1 files changed, 261 insertions, 0 deletions
diff --git a/arch/loongarch/mm/fault.c b/arch/loongarch/mm/fault.c
new file mode 100644
index 000000000..b829ab911
--- /dev/null
+++ b/arch/loongarch/mm/fault.c
@@ -0,0 +1,261 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ *
+ * Derived from MIPS:
+ * Copyright (C) 1995 - 2000 by Ralf Baechle
+ */
+#include <linux/context_tracking.h>
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/entry-common.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/ptrace.h>
+#include <linux/ratelimit.h>
+#include <linux/mman.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/kdebug.h>
+#include <linux/kprobes.h>
+#include <linux/perf_event.h>
+#include <linux/uaccess.h>
+
+#include <asm/branch.h>
+#include <asm/mmu_context.h>
+#include <asm/ptrace.h>
+
+int show_unhandled_signals = 1;
+
+static void __kprobes no_context(struct pt_regs *regs, unsigned long address)
+{
+	const int field = sizeof(unsigned long) * 2;
+
+	/* 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("CPU %d Unable to handle kernel paging request at "
+	       "virtual address %0*lx, era == %0*lx, ra == %0*lx\n",
+	       raw_smp_processor_id(), field, address, field, regs->csr_era,
+	       field,  regs->regs[1]);
+	die("Oops", regs);
+}
+
+static void __kprobes do_out_of_memory(struct pt_regs *regs, unsigned long address)
+{
+	/*
+	 * 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, address);
+		return;
+	}
+	pagefault_out_of_memory();
+}
+
+static void __kprobes do_sigbus(struct pt_regs *regs,
+		unsigned long write, unsigned long address, int si_code)
+{
+	/* Kernel mode? Handle exceptions or die */
+	if (!user_mode(regs)) {
+		no_context(regs, address);
+		return;
+	}
+
+	/*
+	 * Send a sigbus, regardless of whether we were in kernel
+	 * or user mode.
+	 */
+	current->thread.csr_badvaddr = address;
+	current->thread.trap_nr = read_csr_excode();
+	force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
+}
+
+static void __kprobes do_sigsegv(struct pt_regs *regs,
+		unsigned long write, unsigned long address, int si_code)
+{
+	const int field = sizeof(unsigned long) * 2;
+	static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
+
+	/* Kernel mode? Handle exceptions or die */
+	if (!user_mode(regs)) {
+		no_context(regs, address);
+		return;
+	}
+
+	/* User mode accesses just cause a SIGSEGV */
+	current->thread.csr_badvaddr = address;
+	if (!write)
+		current->thread.error_code = 1;
+	else
+		current->thread.error_code = 2;
+	current->thread.trap_nr = read_csr_excode();
+
+	if (show_unhandled_signals &&
+	    unhandled_signal(current, SIGSEGV) && __ratelimit(&ratelimit_state)) {
+		pr_info("do_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx\n",
+			current->comm,
+			write ? "write access to" : "read access from",
+			field, address);
+		pr_info("era = %0*lx in", field,
+			(unsigned long) regs->csr_era);
+		print_vma_addr(KERN_CONT " ", regs->csr_era);
+		pr_cont("\n");
+		pr_info("ra  = %0*lx in", field,
+			(unsigned long) regs->regs[1]);
+		print_vma_addr(KERN_CONT " ", regs->regs[1]);
+		pr_cont("\n");
+	}
+	force_sig_fault(SIGSEGV, si_code, (void __user *)address);
+}
+
+/*
+ * This routine handles page faults.  It determines the address,
+ * and the problem, and then passes it off to one of the appropriate
+ * routines.
+ */
+static void __kprobes __do_page_fault(struct pt_regs *regs,
+			unsigned long write, unsigned long address)
+{
+	int si_code = SEGV_MAPERR;
+	unsigned int flags = FAULT_FLAG_DEFAULT;
+	struct task_struct *tsk = current;
+	struct mm_struct *mm = tsk->mm;
+	struct vm_area_struct *vma = NULL;
+	vm_fault_t fault;
+
+	/*
+	 * We 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 (address & __UA_LIMIT) {
+		if (!user_mode(regs))
+			no_context(regs, address);
+		else
+			do_sigsegv(regs, write, address, si_code);
+		return;
+	}
+
+	/*
+	 * If we're in an interrupt or have no user
+	 * context, we must not take the fault..
+	 */
+	if (faulthandler_disabled() || !mm) {
+		do_sigsegv(regs, write, address, si_code);
+		return;
+	}
+
+	if (user_mode(regs))
+		flags |= FAULT_FLAG_USER;
+
+	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
+retry:
+	vma = lock_mm_and_find_vma(mm, address, regs);
+	if (unlikely(!vma))
+		goto bad_area_nosemaphore;
+	goto good_area;
+
+/*
+ * 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:
+	mmap_read_unlock(mm);
+bad_area_nosemaphore:
+	do_sigsegv(regs, write, address, si_code);
+	return;
+
+/*
+ * Ok, we have a good vm_area for this memory access, so
+ * we can handle it..
+ */
+good_area:
+	si_code = SEGV_ACCERR;
+
+	if (write) {
+		flags |= FAULT_FLAG_WRITE;
+		if (!(vma->vm_flags & VM_WRITE))
+			goto bad_area;
+	} else {
+		if (!(vma->vm_flags & VM_READ) && address != exception_era(regs))
+			goto bad_area;
+		if (!(vma->vm_flags & VM_EXEC) && address == exception_era(regs))
+			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.
+	 */
+	fault = handle_mm_fault(vma, address, flags, regs);
+
+	if (fault_signal_pending(fault, regs)) {
+		if (!user_mode(regs))
+			no_context(regs, address);
+		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_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;
+	}
+	if (unlikely(fault & VM_FAULT_ERROR)) {
+		mmap_read_unlock(mm);
+		if (fault & VM_FAULT_OOM) {
+			do_out_of_memory(regs, address);
+			return;
+		} else if (fault & VM_FAULT_SIGSEGV) {
+			do_sigsegv(regs, write, address, si_code);
+			return;
+		} else if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
+			do_sigbus(regs, write, address, si_code);
+			return;
+		}
+		BUG();
+	}
+
+	mmap_read_unlock(mm);
+}
+
+asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
+			unsigned long write, unsigned long address)
+{
+	irqentry_state_t state = irqentry_enter(regs);
+
+	/* Enable interrupt if enabled in parent context */
+	if (likely(regs->csr_prmd & CSR_PRMD_PIE))
+		local_irq_enable();
+
+	__do_page_fault(regs, write, address);
+
+	local_irq_disable();
+
+	irqentry_exit(regs, state);
+}