Litmus core: add copy_and_chomp() helper

We read in a line from userspace and remove the trailing newline in a
number of places. This function extracts the common code to avoid
future duplication.

2 files changed, 44 insertions, 28 deletions

diff --git a/include/litmus/litmus_proc.h b/include/litmus/litmus_proc.h
index fbc0082b2d21..6800e725d48c 100644
--- a/include/litmus/litmus_proc.h
+++ b/include/litmus/litmus_proc.h
@@ -17,3 +17,9 @@ long make_plugin_proc_dir(struct sched_plugin* plugin,
  */
 void remove_plugin_proc_dir(struct sched_plugin* plugin);
 
+
+/* Copy at most size-1 bytes from ubuf into kbuf, null-terminate buf, and
+ * remove a '\n' if present. Returns the number of bytes that were read or
+ * -EFAULT. */
+int copy_and_chomp(char *kbuf, unsigned long ksize,
+                   __user const char* ubuf, unsigned long ulength);
diff --git a/litmus/litmus_proc.c b/litmus/litmus_proc.c
index 81ea5c35d291..e3f3f11f80e1 100644
--- a/litmus/litmus_proc.c
+++ b/litmus/litmus_proc.c
@@ -69,18 +69,9 @@ static int proc_write_curr(struct file *file,
         char name[65];
         struct sched_plugin* found;
 
-        if(count > 64)
-                len = 64;
-        else
-                len = count;
-
-        if(copy_from_user(name, buffer, len))
-                return -EFAULT;
-
-        name[len] = '\0';
-        /* chomp name */
-        if (len > 1 && name[len - 1] == '\n')
-                name[len - 1] = '\0';
+        len = copy_and_chomp(name, sizeof(name), buffer, count);
+        if (len < 0)
+                return len;
 
         found = find_sched_plugin(name);
 
@@ -113,36 +104,28 @@ static int proc_write_release_master(struct file *file,
                                      unsigned long count,
                                      void *data)
 {
-        int cpu, err, online = 0;
+        int cpu, err, len, online = 0;
         char msg[64];
 
-        if (count > 63)
-                return -EINVAL;
-
-        if (copy_from_user(msg, buffer, count))
-                return -EFAULT;
+        len = copy_and_chomp(msg, sizeof(msg), buffer, count);
 
-        /* terminate */
-        msg[count] = '\0';
-        /* chomp */
-        if (count > 1 && msg[count - 1] == '\n')
-                msg[count - 1] = '\0';
+        if (len < 0)
+                return len;
 
-        if (strcmp(msg, "NO_CPU") == 0) {
+        if (strcmp(msg, "NO_CPU") == 0)
                 atomic_set(&release_master_cpu, NO_CPU);
-                return count;
-        } else {
+        else {
                 err = sscanf(msg, "%d", &cpu);
                 if (err == 1 && cpu >= 0 && (online = cpu_online(cpu))) {
                         atomic_set(&release_master_cpu, cpu);
-                        return count;
                 } else {
                         TRACE("invalid release master: '%s' "
                               "(err:%d cpu:%d online:%d)\n",
                               msg, err, cpu, online);
-                        return -EINVAL;
+                        len = -EINVAL;
                 }
         }
+        return len;
 }
 #endif
 
@@ -257,3 +240,30 @@ void remove_plugin_proc_dir(struct sched_plugin* plugin)
         }
         remove_proc_entry(plugin->plugin_name, plugs_dir);
 }
+
+
+
+/* misc. I/O helper functions */
+
+int copy_and_chomp(char *kbuf, unsigned long ksize,
+                   __user const char* ubuf, unsigned long ulength)
+{
+        /* caller must provide buffer space */
+        BUG_ON(!ksize);
+
+        ksize--; /* leave space for null byte */
+
+        if (ksize > ulength)
+                ksize = ulength;
+
+        if(copy_from_user(kbuf, ubuf, ksize))
+                return -EFAULT;
+
+        kbuf[ksize] = '\0';
+
+        /* chomp kbuf */
+        if (ksize > 0 && kbuf[ksize - 1] == '\n')
+                kbuf[ksize - 1] = '\0';
+
+        return ksize;
+}