[PATCH] Support /dev/kmem access to vmalloc space (Marc Boucher)

From 2.4.17

drivers/char/mem.c

@@ -273,6 +273,8 @@ static ssize_t read_kmem(struct file *file, char *buf,
  	return virtr + read;
 }
 
+extern long vwrite(char *buf, char *addr, unsigned long count);
+
 /*
  * This function writes to the *virtual* memory as seen by the kernel.
  */
@@ -280,12 +282,46 @@ static ssize_t write_kmem(struct file * file, const char * buf,
 			  size_t count, loff_t *ppos)
 {
 	unsigned long p = *ppos;
+	ssize_t wrote = 0;
+	ssize_t virtr = 0;
+	char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 
-	if (p >= (unsigned long) high_memory)
-		return 0;
-	if (count > (unsigned long) high_memory - p)
-		count = (unsigned long) high_memory - p;
-	return do_write_mem(file, (void*)p, p, buf, count, ppos);
+	if (p < (unsigned long) high_memory) {
+		wrote = count;
+		if (count > (unsigned long) high_memory - p)
+			wrote = (unsigned long) high_memory - p;
+
+		wrote = do_write_mem(file, (void*)p, p, buf, wrote, ppos);
+
+		p += wrote;
+		buf += wrote;
+		count -= wrote;
+	}
+
+	if (count > 0) {
+		kbuf = (char *)__get_free_page(GFP_KERNEL);
+		if (!kbuf)
+			return -ENOMEM;
+		while (count > 0) {
+			int len = count;
+
+			if (len > PAGE_SIZE)
+				len = PAGE_SIZE;
+			if (len && copy_from_user(kbuf, buf, len)) {
+				free_page((unsigned long)kbuf);
+				return -EFAULT;
+			}
+			len = vwrite(kbuf, (char *)p, len);
+			count -= len;
+			buf += len;
+			virtr += len;
+			p += len;
+		}
+		free_page((unsigned long)kbuf);
+	}
+
+ 	*ppos = p;
+ 	return virtr + wrote;
 }
 
 #if !defined(__mc68000__)

mm/vmalloc.c

@@ -6,6 +6,7 @@
  *  SMP-safe vmalloc/vfree/ioremap, Tigran Aivazian <tigran@veritas.com>, May 2000
  */
 
+#include <linux/config.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/spinlock.h>
@@ -163,6 +164,7 @@ inline int vmalloc_area_pages (unsigned long address, unsigned long size,
 		ret = 0;
 	} while (address && (address < end));
 	spin_unlock(&init_mm.page_table_lock);
+	flush_cache_all();
 	return ret;
 }
 
@@ -282,3 +284,40 @@ long vread(char *buf, char *addr, unsigned long count)
 	read_unlock(&vmlist_lock);
 	return buf - buf_start;
 }
+
+long vwrite(char *buf, char *addr, unsigned long count)
+{
+	struct vm_struct *tmp;
+	char *vaddr, *buf_start = buf;
+	unsigned long n;
+
+	/* Don't allow overflow */
+	if ((unsigned long) addr + count < count)
+		count = -(unsigned long) addr;
+
+	read_lock(&vmlist_lock);
+	for (tmp = vmlist; tmp; tmp = tmp->next) {
+		vaddr = (char *) tmp->addr;
+		if (addr >= vaddr + tmp->size - PAGE_SIZE)
+			continue;
+		while (addr < vaddr) {
+			if (count == 0)
+				goto finished;
+			buf++;
+			addr++;
+			count--;
+		}
+		n = vaddr + tmp->size - PAGE_SIZE - addr;
+		do {
+			if (count == 0)
+				goto finished;
+			*addr = *buf;
+			buf++;
+			addr++;
+			count--;
+		} while (--n > 0);
+	}
+finished:
+	read_unlock(&vmlist_lock);
+	return buf - buf_start;
+}