Re: exception tables in 2.5.55

Greg Ungerer
2003-01-13T03:41:54Z

Hi Linus,

Linus Torvalds wrote:
> On Mon, 13 Jan 2003, Greg Ungerer wrote:
>
>>Tested and working on m68knommu architecture.
>
>
> Why does exceptions have anything to do with no-mmu?
>
> There are exceptions that have nothing to do with MMU's, and a no-mmu
> architecture should still support them. On x86, we have a number of such
> exceptions, for example general protection stuff for wrong values for
> special registers etc.
>
> In other words, not applied.

Good thing I was only after comments then :-)

> Page table exceptions are just the most
> _common_ exception type, but there's absolutely nothing in the mechanism
> that has anything at all to do with MMU-less.
>
> If some archtiecture happens to have an empty exception table, that's
> fine.

OK, heres an alternative patch that fully supports exception tables
for m68knommu (Miles you'll need to do the same for v850).

This is tested on my ColdFire targets...

Regards
Greg

diff -Naur linux-2.5.56/arch/m68knommu/mm/Makefile
linux-2.5.56-uc0/arch/m68knommu/mm/Makefile
--- linux-2.5.56/arch/m68knommu/mm/Makefile Sat Jan 11 06:12:25 2003
+++ linux-2.5.56-uc0/arch/m68knommu/mm/Makefile Mon Jan 13 13:43:22 2003
@@ -2,4 +2,4 @@
# Makefile for the linux m68knommu specific parts of the memory manager.
#

-obj-y += init.o fault.o memory.o kmap.o
+obj-y += init.o fault.o memory.o kmap.o extable.o
diff -Naur linux-2.5.56/arch/m68knommu/mm/extable.c
linux-2.5.56-uc0/arch/m68knommu/mm/extable.c
--- linux-2.5.56/arch/m68knommu/mm/extable.c Thu Jan 1 10:00:00 1970
+++ linux-2.5.56-uc0/arch/m68knommu/mm/extable.c Mon Jan 13 13:43:08
2003@@ -0,0 +1,30 @@
+/*
+ * linux/arch/m68knommu/mm/extable.c
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <asm/uaccess.h>
+
+/* Simple binary search */
+const struct exception_table_entry *
+search_extable(const struct exception_table_entry *first,
+ const struct exception_table_entry *last,
+ unsigned long value)
+{
+ while (first <= last) {
+ const struct exception_table_entry *mid;
+ long diff;
+
+ mid = (last - first) / 2 + first;
+ diff = mid->insn - value;
+ if (diff == 0)
+ return mid;
+ else if (diff < 0)
+ first = mid+1;
+ else
+ last = mid-1;
+ }
+ return NULL;
+}

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