[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>
diff --git a/arch/xtensa/mm/fault.c b/arch/xtensa/mm/fault.c
new file mode 100644
index 0000000..a945a33
--- /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);
+}
+