Changeset 38ff925 in mainline for kernel/generic/src/proc/thread.c

Timestamp:

2011-11-28T21:51:44Z (12 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

481a9380

Parents:

40c8c17

Message:

Force kernel stacks to be allocated from the low-memory.

File:

• kernel/generic/src/proc/thread.c (modified) (1 diff)

kernel/generic/src/proc/thread.c

@@ -173 +173 @@
 #endif /* CONFIG_FPU */
         
+        /*
+         * Allocate the kernel stack from the low-memory to prevent an infinite
+         * nesting of TLB-misses when accessing the stack from the part of the
+         * TLB-miss handler written in C.
+         *
+         * Note that low-memory is safe to be used for the stack as it will be
+         * covered by the kernel identity mapping, which guarantees not to
+         * nest TLB-misses infinitely (either via some hardware mechanism or
+         * by the construciton of the assembly-language part of the TLB-miss
+         * handler).
+         *
+         * This restriction can be lifted once each architecture provides
+         * a similar guarantee, for example by locking the kernel stack
+         * in the TLB whenever it is allocated from the high-memory and the
+         * thread is being scheduled to run.
+         */
+        kmflags |= FRAME_LOWMEM;
+        kmflags &= ~FRAME_HIGHMEM;
+
         thread->kstack = (uint8_t *) frame_alloc(STACK_FRAMES, FRAME_KA | kmflags);
         if (!thread->kstack) {