/* * 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 static inline bool notify_page_fault(struct pt_regs *regs) { bool ret = false; #ifdef CONFIG_KPROBES /* kprobe_running() needs smp_processor_id() */ if (!user_mode(regs)) { preempt_disable(); if (kprobe_running() && kprobe_fault_handler(regs, 11)) ret = true; preempt_enable(); } #endif /* CONFIG_KPROBES */ if (unlikely(debugger_fault_handler(regs))) ret = true; return ret; } /* * Check whether the instruction inst is a store using * an update addressing form which will update r1. */ static bool store_updates_sp(unsigned int inst) { /* check for 1 in the rA field */ if (((inst >> 16) & 0x1f) != 1) return false; /* check major opcode */ switch (inst >> 26) { case OP_STWU: case OP_STBU: case OP_STHU: case OP_STFSU: case OP_STFDU: return true; case OP_STD: /* std or stdu */ return (inst & 3) == 1; case OP_31: /* check minor opcode */ switch ((inst >> 1) & 0x3ff) { case OP_31_XOP_STDUX: case OP_31_XOP_STWUX: case OP_31_XOP_STBUX: case OP_31_XOP_STHUX: case OP_31_XOP_STFSUX: case OP_31_XOP_STFDUX: return true; } } return false; } /* * do_page_fault error handling helpers */ static int __bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code) { /* * If we are in kernel mode, bail out with a SEGV, this will * be caught by the assembly which will restore the non-volatile * registers before calling bad_page_fault() */ if (!user_mode(regs)) return SIGSEGV; _exception(SIGSEGV, regs, si_code, address); return 0; } static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address) { return __bad_area_nosemaphore(regs, address, SEGV_MAPERR); } static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code) { struct mm_struct *mm = current->mm; /* * Something tried to access memory that isn't in our memory map.. * Fix it, but check if it's kernel or user first.. */ up_read(&mm->mmap_sem); return __bad_area_nosemaphore(regs, address, si_code); } static noinline int bad_area(struct pt_regs *regs, unsigned long address) { return __bad_area(regs, address, SEGV_MAPERR); } static int bad_key_fault_exception(struct pt_regs *regs, unsigned long address, int pkey) { /* * If we are in kernel mode, bail out with a SEGV, this will * be caught by the assembly which will restore the non-volatile * registers before calling bad_page_fault() */ if (!user_mode(regs)) return SIGSEGV; _exception_pkey(regs, address, pkey); return 0; } static noinline int bad_access(struct pt_regs *regs, unsigned long address) { return __bad_area(regs, address, SEGV_ACCERR); } static int do_sigbus(struct pt_regs *regs, unsigned long address, vm_fault_t fault) { if (!user_mode(regs)) return SIGBUS; current->thread.trap_nr = BUS_ADRERR; #ifdef CONFIG_MEMORY_FAILURE if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { unsigned int lsb = 0; /* shutup gcc */ pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", current->comm, current->pid, address); if (fault & VM_FAULT_HWPOISON_LARGE) lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); if (fault & VM_FAULT_HWPOISON) lsb = PAGE_SHIFT; force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb, current); return 0; } #endif force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address, current); return 0; } static int mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault) { /* * Kernel page fault interrupted by SIGKILL. We have no reason to * continue processing. */ if (fatal_signal_pending(current) && !user_mode(regs)) return SIGKILL; /* Out of memory */ if (fault & VM_FAULT_OOM) { /* * 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 SIGSEGV; pagefault_out_of_memory(); } else { if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| VM_FAULT_HWPOISON_LARGE)) return do_sigbus(regs, addr, fault); else if (fault & VM_FAULT_SIGSEGV) return bad_area_nosemaphore(regs, addr); else BUG(); } return 0; } /* Is this a bad kernel fault ? */ static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address, bool is_write) { int is_exec = TRAP(regs) == 0x400; /* NX faults set DSISR_PROTFAULT on the 8xx, DSISR_NOEXEC_OR_G on others */ if (is_exec && (error_code & (DSISR_NOEXEC_OR_G | DSISR_KEYFAULT | DSISR_PROTFAULT))) { pr_crit_ratelimited("kernel tried to execute %s page (%lx) - exploit attempt? (uid: %d)\n", address >= TASK_SIZE ? "exec-protected" : "user", address, from_kuid(&init_user_ns, current_uid())); // Kernel exec fault is always bad return true; } if (!is_exec && address < TASK_SIZE && (error_code & DSISR_PROTFAULT) && !search_exception_tables(regs->nip)) { pr_crit_ratelimited("Kernel attempted to access user page (%lx) - exploit attempt? (uid: %d)\n", address, from_kuid(&init_user_ns, current_uid())); } // Kernel fault on kernel address is bad if (address >= TASK_SIZE) return true; // Fault on user outside of certain regions (eg. copy_tofrom_user()) is bad if (!search_exception_tables(regs->nip)) return true; // Read/write fault in a valid region (the exception table search passed // above), but blocked by KUAP is bad, it can never succeed. if (bad_kuap_fault(regs, is_write)) return true; // What's left? Kernel fault on user in well defined regions (extable // matched), and allowed by KUAP in the faulting context. return false; } static bool bad_stack_expansion(struct pt_regs *regs, unsigned long address, struct vm_area_struct *vma, unsigned int flags, bool *must_retry) { /* * 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) { unsigned int __user *nip = (unsigned int __user *)regs->nip; /* get user regs even if this fault is in kernel mode */ struct pt_regs *uregs = current->thread.regs; if (uregs == NULL) return true; /* * 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]) return false; if ((flags & FAULT_FLAG_WRITE) && (flags & FAULT_FLAG_USER) && access_ok(nip, sizeof(*nip))) { unsigned int inst; int res; pagefault_disable(); res = __get_user_inatomic(inst, nip); pagefault_enable(); if (!res) return !store_updates_sp(inst); *must_retry = true; } return true; } return false; } static bool access_error(bool is_write, bool is_exec, struct vm_area_struct *vma) { /* * 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 (is_exec) { return !(vma->vm_flags & VM_EXEC) && (cpu_has_feature(CPU_FTR_NOEXECUTE) || !(vma->vm_flags & (VM_READ | VM_WRITE))); } if (is_write) { if (unlikely(!(vma->vm_flags & VM_WRITE))) return true; return false; } if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) return true; /* * We should ideally do the vma pkey access check here. But in the * fault path, handle_mm_fault() also does the same check. To avoid * these multiple checks, we skip it here and handle access error due * to pkeys later. */ return false; } #ifdef CONFIG_PPC_SMLPAR static inline void cmo_account_page_fault(void) { 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(); } } #else static inline void cmo_account_page_fault(void) { } #endif /* CONFIG_PPC_SMLPAR */ #ifdef CONFIG_PPC_BOOK3S static void sanity_check_fault(bool is_write, bool is_user, unsigned long error_code, unsigned long address) { /* * Userspace trying to access kernel address, we get PROTFAULT for that. */ if (is_user && address >= TASK_SIZE) { pr_crit_ratelimited("%s[%d]: User access of kernel address (%lx) - exploit attempt? (uid: %d)\n", current->comm, current->pid, address, from_kuid(&init_user_ns, current_uid())); return; } /* * For hash translation mode, we should never get a * PROTFAULT. Any update to pte to reduce access will result in us * removing the hash page table entry, thus resulting in a DSISR_NOHPTE * fault instead of DSISR_PROTFAULT. * * A pte update to relax the access will not result in a hash page table * entry invalidate and hence can result in DSISR_PROTFAULT. * ptep_set_access_flags() doesn't do a hpte flush. This is why we have * the special !is_write in the below conditional. * * For platforms that doesn't supports coherent icache and do support * per page noexec bit, we do setup things such that we do the * sync between D/I cache via fault. But that is handled via low level * hash fault code (hash_page_do_lazy_icache()) and we should not reach * here in such case. * * For wrong access that can result in PROTFAULT, the above vma->vm_flags * check should handle those and hence we should fall to the bad_area * handling correctly. * * For embedded with per page exec support that doesn't support coherent * icache we do get PROTFAULT and we handle that D/I cache sync in * set_pte_at while taking the noexec/prot fault. Hence this is WARN_ON * is conditional for server MMU. * * For radix, we can get prot fault for autonuma case, because radix * page table will have them marked noaccess for user. */ if (radix_enabled() || is_write) return; WARN_ON_ONCE(error_code & DSISR_PROTFAULT); } #else static void sanity_check_fault(bool is_write, bool is_user, unsigned long error_code, unsigned long address) { } #endif /* CONFIG_PPC_BOOK3S */ /* * Define the correct "is_write" bit in error_code based * on the processor family */ #if (defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) #define page_fault_is_write(__err) ((__err) & ESR_DST) #define page_fault_is_bad(__err) (0) #else #define page_fault_is_write(__err) ((__err) & DSISR_ISSTORE) #if defined(CONFIG_PPC_8xx) #define page_fault_is_bad(__err) ((__err) & DSISR_NOEXEC_OR_G) #elif defined(CONFIG_PPC64) #define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_64S) #else #define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_32S) #endif #endif /* * 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. */ static int __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; unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; int is_exec = TRAP(regs) == 0x400; int is_user = user_mode(regs); int is_write = page_fault_is_write(error_code); vm_fault_t fault, major = 0; bool must_retry = false; if (notify_page_fault(regs)) return 0; if (unlikely(page_fault_is_bad(error_code))) { if (is_user) { _exception(SIGBUS, regs, BUS_OBJERR, address); return 0; } return SIGBUS; } /* Additional sanity check(s) */ sanity_check_fault(is_write, is_user, error_code, address); /* * The kernel should never take an execute fault nor should it * take a page fault to a kernel address or a page fault to a user * address outside of dedicated places */ if (unlikely(!is_user && bad_kernel_fault(regs, error_code, address, is_write))) return SIGSEGV; /* * If we're in an interrupt, have no user context or are running * in a region with pagefaults disabled then we must not take the fault */ if (unlikely(faulthandler_disabled() || !mm)) { if (is_user) printk_ratelimited(KERN_ERR "Page fault in user mode" " with faulthandler_disabled()=%d" " mm=%p\n", faulthandler_disabled(), mm); return bad_area_nosemaphore(regs, address); } /* We restore the interrupt state now */ if (!arch_irq_disabled_regs(regs)) local_irq_enable(); perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); if (error_code & DSISR_KEYFAULT) return bad_key_fault_exception(regs, address, get_mm_addr_key(mm, 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 (is_user) flags |= FAULT_FLAG_USER; if (is_write) flags |= FAULT_FLAG_WRITE; if (is_exec) flags |= FAULT_FLAG_INSTRUCTION; /* 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 (unlikely(!down_read_trylock(&mm->mmap_sem))) { if (!is_user && !search_exception_tables(regs->nip)) return bad_area_nosemaphore(regs, address); 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 (unlikely(!vma)) return bad_area(regs, address); if (likely(vma->vm_start <= address)) goto good_area; if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) return bad_area(regs, address); /* The stack is being expanded, check if it's valid */ if (unlikely(bad_stack_expansion(regs, address, vma, flags, &must_retry))) { if (!must_retry) return bad_area(regs, address); up_read(&mm->mmap_sem); if (fault_in_pages_readable((const char __user *)regs->nip, sizeof(unsigned int))) return bad_area_nosemaphore(regs, address); goto retry; } /* Try to expand it */ if (unlikely(expand_stack(vma, address))) return bad_area(regs, address); good_area: if (unlikely(access_error(is_write, is_exec, vma))) return bad_access(regs, address); /* * 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(vma, address, flags); #ifdef CONFIG_PPC_MEM_KEYS /* * we skipped checking for access error due to key earlier. * Check that using handle_mm_fault error return. */ if (unlikely(fault & VM_FAULT_SIGSEGV) && !arch_vma_access_permitted(vma, is_write, is_exec, 0)) { int pkey = vma_pkey(vma); up_read(&mm->mmap_sem); return bad_key_fault_exception(regs, address, pkey); } #endif /* CONFIG_PPC_MEM_KEYS */ major |= fault & VM_FAULT_MAJOR; /* * Handle the retry right now, the mmap_sem has been released in that * case. */ if (unlikely(fault & VM_FAULT_RETRY)) { /* We retry only once */ if (flags & FAULT_FLAG_ALLOW_RETRY) { /* * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk * of starvation. */ flags &= ~FAULT_FLAG_ALLOW_RETRY; flags |= FAULT_FLAG_TRIED; if (!fatal_signal_pending(current)) goto retry; } /* * User mode? Just return to handle the fatal exception otherwise * return to bad_page_fault */ return is_user ? 0 : SIGBUS; } up_read(¤t->mm->mmap_sem); if (unlikely(fault & VM_FAULT_ERROR)) return mm_fault_error(regs, address, fault); /* * Major/minor page fault accounting. */ if (major) { current->maj_flt++; perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); cmo_account_page_fault(); } else { current->min_flt++; perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); } return 0; } NOKPROBE_SYMBOL(__do_page_fault); int do_page_fault(struct pt_regs *regs, unsigned long address, unsigned long error_code) { enum ctx_state prev_state = exception_enter(); int rc = __do_page_fault(regs, address, error_code); exception_exit(prev_state); return rc; } NOKPROBE_SYMBOL(do_page_fault); /* * 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 = extable_fixup(entry); return; } /* kernel has accessed a bad area */ switch (TRAP(regs)) { case 0x300: case 0x380: case 0xe00: pr_alert("BUG: %s at 0x%08lx\n", regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" : "Unable to handle kernel data access", regs->dar); break; case 0x400: case 0x480: pr_alert("BUG: Unable to handle kernel instruction fetch%s", regs->nip < PAGE_SIZE ? " (NULL pointer?)\n" : "\n"); break; case 0x600: pr_alert("BUG: Unable to handle kernel unaligned access at 0x%08lx\n", regs->dar); break; default: pr_alert("BUG: Unable to handle unknown paging fault at 0x%08lx\n", regs->dar); break; } printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", regs->nip); if (task_stack_end_corrupted(current)) printk(KERN_ALERT "Thread overran stack, or stack corrupted\n"); die("Kernel access of bad area", regs, sig); }