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Commit a0a07b87 authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Linus Torvalds
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proc: less code duplication in /proc/*/cmdline 

After staring at this code for a while I've figured using small 2-entry
array describing ARGV and ENVP is the way to address code duplication
critique.

Link: http://lkml.kernel.org/r/20170105185724.GA12027@avx2


Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4e4a7fb7

fs/proc/base.c

+56 −88
Original line number Diff line number Diff line
@@ -292,16 +292,27 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, 
		}

	} else {

		/*

		 * Command line (1 string) occupies ARGV and maybe

		 * Command line (1 string) occupies ARGV and

		 * extends into ENVP.

		 */

		if (len1 + len2 <= *pos)

			goto skip_argv_envp;

		if (len1 <= *pos)

			goto skip_argv;

		struct {

			unsigned long p;

			unsigned long len;

		} cmdline[2] = {

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

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

		};

		loff_t pos1 = *pos;

		unsigned int i;



		p = arg_start + *pos;

		len = len1 - *pos;

		i = 0;

		while (i < 2 && pos1 >= cmdline[i].len) {

			pos1 -= cmdline[i].len;

			i++;

		}

		while (i < 2) {

			p = cmdline[i].p + pos1;

			len = cmdline[i].len - pos1;

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

				unsigned int _count, l;

				int nr_read;
@@ -339,54 +350,11 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, 
				if (final)

					goto out_free_page;

			}

skip_argv:

		/*

		 * Command line (1 string) occupies ARGV and

		 * extends into ENVP.

		 */

		if (len1 <= *pos) {

			p = env_start + *pos - len1;

			len = len1 + len2 - *pos;

		} else {

			p = env_start;

			len = len2;

		}

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

			unsigned int _count, l;

			int nr_read;

			bool final;



			_count = min3(count, len, PAGE_SIZE);

			nr_read = access_remote_vm(mm, p, page, _count, 0);

			if (nr_read < 0)

				rv = nr_read;

			if (nr_read <= 0)

				goto out_free_page;



			/* Find EOS. */

			final = false;

			l = strnlen(page, nr_read);

			if (l < nr_read) {

				nr_read = l;

				final = true;

			}



			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;

			rv	+= nr_read;



			if (final)

				goto out_free_page;

			/* Only first chunk can be read partially. */

			pos1 = 0;

			i++;

		}

skip_argv_envp:

		;

	}



out_free_page: