[PATCH v2 07/29] nios2: MMU Fault handling

Ley Foon Tan
2014-07-15T08:48:09Z

This patch adds support for the handling of the MMU faults (exception
entry code introduced by a previous patch, kernel/entry.S).

Signed-off-by: Ley Foon Tan <lftan@altera.com>
---
arch/nios2/mm/extable.c | 25 +++++
arch/nios2/mm/fault.c | 245 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 270 insertions(+)
create mode 100644 arch/nios2/mm/extable.c
create mode 100644 arch/nios2/mm/fault.c

diff --git a/arch/nios2/mm/extable.c b/arch/nios2/mm/extable.c
new file mode 100644
index 0000000..4d2fc5a
--- /dev/null
+++ b/arch/nios2/mm/extable.c
@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2010, Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2009, Wind River Systems Inc
+ * Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/uaccess.h>
+
+int fixup_exception(struct pt_regs *regs)
+{
+ const struct exception_table_entry *fixup;
+
+ fixup = search_exception_tables(regs->ea);
+ if (fixup) {
+ regs->ea = fixup->fixup;
+ return 1;
+ }
+
+ return 0;
+}
diff --git a/arch/nios2/mm/fault.c b/arch/nios2/mm/fault.c
new file mode 100644
index 0000000..a12098d
--- /dev/null
+++ b/arch/nios2/mm/fault.c
@@ -0,0 +1,245 @@
+/*
+ * Copyright (C) 2009 Wind River Systems Inc
+ * Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
+ *
+ * based on arch/mips/mm/fault.c which is:
+ *
+ * Copyright (C) 1995-2000 Ralf Baechle
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/ptrace.h>
+#include <linux/mman.h>
+#include <linux/mm.h>
+#include <linux/uaccess.h>
+#include <linux/ptrace.h>
+
+#include <asm/mmu_context.h>
+#include <asm/traps.h>
+
+#define EXC_SUPERV_INSN_ACCESS 9 /* Supervisor only instruction address */
+#define EXC_SUPERV_DATA_ACCESS 11 /* Supervisor only data address */
+#define EXC_X_PROTECTION_FAULT 13 /* TLB permission violation (x) */
+#define EXC_R_PROTECTION_FAULT 14 /* TLB permission violation (r) */
+#define EXC_W_PROTECTION_FAULT 15 /* TLB permission violation (w) */
+
+/*
+ * 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, unsigned long cause,
+ unsigned long address)
+{
+ struct vm_area_struct *vma = NULL;
+ struct task_struct *tsk = current;
+ struct mm_struct *mm = tsk->mm;
+ int code = SEGV_MAPERR;
+ int fault;
+ unsigned int flags = 0;
+
+ cause >>= 2;
+
+ /* Restart the instruction */
+ regs->ea -= 4;
+
+ /*
+ * 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 (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) {
+ if (user_mode(regs))
+ goto bad_area_nosemaphore;
+ else
+ goto vmalloc_fault;
+ }
+
+ if (unlikely(address >= TASK_SIZE))
+ goto bad_area_nosemaphore;
+
+ /*
+ * If we're in an interrupt or have no user
+ * context, we must not take the fault..
+ */
+ if (in_atomic() || !mm)
+ goto bad_area_nosemaphore;
+
+ if (user_mode(regs))
+ flags |= FAULT_FLAG_USER;
+
+ down_read(&mm->mmap_sem);
+ 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 (expand_stack(vma, address))
+ goto bad_area;
+/*
+ * Ok, we have a good vm_area for this memory access, so
+ * we can handle it..
+ */
+good_area:
+ code = SEGV_ACCERR;
+
+ switch (cause) {
+ case EXC_SUPERV_INSN_ACCESS:
+ goto bad_area;
+ case EXC_SUPERV_DATA_ACCESS:
+ goto bad_area;
+ case EXC_X_PROTECTION_FAULT:
+ if (!(vma->vm_flags & VM_EXEC))
+ goto bad_area;
+ break;
+ case EXC_R_PROTECTION_FAULT:
+ if (!(vma->vm_flags & VM_READ))
+ goto bad_area;
+ break;
+ case EXC_W_PROTECTION_FAULT:
+ if (!(vma->vm_flags & VM_WRITE))
+ goto bad_area;
+ flags = FAULT_FLAG_WRITE;
+ break;
+ }
+
+survive:
+ /*
+ * 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(mm, vma, address, flags);
+ if (unlikely(fault & VM_FAULT_ERROR)) {
+ if (fault & VM_FAULT_OOM)
+ goto out_of_memory;
+ else if (fault & VM_FAULT_SIGBUS)
+ goto do_sigbus;
+ BUG();
+ }
+ if (fault & VM_FAULT_MAJOR)
+ tsk->maj_flt++;
+ else
+ tsk->min_flt++;
+
+ 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)) {
+ pr_alert("%s: unhandled page fault (%d) at 0x%08lx, "
+ "cause %ld\n", current->comm, SIGSEGV, address, cause);
+ show_regs(regs);
+ _exception(SIGSEGV, regs, code, address);
+ return;
+ }
+
+no_context:
+ /* 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 %s at virtual address %08lx",
+ address < PAGE_SIZE ? "NULL pointer dereference" :
+ "paging request", address);
+ pr_alert("ea = %08lx, ra = %08lx, cause = %ld\n", regs->ea, regs->ra,
+ cause);
+ panic("Oops");
+ 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 (is_global_init(tsk)) {
+ yield();
+ down_read(&mm->mmap_sem);
+ goto survive;
+ }
+ 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;
+
+ _exception(SIGBUS, regs, BUS_ADRERR, address);
+ return;
+
+vmalloc_fault:
+ {
+ /*
+ * 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..
+ */
+ int offset = pgd_index(address);
+ pgd_t *pgd, *pgd_k;
+ pud_t *pud, *pud_k;
+ pmd_t *pmd, *pmd_k;
+ pte_t *pte_k;
+
+ pgd = pgd_current + offset;
+ pgd_k = init_mm.pgd + offset;
+
+ if (!pgd_present(*pgd_k))
+ goto no_context;
+ set_pgd(pgd, *pgd_k);
+
+ pud = pud_offset(pgd, address);
+ pud_k = pud_offset(pgd_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 no_context;
+ set_pmd(pmd, *pmd_k);
+
+ pte_k = pte_offset_kernel(pmd_k, address);
+ if (!pte_present(*pte_k))
+ goto no_context;
+
+ flush_tlb_one(address);
+ return;
+ }
+}
--
1.8.2.1