1a3b1	194	#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
16d69265 AM	195	void arch_pick_mmap_layout(struct mm_struct *mm)
	196	{
	197	mm->mmap_base = TASK_UNMAPPED_BASE;
	198	mm->get_unmapped_area = arch_get_unmapped_area;
16d69265 AM	199	}
16d69265 AM	200	#endif
912985dc	201
45888a0c XG	202	/*
	203	* Like get_user_pages_fast() except its IRQ-safe in that it won't fall
	204	* back to the regular GUP.
25985edc	205	* If the architecture not support this function, simply return with no
45888a0c XG	206	* page pinned
45888a0c XG	207	*/
3b32123d	208	int __weak __get_user_pages_fast(unsigned long start,
45888a0c XG	209	int nr_pages, int write, struct page **pages)
	210	{
	211	return 0;
	212	}
	213	EXPORT_SYMBOL_GPL(__get_user_pages_fast);
	214
9de100d0 AG	215	/**
	216	* get_user_pages_fast() - pin user pages in memory
	217	* @start: starting user address
	218	* @nr_pages: number of pages from start to pin
	219	* @write: whether pages will be written to
	220	* @pages: array that receives pointers to the pages pinned.
	221	* Should be at least nr_pages long.
	222	*
9de100d0 AG	223	* Returns number of pages pinned. This may be fewer than the number
	224	* requested. If nr_pages is 0 or negative, returns 0. If no pages
	225	* were pinned, returns -errno.
d2bf6be8 NP	226	*
	227	* get_user_pages_fast provides equivalent functionality to get_user_pages,
	228	* operating on current and current->mm, with force=0 and vma=NULL. However
	229	* unlike get_user_pages, it must be called without mmap_sem held.
	230	*
	231	* get_user_pages_fast may take mmap_sem and page table locks, so no
	232	* assumptions can be made about lack of locking. get_user_pages_fast is to be
	233	* implemented in a way that is advantageous (vs get_user_pages()) when the
	234	* user memory area is already faulted in and present in ptes. However if the
	235	* pages have to be faulted in, it may turn out to be slightly slower so
	236	* callers need to carefully consider what to use. On many architectures,
	237	* get_user_pages_fast simply falls back to get_user_pages.
9de100d0	238	*/
3b32123d	239	int __weak get_user_pages_fast(unsigned long start,
912985dc RR	240	int nr_pages, int write, struct page **pages)
	241	{
	242	struct mm_struct *mm = current->mm;
	243	int ret;
	244
	245	down_read(&mm->mmap_sem);
	246	ret = get_user_pages(current, mm, start, nr_pages,
	247	write, 0, pages, NULL);
	248	up_read(&mm->mmap_sem);
	249
	250	return ret;
	251	}
	252	EXPORT_SYMBOL_GPL(get_user_pages_fast);
ca2b84cb	253
eb36c587 AV	254	unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
	255	unsigned long len, unsigned long prot,
	256	unsigned long flag, unsigned long pgoff)
	257	{
	258	unsigned long ret;
	259	struct mm_struct *mm = current->mm;
41badc15	260	unsigned long populate;
eb36c587 AV	261
	262	ret = security_mmap_file(file, prot, flag);
	263	if (!ret) {
	264	down_write(&mm->mmap_sem);
bebeb3d6 ML	265	ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
bebeb3d6 ML	266	&populate);
eb36c587	267	up_write(&mm->mmap_sem);
41badc15 ML	268	if (populate)
41badc15 ML	269	mm_populate(ret, populate);
eb36c587 AV	270	}
	271	return ret;
	272	}
	273
	274	unsigned long vm_mmap(struct file *file, unsigned long addr,
	275	unsigned long len, unsigned long prot,
	276	unsigned long flag, unsigned long offset)
	277	{
	278	if (unlikely(offset + PAGE_ALIGN(len) < offset))
	279	return -EINVAL;
	280	if (unlikely(offset & ~PAGE_MASK))
	281	return -EINVAL;
	282
	283	return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
	284	}
	285	EXPORT_SYMBOL(vm_mmap);
	286
39f1f78d AV	287	void kvfree(const void *addr)
	288	{
	289	if (is_vmalloc_addr(addr))
	290	vfree(addr);
	291	else
	292	kfree(addr);
	293	}
	294	EXPORT_SYMBOL(kvfree);
	295
9800339b SL	296	struct address_space page_mapping(struct page page)
	297	{
	298	struct address_space *mapping = page->mapping;
	299
03e5ac2f MP	300	/* This happens if someone calls flush_dcache_page on slab page */
	301	if (unlikely(PageSlab(page)))
	302	return NULL;
	303
33806f06 SL	304	if (unlikely(PageSwapCache(page))) {
	305	swp_entry_t entry;
	306
	307	entry.val = page_private(page);
	308	mapping = swap_address_space(entry);
d2cf5ad6	309	} else if ((unsigned long)mapping & PAGE_MAPPING_ANON)
9800339b SL	310	mapping = NULL;
	311	return mapping;
	312	}
	313
49f0ce5f JM	314	int overcommit_ratio_handler(struct ctl_table *table, int write,
	315	void __user buffer, size_t lenp,
	316	loff_t *ppos)
	317	{
	318	int ret;
	319
	320	ret = proc_dointvec(table, write, buffer, lenp, ppos);
	321	if (ret == 0 && write)
	322	sysctl_overcommit_kbytes = 0;
	323	return ret;
	324	}
	325
	326	int overcommit_kbytes_handler(struct ctl_table *table, int write,
	327	void __user buffer, size_t lenp,
	328	loff_t *ppos)
	329	{
	330	int ret;
	331
	332	ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
	333	if (ret == 0 && write)
	334	sysctl_overcommit_ratio = 0;
	335	return ret;
	336	}
	337
00619bcc JM	338	/*
	339	* Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
	340	*/
	341	unsigned long vm_commit_limit(void)
	342	{
49f0ce5f JM	343	unsigned long allowed;
	344
	345	if (sysctl_overcommit_kbytes)
	346	allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
	347	else
	348	allowed = ((totalram_pages - hugetlb_total_pages())
	349	* sysctl_overcommit_ratio / 100);
	350	allowed += total_swap_pages;
	351
	352	return allowed;
00619bcc JM	353	}
00619bcc JM	354
a9090253 WR	355	/**
	356	* get_cmdline() - copy the cmdline value to a buffer.
	357	* @task: the task whose cmdline value to copy.
	358	* @buffer: the buffer to copy to.
	359	* @buflen: the length of the buffer. Larger cmdline values are truncated
	360	* to this length.
	361	* Returns the size of the cmdline field copied. Note that the copy does
	362	* not guarantee an ending NULL byte.
	363	*/
	364	int get_cmdline(struct task_struct task, char buffer, int buflen)
	365	{
	366	int res = 0;
	367	unsigned int len;
	368	struct mm_struct *mm = get_task_mm(task);
	369	if (!mm)
	370	goto out;
	371	if (!mm->arg_end)
	372	goto out_mm; /* Shh! No looking before we're done */
	373
	374	len = mm->arg_end - mm->arg_start;
	375
	376	if (len > buflen)
	377	len = buflen;
	378
	379	res = access_process_vm(task, mm->arg_start, buffer, len, 0);
	380
	381	/*
	382	* If the nul at the end of args has been overwritten, then
	383	* assume application is using setproctitle(3).
	384	*/
	385	if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
	386	len = strnlen(buffer, res);
	387	if (len < res) {
	388	res = len;
	389	} else {
	390	len = mm->env_end - mm->env_start;
	391	if (len > buflen - res)
	392	len = buflen - res;
	393	res += access_process_vm(task, mm->env_start,
	394	buffer+res, len, 0);
	395	res = strnlen(buffer, res);
	396	}
	397	}
	398	out_mm:
	399	mmput(mm);
	400	out:
	401	return res;
	402	}