[RFC 4/6] Use thread->kernel_stack_top consistently.

For vm86 mode the kernel stack top is adjusted -> do not rely on the
kernel_stack_base + KERNEL_STACK_SIZE calculation.
---
 src/system/kernel/arch/x86/arch_debug.cpp  |    4 ++--
 src/system/kernel/arch/x86/arch_thread.cpp |   10 +++++-----
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/system/kernel/arch/x86/arch_debug.cpp b/src/system/kernel/arch/x86/arch_debug.cpp
index 2538fd5..222349e 100644
--- a/src/system/kernel/arch/x86/arch_debug.cpp
+++ b/src/system/kernel/arch/x86/arch_debug.cpp
@@ -213,7 +213,7 @@ is_kernel_stack_address(struct thread* thread, addr_t address)
 		return IS_KERNEL_ADDRESS(address);
 
 	return address >= thread->kernel_stack_base
-		&& address < thread->kernel_stack_base + KERNEL_STACK_SIZE;
+		&& address < thread->kernel_stack_top;
 }
 
 
@@ -281,7 +281,7 @@ stack_trace(int argc, char **argv)
 
 		kprintf("    kernel stack: %p to %p\n",
 			(void *)thread->kernel_stack_base,
-			(void *)(thread->kernel_stack_base + KERNEL_STACK_SIZE));
+			(void *)(thread->kernel_stack_top));
 		if (thread->user_stack_base != 0) {
 			kprintf("      user stack: %p to %p\n",
 				(void *)thread->user_stack_base,
diff --git a/src/system/kernel/arch/x86/arch_thread.cpp b/src/system/kernel/arch/x86/arch_thread.cpp
index d9ad8ff..8f44638 100644
--- a/src/system/kernel/arch/x86/arch_thread.cpp
+++ b/src/system/kernel/arch/x86/arch_thread.cpp
@@ -92,7 +92,7 @@ find_previous_iframe(addr_t frame)
 
 	// iterate backwards through the stack frames, until we hit an iframe
 	while (frame >= thread->kernel_stack_base
-		&& frame < thread->kernel_stack_base + KERNEL_STACK_SIZE) {
+		&& frame < thread->kernel_stack_top) {
 		addr_t previousFrame = *(addr_t*)frame;
 		if ((previousFrame & ~IFRAME_TYPE_MASK) == 0) {
 			if (previousFrame == 0)
@@ -251,7 +251,7 @@ arch_thread_init_kthread_stack(struct thread *t, int (*start_func)(void),
 	void (*entry_func)(void), void (*exit_func)(void))
 {
 	addr_t *kstack = (addr_t *)t->kernel_stack_base;
-	addr_t *kstack_top = kstack + KERNEL_STACK_SIZE / sizeof(addr_t);
+	addr_t *kstack_top = (addr_t *)t->kernel_stack_top;
 	int i;
 
 	TRACE(("arch_thread_initialize_kthread_stack: kstack 0x%p, start_func 0x%p, entry_func 0x%p\n",
@@ -349,7 +349,7 @@ arch_thread_context_switch(struct thread *from, struct thread *to)
 	for (i = 0; i < 11; i++)
 		dprintf("*esp[%d] (0x%x) = 0x%x\n", i, ((unsigned int *)new_at->esp + i), *((unsigned int *)new_at->esp + i));
 #endif
-	i386_set_tss_and_kstack(to->kernel_stack_base + KERNEL_STACK_SIZE);
+	i386_set_tss_and_kstack(to->kernel_stack_top);
 
 	// set TLS GDT entry to the current thread - since this action is
 	// dependent on the current CPU, we have to do it here
@@ -409,7 +409,7 @@ arch_thread_enter_userspace(struct thread *t, addr_t entry, void *args1,
 
 	disable_interrupts();
 
-	i386_set_tss_and_kstack(t->kernel_stack_base + KERNEL_STACK_SIZE);
+	i386_set_tss_and_kstack(t->kernel_stack_top);
 
 	// set the CPU dependent GDT entry for TLS
 	set_tls_context(t);
@@ -605,7 +605,7 @@ arch_restore_fork_frame(struct arch_fork_arg *arg)
 
 	disable_interrupts();
 
-	i386_set_tss_and_kstack(thread->kernel_stack_base + KERNEL_STACK_SIZE);
+	i386_set_tss_and_kstack(thread->kernel_stack_top);
 
 	// set the CPU dependent GDT entry for TLS (set the current %fs register)
 	set_tls_context(thread);
-- 
1.5.4.2


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