1 files changed, 298 insertions, 0 deletions
diff --git a/arch/csky/mm/fault.c b/arch/csky/mm/fault.c
new file mode 100644
index 000000000..a885518ce
--- /dev/null
+++ b/arch/csky/mm/fault.c
@@ -0,0 +1,298 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
+
+#include <linux/extable.h>
+#include <linux/kprobes.h>
+#include <linux/mmu_context.h>
+#include <linux/perf_event.h>
+
+int fixup_exception(struct pt_regs *regs)
+{
+	const struct exception_table_entry *fixup;
+
+	fixup = search_exception_tables(instruction_pointer(regs));
+	if (fixup) {
+		regs->pc = fixup->fixup;
+
+		return 1;
+	}
+
+	return 0;
+}
+
+static inline bool is_write(struct pt_regs *regs)
+{
+	switch (trap_no(regs)) {
+	case VEC_TLBINVALIDS:
+		return true;
+	case VEC_TLBMODIFIED:
+		return true;
+	}
+
+	return false;
+}
+
+#ifdef CONFIG_CPU_HAS_LDSTEX
+static inline void csky_cmpxchg_fixup(struct pt_regs *regs)
+{
+	return;
+}
+#else
+extern unsigned long csky_cmpxchg_ldw;
+extern unsigned long csky_cmpxchg_stw;
+static inline void csky_cmpxchg_fixup(struct pt_regs *regs)
+{
+	if (trap_no(regs) != VEC_TLBMODIFIED)
+		return;
+
+	if (instruction_pointer(regs) == csky_cmpxchg_stw)
+		instruction_pointer_set(regs, csky_cmpxchg_ldw);
+	return;
+}
+#endif
+
+static inline void no_context(struct pt_regs *regs, unsigned long addr)
+{
+	current->thread.trap_no = trap_no(regs);
+
+	/* Are we prepared to handle this kernel fault? */
+	if (fixup_exception(regs))
+		return;
+
+	/*
+	 * Oops. The kernel tried to access some bad page. We'll have to
+	 * terminate things with extreme prejudice.
+	 */
+	bust_spinlocks(1);
+	pr_alert("Unable to handle kernel paging request at virtual "
+		 "addr 0x%08lx, pc: 0x%08lx\n", addr, regs->pc);
+	die(regs, "Oops");
+	make_task_dead(SIGKILL);
+}
+
+static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault)
+{
+	current->thread.trap_no = trap_no(regs);
+
+	if (fault & VM_FAULT_OOM) {
+		/*
+		 * We ran out of memory, call the OOM killer, and return the userspace
+		 * (which will retry the fault, or kill us if we got oom-killed).
+		 */
+		if (!user_mode(regs)) {
+			no_context(regs, addr);
+			return;
+		}
+		pagefault_out_of_memory();
+		return;
+	} else if (fault & VM_FAULT_SIGBUS) {
+		/* Kernel mode? Handle exceptions or die */
+		if (!user_mode(regs)) {
+			no_context(regs, addr);
+			return;
+		}
+		do_trap(regs, SIGBUS, BUS_ADRERR, addr);
+		return;
+	}
+	BUG();
+}
+
+static inline void bad_area_nosemaphore(struct pt_regs *regs, struct mm_struct *mm, int code, unsigned long addr)
+{
+	/*
+	 * Something tried to access memory that isn't in our memory map.
+	 * Fix it, but check if it's kernel or user first.
+	 */
+	/* User mode accesses just cause a SIGSEGV */
+	if (user_mode(regs)) {
+		do_trap(regs, SIGSEGV, code, addr);
+		return;
+	}
+
+	no_context(regs, addr);
+}
+
+static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr)
+{
+	pgd_t *pgd, *pgd_k;
+	pud_t *pud, *pud_k;
+	pmd_t *pmd, *pmd_k;
+	pte_t *pte_k;
+	int offset;
+
+	/* User mode accesses just cause a SIGSEGV */
+	if (user_mode(regs)) {
+		do_trap(regs, SIGSEGV, code, addr);
+		return;
+	}
+
+	/*
+	 * Synchronize this task's top level page-table
+	 * with the 'reference' page table.
+	 *
+	 * Do _not_ use "tsk" here. We might be inside
+	 * an interrupt in the middle of a task switch..
+	 */
+	offset = pgd_index(addr);
+
+	pgd = get_pgd() + offset;
+	pgd_k = init_mm.pgd + offset;
+
+	if (!pgd_present(*pgd_k)) {
+		no_context(regs, addr);
+		return;
+	}
+	set_pgd(pgd, *pgd_k);
+
+	pud = (pud_t *)pgd;
+	pud_k = (pud_t *)pgd_k;
+	if (!pud_present(*pud_k)) {
+		no_context(regs, addr);
+		return;
+	}
+
+	pmd = pmd_offset(pud, addr);
+	pmd_k = pmd_offset(pud_k, addr);
+	if (!pmd_present(*pmd_k)) {
+		no_context(regs, addr);
+		return;
+	}
+	set_pmd(pmd, *pmd_k);
+
+	pte_k = pte_offset_kernel(pmd_k, addr);
+	if (!pte_present(*pte_k)) {
+		no_context(regs, addr);
+		return;
+	}
+
+	flush_tlb_one(addr);
+}
+
+static inline bool access_error(struct pt_regs *regs, struct vm_area_struct *vma)
+{
+	if (is_write(regs)) {
+		if (!(vma->vm_flags & VM_WRITE))
+			return true;
+	} else {
+		if (unlikely(!vma_is_accessible(vma)))
+			return true;
+	}
+	return false;
+}
+
+/*
+ * This routine handles page faults.  It determines the address and the
+ * problem, and then passes it off to one of the appropriate routines.
+ */
+asmlinkage void do_page_fault(struct pt_regs *regs)
+{
+	struct task_struct *tsk;
+	struct vm_area_struct *vma;
+	struct mm_struct *mm;
+	unsigned long addr = read_mmu_entryhi() & PAGE_MASK;
+	unsigned int flags = FAULT_FLAG_DEFAULT;
+	int code = SEGV_MAPERR;
+	vm_fault_t fault;
+
+	tsk = current;
+	mm = tsk->mm;
+
+	csky_cmpxchg_fixup(regs);
+
+	if (kprobe_page_fault(regs, tsk->thread.trap_no))
+		return;
+
+	/*
+	 * Fault-in kernel-space virtual memory on-demand.
+	 * The 'reference' page table is init_mm.pgd.
+	 *
+	 * NOTE! We MUST NOT take any locks for this case. We may
+	 * be in an interrupt or a critical region, and should
+	 * only copy the information from the master page table,
+	 * nothing more.
+	 */
+	if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END))) {
+		vmalloc_fault(regs, code, addr);
+		return;
+	}
+
+	/* Enable interrupts if they were enabled in the parent context. */
+	if (likely(regs->sr & BIT(6)))
+		local_irq_enable();
+
+	/*
+	 * If we're in an interrupt, have no user context, or are running
+	 * in an atomic region, then we must not take the fault.
+	 */
+	if (unlikely(faulthandler_disabled() || !mm)) {
+		no_context(regs, addr);
+		return;
+	}
+
+	if (user_mode(regs))
+		flags |= FAULT_FLAG_USER;
+
+	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
+
+	if (is_write(regs))
+		flags |= FAULT_FLAG_WRITE;
+retry:
+	vma = lock_mm_and_find_vma(mm, addr, regs);
+	if (unlikely(!vma)) {
+		bad_area_nosemaphore(regs, mm, code, addr);
+		return;
+	}
+
+	/*
+	 * Ok, we have a good vm_area for this memory access, so
+	 * we can handle it.
+	 */
+	code = SEGV_ACCERR;
+
+	if (unlikely(access_error(regs, vma))) {
+		mmap_read_unlock(mm);
+		bad_area_nosemaphore(regs, mm, code, addr);
+		return;
+	}
+
+	/*
+	 * If for any reason at all we could not handle the fault,
+	 * make sure we exit gracefully rather than endlessly redo
+	 * the fault.
+	 */
+	fault = handle_mm_fault(vma, addr, flags, regs);
+
+	/*
+	 * If we need to retry but a fatal signal is pending, handle the
+	 * signal first. We do not need to release the mmap_lock because it
+	 * would already be released in __lock_page_or_retry in mm/filemap.c.
+	 */
+	if (fault_signal_pending(fault, regs)) {
+		if (!user_mode(regs))
+			no_context(regs, addr);
+		return;
+	}
+
+	/* The fault is fully completed (including releasing mmap lock) */
+	if (fault & VM_FAULT_COMPLETED)
+		return;
+
+	if (unlikely((fault & VM_FAULT_RETRY) && (flags & FAULT_FLAG_ALLOW_RETRY))) {
+		flags |= FAULT_FLAG_TRIED;
+
+		/*
+		 * No need to mmap_read_unlock(mm) as we would
+		 * have already released it in __lock_page_or_retry
+		 * in mm/filemap.c.
+		 */
+		goto retry;
+	}
+
+	mmap_read_unlock(mm);
+
+	if (unlikely(fault & VM_FAULT_ERROR)) {
+		mm_fault_error(regs, addr, fault);
+		return;
+	}
+	return;
+}