/* * arch/s390/mm/fault.c * * S390 version * Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation * Author(s): Hartmut Penner (hp@de.ibm.com) * Ulrich Weigand (uweigand@de.ibm.com) * * Derived from "arch/i386/mm/fault.c" * Copyright (C) 1995 Linus Torvalds */ #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/smp.h> #include <linux/kdebug.h> #include <linux/smp_lock.h> #include <linux/init.h> #include <linux/console.h> #include <linux/module.h> #include <linux/hardirq.h> #include <linux/kprobes.h> #include <linux/uaccess.h> #include <linux/hugetlb.h> #include <asm/system.h> #include <asm/pgtable.h> #include <asm/s390_ext.h> #include <asm/mmu_context.h> #include "../kernel/entry.h" #ifndef CONFIG_64BIT #define __FAIL_ADDR_MASK 0x7ffff000 #define __FIXUP_MASK 0x7fffffff #define __SUBCODE_MASK 0x0200 #define __PF_RES_FIELD 0ULL #else /* CONFIG_64BIT */ #define __FAIL_ADDR_MASK -4096L #define __FIXUP_MASK ~0L #define __SUBCODE_MASK 0x0600 #define __PF_RES_FIELD 0x8000000000000000ULL #endif /* CONFIG_64BIT */ #ifdef CONFIG_SYSCTL extern int sysctl_userprocess_debug; #endif #ifdef CONFIG_KPROBES static inline int notify_page_fault(struct pt_regs *regs, long err) { int ret = 0; /* kprobe_running() needs smp_processor_id() */ if (!user_mode(regs)) { preempt_disable(); if (kprobe_running() && kprobe_fault_handler(regs, 14)) ret = 1; preempt_enable(); } return ret; } #else static inline int notify_page_fault(struct pt_regs *regs, long err) { return 0; } #endif /* * Unlock any spinlocks which will prevent us from getting the * message out. */ void bust_spinlocks(int yes) { if (yes) { oops_in_progress = 1; } else { int loglevel_save = console_loglevel; console_unblank(); oops_in_progress = 0; /* * OK, the message is on the console. Now we call printk() * without oops_in_progress set so that printk will give klogd * a poke. Hold onto your hats... */ console_loglevel = 15; printk(" "); console_loglevel = loglevel_save; } } /* * Returns the address space associated with the fault. * Returns 0 for kernel space, 1 for user space and * 2 for code execution in user space with noexec=on. */ static inline int check_space(struct task_struct *tsk) { /* * The lowest two bits of S390_lowcore.trans_exc_code * indicate which paging table was used. */ int desc = S390_lowcore.trans_exc_code & 3; if (desc == 3) /* Home Segment Table Descriptor */ return switch_amode == 0; if (desc == 2) /* Secondary Segment Table Descriptor */ return tsk->thread.mm_segment.ar4; #ifdef CONFIG_S390_SWITCH_AMODE if (unlikely(desc == 1)) { /* STD determined via access register */ /* %a0 always indicates primary space. */ if (S390_lowcore.exc_access_id != 0) { save_access_regs(tsk->thread.acrs); /* * An alet of 0 indicates primary space. * An alet of 1 indicates secondary space. * Any other alet values generate an * alen-translation exception. */ if (tsk->thread.acrs[S390_lowcore.exc_access_id]) return tsk->thread.mm_segment.ar4; } } #endif /* Primary Segment Table Descriptor */ return switch_amode << s390_noexec; } /* * Send SIGSEGV to task. This is an external routine * to keep the stack usage of do_page_fault small. */ static void do_sigsegv(struct pt_regs *regs, unsigned long error_code, int si_code, unsigned long address) { struct siginfo si; #if defined(CONFIG_SYSCTL) || defined(CONFIG_PROCESS_DEBUG) #if defined(CONFIG_SYSCTL) if (sysctl_userprocess_debug) #endif { printk("User process fault: interruption code 0x%lX\n", error_code); printk("failing address: %lX\n", address); show_regs(regs); } #endif si.si_signo = SIGSEGV; si.si_code = si_code; si.si_addr = (void __user *) address; force_sig_info(SIGSEGV, &si, current); } static void do_no_context(struct pt_regs *regs, unsigned long error_code, unsigned long address) { const struct exception_table_entry *fixup; /* Are we prepared to handle this kernel fault? */ fixup = search_exception_tables(regs->psw.addr & __FIXUP_MASK); if (fixup) { regs->psw.addr = fixup->fixup | PSW_ADDR_AMODE; return; } /* * Oops. The kernel tried to access some bad page. We'll have to * terminate things with extreme prejudice. */ if (check_space(current) == 0) printk(KERN_ALERT "Unable to handle kernel pointer dereference" " at virtual kernel address %p\n", (void *)address); else printk(KERN_ALERT "Unable to handle kernel paging request" " at virtual user address %p\n", (void *)address); die("Oops", regs, error_code); do_exit(SIGKILL); } static void do_low_address(struct pt_regs *regs, unsigned long error_code) { /* Low-address protection hit in kernel mode means NULL pointer write access in kernel mode. */ if (regs->psw.mask & PSW_MASK_PSTATE) { /* Low-address protection hit in user mode 'cannot happen'. */ die ("Low-address protection", regs, error_code); do_exit(SIGKILL); } do_no_context(regs, error_code, 0); } /* * We ran out of memory, or some other thing happened to us that made * us unable to handle the page fault gracefully. */ static int do_out_of_memory(struct pt_regs *regs, unsigned long error_code, unsigned long address) { struct task_struct *tsk = current; struct mm_struct *mm = tsk->mm; up_read(&mm->mmap_sem); if (is_global_init(tsk)) { yield(); down_read(&mm->mmap_sem); return 1; } printk("VM: killing process %s\n", tsk->comm); if (regs->psw.mask & PSW_MASK_PSTATE) do_group_exit(SIGKILL); do_no_context(regs, error_code, address); return 0; } static void do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address) { struct task_struct *tsk = current; struct mm_struct *mm = tsk->mm; up_read(&mm->mmap_sem); /* * Send a sigbus, regardless of whether we were in kernel * or user mode. */ tsk->thread.prot_addr = address; tsk->thread.trap_no = error_code; force_sig(SIGBUS, tsk); /* Kernel mode? Handle exceptions or die */ if (!(regs->psw.mask & PSW_MASK_PSTATE)) do_no_context(regs, error_code, address); } #ifdef CONFIG_S390_EXEC_PROTECT static int signal_return(struct mm_struct *mm, struct pt_regs *regs, unsigned long address, unsigned long error_code) { u16 instruction; int rc; #ifdef CONFIG_COMPAT int compat; #endif pagefault_disable(); rc = __get_user(instruction, (u16 __user *) regs->psw.addr); pagefault_enable(); if (rc) return -EFAULT; up_read(&mm->mmap_sem); clear_tsk_thread_flag(current, TIF_SINGLE_STEP); #ifdef CONFIG_COMPAT compat = test_tsk_thread_flag(current, TIF_31BIT); if (compat && instruction == 0x0a77) sys32_sigreturn(); else if (compat && instruction == 0x0aad) sys32_rt_sigreturn(); else #endif if (instruction == 0x0a77) sys_sigreturn(); else if (instruction == 0x0aad) sys_rt_sigreturn(); else { current->thread.prot_addr = address; current->thread.trap_no = error_code; do_sigsegv(regs, error_code, SEGV_MAPERR, address); } return 0; } #endif /* CONFIG_S390_EXEC_PROTECT */ /* * This routine handles page faults. It determines the address, * and the problem, and then passes it off to one of the appropriate * routines. * * error_code: * 04 Protection -> Write-Protection (suprression) * 10 Segment translation -> Not present (nullification) * 11 Page translation -> Not present (nullification) * 3b Region third trans. -> Not present (nullification) */ static inline void do_exception(struct pt_regs *regs, unsigned long error_code, int write) { struct task_struct *tsk; struct mm_struct *mm; struct vm_area_struct *vma; unsigned long address; int space; int si_code; int fault; if (notify_page_fault(regs, error_code)) return; tsk = current; mm = tsk->mm; /* get the failing address and the affected space */ address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK; space = check_space(tsk); /* * Verify that the fault happened in user space, that * we are not in an interrupt and that there is a * user context. */ if (unlikely(space == 0 || in_atomic() || !mm)) goto no_context; /* * When we get here, the fault happened in the current * task's user address space, so we can switch on the * interrupts again and then search the VMAs */ local_irq_enable(); down_read(&mm->mmap_sem); si_code = SEGV_MAPERR; vma = find_vma(mm, address); if (!vma) goto bad_area; #ifdef CONFIG_S390_EXEC_PROTECT if (unlikely((space == 2) && !(vma->vm_flags & VM_EXEC))) if (!signal_return(mm, regs, address, error_code)) /* * signal_return() has done an up_read(&mm->mmap_sem) * if it returns 0. */ return; #endif 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: si_code = SEGV_ACCERR; if (!write) { /* page not present, check vm flags */ if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) goto bad_area; } else { if (!(vma->vm_flags & VM_WRITE)) goto bad_area; } survive: if (is_vm_hugetlb_page(vma)) address &= HPAGE_MASK; /* * 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, write); if (unlikely(fault & VM_FAULT_ERROR)) { if (fault & VM_FAULT_OOM) { if (do_out_of_memory(regs, error_code, address)) goto survive; return; } else if (fault & VM_FAULT_SIGBUS) { do_sigbus(regs, error_code, address); return; } BUG(); } if (fault & VM_FAULT_MAJOR) tsk->maj_flt++; else tsk->min_flt++; up_read(&mm->mmap_sem); /* * The instruction that caused the program check will * be repeated. Don't signal single step via SIGTRAP. */ clear_tsk_thread_flag(tsk, TIF_SINGLE_STEP); 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); /* User mode accesses just cause a SIGSEGV */ if (regs->psw.mask & PSW_MASK_PSTATE) { tsk->thread.prot_addr = address; tsk->thread.trap_no = error_code; do_sigsegv(regs, error_code, si_code, address); return; } no_context: do_no_context(regs, error_code, address); } void __kprobes do_protection_exception(struct pt_regs *regs, long error_code) { /* Protection exception is supressing, decrement psw address. */ regs->psw.addr -= (error_code >> 16); /* * Check for low-address protection. This needs to be treated * as a special case because the translation exception code * field is not guaranteed to contain valid data in this case. */ if (unlikely(!(S390_lowcore.trans_exc_code & 4))) { do_low_address(regs, error_code); return; } do_exception(regs, 4, 1); } void __kprobes do_dat_exception(struct pt_regs *regs, long error_code) { do_exception(regs, error_code & 0xff, 0); } #ifdef CONFIG_64BIT void __kprobes do_asce_exception(struct pt_regs *regs, unsigned long error_code) { struct mm_struct *mm; struct vm_area_struct *vma; unsigned long address; int space; mm = current->mm; address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK; space = check_space(current); if (unlikely(space == 0 || in_atomic() || !mm)) goto no_context; local_irq_enable(); down_read(&mm->mmap_sem); vma = find_vma(mm, address); up_read(&mm->mmap_sem); if (vma) { update_mm(mm, current); return; } /* User mode accesses just cause a SIGSEGV */ if (regs->psw.mask & PSW_MASK_PSTATE) { current->thread.prot_addr = address; current->thread.trap_no = error_code; do_sigsegv(regs, error_code, SEGV_MAPERR, address); return; } no_context: do_no_context(regs, error_code, address); } #endif #ifdef CONFIG_PFAULT /* * 'pfault' pseudo page faults routines. */ static ext_int_info_t ext_int_pfault; static int pfault_disable = 0; static int __init nopfault(char *str) { pfault_disable = 1; return 1; } __setup("nopfault", nopfault); typedef struct { __u16 refdiagc; __u16 reffcode; __u16 refdwlen; __u16 refversn; __u64 refgaddr; __u64 refselmk; __u64 refcmpmk; __u64 reserved; } __attribute__ ((packed, aligned(8))) pfault_refbk_t; int pfault_init(void) { pfault_refbk_t refbk = { 0x258, 0, 5, 2, __LC_CURRENT, 1ULL << 48, 1ULL << 48, __PF_RES_FIELD }; int rc; if (!MACHINE_IS_VM || pfault_disable) return -1; asm volatile( " diag %1,%0,0x258\n" "0: j 2f\n" "1: la %0,8\n" "2:\n" EX_TABLE(0b,1b) : "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc"); __ctl_set_bit(0, 9); return rc; } void pfault_fini(void) { pfault_refbk_t refbk = { 0x258, 1, 5, 2, 0ULL, 0ULL, 0ULL, 0ULL }; if (!MACHINE_IS_VM || pfault_disable) return; __ctl_clear_bit(0,9); asm volatile( " diag %0,0,0x258\n" "0:\n" EX_TABLE(0b,0b) : : "a" (&refbk), "m" (refbk) : "cc"); } static void pfault_interrupt(__u16 error_code) { struct task_struct *tsk; __u16 subcode; /* * Get the external interruption subcode & pfault * initial/completion signal bit. VM stores this * in the 'cpu address' field associated with the * external interrupt. */ subcode = S390_lowcore.cpu_addr; if ((subcode & 0xff00) != __SUBCODE_MASK) return; /* * Get the token (= address of the task structure of the affected task). */ tsk = *(struct task_struct **) __LC_PFAULT_INTPARM; if (subcode & 0x0080) { /* signal bit is set -> a page has been swapped in by VM */ if (xchg(&tsk->thread.pfault_wait, -1) != 0) { /* Initial interrupt was faster than the completion * interrupt. pfault_wait is valid. Set pfault_wait * back to zero and wake up the process. This can * safely be done because the task is still sleeping * and can't produce new pfaults. */ tsk->thread.pfault_wait = 0; wake_up_process(tsk); put_task_struct(tsk); } } else { /* signal bit not set -> a real page is missing. */ get_task_struct(tsk); set_task_state(tsk, TASK_UNINTERRUPTIBLE); if (xchg(&tsk->thread.pfault_wait, 1) != 0) { /* Completion interrupt was faster than the initial * interrupt (swapped in a -1 for pfault_wait). Set * pfault_wait back to zero and exit. This can be * done safely because tsk is running in kernel * mode and can't produce new pfaults. */ tsk->thread.pfault_wait = 0; set_task_state(tsk, TASK_RUNNING); put_task_struct(tsk); } else set_tsk_need_resched(tsk); } } void __init pfault_irq_init(void) { if (!MACHINE_IS_VM) return; /* * Try to get pfault pseudo page faults going. */ if (register_early_external_interrupt(0x2603, pfault_interrupt, &ext_int_pfault) != 0) panic("Couldn't request external interrupt 0x2603"); if (pfault_init() == 0) return; /* Tough luck, no pfault. */ pfault_disable = 1; unregister_early_external_interrupt(0x2603, pfault_interrupt, &ext_int_pfault); } #endif