/* * linux/arch/cris/mm/fault.c * * Copyright (C) 2000 Axis Communications AB * * Authors: Bjorn Wesen * * $Log: fault.c,v $ * Revision 1.8 2000/11/22 14:45:31 bjornw * * 2.4.0-test10 removed the set_pgdir instantaneous kernel global mapping * into all processes. Instead we fill in the missing PTE entries on demand. * * Revision 1.7 2000/11/21 16:39:09 bjornw * fixup switches frametype * * Revision 1.6 2000/11/17 16:54:08 bjornw * More detailed siginfo reporting * * */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include extern void die_if_kernel(const char *,struct pt_regs *,long); asmlinkage void do_invalid_op (struct pt_regs *, unsigned long); asmlinkage void do_page_fault(unsigned long address, struct pt_regs *regs, int error_code); /* debug of low-level TLB reload */ #define D(x) /* debug of higher-level faults */ #define DPG(x) /* fast TLB-fill fault handler */ void handle_mmu_bus_fault(struct pt_regs *regs) { int cause, select; int index; int page_id; int miss, we, acc, inv; struct mm_struct *mm = current->active_mm; pmd_t *pmd; pte_t pte; int errcode = 0; unsigned long address; cause = *R_MMU_CAUSE; select = *R_TLB_SELECT; address = cause & PAGE_MASK; /* get faulting address */ page_id = IO_EXTRACT(R_MMU_CAUSE, page_id, cause); miss = IO_EXTRACT(R_MMU_CAUSE, miss_excp, cause); we = IO_EXTRACT(R_MMU_CAUSE, we_excp, cause); acc = IO_EXTRACT(R_MMU_CAUSE, acc_excp, cause); inv = IO_EXTRACT(R_MMU_CAUSE, inv_excp, cause); index = IO_EXTRACT(R_TLB_SELECT, index, select); D(printk("bus_fault from IRP 0x%x: addr 0x%x, miss %d, inv %d, we %d, acc %d, " "idx %d pid %d\n", regs->irp, address, miss, inv, we, acc, index, page_id)); /* for a miss, we need to reload the TLB entry */ if(miss) { /* see if the pte exists at all */ pmd = (pmd_t *)pgd_offset(mm, address); if(pmd_none(*pmd)) goto dofault; if(pmd_bad(*pmd)) { printk("bad pgdir entry 0x%x at 0x%x\n", *pmd, pmd); pmd_clear(pmd); return; } pte = *pte_offset(pmd, address); if(!pte_present(pte)) goto dofault; D(printk(" found pte %x pg %x ", pte_val(pte), pte_page(pte))); D( { if(pte_val(pte) & _PAGE_SILENT_WRITE) printk("Silent-W "); if(pte_val(pte) & _PAGE_KERNEL) printk("Kernel "); if(pte_val(pte) & _PAGE_SILENT_READ) printk("Silent-R "); if(pte_val(pte) & _PAGE_GLOBAL) printk("Global "); if(pte_val(pte) & _PAGE_PRESENT) printk("Present "); if(pte_val(pte) & _PAGE_ACCESSED) printk("Accessed "); if(pte_val(pte) & _PAGE_MODIFIED) printk("Modified "); if(pte_val(pte) & _PAGE_READ) printk("Readable "); if(pte_val(pte) & _PAGE_WRITE) printk("Writeable "); printk("\n"); }); /* load up the chosen TLB entry * this assumes the pte format is the same as the TLB_LO layout. * * the write to R_TLB_LO also writes the vpn and page_id fields from * R_MMU_CAUSE, which we in this case obviously want to keep */ *R_TLB_LO = pte_val(pte); return; } errcode = 0x01 | (we << 1); dofault: /* leave it to the MM system fault handler below */ D(printk("do_page_fault %p errcode %d\n", address, errcode)); do_page_fault(address, regs, errcode); } /* * 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 * occured 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 error_code) { struct task_struct *tsk; struct mm_struct *mm; struct vm_area_struct * vma; int writeaccess; int fault; unsigned long fixup; siginfo_t info; 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. * * TODO: On CRIS, we have a PTE Global bit which should be set in * all the PTE's related to vmalloc in all processes - that means if * we switch process and a vmalloc PTE is still in the TLB, it won't * need to be reloaded. It's an optimization. * * Linux/CRIS's kernel is not page-mapped, so the comparision below * should really be >= VMALLOC_START, however, kernel fixup errors * will be handled more quickly by going through vmalloc_fault and then * into bad_area_nosemaphore than falling through the find_vma user-mode * tests. */ if (address >= TASK_SIZE) goto vmalloc_fault; mm = tsk->mm; writeaccess = error_code & 2; info.si_code = SEGV_MAPERR; /* * If we're in an interrupt or have no user * context, we must not take the fault.. */ if (in_interrupt() || !mm) goto no_context; down(&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) { if (!(vma->vm_flags & VM_WRITE)) goto bad_area; } 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. */ switch (handle_mm_fault(mm, vma, address, writeaccess)) { case 1: tsk->min_flt++; break; case 2: tsk->maj_flt++; break; case 0: goto do_sigbus; default: goto out_of_memory; } up(&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(&mm->mmap_sem); bad_area_nosemaphore: DPG(show_registers(regs)); /* User mode accesses just cause a SIGSEGV */ if (user_mode(regs)) { 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); 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) */ if ((fixup = search_exception_table(regs->irp)) != 0) { regs->irp = fixup; regs->frametype = CRIS_FRAME_FIXUP; D(printk("doing fixup to 0x%x\n", fixup)); return; } /* * Oops. The kernel tried to access some bad page. We'll have to * terminate things with extreme prejudice. */ 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"); printk(" at virtual address %08lx\n",address); die_if_kernel("Oops", regs, error_code); 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(&mm->mmap_sem); printk("VM: killing process %s\n", tsk->comm); if(user_mode(regs)) do_exit(SIGKILL); goto no_context; do_sigbus: up(&mm->mmap_sem); /* * Send a sigbus, regardless of whether we were in kernel * or user mode. */ info.si_code = 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. */ int offset = pgd_index(address); pgd_t *pgd, *pgd_k; pmd_t *pmd, *pmd_k; pgd = tsk->active_mm->pgd + offset; pgd_k = init_mm.pgd + offset; if (!pgd_present(*pgd)) { if (!pgd_present(*pgd_k)) goto bad_area_nosemaphore; set_pgd(pgd, *pgd_k); return; } pmd = pmd_offset(pgd, address); pmd_k = pmd_offset(pgd_k, address); if (pmd_present(*pmd) || !pmd_present(*pmd_k)) goto bad_area_nosemaphore; set_pmd(pmd, *pmd_k); return; } }