diff options
Diffstat (limited to 'kernel/arch/cris/mm/fault.c')
| -rw-r--r-- | kernel/arch/cris/mm/fault.c | 388 |
1 files changed, 388 insertions, 0 deletions
diff --git a/kernel/arch/cris/mm/fault.c b/kernel/arch/cris/mm/fault.c new file mode 100644 index 000000000..3066d40a6 --- /dev/null +++ b/kernel/arch/cris/mm/fault.c @@ -0,0 +1,388 @@ +/* + * arch/cris/mm/fault.c + * + * Copyright (C) 2000-2010 Axis Communications AB + */ + +#include <linux/mm.h> +#include <linux/interrupt.h> +#include <linux/module.h> +#include <linux/wait.h> +#include <linux/uaccess.h> +#include <arch/system.h> + +extern int find_fixup_code(struct pt_regs *); +extern void die_if_kernel(const char *, struct pt_regs *, long); +extern void show_registers(struct pt_regs *regs); + +/* debug of low-level TLB reload */ +#undef DEBUG + +#ifdef DEBUG +#define D(x) x +#else +#define D(x) +#endif + +/* debug of higher-level faults */ +#define DPG(x) + +/* current active page directory */ + +DEFINE_PER_CPU(pgd_t *, current_pgd); +unsigned long cris_signal_return_page; + +/* + * This routine handles page faults. It determines the address, + * and the problem, and then passes it off to one of the appropriate + * routines. + * + * Notice that the address we're given is aligned to the page the fault + * occurred in, since we only get the PFN in R_MMU_CAUSE not the complete + * address. + * + * error_code: + * bit 0 == 0 means no page found, 1 means protection fault + * bit 1 == 0 means read, 1 means write + * + * If this routine detects a bad access, it returns 1, otherwise it + * returns 0. + */ + +asmlinkage void +do_page_fault(unsigned long address, struct pt_regs *regs, + int protection, int writeaccess) +{ + struct task_struct *tsk; + struct mm_struct *mm; + struct vm_area_struct * vma; + siginfo_t info; + int fault; + unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; + + D(printk(KERN_DEBUG + "Page fault for %lX on %X at %lX, prot %d write %d\n", + address, smp_processor_id(), instruction_pointer(regs), + protection, writeaccess)); + + 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 (error_code & 1). + */ + + if (address >= VMALLOC_START && + !protection && + !user_mode(regs)) + goto vmalloc_fault; + + /* When stack execution is not allowed we store the signal + * trampolines in the reserved cris_signal_return_page. + * Handle this in the exact same way as vmalloc (we know + * that the mapping is there and is valid so no need to + * call handle_mm_fault). + */ + if (cris_signal_return_page && + address == cris_signal_return_page && + !protection && user_mode(regs)) + goto vmalloc_fault; + + /* we can and should enable interrupts at this point */ + local_irq_enable(); + + mm = tsk->mm; + info.si_code = SEGV_MAPERR; + + /* + * If we're in an interrupt, have pagefaults disabled or have no + * user context, we must not take the fault. + */ + + if (faulthandler_disabled() || !mm) + goto no_context; + + if (user_mode(regs)) + flags |= FAULT_FLAG_USER; +retry: + 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 (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 < rdusp()) + 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: + info.si_code = SEGV_ACCERR; + + /* first do some preliminary protection checks */ + + if (writeaccess == 2){ + if (!(vma->vm_flags & VM_EXEC)) + goto bad_area; + } else if (writeaccess == 1) { + if (!(vma->vm_flags & VM_WRITE)) + goto bad_area; + flags |= FAULT_FLAG_WRITE; + } else { + if (!(vma->vm_flags & (VM_READ | VM_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(mm, vma, address, flags); + + if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) + 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(); + } + + 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: + DPG(show_registers(regs)); + + /* User mode accesses just cause a SIGSEGV */ + + if (user_mode(regs)) { +#ifdef CONFIG_NO_SEGFAULT_TERMINATION + DECLARE_WAIT_QUEUE_HEAD(wq); +#endif + printk(KERN_NOTICE "%s (pid %d) segfaults for page " + "address %08lx at pc %08lx\n", + tsk->comm, tsk->pid, + address, instruction_pointer(regs)); + + /* With DPG on, we've already dumped registers above. */ + DPG(if (0)) + show_registers(regs); + +#ifdef CONFIG_NO_SEGFAULT_TERMINATION + wait_event_interruptible(wq, 0 == 1); +#else + info.si_signo = SIGSEGV; + info.si_errno = 0; + /* info.si_code has been set above */ + info.si_addr = (void *)address; + force_sig_info(SIGSEGV, &info, tsk); +#endif + return; + } + + no_context: + + /* Are we prepared to handle this kernel fault? + * + * (The kernel has valid exception-points in the source + * when it accesses 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) + */ + + if (find_fixup_code(regs)) + return; + + /* + * Oops. The kernel tried to access some bad page. We'll have to + * terminate things with extreme prejudice. + */ + + if (!oops_in_progress) { + oops_in_progress = 1; + 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" + " at virtual address %08lx\n", address); + + die_if_kernel("Oops", regs, (writeaccess << 1) | protection); + oops_in_progress = 0; + } + + do_exit(SIGKILL); + + /* + * 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); + + /* + * Send a sigbus, regardless of whether we were in kernel + * or user mode. + */ + info.si_signo = SIGBUS; + info.si_errno = 0; + info.si_code = BUS_ADRERR; + info.si_addr = (void *)address; + force_sig_info(SIGBUS, &info, tsk); + + /* 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; + pud_t *pud, *pud_k; + pmd_t *pmd, *pmd_k; + pte_t *pte_k; + + pgd = (pgd_t *)per_cpu(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. + */ + + 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 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; + } +} + +/* Find fixup code. */ +int +find_fixup_code(struct pt_regs *regs) +{ + const struct exception_table_entry *fixup; + /* in case of delay slot fault (v32) */ + unsigned long ip = (instruction_pointer(regs) & ~0x1); + + fixup = search_exception_tables(ip); + if (fixup != 0) { + /* Adjust the instruction pointer in the stackframe. */ + instruction_pointer(regs) = fixup->fixup; + arch_fixup(regs); + return 1; + } + + return 0; +} |