diff options
Diffstat (limited to 'arch/powerpc/mm/fault.c')
-rw-r--r-- | arch/powerpc/mm/fault.c | 410 |
1 files changed, 410 insertions, 0 deletions
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c new file mode 100644 index 00000000000..93d4fbfdb72 --- /dev/null +++ b/arch/powerpc/mm/fault.c @@ -0,0 +1,410 @@ +/* + * arch/ppc/mm/fault.c + * + * 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 <linux/config.h> +#include <linux/signal.h> +#include <linux/sched.h> +#include <linux/kernel.h> +#include <linux/errno.h> +#include <linux/string.h> +#include <linux/types.h> +#include <linux/ptrace.h> +#include <linux/mman.h> +#include <linux/mm.h> +#include <linux/interrupt.h> +#include <linux/highmem.h> +#include <linux/module.h> +#include <linux/kprobes.h> + +#include <asm/page.h> +#include <asm/pgtable.h> +#include <asm/mmu.h> +#include <asm/mmu_context.h> +#include <asm/system.h> +#include <asm/uaccess.h> +#include <asm/tlbflush.h> +#include <asm/kdebug.h> +#include <asm/siginfo.h> + +/* + * 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; +} + +#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) +static void do_dabr(struct pt_regs *regs, unsigned long error_code) +{ + siginfo_t info; + + if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code, + 11, SIGSEGV) == NOTIFY_STOP) + return; + + if (debugger_dabr_match(regs)) + return; + + /* Clear the DABR */ + set_dabr(0); + + /* Deliver the signal to userspace */ + info.si_signo = SIGTRAP; + info.si_errno = 0; + info.si_code = TRAP_HWBKPT; + info.si_addr = (void __user *)regs->nip; + force_sig_info(SIGTRAP, &info, current); +} +#endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ + +/* + * 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) +{ + struct vm_area_struct * vma; + struct mm_struct *mm = current->mm; + siginfo_t info; + int code = SEGV_MAPERR; + int is_write = 0; + int trap = TRAP(regs); + int is_exec = trap == 0x400; + +#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 (notify_die(DIE_PAGE_FAULT, "page_fault", regs, error_code, + 11, SIGSEGV) == NOTIFY_STOP) + return 0; + + if (trap == 0x300) { + if (debugger_fault_handler(regs)) + return 0; + } + + /* On a kernel SLB miss we can only check for a valid exception entry */ + if (!user_mode(regs) && (address >= TASK_SIZE)) + return SIGSEGV; + +#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) + if (error_code & DSISR_DABRMATCH) { + /* DABR match */ + do_dabr(regs, error_code); + return 0; + } +#endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ + + if (in_atomic() || mm == NULL) { + if (!user_mode(regs)) + return SIGSEGV; + /* 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); + } + + /* 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. Unfortunatly, in the case of an + * erroneous fault occuring 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 possibilty 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; + + 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; + + /* + * 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] + && (!user_mode(regs) || !store_updates_sp(regs))) + 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) + /* 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_PPC64 + /* protection fault */ + if (error_code & DSISR_PROTFAULT) + goto bad_area; + if (!(vma->vm_flags & VM_EXEC)) + goto bad_area; +#endif +#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE) + pte_t *ptep; + + /* Since 4xx/Book-E supports per-page execute permission, + * we lazily flush dcache to icache. */ + ptep = NULL; + if (get_pteptr(mm, address, &ptep) && pte_present(*ptep)) { + struct page *page = pte_page(*ptep); + + if (! test_bit(PG_arch_1, &page->flags)) { + flush_dcache_icache_page(page); + set_bit(PG_arch_1, &page->flags); + } + pte_update(ptep, 0, _PAGE_HWEXEC); + _tlbie(address); + pte_unmap(ptep); + up_read(&mm->mmap_sem); + return 0; + } + if (ptep != NULL) + pte_unmap(ptep); +#endif + /* 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))) + 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 0; + +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); + return 0; + } + + if (is_exec && (error_code & DSISR_PROTFAULT) + && printk_ratelimit()) + printk(KERN_CRIT "kernel tried to execute NX-protected" + " page (%lx) - exploit attempt? (uid: %d)\n", + address, current->uid); + + return SIGSEGV; + +/* + * 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); + return SIGKILL; + +do_sigbus: + up_read(&mm->mmap_sem); + if (user_mode(regs)) { + 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 0; + } + return SIGBUS; +} + +/* + * 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; + + /* 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 */ + + printk(KERN_ALERT "Unable to handle kernel paging request for "); + switch (regs->trap) { + case 0x300: + case 0x380: + printk("data at address 0x%08lx\n", regs->dar); + break; + case 0x400: + case 0x480: + printk("instruction fetch\n"); + break; + default: + printk("unknown fault\n"); + } + printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", + regs->nip); + + die("Kernel access of bad area", regs, sig); +} |