[PATCH] Make modules work in Linus' tree on ARM

Russell King
2003-08-14T12:09:20Z

This patch allows modules to work in Linus' tree for ARM, and is the one
thing which prevents Linus' tree from building for any ARM machine.

After reviewing the /proc/kcore and kclist issues, I've decided that I'm
no longer prepared to even _think_ about supporting /proc/kcore on ARM -
it just gets too ugly, and adds too much code to make it worth the effort,
the time or the energy to implement a solution to that problem. This is
especially true since most people use kgdb or similar rather than
/proc/kcore anyway. /proc/kcore is a "wouldn't it be nice" feature.

The reasons that I'm going with this solution rather than fixing
/proc/kcore is that:

- to add a kclist entry for each module would mean hacking the kclist
structure into vm_struct's ->page pointer with disgusting hacks.
I think we can all agree that this isn't the way to go. The
alternative is to create Yet Another Memory Allocator, and this
isn't something I want to see in what is now an embedded architecture.

- we'd need to find some way to dynamically reserve the virtual mapped
memory regions for the kernel direct mapped RAM. Since ARM uses a
generic memory initialisation implementation which handles contiguous
and discontiguous memory, it doesn't lend itself well to the kclist
approach, and I'm not about to add extra callbacks from init/main.c
(so we have kmalloc available) just to support this.

If someone _else_ wants to put the effort into fixing ARM modules to work
nicely with /proc/kcore, be my guest - I'm just no longer interested in
this problem space.

Maybe in 2.7 a generic "reserve an area of memory in this region"
function like __get_vm_area below is in order?

Therefore, I'm providing a patch which adds the necessary changes to the
core kernel code to make the current modules solution work for ARM.

Please merge.

--- orig/mm/vmalloc.c Tue May 27 10:05:48 2003
+++ linux/mm/vmalloc.c Tue May 27 10:14:45 2003
@@ -178,21 +178,11 @@
return err;
}

-
-/**
- * get_vm_area - reserve a contingous kernel virtual area
- *
- * @size: size of the area
- * @flags: %VM_IOREMAP for I/O mappings or VM_ALLOC
- *
- * Search an area of @size in the kernel virtual mapping area,
- * and reserved it for out purposes. Returns the area descriptor
- * on success or %NULL on failure.
- */
-struct vm_struct *get_vm_area(unsigned long size, unsigned long flags)
+struct vm_struct *__get_vm_area(unsigned long size, unsigned long flags,
+ unsigned long start, unsigned long end)
{
struct vm_struct **p, *tmp, *area;
- unsigned long addr = VMALLOC_START;
+ unsigned long addr = start;

area = kmalloc(sizeof(*area), GFP_KERNEL);
if (unlikely(!area))
@@ -209,12 +199,14 @@

write_lock(&vmlist_lock);
for (p = &vmlist; (tmp = *p) ;p = &tmp->next) {
+ if ((unsigned long)tmp->addr < addr)
+ continue;
if ((size + addr) < addr)
goto out;
if (size + addr <= (unsigned long)tmp->addr)
goto found;
addr = tmp->size + (unsigned long)tmp->addr;
- if (addr > VMALLOC_END-size)
+ if (addr > end - size)
goto out;
}

@@ -239,6 +231,21 @@
}

/**
+ * get_vm_area - reserve a contingous kernel virtual area
+ *
+ * @size: size of the area
+ * @flags: %VM_IOREMAP for I/O mappings or VM_ALLOC
+ *
+ * Search an area of @size in the kernel virtual mapping area,
+ * and reserved it for out purposes. Returns the area descriptor
+ * on success or %NULL on failure.
+ */
+struct vm_struct *get_vm_area(unsigned long size, unsigned long flags)
+{
+ return __get_vm_area(size, flags, VMALLOC_START, VMALLOC_END);
+}
+
+/**
* remove_vm_area - find and remove a contingous kernel virtual area
*
* @addr: base address

--
Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux