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Subject[PATCH v7 11/37] nds32: MMU fault handling and page table management
Date
This patch includes page fault handler, mmap and fixup implementations.

Signed-off-by: Vincent Chen <vincentc@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
---
arch/nds32/lib/copy_page.S | 37 ++++
arch/nds32/mm/extable.c | 16 ++
arch/nds32/mm/fault.c | 410 +++++++++++++++++++++++++++++++++++++++++++++
arch/nds32/mm/mmap.c | 73 ++++++++
4 files changed, 536 insertions(+)
create mode 100644 arch/nds32/lib/copy_page.S
create mode 100644 arch/nds32/mm/extable.c
create mode 100644 arch/nds32/mm/fault.c
create mode 100644 arch/nds32/mm/mmap.c

diff --git a/arch/nds32/lib/copy_page.S b/arch/nds32/lib/copy_page.S
new file mode 100644
index 000000000000..4a2ff85f17ee
--- /dev/null
+++ b/arch/nds32/lib/copy_page.S
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+#include <linux/linkage.h>
+#include <asm/page.h>
+
+ .text
+ENTRY(copy_page)
+ pushm $r2, $r10
+ movi $r2, PAGE_SIZE >> 5
+.Lcopy_loop:
+ lmw.bim $r3, [$r1], $r10
+ smw.bim $r3, [$r0], $r10
+ subi45 $r2, #1
+ bnez38 $r2, .Lcopy_loop
+ popm $r2, $r10
+ ret
+ENDPROC(copy_page)
+
+ENTRY(clear_page)
+ pushm $r1, $r9
+ movi $r1, PAGE_SIZE >> 5
+ movi55 $r2, #0
+ movi55 $r3, #0
+ movi55 $r4, #0
+ movi55 $r5, #0
+ movi55 $r6, #0
+ movi55 $r7, #0
+ movi55 $r8, #0
+ movi55 $r9, #0
+.Lclear_loop:
+ smw.bim $r2, [$r0], $r9
+ subi45 $r1, #1
+ bnez38 $r1, .Lclear_loop
+ popm $r1, $r9
+ ret
+ENDPROC(clear_page)
diff --git a/arch/nds32/mm/extable.c b/arch/nds32/mm/extable.c
new file mode 100644
index 000000000000..db7f0a7c8966
--- /dev/null
+++ b/arch/nds32/mm/extable.c
@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+#include <linux/extable.h>
+#include <linux/uaccess.h>
+
+int fixup_exception(struct pt_regs *regs)
+{
+ const struct exception_table_entry *fixup;
+
+ fixup = search_exception_tables(instruction_pointer(regs));
+ if (fixup)
+ regs->ipc = fixup->fixup;
+
+ return fixup != NULL;
+}
diff --git a/arch/nds32/mm/fault.c b/arch/nds32/mm/fault.c
new file mode 100644
index 000000000000..3a246fb8098c
--- /dev/null
+++ b/arch/nds32/mm/fault.c
@@ -0,0 +1,410 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+#include <linux/extable.h>
+#include <linux/module.h>
+#include <linux/signal.h>
+#include <linux/ptrace.h>
+#include <linux/mm.h>
+#include <linux/init.h>
+#include <linux/hardirq.h>
+#include <linux/uaccess.h>
+
+#include <asm/pgtable.h>
+#include <asm/tlbflush.h>
+
+extern void die(const char *str, struct pt_regs *regs, long err);
+
+/*
+ * This is useful to dump out the page tables associated with
+ * 'addr' in mm 'mm'.
+ */
+void show_pte(struct mm_struct *mm, unsigned long addr)
+{
+ pgd_t *pgd;
+ if (!mm)
+ mm = &init_mm;
+
+ pr_alert("pgd = %p\n", mm->pgd);
+ pgd = pgd_offset(mm, addr);
+ pr_alert("[%08lx] *pgd=%08lx", addr, pgd_val(*pgd));
+
+ do {
+ pmd_t *pmd;
+
+ if (pgd_none(*pgd))
+ break;
+
+ if (pgd_bad(*pgd)) {
+ pr_alert("(bad)");
+ break;
+ }
+
+ pmd = pmd_offset(pgd, addr);
+#if PTRS_PER_PMD != 1
+ pr_alert(", *pmd=%08lx", pmd_val(*pmd));
+#endif
+
+ if (pmd_none(*pmd))
+ break;
+
+ if (pmd_bad(*pmd)) {
+ pr_alert("(bad)");
+ break;
+ }
+
+ if (IS_ENABLED(CONFIG_HIGHMEM))
+ {
+ pte_t *pte;
+ /* We must not map this if we have highmem enabled */
+ pte = pte_offset_map(pmd, addr);
+ pr_alert(", *pte=%08lx", pte_val(*pte));
+ pte_unmap(pte);
+ }
+ } while (0);
+
+ pr_alert("\n");
+}
+
+void do_page_fault(unsigned long entry, unsigned long addr,
+ unsigned int error_code, struct pt_regs *regs)
+{
+ struct task_struct *tsk;
+ struct mm_struct *mm;
+ struct vm_area_struct *vma;
+ siginfo_t info;
+ int fault;
+ unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
+ unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
+
+ error_code = error_code & (ITYPE_mskINST | ITYPE_mskETYPE);
+ tsk = current;
+ mm = tsk->mm;
+ info.si_code = SEGV_MAPERR;
+ /*
+ * 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 (addr >= TASK_SIZE) {
+ if (user_mode(regs))
+ goto bad_area_nosemaphore;
+
+ if (addr >= TASK_SIZE && addr < VMALLOC_END
+ && (entry == ENTRY_PTE_NOT_PRESENT))
+ goto vmalloc_fault;
+ else
+ goto no_context;
+ }
+
+ /* Send a signal to the task for handling the unalignment access. */
+ if (entry == ENTRY_GENERAL_EXCPETION
+ && error_code == ETYPE_ALIGNMENT_CHECK) {
+ if (user_mode(regs))
+ goto bad_area_nosemaphore;
+ else
+ goto no_context;
+ }
+
+ /*
+ * If we're in an interrupt or have no user
+ * context, we must not take the fault..
+ */
+ if (unlikely(faulthandler_disabled() || !mm))
+ goto no_context;
+
+ /*
+ * As per x86, we may deadlock here. However, since the kernel only
+ * validly references user space from well defined areas of the code,
+ * we can bug out early if this is from code which shouldn't.
+ */
+ if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
+ if (!user_mode(regs) &&
+ !search_exception_tables(instruction_pointer(regs)))
+ goto no_context;
+retry:
+ down_read(&mm->mmap_sem);
+ } else {
+ /*
+ * The above down_read_trylock() might have succeeded in which
+ * case, we'll have missed the might_sleep() from down_read().
+ */
+ might_sleep();
+ if (IS_ENABLED(CONFIG_DEBUG_VM)) {
+ if (!user_mode(regs) &&
+ !search_exception_tables(instruction_pointer(regs)))
+ goto no_context;
+ }
+ }
+
+ vma = find_vma(mm, addr);
+
+ if (unlikely(!vma))
+ goto bad_area;
+
+ if (vma->vm_start <= addr)
+ goto good_area;
+
+ if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
+ goto bad_area;
+
+ if (unlikely(expand_stack(vma, addr)))
+ 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;
+
+ /* first do some preliminary protection checks */
+ if (entry == ENTRY_PTE_NOT_PRESENT) {
+ if (error_code & ITYPE_mskINST)
+ mask = VM_EXEC;
+ else {
+ mask = VM_READ | VM_WRITE;
+ if (vma->vm_flags & VM_WRITE)
+ flags |= FAULT_FLAG_WRITE;
+ }
+ } else if (entry == ENTRY_TLB_MISC) {
+ switch (error_code & ITYPE_mskETYPE) {
+ case RD_PROT:
+ mask = VM_READ;
+ break;
+ case WRT_PROT:
+ mask = VM_WRITE;
+ flags |= FAULT_FLAG_WRITE;
+ break;
+ case NOEXEC:
+ mask = VM_EXEC;
+ break;
+ case PAGE_MODIFY:
+ mask = VM_WRITE;
+ flags |= FAULT_FLAG_WRITE;
+ break;
+ case ACC_BIT:
+ BUG();
+ default:
+ break;
+ }
+
+ }
+ if (!(vma->vm_flags & mask))
+ 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, addr, flags);
+
+ /*
+ * If we need to retry but a fatal signal is pending, handle the
+ * signal first. We do not need to release the mmap_sem because it
+ * would already be released in __lock_page_or_retry in mm/filemap.c.
+ */
+ if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) {
+ if (!user_mode(regs))
+ goto no_context;
+ return;
+ }
+
+ if (unlikely(fault & VM_FAULT_ERROR)) {
+ if (fault & VM_FAULT_OOM)
+ goto out_of_memory;
+ else if (fault & VM_FAULT_SIGBUS)
+ goto do_sigbus;
+ else
+ goto bad_area;
+ }
+
+ /*
+ * Major/minor page fault accounting is only done on the initial
+ * attempt. If we go through a retry, it is extremely likely that the
+ * page will be found in page cache at that point.
+ */
+ if (flags & FAULT_FLAG_ALLOW_RETRY) {
+ if (fault & VM_FAULT_MAJOR)
+ tsk->maj_flt++;
+ else
+ tsk->min_flt++;
+ if (fault & VM_FAULT_RETRY) {
+ flags &= ~FAULT_FLAG_ALLOW_RETRY;
+ flags |= FAULT_FLAG_TRIED;
+
+ /* No need to up_read(&mm->mmap_sem) as we would
+ * have already released it in __lock_page_or_retry
+ * in mm/filemap.c.
+ */
+ goto retry;
+ }
+ }
+
+ 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);
+
+bad_area_nosemaphore:
+
+ /* User mode accesses just cause a SIGSEGV */
+
+ if (user_mode(regs)) {
+ tsk->thread.address = addr;
+ tsk->thread.error_code = error_code;
+ tsk->thread.trap_no = entry;
+ info.si_signo = SIGSEGV;
+ info.si_errno = 0;
+ /* info.si_code has been set above */
+ info.si_addr = (void *)addr;
+ force_sig_info(SIGSEGV, &info, tsk);
+ 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(instruction_pointer(regs))) !=
+ NULL) {
+ /* Adjust the instruction pointer in the stackframe */
+ instruction_pointer(regs) = entry->fixup;
+ 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 %s at virtual address %08lx\n",
+ (addr < PAGE_SIZE) ? "NULL pointer dereference" :
+ "paging request", addr);
+
+ show_pte(mm, addr);
+ die("Oops", regs, error_code);
+ bust_spinlocks(0);
+ do_exit(SIGKILL);
+
+ 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 (!user_mode(regs))
+ goto no_context;
+ pagefault_out_of_memory();
+ return;
+
+do_sigbus:
+ up_read(&mm->mmap_sem);
+
+ /* Kernel mode? Handle exceptions or die */
+ if (!user_mode(regs))
+ goto no_context;
+
+ /*
+ * Send a sigbus
+ */
+ tsk->thread.address = addr;
+ tsk->thread.error_code = error_code;
+ tsk->thread.trap_no = entry;
+ info.si_signo = SIGBUS;
+ info.si_errno = 0;
+ info.si_code = BUS_ADRERR;
+ info.si_addr = (void *)addr;
+ force_sig_info(SIGBUS, &info, tsk);
+
+ 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...).
+ */
+
+ unsigned int index = pgd_index(addr);
+ pgd_t *pgd, *pgd_k;
+ pud_t *pud, *pud_k;
+ pmd_t *pmd, *pmd_k;
+ pte_t *pte_k;
+
+ pgd = (pgd_t *) __va(__nds32__mfsr(NDS32_SR_L1_PPTB)) + index;
+ pgd_k = init_mm.pgd + index;
+
+ if (!pgd_present(*pgd_k))
+ goto no_context;
+
+ pud = pud_offset(pgd, addr);
+ pud_k = pud_offset(pgd_k, addr);
+ if (!pud_present(*pud_k))
+ goto no_context;
+
+ pmd = pmd_offset(pud, addr);
+ pmd_k = pmd_offset(pud_k, addr);
+ if (!pmd_present(*pmd_k))
+ goto no_context;
+
+ if (!pmd_present(*pmd))
+ set_pmd(pmd, *pmd_k);
+ else
+ BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
+
+ /*
+ * 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.
+ */
+
+ /* Make sure the actual PTE exists as well to
+ * catch kernel vmalloc-area accesses to non-mapped
+ * addres. 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))
+ goto no_context;
+
+ return;
+ }
+}
diff --git a/arch/nds32/mm/mmap.c b/arch/nds32/mm/mmap.c
new file mode 100644
index 000000000000..c206b31ce07a
--- /dev/null
+++ b/arch/nds32/mm/mmap.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+#include <linux/sched.h>
+#include <linux/mman.h>
+#include <linux/shm.h>
+
+#define COLOUR_ALIGN(addr,pgoff) \
+ ((((addr)+SHMLBA-1)&~(SHMLBA-1)) + \
+ (((pgoff)<<PAGE_SHIFT) & (SHMLBA-1)))
+
+/*
+ * We need to ensure that shared mappings are correctly aligned to
+ * avoid aliasing issues with VIPT caches. We need to ensure that
+ * a specific page of an object is always mapped at a multiple of
+ * SHMLBA bytes.
+ *
+ * We unconditionally provide this function for all cases, however
+ * in the VIVT case, we optimise out the alignment rules.
+ */
+unsigned long
+arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ unsigned long len, unsigned long pgoff,
+ unsigned long flags)
+{
+ struct mm_struct *mm = current->mm;
+ struct vm_area_struct *vma;
+ int do_align = 0;
+ struct vm_unmapped_area_info info;
+ int aliasing = 0;
+ if(IS_ENABLED(CONFIG_CPU_CACHE_ALIASING))
+ aliasing = 1;
+
+ /*
+ * We only need to do colour alignment if either the I or D
+ * caches alias.
+ */
+ if (aliasing)
+ do_align = filp || (flags & MAP_SHARED);
+
+ /*
+ * We enforce the MAP_FIXED case.
+ */
+ if (flags & MAP_FIXED) {
+ if (aliasing && flags & MAP_SHARED &&
+ (addr - (pgoff << PAGE_SHIFT)) & (SHMLBA - 1))
+ return -EINVAL;
+ return addr;
+ }
+
+ if (len > TASK_SIZE)
+ return -ENOMEM;
+
+ if (addr) {
+ if (do_align)
+ addr = COLOUR_ALIGN(addr, pgoff);
+ else
+ addr = PAGE_ALIGN(addr);
+
+ vma = find_vma(mm, addr);
+ if (TASK_SIZE - len >= addr &&
+ (!vma || addr + len <= vma->vm_start))
+ return addr;
+ }
+
+ info.flags = 0;
+ info.length = len;
+ info.low_limit = mm->mmap_base;
+ info.high_limit = TASK_SIZE;
+ info.align_mask = do_align ? (PAGE_MASK & (SHMLBA - 1)) : 0;
+ info.align_offset = pgoff << PAGE_SHIFT;
+ return vm_unmapped_area(&info);
+}
--
2.16.1
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