| // TODO VM_EXEC flag work-around, cache aliasing |
| /* |
| * arch/xtensa/mm/fault.c |
| * |
| * 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. |
| * |
| * Copyright (C) 2001 - 2010 Tensilica Inc. |
| * |
| * Chris Zankel <chris@zankel.net> |
| * Joe Taylor <joe@tensilica.com, joetylr@yahoo.com> |
| */ |
| |
| #include <linux/mm.h> |
| #include <linux/extable.h> |
| #include <linux/hardirq.h> |
| #include <linux/perf_event.h> |
| #include <linux/uaccess.h> |
| #include <asm/mmu_context.h> |
| #include <asm/cacheflush.h> |
| #include <asm/hardirq.h> |
| |
| void bad_page_fault(struct pt_regs*, unsigned long, int); |
| |
| static void vmalloc_fault(struct pt_regs *regs, unsigned int address) |
| { |
| #ifdef CONFIG_MMU |
| /* Synchronize this task's top level page-table |
| * with the 'reference' page table. |
| */ |
| struct mm_struct *act_mm = current->active_mm; |
| int index = 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; |
| |
| if (act_mm == NULL) |
| goto bad_page_fault; |
| |
| pgd = act_mm->pgd + index; |
| pgd_k = init_mm.pgd + index; |
| |
| if (!pgd_present(*pgd_k)) |
| goto bad_page_fault; |
| |
| pgd_val(*pgd) = pgd_val(*pgd_k); |
| |
| p4d = p4d_offset(pgd, address); |
| p4d_k = p4d_offset(pgd_k, address); |
| if (!p4d_present(*p4d) || !p4d_present(*p4d_k)) |
| goto bad_page_fault; |
| |
| pud = pud_offset(p4d, address); |
| pud_k = pud_offset(p4d_k, address); |
| if (!pud_present(*pud) || !pud_present(*pud_k)) |
| goto bad_page_fault; |
| |
| pmd = pmd_offset(pud, address); |
| pmd_k = pmd_offset(pud_k, address); |
| if (!pmd_present(*pmd) || !pmd_present(*pmd_k)) |
| goto bad_page_fault; |
| |
| pmd_val(*pmd) = pmd_val(*pmd_k); |
| pte_k = pte_offset_kernel(pmd_k, address); |
| |
| if (!pte_present(*pte_k)) |
| goto bad_page_fault; |
| return; |
| |
| bad_page_fault: |
| bad_page_fault(regs, address, SIGKILL); |
| #else |
| WARN_ONCE(1, "%s in noMMU configuration\n", __func__); |
| #endif |
| } |
| /* |
| * This routine handles page faults. It determines the address, |
| * and the problem, and then passes it off to one of the appropriate |
| * routines. |
| * |
| * Note: does not handle Miss and MultiHit. |
| */ |
| |
| void do_page_fault(struct pt_regs *regs) |
| { |
| struct vm_area_struct * vma; |
| struct mm_struct *mm = current->mm; |
| unsigned int exccause = regs->exccause; |
| unsigned int address = regs->excvaddr; |
| int code; |
| |
| int is_write, is_exec; |
| vm_fault_t fault; |
| unsigned int flags = FAULT_FLAG_DEFAULT; |
| |
| code = SEGV_MAPERR; |
| |
| /* We fault-in kernel-space virtual memory on-demand. The |
| * 'reference' page table is init_mm.pgd. |
| */ |
| if (address >= TASK_SIZE && !user_mode(regs)) { |
| vmalloc_fault(regs, address); |
| return; |
| } |
| |
| /* If we're in an interrupt or have no user |
| * context, we must not take the fault.. |
| */ |
| if (faulthandler_disabled() || !mm) { |
| bad_page_fault(regs, address, SIGSEGV); |
| return; |
| } |
| |
| is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0; |
| is_exec = (exccause == EXCCAUSE_ITLB_PRIVILEGE || |
| exccause == EXCCAUSE_ITLB_MISS || |
| exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0; |
| |
| pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n", |
| current->comm, current->pid, |
| address, exccause, regs->pc, |
| is_write ? "w" : "", is_exec ? "x" : ""); |
| |
| if (user_mode(regs)) |
| flags |= FAULT_FLAG_USER; |
| |
| perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); |
| |
| retry: |
| vma = lock_mm_and_find_vma(mm, address, regs); |
| if (!vma) |
| goto bad_area_nosemaphore; |
| |
| /* Ok, we have a good vm_area for this memory access, so |
| * we can handle it.. |
| */ |
| |
| code = SEGV_ACCERR; |
| |
| if (is_write) { |
| if (!(vma->vm_flags & VM_WRITE)) |
| goto bad_area; |
| flags |= FAULT_FLAG_WRITE; |
| } else if (is_exec) { |
| if (!(vma->vm_flags & VM_EXEC)) |
| goto bad_area; |
| } else /* Allow read even from write-only pages. */ |
| if (!(vma->vm_flags & (VM_READ | VM_WRITE))) |
| 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)) |
| bad_page_fault(regs, address, SIGKILL); |
| 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(); |
| } |
| |
| 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: |
| if (user_mode(regs)) { |
| current->thread.bad_vaddr = address; |
| current->thread.error_code = is_write; |
| force_sig_fault(SIGSEGV, code, (void *) address); |
| return; |
| } |
| bad_page_fault(regs, address, SIGSEGV); |
| 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: |
| mmap_read_unlock(mm); |
| if (!user_mode(regs)) |
| bad_page_fault(regs, address, SIGKILL); |
| else |
| pagefault_out_of_memory(); |
| return; |
| |
| do_sigbus: |
| mmap_read_unlock(mm); |
| |
| /* Send a sigbus, regardless of whether we were in kernel |
| * or user mode. |
| */ |
| current->thread.bad_vaddr = address; |
| force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address); |
| |
| /* Kernel mode? Handle exceptions or die */ |
| if (!user_mode(regs)) |
| bad_page_fault(regs, address, SIGBUS); |
| return; |
| } |
| |
| |
| void |
| bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) |
| { |
| extern void __noreturn die(const char*, struct pt_regs*, long); |
| const struct exception_table_entry *entry; |
| |
| /* Are we prepared to handle this kernel fault? */ |
| if ((entry = search_exception_tables(regs->pc)) != NULL) { |
| pr_debug("%s: Exception at pc=%#010lx (%lx)\n", |
| current->comm, regs->pc, entry->fixup); |
| current->thread.bad_uaddr = address; |
| regs->pc = entry->fixup; |
| return; |
| } |
| |
| /* Oops. The kernel tried to access some bad page. We'll have to |
| * terminate things with extreme prejudice. |
| */ |
| pr_alert("Unable to handle kernel paging request at virtual " |
| "address %08lx\n pc = %08lx, ra = %08lx\n", |
| address, regs->pc, regs->areg[0]); |
| die("Oops", regs, sig); |
| } |