Some of the things that I have want to do are related specialized
exception handlers. One idea comes to mind with respect to making a
fast dma dispatch mechanism which doesn't actually involve the kernel.
So as not to taint the kernel in some non standard way we might
consider just EXPORT_SYMBOL(extable) so that a kernel loadable module
can modify the exception handler table.
Places where this seems to be interesting to me are.
1. fast 2d-dma drivers for video
2. performance modeling drivers i.e. install specialized excpt handler
for performance counters.
3. ...
The key here is that the kernel can be extended with out
recompilation. This might allow us to provide a set of specialized
optimized drivers that reconfigure the kernel at runtime via the
module API.
Does this feature make sense, has anyone else wanted to do something
along these lines. The modification which I'm thinking is very
simple but I think it opens up a lot of doors for the loadable
module.
I think we should do this for isrs as well.
Marc
--- /Users/mmh/r7/uClinux-dist/linux-2.6.x/arch/blackfin/mach-common/entry.S
2007-04-06 10:23:26.000000000 -0400
+++ linux-2.6.x/arch/blackfin/mach-common/entry.S 2007-04-06
21:07:25.000000000 -0400
@@ -761,7 +759,7 @@
.data
#endif
ALIGN
-_extable:
+ENTRY(_extable)
/* entry for each EXCAUSE[5:0]
* This table bmust be in sync with the table in ./kernel/traps.c
* EXCPT instruction can provide 4 bits of EXCAUSE, allowing 16 to be
user defined
--- /Users/mmh/r7/uClinux-dist/linux-2.6.x/arch/blackfin/kernel/traps.c
2007-04-06 10:23:25.000000000 -0400
+++ linux-2.6.x/arch/blackfin/kernel/traps.c 2007-04-06 20:25:13.000000000
-0400
@@ -653,3 +648,10 @@
dump_stack();
panic("Unrecoverable event\n");
}
+
+
+extern unsigned long extable[];
+EXPORT_SYMBOL(extable);
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