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Commit 3cb4e162 authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Linus Torvalds
Browse files

proc: deduplicate /proc/*/cmdline implementation 

Code can be sonsolidated if a dummy region of 0 length is used in normal
case of \0-separated command line:

1) [arg_start, arg_end) + [dummy len=0]
2) [arg_start, arg_end) + [env_start, env_end)

Link: http://lkml.kernel.org/r/20180221193335.GB28678@avx2


Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6a6cbe75

fs/proc/base.c

+20 −33
Original line number Diff line number Diff line
@@ -213,9 +213,12 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, 
	char *page;

	unsigned long count = _count;

	unsigned long arg_start, arg_end, env_start, env_end;

	unsigned long len1, len2, len;

	unsigned long p;

	unsigned long len1, len2;

	char __user *buf0 = buf;

	struct {

		unsigned long p;

		unsigned long len;

	} cmdline[2];

	char c;

	int rv;
@@ -264,43 +267,21 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, 
	if (access_remote_vm(mm, arg_end - 1, &c, 1, FOLL_ANON) != 1)

		goto end;



	cmdline[0].p = arg_start;

	cmdline[0].len = len1;

	if (c == '\0') {

		/* Command line (set of strings) occupies whole ARGV. */

		if (len1 <= *pos)

			goto end;



		p = arg_start + *pos;

		len = len1 - *pos;

		while (count > 0 && len > 0) {

			unsigned int nr_read;



			nr_read = min3(count, len, PAGE_SIZE);

			nr_read = access_remote_vm(mm, p, page, nr_read, FOLL_ANON);

			if (nr_read == 0)

				goto end;



			if (copy_to_user(buf, page, nr_read)) {

				rv = -EFAULT;

				goto out_free_page;

			}



			p	+= nr_read;

			len	-= nr_read;

			buf	+= nr_read;

			count	-= nr_read;

		}

		cmdline[1].len = 0;

	} else {

		/*

		 * Command line (1 string) occupies ARGV and

		 * extends into ENVP.

		 */

		struct {

			unsigned long p;

			unsigned long len;

		} cmdline[2] = {

			{ .p = arg_start, .len = len1 },

			{ .p = env_start, .len = len2 },

		};

		cmdline[1].p = env_start;

		cmdline[1].len = len2;

	}



	{

		loff_t pos1 = *pos;

		unsigned int i;
@@ -310,6 +291,9 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, 
			i++;

		}

		while (i < 2) {

			unsigned long p;

			unsigned long len;



			p = cmdline[i].p + pos1;

			len = cmdline[i].len - pos1;

			while (count > 0 && len > 0) {
@@ -324,6 +308,9 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, 
				 * Command line can be shorter than whole ARGV

				 * even if last "marker" byte says it is not.

				 */

				if (c == '\0')

					nr_write = nr_read;

				else

					nr_write = strnlen(page, nr_read);



				if (copy_to_user(buf, page, nr_write)) {