[PATCH] xtensa: Architecture support for Tensilica Xtensa Part 5

The attached patches provides part 5 of an architecture implementation for the
Tensilica Xtensa CPU series.

Signed-off-by: Chris Zankel <chris@zankel.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 241 insertions, 0 deletions

diff --git a/arch/xtensa/mm/fault.c b/arch/xtensa/mm/fault.c
new file mode 100644
index 00000000000..a945a33e85a
--- /dev/null
+++ b/arch/xtensa/mm/fault.c
@@ -0,0 +1,241 @@
+// TODO VM_EXEC flag work-around, cache aliasing
+/*
+ * arch/xtensa/mm/fault.c
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2001 - 2005 Tensilica Inc.
+ *
+ * Chris Zankel <chris@zankel.net>
+ * Joe Taylor	<joe@tensilica.com, joetylr@yahoo.com>
+ */
+
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <asm/mmu_context.h>
+#include <asm/cacheflush.h>
+#include <asm/hardirq.h>
+#include <asm/uaccess.h>
+#include <asm/system.h>
+#include <asm/pgalloc.h>
+
+unsigned long asid_cache = ASID_FIRST_VERSION;
+void bad_page_fault(struct pt_regs*, unsigned long, int);
+
+/*
+ * This routine handles page faults.  It determines the address,
+ * and the problem, and then passes it off to one of the appropriate
+ * routines.
+ *
+ * Note: does not handle Miss and MultiHit.
+ */
+
+void do_page_fault(struct pt_regs *regs)
+{
+	struct vm_area_struct * vma;
+	struct mm_struct *mm = current->mm;
+	unsigned int exccause = regs->exccause;
+	unsigned int address = regs->excvaddr;
+	siginfo_t info;
+
+	int is_write, is_exec;
+
+	info.si_code = SEGV_MAPERR;
+
+	/* We fault-in kernel-space virtual memory on-demand. The
+	 * 'reference' page table is init_mm.pgd.
+	 */
+	if (address >= TASK_SIZE && !user_mode(regs))
+		goto vmalloc_fault;
+
+	/* If we're in an interrupt or have no user
+	 * context, we must not take the fault..
+	 */
+	if (in_atomic() || !mm) {
+		bad_page_fault(regs, address, SIGSEGV);
+		return;
+	}
+
+	is_write = (exccause == XCHAL_EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
+	is_exec =  (exccause == XCHAL_EXCCAUSE_ITLB_PRIVILEGE ||
+		    exccause == XCHAL_EXCCAUSE_ITLB_MISS ||
+		    exccause == XCHAL_EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
+
+#if 0
+	printk("[%s:%d:%08x:%d:%08x:%s%s]\n", current->comm, current->pid,
+	       address, exccause, regs->pc, is_write? "w":"", is_exec? "x":"");
+#endif
+
+	down_read(&mm->mmap_sem);
+	vma = find_vma(mm, address);
+
+	if (!vma)
+		goto bad_area;
+	if (vma->vm_start <= address)
+		goto good_area;
+	if (!(vma->vm_flags & VM_GROWSDOWN))
+		goto bad_area;
+	if (expand_stack(vma, address))
+		goto bad_area;
+
+	/* Ok, we have a good vm_area for this memory access, so
+	 * we can handle it..
+	 */
+
+good_area:
+	info.si_code = SEGV_ACCERR;
+
+	if (is_write) {
+		if (!(vma->vm_flags & VM_WRITE))
+			goto bad_area;
+	} else if (is_exec) {
+		if (!(vma->vm_flags & VM_EXEC))
+			goto bad_area;
+	} else	/* Allow read even from write-only pages. */
+		if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
+			goto bad_area;
+
+	/* If for any reason at all we couldn't handle the fault,
+	 * make sure we exit gracefully rather than endlessly redo
+	 * the fault.
+	 */
+survive:
+	switch (handle_mm_fault(mm, vma, address, is_write)) {
+	case VM_FAULT_MINOR:
+		current->min_flt++;
+		break;
+	case VM_FAULT_MAJOR:
+		current->maj_flt++;
+		break;
+	case VM_FAULT_SIGBUS:
+		goto do_sigbus;
+	case VM_FAULT_OOM:
+		goto out_of_memory;
+	default:
+		BUG();
+	}
+
+	up_read(&mm->mmap_sem);
+	return;
+
+	/* Something tried to access memory that isn't in our memory map..
+	 * Fix it, but check if it's kernel or user first..
+	 */
+bad_area:
+	up_read(&mm->mmap_sem);
+	if (user_mode(regs)) {
+		current->thread.bad_vaddr = address;
+		current->thread.error_code = is_write;
+		info.si_signo = SIGSEGV;
+		info.si_errno = 0;
+		/* info.si_code has been set above */
+		info.si_addr = (void *) address;
+		force_sig_info(SIGSEGV, &info, current);
+		return;
+	}
+	bad_page_fault(regs, address, SIGSEGV);
+	return;
+
+
+	/* We ran out of memory, or some other thing happened to us that made
+	 * us unable to handle the page fault gracefully.
+	 */
+out_of_memory:
+	up_read(&mm->mmap_sem);
+	if (current->pid == 1) {
+		yield();
+		down_read(&mm->mmap_sem);
+		goto survive;
+	}
+	printk("VM: killing process %s\n", current->comm);
+	if (user_mode(regs))
+		do_exit(SIGKILL);
+	bad_page_fault(regs, address, SIGKILL);
+	return;
+
+do_sigbus:
+	up_read(&mm->mmap_sem);
+
+	/* Send a sigbus, regardless of whether we were in kernel
+	 * or user mode.
+	 */
+	current->thread.bad_vaddr = address;
+	info.si_code = SIGBUS;
+	info.si_errno = 0;
+	info.si_code = BUS_ADRERR;
+	info.si_addr = (void *) address;
+	force_sig_info(SIGBUS, &info, current);
+
+	/* Kernel mode? Handle exceptions or die */
+	if (!user_mode(regs))
+		bad_page_fault(regs, address, SIGBUS);
+
+vmalloc_fault:
+	{
+		/* Synchronize this task's top level page-table
+		 * with the 'reference' page table.
+		 */
+		struct mm_struct *act_mm = current->active_mm;
+		int index = pgd_index(address);
+		pgd_t *pgd, *pgd_k;
+		pmd_t *pmd, *pmd_k;
+		pte_t *pte_k;
+
+		if (act_mm == NULL)
+			goto bad_page_fault;
+
+		pgd = act_mm->pgd + index;
+		pgd_k = init_mm.pgd + index;
+
+		if (!pgd_present(*pgd_k))
+			goto bad_page_fault;
+
+		pgd_val(*pgd) = pgd_val(*pgd_k);
+
+		pmd = pmd_offset(pgd, address);
+		pmd_k = pmd_offset(pgd_k, address);
+		if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
+			goto bad_page_fault;
+
+		pmd_val(*pmd) = pmd_val(*pmd_k);
+		pte_k = pte_offset_kernel(pmd_k, address);
+
+		if (!pte_present(*pte_k))
+			goto bad_page_fault;
+		return;
+	}
+bad_page_fault:
+	bad_page_fault(regs, address, SIGKILL);
+	return;
+}
+
+
+void
+bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
+{
+	extern void die(const char*, struct pt_regs*, long);
+	const struct exception_table_entry *entry;
+
+	/* Are we prepared to handle this kernel fault?  */
+	if ((entry = search_exception_tables(regs->pc)) != NULL) {
+#if 1
+		printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n",
+				current->comm, regs->pc, entry->fixup);
+#endif
+		current->thread.bad_uaddr = address;
+		regs->pc = entry->fixup;
+		return;
+	}
+
+	/* Oops. The kernel tried to access some bad page. We'll have to
+	 * terminate things with extreme prejudice.
+	 */
+	printk(KERN_ALERT "Unable to handle kernel paging request at virtual "
+	       "address %08lx\n pc = %08lx, ra = %08lx\n",
+	       address, regs->pc, regs->areg[0]);
+	die("Oops", regs, sig);
+	do_exit(sig);
+}
+