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Date: Thu, 5 Jan 2017 21:57:24 +0300
From: Alexey Dobriyan <adobriyan@...il.com>
To: akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH] 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.
Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---
fs/proc/base.c | 144 ++++++++++++++++++++++-----------------------------------
1 file changed, 56 insertions(+), 88 deletions(-)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -292,101 +292,69 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf,
}
} else {
/*
- * Command line (1 string) occupies ARGV and maybe
- * extends into ENVP.
- */
- if (len1 + len2 <= *pos)
- goto skip_argv_envp;
- if (len1 <= *pos)
- goto skip_argv;
-
- p = arg_start + *pos;
- len = len1 - *pos;
- 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;
-
- /*
- * Command line can be shorter than whole ARGV
- * even if last "marker" byte says it is not.
- */
- 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;
- }
-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;
+ 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;
+
+ i = 0;
+ while (i < 2 && pos1 >= cmdline[i].len) {
+ pos1 -= cmdline[i].len;
+ i++;
}
- 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;
+ 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;
+ 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;
+
+ /*
+ * Command line can be shorter than whole ARGV
+ * even if last "marker" byte says it is not.
+ */
+ 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;
}
- 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:
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