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-rw-r--r--arch/openrisc/mm/fault.c353
1 files changed, 353 insertions, 0 deletions
diff --git a/arch/openrisc/mm/fault.c b/arch/openrisc/mm/fault.c
new file mode 100644
index 0000000000..29e232d78d
--- /dev/null
+++ b/arch/openrisc/mm/fault.c
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+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * OpenRISC fault.c
+ *
+ * Linux architectural port borrowing liberally from similar works of
+ * others. All original copyrights apply as per the original source
+ * declaration.
+ *
+ * Modifications for the OpenRISC architecture:
+ * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
+ * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
+ */
+
+#include <linux/mm.h>
+#include <linux/interrupt.h>
+#include <linux/extable.h>
+#include <linux/sched/signal.h>
+#include <linux/perf_event.h>
+
+#include <linux/uaccess.h>
+#include <asm/bug.h>
+#include <asm/mmu_context.h>
+#include <asm/siginfo.h>
+#include <asm/signal.h>
+
+#define NUM_TLB_ENTRIES 64
+#define TLB_OFFSET(add) (((add) >> PAGE_SHIFT) & (NUM_TLB_ENTRIES-1))
+
+/* __PHX__ :: - check the vmalloc_fault in do_page_fault()
+ * - also look into include/asm/mmu_context.h
+ */
+volatile pgd_t *current_pgd[NR_CPUS];
+
+asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address,
+ unsigned long vector, int write_acc);
+
+/*
+ * This routine handles page faults. It determines the address,
+ * and the problem, and then passes it off to one of the appropriate
+ * routines.
+ *
+ * If this routine detects a bad access, it returns 1, otherwise it
+ * returns 0.
+ */
+
+asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address,
+ unsigned long vector, int write_acc)
+{
+ struct task_struct *tsk;
+ struct mm_struct *mm;
+ struct vm_area_struct *vma;
+ int si_code;
+ vm_fault_t fault;
+ unsigned int flags = FAULT_FLAG_DEFAULT;
+
+ tsk = current;
+
+ /*
+ * 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.
+ *
+ * NOTE2: This is done so that, when updating the vmalloc
+ * mappings we don't have to walk all processes pgdirs and
+ * add the high mappings all at once. Instead we do it as they
+ * are used. However vmalloc'ed page entries have the PAGE_GLOBAL
+ * bit set so sometimes the TLB can use a lingering entry.
+ *
+ * This verifies that the fault happens in kernel space
+ * and that the fault was not a protection error.
+ */
+
+ if (address >= VMALLOC_START &&
+ (vector != 0x300 && vector != 0x400) &&
+ !user_mode(regs))
+ goto vmalloc_fault;
+
+ /* If exceptions were enabled, we can reenable them here */
+ if (user_mode(regs)) {
+ /* Exception was in userspace: reenable interrupts */
+ local_irq_enable();
+ flags |= FAULT_FLAG_USER;
+ } else {
+ /* If exception was in a syscall, then IRQ's may have
+ * been enabled or disabled. If they were enabled,
+ * reenable them.
+ */
+ if (regs->sr && (SPR_SR_IEE | SPR_SR_TEE))
+ local_irq_enable();
+ }
+
+ mm = tsk->mm;
+ si_code = SEGV_MAPERR;
+
+ /*
+ * If we're in an interrupt or have no user
+ * context, we must not take the fault..
+ */
+
+ if (in_interrupt() || !mm)
+ goto no_context;
+
+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
+
+retry:
+ mmap_read_lock(mm);
+ 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 (user_mode(regs)) {
+ /*
+ * accessing the stack below usp is always a bug.
+ * we get page-aligned addresses so we can only check
+ * if we're within a page from usp, but that might be
+ * enough to catch brutal errors at least.
+ */
+ if (address + PAGE_SIZE < regs->sp)
+ goto bad_area;
+ }
+ vma = expand_stack(mm, address);
+ if (!vma)
+ goto bad_area_nosemaphore;
+
+ /*
+ * Ok, we have a good vm_area for this memory access, so
+ * we can handle it..
+ */
+
+good_area:
+ si_code = SEGV_ACCERR;
+
+ /* first do some preliminary protection checks */
+
+ if (write_acc) {
+ if (!(vma->vm_flags & VM_WRITE))
+ goto bad_area;
+ flags |= FAULT_FLAG_WRITE;
+ } else {
+ /* not present */
+ if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
+ goto bad_area;
+ }
+
+ /* are we trying to execute nonexecutable area */
+ if ((vector == 0x400) && !(vma->vm_page_prot.pgprot & _PAGE_EXEC))
+ 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))
+ goto no_context;
+ return;
+ }
+
+ /* The fault is fully completed (including releasing mmap lock) */
+ if (fault & VM_FAULT_COMPLETED)
+ return;
+
+ if (unlikely(fault & VM_FAULT_ERROR)) {
+ if (fault & VM_FAULT_OOM)
+ goto out_of_memory;
+ else if (fault & VM_FAULT_SIGSEGV)
+ goto bad_area;
+ else if (fault & VM_FAULT_SIGBUS)
+ goto do_sigbus;
+ BUG();
+ }
+
+ /*RGD modeled on Cris */
+ if (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);
+ 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:
+ mmap_read_unlock(mm);
+
+bad_area_nosemaphore:
+
+ /* User mode accesses just cause a SIGSEGV */
+
+ if (user_mode(regs)) {
+ force_sig_fault(SIGSEGV, si_code, (void __user *)address);
+ return;
+ }
+
+no_context:
+
+ /* Are we prepared to handle this kernel fault?
+ *
+ * (The kernel has valid exception-points in the source
+ * when it acesses user-memory. When it fails in one
+ * of those points, we find it in a table and do a jump
+ * to some fixup code that loads an appropriate error
+ * code)
+ */
+
+ {
+ const struct exception_table_entry *entry;
+
+ if ((entry = search_exception_tables(regs->pc)) != NULL) {
+ /* Adjust the instruction pointer in the stackframe */
+ regs->pc = entry->fixup;
+ return;
+ }
+ }
+
+ /*
+ * Oops. The kernel tried to access some bad page. We'll have to
+ * terminate things with extreme prejudice.
+ */
+
+ if ((unsigned long)(address) < PAGE_SIZE)
+ printk(KERN_ALERT
+ "Unable to handle kernel NULL pointer dereference");
+ else
+ printk(KERN_ALERT "Unable to handle kernel access");
+ printk(" at virtual address 0x%08lx\n", address);
+
+ die("Oops", regs, write_acc);
+
+ /*
+ * 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:
+ mmap_read_unlock(mm);
+ if (!user_mode(regs))
+ goto no_context;
+ pagefault_out_of_memory();
+ return;
+
+do_sigbus:
+ mmap_read_unlock(mm);
+
+ /*
+ * Send a sigbus, regardless of whether we were in kernel
+ * or user mode.
+ */
+ force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
+
+ /* Kernel mode? Handle exceptions or die */
+ if (!user_mode(regs))
+ goto no_context;
+ return;
+
+vmalloc_fault:
+ {
+ /*
+ * Synchronize this task's top level page-table
+ * with the 'reference' page table.
+ *
+ * Use current_pgd instead of tsk->active_mm->pgd
+ * since the latter might be unavailable if this
+ * code is executed in a misfortunately run irq
+ * (like inside schedule() between switch_mm and
+ * switch_to...).
+ */
+
+ int offset = pgd_index(address);
+ pgd_t *pgd, *pgd_k;
+ p4d_t *p4d, *p4d_k;
+ pud_t *pud, *pud_k;
+ pmd_t *pmd, *pmd_k;
+ pte_t *pte_k;
+
+/*
+ phx_warn("do_page_fault(): vmalloc_fault will not work, "
+ "since current_pgd assign a proper value somewhere\n"
+ "anyhow we don't need this at the moment\n");
+
+ phx_mmu("vmalloc_fault");
+*/
+ pgd = (pgd_t *)current_pgd[smp_processor_id()] + offset;
+ pgd_k = init_mm.pgd + offset;
+
+ /* Since we're two-level, we don't need to do both
+ * set_pgd and set_pmd (they do the same thing). If
+ * we go three-level at some point, do the right thing
+ * with pgd_present and set_pgd here.
+ *
+ * Also, since the vmalloc area is global, we don't
+ * need to copy individual PTE's, it is enough to
+ * copy the pgd pointer into the pte page of the
+ * root task. If that is there, we'll find our pte if
+ * it exists.
+ */
+
+ p4d = p4d_offset(pgd, address);
+ p4d_k = p4d_offset(pgd_k, address);
+ if (!p4d_present(*p4d_k))
+ goto no_context;
+
+ pud = pud_offset(p4d, address);
+ pud_k = pud_offset(p4d_k, address);
+ if (!pud_present(*pud_k))
+ goto no_context;
+
+ pmd = pmd_offset(pud, address);
+ pmd_k = pmd_offset(pud_k, address);
+
+ if (!pmd_present(*pmd_k))
+ goto bad_area_nosemaphore;
+
+ set_pmd(pmd, *pmd_k);
+
+ /* 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, address);
+ if (!pte_present(*pte_k))
+ goto no_context;
+
+ return;
+ }
+}
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