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

* [PATCH] Make modules work in Linus' tree on ARM
@ 2003-08-14 12:08 Russell King
  2003-08-14 16:19 ` Linus Torvalds
  0 siblings, 1 reply; 17+ messages in thread
From: Russell King @ 2003-08-14 12:08 UTC (permalink / raw)
  To: Linus Torvalds, Linux Kernel List

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
             http://www.arm.linux.org.uk/personal/aboutme.html


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