/* * PowerPC version * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) * * Derived from "arch/i386/mm/fault.c" * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds * * Modified by Cort Dougan and Paul Mackerras. * * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "icswx.h" #ifdef CONFIG_KPROBES static inline int notify_page_fault(struct pt_regs *regs) { int ret = 0; /* kprobe_running() needs smp_processor_id() */ if (!user_mode(regs)) { preempt_disable(); if (kprobe_running() && kprobe_fault_handler(regs, 11)) ret = 1; preempt_enable(); } return ret; } #else static inline int notify_page_fault(struct pt_regs *regs) { return 0; } #endif /* * Check whether the instruction at regs->nip is a store using * an update addressing form which will update r1. */ static int store_updates_sp(struct pt_regs *regs) { unsigned int inst; if (get_user(inst, (unsigned int __user *)regs->nip)) return 0; /* check for 1 in the rA field */ if (((inst >> 16) & 0x1f) != 1) return 0; /* check major opcode */ switch (inst >> 26) { case 37: /* stwu */ case 39: /* stbu */ case 45: /* sthu */ case 53: /* stfsu */ case 55: /* stfdu */ return 1; case 62: /* std or stdu */ return (inst & 3) == 1; case 31: /* check minor opcode */ switch ((inst >> 1) & 0x3ff) { case 181: /* stdux */ case 183: /* stwux */ case 247: /* stbux */ case 439: /* sthux */ case 695: /* stfsux */ case 759: /* stfdux */ return 1; } } return 0; } /* * do_page_fault error handling helpers */ #define MM_FAULT_RETURN 0 #define MM_FAULT_CONTINUE -1 #define MM_FAULT_ERR(sig) (sig) static int do_sigbus(struct pt_regs *regs, unsigned long address) { siginfo_t info; up_read(¤t->mm->mmap_sem); if (user_mode(regs)) { current->thread.trap_nr = BUS_ADRERR; info.si_signo = SIGBUS; info.si_errno = 0; info.si_code = BUS_ADRERR; info.si_addr = (void __user *)address; force_sig_info(SIGBUS, &info, current); return MM_FAULT_RETURN; } return MM_FAULT_ERR(SIGBUS); } static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault) { /* * Pagefault was interrupted by SIGKILL. We have no reason to * continue the pagefault. */ if (fatal_signal_pending(current)) { /* * If we have retry set, the mmap semaphore will have * alrady been released in __lock_page_or_retry(). Else * we release it now. */ if (!(fault & VM_FAULT_RETRY)) up_read(¤t->mm->mmap_sem); /* Coming from kernel, we need to deal with uaccess fixups */ if (user_mode(regs)) return MM_FAULT_RETURN; return MM_FAULT_ERR(SIGKILL); } /* No fault: be happy */ if (!(fault & VM_FAULT_ERROR)) return MM_FAULT_CONTINUE; /* Out of memory */ if (fault & VM_FAULT_OOM) { up_read(¤t->mm->mmap_sem); /* * We ran out of memory, or some other thing happened to us that * made us unable to handle the page fault gracefully. */ if (!user_mode(regs)) return MM_FAULT_ERR(SIGKILL); pagefault_out_of_memory(); return MM_FAULT_RETURN; } /* Bus error. x86 handles HWPOISON here, we'll add this if/when * we support the feature in HW */ if (fault & VM_FAULT_SIGBUS) return do_sigbus(regs, addr); /* We don't understand the fault code, this is fatal */ BUG(); return MM_FAULT_CONTINUE; } /* * For 600- and 800-family processors, the error_code parameter is DSISR * for a data fault, SRR1 for an instruction fault. For 400-family processors * the error_code parameter is ESR for a data fault, 0 for an instruction * fault. * For 64-bit processors, the error_code parameter is * - DSISR for a non-SLB data access fault, * - SRR1 & 0x08000000 for a non-SLB instruction access fault * - 0 any SLB fault. * * The return value is 0 if the fault was handled, or the signal * number if this is a kernel fault that can't be handled here. */ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address, unsigned long error_code) { enum ctx_state prev_state = exception_enter(); struct vm_area_struct * vma; struct mm_struct *mm = current->mm; unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; int code = SEGV_MAPERR; int is_write = 0; int trap = TRAP(regs); int is_exec = trap == 0x400; int fault; int rc = 0, store_update_sp = 0; #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) /* * Fortunately the bit assignments in SRR1 for an instruction * fault and DSISR for a data fault are mostly the same for the * bits we are interested in. But there are some bits which * indicate errors in DSISR but can validly be set in SRR1. */ if (trap == 0x400) error_code &= 0x48200000; else is_write = error_code & DSISR_ISSTORE; #else is_write = error_code & ESR_DST; #endif /* CONFIG_4xx || CONFIG_BOOKE */ if (is_write) flags |= FAULT_FLAG_WRITE; #ifdef CONFIG_PPC_ICSWX /* * we need to do this early because this "data storage * interrupt" does not update the DAR/DEAR so we don't want to * look at it */ if (error_code & ICSWX_DSI_UCT) { rc = acop_handle_fault(regs, address, error_code); if (rc) goto bail; } #endif /* CONFIG_PPC_ICSWX */ if (notify_page_fault(regs)) goto bail; if (unlikely(debugger_fault_handler(regs))) goto bail; /* On a kernel SLB miss we can only check for a valid exception entry */ if (!user_mode(regs) && (address >= TASK_SIZE)) { rc = SIGSEGV; goto bail; } #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || \ defined(CONFIG_PPC_BOOK3S_64)) if (error_code & DSISR_DABRMATCH) { /* breakpoint match */ do_break(regs, address, error_code); goto bail; } #endif /* We restore the interrupt state now */ if (!arch_irq_disabled_regs(regs)) local_irq_enable(); if (in_atomic() || mm == NULL) { if (!user_mode(regs)) { rc = SIGSEGV; goto bail; } /* in_atomic() in user mode is really bad, as is current->mm == NULL. */ printk(KERN_EMERG "Page fault in user mode with " "in_atomic() = %d mm = %p\n", in_atomic(), mm); printk(KERN_EMERG "NIP = %lx MSR = %lx\n", regs->nip, regs->msr); die("Weird page fault", regs, SIGSEGV); } perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); /* * We want to do this outside mmap_sem, because reading code around nip * can result in fault, which will cause a deadlock when called with * mmap_sem held */ if (user_mode(regs)) store_update_sp = store_updates_sp(regs); /* When running in the kernel we expect faults to occur only to * addresses in user space. All other faults represent errors in the * kernel and should generate an OOPS. Unfortunately, in the case of an * erroneous fault occurring in a code path which already holds mmap_sem * we will deadlock attempting to validate the fault against the * address space. Luckily the kernel only validly references user * space from well defined areas of code, which are listed in the * exceptions table. * * As the vast majority of faults will be valid we will only perform * the source reference check when there is a possibility of a deadlock. * Attempt to lock the address space, if we cannot we then validate the * source. If this is invalid we can skip the address space check, * thus avoiding the deadlock. */ if (!down_read_trylock(&mm->mmap_sem)) { if (!user_mode(regs) && !search_exception_tables(regs->nip)) goto bad_area_nosemaphore; retry: down_read(&mm->mmap_sem); } else { /* * The above down_read_trylock() might have succeeded in * which case we'll have missed the might_sleep() from * down_read(): */ might_sleep(); } 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; /* * N.B. The POWER/Open ABI allows programs to access up to * 288 bytes below the stack pointer. * The kernel signal delivery code writes up to about 1.5kB * below the stack pointer (r1) before decrementing it. * The exec code can write slightly over 640kB to the stack * before setting the user r1. Thus we allow the stack to * expand to 1MB without further checks. */ if (address + 0x100000 < vma->vm_end) { /* get user regs even if this fault is in kernel mode */ struct pt_regs *uregs = current->thread.regs; if (uregs == NULL) goto bad_area; /* * A user-mode access to an address a long way below * the stack pointer is only valid if the instruction * is one which would update the stack pointer to the * address accessed if the instruction completed, * i.e. either stwu rs,n(r1) or stwux rs,r1,rb * (or the byte, halfword, float or double forms). * * If we don't check this then any write to the area * between the last mapped region and the stack will * expand the stack rather than segfaulting. */ if (address + 2048 < uregs->gpr[1] && !store_update_sp) goto bad_area; } if (expand_stack(vma, address)) goto bad_area; good_area: code = SEGV_ACCERR; #if defined(CONFIG_6xx) if (error_code & 0x95700000) /* an error such as lwarx to I/O controller space, address matching DABR, eciwx, etc. */ goto bad_area; #endif /* CONFIG_6xx */ #if defined(CONFIG_8xx) /* 8xx sometimes need to load a invalid/non-present TLBs. * These must be invalidated separately as linux mm don't. */ if (error_code & 0x40000000) /* no translation? */ _tlbil_va(address, 0, 0, 0); /* The MPC8xx seems to always set 0x80000000, which is * "undefined". Of those that can be set, this is the only * one which seems bad. */ if (error_code & 0x10000000) /* Guarded storage error. */ goto bad_area; #endif /* CONFIG_8xx */ if (is_exec) { #ifdef CONFIG_PPC_STD_MMU /* Protection fault on exec go straight to failure on * Hash based MMUs as they either don't support per-page * execute permission, or if they do, it's handled already * at the hash level. This test would probably have to * be removed if we change the way this works to make hash * processors use the same I/D cache coherency mechanism * as embedded. */ if (error_code & DSISR_PROTFAULT) goto bad_area; #endif /* CONFIG_PPC_STD_MMU */ /* * Allow execution from readable areas if the MMU does not * provide separate controls over reading and executing. * * Note: That code used to not be enabled for 4xx/BookE. * It is now as I/D cache coherency for these is done at * set_pte_at() time and I see no reason why the test * below wouldn't be valid on those processors. This -may- * break programs compiled with a really old ABI though. */ if (!(vma->vm_flags & VM_EXEC) && (cpu_has_feature(CPU_FTR_NOEXECUTE) || !(vma->vm_flags & (VM_READ | VM_WRITE)))) goto bad_area; /* a write */ } else if (is_write) { if (!(vma->vm_flags & VM_WRITE)) goto bad_area; /* a read */ } else { /* protection fault */ if (error_code & 0x08000000) goto bad_area; if (!(vma->vm_flags & (VM_READ | VM_EXEC | 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(mm, vma, address, flags); if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) { rc = mm_fault_error(regs, address, fault); if (rc >= MM_FAULT_RETURN) goto bail; else rc = 0; } /* * Major/minor page fault accounting is only done on the * initial attempt. If we go through a retry, it is extremely * likely that the page will be found in page cache at that point. */ if (flags & FAULT_FLAG_ALLOW_RETRY) { if (fault & VM_FAULT_MAJOR) { current->maj_flt++; perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); #ifdef CONFIG_PPC_SMLPAR if (firmware_has_feature(FW_FEATURE_CMO)) { u32 page_ins; preempt_disable(); page_ins = be32_to_cpu(get_lppaca()->page_ins); page_ins += 1 << PAGE_FACTOR; get_lppaca()->page_ins = cpu_to_be32(page_ins); preempt_enable(); } #endif /* CONFIG_PPC_SMLPAR */ } else { current->min_flt++; perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); } if (fault & VM_FAULT_RETRY) { /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk * of starvation. */ flags &= ~FAULT_FLAG_ALLOW_RETRY; flags |= FAULT_FLAG_TRIED; goto retry; } } up_read(&mm->mmap_sem); goto bail; bad_area: up_read(&mm->mmap_sem); bad_area_nosemaphore: /* User mode accesses cause a SIGSEGV */ if (user_mode(regs)) { _exception(SIGSEGV, regs, code, address); goto bail; } if (is_exec && (error_code & DSISR_PROTFAULT)) printk_ratelimited(KERN_CRIT "kernel tried to execute NX-protected" " page (%lx) - exploit attempt? (uid: %d)\n", address, from_kuid(&init_user_ns, current_uid())); rc = SIGSEGV; bail: exception_exit(prev_state); return rc; } /* * bad_page_fault is called when we have a bad access from the kernel. * It is called from the DSI and ISI handlers in head.S and from some * of the procedures in traps.c. */ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) { const struct exception_table_entry *entry; unsigned long *stackend; /* Are we prepared to handle this fault? */ if ((entry = search_exception_tables(regs->nip)) != NULL) { regs->nip = entry->fixup; return; } /* kernel has accessed a bad area */ switch (regs->trap) { case 0x300: case 0x380: printk(KERN_ALERT "Unable to handle kernel paging request for " "data at address 0x%08lx\n", regs->dar); break; case 0x400: case 0x480: printk(KERN_ALERT "Unable to handle kernel paging request for " "instruction fetch\n"); break; default: printk(KERN_ALERT "Unable to handle kernel paging request for " "unknown fault\n"); break; } printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", regs->nip); stackend = end_of_stack(current); if (current != &init_task && *stackend != STACK_END_MAGIC) printk(KERN_ALERT "Thread overran stack, or stack corrupted\n"); die("Kernel access of bad area", regs, sig); }