summaryrefslogtreecommitdiffstats
path: root/arch/riscv/mm/fault.c
diff options
context:
space:
mode:
Diffstat (limited to 'arch/riscv/mm/fault.c')
-rw-r--r--arch/riscv/mm/fault.c377
1 files changed, 377 insertions, 0 deletions
diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
new file mode 100644
index 0000000000..90d4ba36d1
--- /dev/null
+++ b/arch/riscv/mm/fault.c
@@ -0,0 +1,377 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
+ * Lennox Wu <lennox.wu@sunplusct.com>
+ * Chen Liqin <liqin.chen@sunplusct.com>
+ * Copyright (C) 2012 Regents of the University of California
+ */
+
+
+#include <linux/mm.h>
+#include <linux/kernel.h>
+#include <linux/interrupt.h>
+#include <linux/perf_event.h>
+#include <linux/signal.h>
+#include <linux/uaccess.h>
+#include <linux/kprobes.h>
+#include <linux/kfence.h>
+#include <linux/entry-common.h>
+
+#include <asm/ptrace.h>
+#include <asm/tlbflush.h>
+
+#include "../kernel/head.h"
+
+static void die_kernel_fault(const char *msg, unsigned long addr,
+ struct pt_regs *regs)
+{
+ bust_spinlocks(1);
+
+ pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", msg,
+ addr);
+
+ bust_spinlocks(0);
+ die(regs, "Oops");
+ make_task_dead(SIGKILL);
+}
+
+static inline void no_context(struct pt_regs *regs, unsigned long addr)
+{
+ const char *msg;
+
+ /* 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.
+ */
+ if (addr < PAGE_SIZE)
+ msg = "NULL pointer dereference";
+ else {
+ if (kfence_handle_page_fault(addr, regs->cause == EXC_STORE_PAGE_FAULT, regs))
+ return;
+
+ msg = "paging request";
+ }
+
+ die_kernel_fault(msg, addr, regs);
+}
+
+static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault)
+{
+ 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 | VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE)) {
+ /* 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, 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
+bad_area(struct pt_regs *regs, struct mm_struct *mm, int code,
+ unsigned long addr)
+{
+ mmap_read_unlock(mm);
+
+ bad_area_nosemaphore(regs, code, addr);
+}
+
+static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr)
+{
+ pgd_t *pgd, *pgd_k;
+ pud_t *pud_k;
+ p4d_t *p4d_k;
+ pmd_t *pmd_k;
+ pte_t *pte_k;
+ int index;
+ unsigned long pfn;
+
+ /* User mode accesses just cause a SIGSEGV */
+ if (user_mode(regs))
+ return do_trap(regs, SIGSEGV, code, addr);
+
+ /*
+ * Synchronize this task's top level page-table
+ * with the 'reference' page table.
+ *
+ * Do _not_ use "tsk->active_mm->pgd" here.
+ * We might be inside an interrupt in the middle
+ * of a task switch.
+ */
+ index = pgd_index(addr);
+ pfn = csr_read(CSR_SATP) & SATP_PPN;
+ pgd = (pgd_t *)pfn_to_virt(pfn) + index;
+ pgd_k = init_mm.pgd + index;
+
+ if (!pgd_present(*pgd_k)) {
+ no_context(regs, addr);
+ return;
+ }
+ set_pgd(pgd, *pgd_k);
+
+ p4d_k = p4d_offset(pgd_k, addr);
+ if (!p4d_present(*p4d_k)) {
+ no_context(regs, addr);
+ return;
+ }
+
+ pud_k = pud_offset(p4d_k, addr);
+ if (!pud_present(*pud_k)) {
+ no_context(regs, addr);
+ return;
+ }
+ if (pud_leaf(*pud_k))
+ goto flush_tlb;
+
+ /*
+ * Since the vmalloc area is global, it is unnecessary
+ * to copy individual PTEs
+ */
+ pmd_k = pmd_offset(pud_k, addr);
+ if (!pmd_present(*pmd_k)) {
+ no_context(regs, addr);
+ return;
+ }
+ if (pmd_leaf(*pmd_k))
+ goto flush_tlb;
+
+ /*
+ * Make sure the actual PTE exists as well to
+ * catch kernel vmalloc-area accesses to non-mapped
+ * addresses. If we don't do this, this will just
+ * silently loop forever.
+ */
+ pte_k = pte_offset_kernel(pmd_k, addr);
+ if (!pte_present(*pte_k)) {
+ no_context(regs, addr);
+ return;
+ }
+
+ /*
+ * The kernel assumes that TLBs don't cache invalid
+ * entries, but in RISC-V, SFENCE.VMA specifies an
+ * ordering constraint, not a cache flush; it is
+ * necessary even after writing invalid entries.
+ */
+flush_tlb:
+ local_flush_tlb_page(addr);
+}
+
+static inline bool access_error(unsigned long cause, struct vm_area_struct *vma)
+{
+ switch (cause) {
+ case EXC_INST_PAGE_FAULT:
+ if (!(vma->vm_flags & VM_EXEC)) {
+ return true;
+ }
+ break;
+ case EXC_LOAD_PAGE_FAULT:
+ /* Write implies read */
+ if (!(vma->vm_flags & (VM_READ | VM_WRITE))) {
+ return true;
+ }
+ break;
+ case EXC_STORE_PAGE_FAULT:
+ if (!(vma->vm_flags & VM_WRITE)) {
+ return true;
+ }
+ break;
+ default:
+ panic("%s: unhandled cause %lu", __func__, cause);
+ }
+ 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.
+ */
+void handle_page_fault(struct pt_regs *regs)
+{
+ struct task_struct *tsk;
+ struct vm_area_struct *vma;
+ struct mm_struct *mm;
+ unsigned long addr, cause;
+ unsigned int flags = FAULT_FLAG_DEFAULT;
+ int code = SEGV_MAPERR;
+ vm_fault_t fault;
+
+ cause = regs->cause;
+ addr = regs->badaddr;
+
+ tsk = current;
+ mm = tsk->mm;
+
+ if (kprobe_page_fault(regs, cause))
+ 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 ((!IS_ENABLED(CONFIG_MMU) || !IS_ENABLED(CONFIG_64BIT)) &&
+ unlikely(addr >= VMALLOC_START && addr < VMALLOC_END)) {
+ vmalloc_fault(regs, code, addr);
+ return;
+ }
+
+ /* Enable interrupts if they were enabled in the parent context. */
+ if (!regs_irqs_disabled(regs))
+ 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)) {
+ tsk->thread.bad_cause = cause;
+ no_context(regs, addr);
+ return;
+ }
+
+ if (user_mode(regs))
+ flags |= FAULT_FLAG_USER;
+
+ if (!user_mode(regs) && addr < TASK_SIZE && unlikely(!(regs->status & SR_SUM))) {
+ if (fixup_exception(regs))
+ return;
+
+ die_kernel_fault("access to user memory without uaccess routines", addr, regs);
+ }
+
+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
+
+ if (cause == EXC_STORE_PAGE_FAULT)
+ flags |= FAULT_FLAG_WRITE;
+ else if (cause == EXC_INST_PAGE_FAULT)
+ flags |= FAULT_FLAG_INSTRUCTION;
+ if (!(flags & FAULT_FLAG_USER))
+ goto lock_mmap;
+
+ vma = lock_vma_under_rcu(mm, addr);
+ if (!vma)
+ goto lock_mmap;
+
+ if (unlikely(access_error(cause, vma))) {
+ vma_end_read(vma);
+ goto lock_mmap;
+ }
+
+ fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
+ if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
+ vma_end_read(vma);
+
+ if (!(fault & VM_FAULT_RETRY)) {
+ count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
+ goto done;
+ }
+ count_vm_vma_lock_event(VMA_LOCK_RETRY);
+
+ if (fault_signal_pending(fault, regs)) {
+ if (!user_mode(regs))
+ no_context(regs, addr);
+ return;
+ }
+lock_mmap:
+
+retry:
+ vma = lock_mm_and_find_vma(mm, addr, regs);
+ if (unlikely(!vma)) {
+ tsk->thread.bad_cause = cause;
+ bad_area_nosemaphore(regs, 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(cause, vma))) {
+ tsk->thread.bad_cause = cause;
+ bad_area(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_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);
+
+done:
+ if (unlikely(fault & VM_FAULT_ERROR)) {
+ tsk->thread.bad_cause = cause;
+ mm_fault_error(regs, addr, fault);
+ return;
+ }
+ return;
+}