// 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 - 2005 Tensilica Inc. * * Chris Zankel <chris@zankel.net> * Joe Taylor <joe@tensilica.com, joetylr@yahoo.com> */ #include <linux/mm.h> #include <linux/module.h> #include <asm/mmu_context.h> #include <asm/cacheflush.h> #include <asm/hardirq.h> #include <asm/uaccess.h> #include <asm/system.h> #include <asm/pgalloc.h> unsigned long asid_cache = ASID_FIRST_VERSION; void bad_page_fault(struct pt_regs*, unsigned long, int); /* * 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; siginfo_t info; int is_write, is_exec; info.si_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)) goto vmalloc_fault; /* If we're in an interrupt or have no user * context, we must not take the fault.. */ if (in_atomic() || !mm) { bad_page_fault(regs, address, SIGSEGV); return; } is_write = (exccause == XCHAL_EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0; is_exec = (exccause == XCHAL_EXCCAUSE_ITLB_PRIVILEGE || exccause == XCHAL_EXCCAUSE_ITLB_MISS || exccause == XCHAL_EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0; #if 0 printk("[%s:%d:%08x:%d:%08x:%s%s]\n", current->comm, current->pid, address, exccause, regs->pc, is_write? "w":"", is_exec? "x":""); #endif 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: info.si_code = SEGV_ACCERR; if (is_write) { if (!(vma->vm_flags & VM_WRITE)) goto bad_area; } 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. */ survive: switch (handle_mm_fault(mm, vma, address, is_write)) { case VM_FAULT_MINOR: current->min_flt++; break; case VM_FAULT_MAJOR: current->maj_flt++; break; case VM_FAULT_SIGBUS: goto do_sigbus; case VM_FAULT_OOM: goto out_of_memory; default: BUG(); } 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); if (user_mode(regs)) { current->thread.bad_vaddr = address; current->thread.error_code = is_write; 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, current); 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: up_read(&mm->mmap_sem); if (current->pid == 1) { yield(); down_read(&mm->mmap_sem); goto survive; } printk("VM: killing process %s\n", current->comm); if (user_mode(regs)) do_exit(SIGKILL); bad_page_fault(regs, address, SIGKILL); return; do_sigbus: up_read(&mm->mmap_sem); /* Send a sigbus, regardless of whether we were in kernel * or user mode. */ current->thread.bad_vaddr = address; info.si_code = SIGBUS; info.si_errno = 0; info.si_code = BUS_ADRERR; info.si_addr = (void *) address; force_sig_info(SIGBUS, &info, current); /* Kernel mode? Handle exceptions or die */ if (!user_mode(regs)) bad_page_fault(regs, address, SIGBUS); vmalloc_fault: { /* 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; 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); pmd = pmd_offset(pgd, address); pmd_k = pmd_offset(pgd_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); return; } void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) { extern void 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) { #if 1 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n", current->comm, regs->pc, entry->fixup); #endif 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. */ printk(KERN_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); do_exit(sig); }