/* * linux/arch/cris/mm/fault.c * * Copyright (C) 2000, 2001 Axis Communications AB * * Authors: Bjorn Wesen * * $Log: fault.c,v $ * Revision 1.20 2005/03/04 08:16:18 starvik * Merge of Linux 2.6.11. * * Revision 1.19 2005/01/14 10:07:59 starvik * Fixed warning. * * Revision 1.18 2005/01/12 08:10:14 starvik * Readded the change of frametype when handling kernel page fault fixup * for v10. This is necessary to avoid that the CPU remakes the faulting * access. * * Revision 1.17 2005/01/11 13:53:05 starvik * Use raw_printk. * * Revision 1.16 2004/12/17 11:39:41 starvik * SMP support. * * Revision 1.15 2004/11/23 18:36:18 starvik * Stack is now non-executable. * Signal handler trampolines are placed in a reserved page mapped into all * processes. * * Revision 1.14 2004/11/23 07:10:21 starvik * Moved find_fixup_code to generic code. * * Revision 1.13 2004/11/23 07:00:54 starvik * Actually use the execute permission bit in the MMU. This makes it possible * to prevent e.g. attacks where executable code is put on the stack. * * Revision 1.12 2004/09/29 06:16:04 starvik * Use instruction_pointer * * Revision 1.11 2004/05/14 07:58:05 starvik * Merge of changes from 2.4 * * Revision 1.10 2003/10/27 14:51:24 starvik * Removed debugcode * * Revision 1.9 2003/10/27 14:50:42 starvik * Changed do_page_fault signature * * Revision 1.8 2003/07/04 13:02:48 tobiasa * Moved code snippet from arch/cris/mm/fault.c that searches for fixup code * to seperate function in arch-specific files. * * Revision 1.7 2003/01/22 06:48:38 starvik * Fixed warnings issued by GCC 3.2.1 * * Revision 1.6 2003/01/09 14:42:52 starvik * Merge of Linux 2.5.55 * * Revision 1.5 2002/12/11 14:44:48 starvik * Extracted v10 (ETRAX 100LX) specific stuff to arch/cris/arch-v10/mm * * Revision 1.4 2002/11/13 15:10:28 starvik * pte_offset has been renamed to pte_offset_kernel * * Revision 1.3 2002/11/05 06:45:13 starvik * Merge of Linux 2.5.45 * * Revision 1.2 2001/12/18 13:35:22 bjornw * Applied the 2.4.13->2.4.16 CRIS patch to 2.5.1 (is a copy of 2.4.15). * * Revision 1.20 2001/11/22 13:34:06 bjornw * * Bug workaround (LX TR89): force a rerun of the whole of an interrupted * unaligned write, because the second half of the write will be corrupted * otherwise. Affected unaligned writes spanning not-yet mapped pages. * * Optimization: use the wr_rd bit in R_MMU_CAUSE to know whether a miss * was due to a read or a write (before we didn't know this until the next * restart of the interrupted instruction, thus wasting one fault-irq) * * Revision 1.19 2001/11/12 19:02:10 pkj * Fixed compiler warnings. * * Revision 1.18 2001/07/18 22:14:32 bjornw * Enable interrupts in the bulk of do_page_fault * * Revision 1.17 2001/07/18 13:07:23 bjornw * * Detect non-existant PTE's in vmalloc pmd synchronization * * Remove comment about fast-paths for VMALLOC_START etc, because all that * was totally bogus anyway it turned out :) * * Fix detection of vmalloc-area synchronization * * Add some comments * * Revision 1.16 2001/06/13 00:06:08 bjornw * current_pgd should be volatile * * Revision 1.15 2001/06/13 00:02:23 bjornw * Use a separate variable to store the current pgd to avoid races in schedule * * Revision 1.14 2001/05/16 17:41:07 hp * Last comment tweak further tweaked. * * Revision 1.13 2001/05/15 00:58:44 hp * Expand a bit on the comment why we compare address >= TASK_SIZE rather * than >= VMALLOC_START. * * Revision 1.12 2001/04/04 10:51:14 bjornw * mmap_sem is grabbed for reading * * Revision 1.11 2001/03/23 07:36:07 starvik * Corrected according to review remarks * * Revision 1.10 2001/03/21 16:10:11 bjornw * CRIS_FRAME_FIXUP not needed anymore, use FRAME_NORMAL * * Revision 1.9 2001/03/05 13:22:20 bjornw * Spell-fix and fix in vmalloc_fault handling * * 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 <linux/mm.h> #include <linux/interrupt.h> #include <linux/module.h> #include <asm/uaccess.h> extern int find_fixup_code(struct pt_regs *); extern void die_if_kernel(const char *, struct pt_regs *, long); extern int raw_printk(const char *fmt, ...); /* 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 */ volatile 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; D(printk("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 or have no user * context, we must not take the fault.. */ if (in_interrupt() || !mm) goto no_context; 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; } 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 & 1)) { case VM_FAULT_MINOR: tsk->min_flt++; break; case VM_FAULT_MAJOR: tsk->maj_flt++; break; case VM_FAULT_SIGBUS: goto do_sigbus; default: goto out_of_memory; } 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)) { 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 (find_fixup_code(regs)) 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) raw_printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference"); else raw_printk(KERN_ALERT "Unable to handle kernel access"); raw_printk(" at virtual address %08lx\n",address); die_if_kernel("Oops", regs, (writeaccess << 1) | protection); 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); printk("VM: killing process %s\n", tsk->comm); if (user_mode(regs)) do_exit(SIGKILL); goto no_context; 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; if ((fixup = search_exception_tables(instruction_pointer(regs))) != 0) { /* Adjust the instruction pointer in the stackframe. */ instruction_pointer(regs) = fixup->fixup; arch_fixup(regs); return 1; } return 0; }