arm64: MMU fault handling and page table management
This patch adds support for the handling of the MMU faults (exception
entry code introduced by a previous patch) and page table management.
The user translation table is pointed to by TTBR0 and the kernel one
(swapper_pg_dir) by TTBR1. There is no translation information shared or
address space overlapping between user and kernel page tables.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
new file mode 100644
index 0000000..1909a69
--- /dev/null
+++ b/arch/arm64/mm/fault.c
@@ -0,0 +1,534 @@
+/*
+ * Based on arch/arm/mm/fault.c
+ *
+ * Copyright (C) 1995 Linus Torvalds
+ * Copyright (C) 1995-2004 Russell King
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/module.h>
+#include <linux/signal.h>
+#include <linux/mm.h>
+#include <linux/hardirq.h>
+#include <linux/init.h>
+#include <linux/kprobes.h>
+#include <linux/uaccess.h>
+#include <linux/page-flags.h>
+#include <linux/sched.h>
+#include <linux/highmem.h>
+#include <linux/perf_event.h>
+
+#include <asm/exception.h>
+#include <asm/debug-monitors.h>
+#include <asm/system_misc.h>
+#include <asm/pgtable.h>
+#include <asm/tlbflush.h>
+
+/*
+ * Dump out the page tables associated with 'addr' in mm 'mm'.
+ */
+void show_pte(struct mm_struct *mm, unsigned long addr)
+{
+ pgd_t *pgd;
+
+ if (!mm)
+ mm = &init_mm;
+
+ pr_alert("pgd = %p\n", mm->pgd);
+ pgd = pgd_offset(mm, addr);
+ pr_alert("[%08lx] *pgd=%016llx", addr, pgd_val(*pgd));
+
+ do {
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *pte;
+
+ if (pgd_none_or_clear_bad(pgd))
+ break;
+
+ pud = pud_offset(pgd, addr);
+ if (pud_none_or_clear_bad(pud))
+ break;
+
+ pmd = pmd_offset(pud, addr);
+ printk(", *pmd=%016llx", pmd_val(*pmd));
+ if (pmd_none_or_clear_bad(pmd))
+ break;
+
+ pte = pte_offset_map(pmd, addr);
+ printk(", *pte=%016llx", pte_val(*pte));
+ pte_unmap(pte);
+ } while(0);
+
+ printk("\n");
+}
+
+/*
+ * The kernel tried to access some page that wasn't present.
+ */
+static void __do_kernel_fault(struct mm_struct *mm, unsigned long addr,
+ unsigned int esr, struct pt_regs *regs)
+{
+ /*
+ * Are we prepared to handle this kernel fault?
+ */
+ if (fixup_exception(regs))
+ return;
+
+ /*
+ * No handler, we'll have to terminate things with extreme prejudice.
+ */
+ bust_spinlocks(1);
+ pr_alert("Unable to handle kernel %s at virtual address %08lx\n",
+ (addr < PAGE_SIZE) ? "NULL pointer dereference" :
+ "paging request", addr);
+
+ show_pte(mm, addr);
+ die("Oops", regs, esr);
+ bust_spinlocks(0);
+ do_exit(SIGKILL);
+}
+
+/*
+ * Something tried to access memory that isn't in our memory map. User mode
+ * accesses just cause a SIGSEGV
+ */
+static void __do_user_fault(struct task_struct *tsk, unsigned long addr,
+ unsigned int esr, unsigned int sig, int code,
+ struct pt_regs *regs)
+{
+ struct siginfo si;
+
+ if (show_unhandled_signals) {
+ pr_info("%s[%d]: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
+ tsk->comm, task_pid_nr(tsk), sig, addr, esr);
+ show_pte(tsk->mm, addr);
+ show_regs(regs);
+ }
+
+ tsk->thread.fault_address = addr;
+ si.si_signo = sig;
+ si.si_errno = 0;
+ si.si_code = code;
+ si.si_addr = (void __user *)addr;
+ force_sig_info(sig, &si, tsk);
+}
+
+void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs)
+{
+ struct task_struct *tsk = current;
+ struct mm_struct *mm = tsk->active_mm;
+
+ /*
+ * If we are in kernel mode at this point, we have no context to
+ * handle this fault with.
+ */
+ if (user_mode(regs))
+ __do_user_fault(tsk, addr, esr, SIGSEGV, SEGV_MAPERR, regs);
+ else
+ __do_kernel_fault(mm, addr, esr, regs);
+}
+
+#define VM_FAULT_BADMAP 0x010000
+#define VM_FAULT_BADACCESS 0x020000
+
+#define ESR_WRITE (1 << 6)
+#define ESR_LNX_EXEC (1 << 24)
+
+/*
+ * Check that the permissions on the VMA allow for the fault which occurred.
+ * If we encountered a write fault, we must have write permission, otherwise
+ * we allow any permission.
+ */
+static inline bool access_error(unsigned int esr, struct vm_area_struct *vma)
+{
+ unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
+
+ if (esr & ESR_WRITE)
+ mask = VM_WRITE;
+ if (esr & ESR_LNX_EXEC)
+ mask = VM_EXEC;
+
+ return vma->vm_flags & mask ? false : true;
+}
+
+static int __do_page_fault(struct mm_struct *mm, unsigned long addr,
+ unsigned int esr, unsigned int flags,
+ struct task_struct *tsk)
+{
+ struct vm_area_struct *vma;
+ int fault;
+
+ vma = find_vma(mm, addr);
+ fault = VM_FAULT_BADMAP;
+ if (unlikely(!vma))
+ goto out;
+ if (unlikely(vma->vm_start > addr))
+ goto check_stack;
+
+ /*
+ * Ok, we have a good vm_area for this memory access, so we can handle
+ * it.
+ */
+good_area:
+ if (access_error(esr, vma)) {
+ fault = VM_FAULT_BADACCESS;
+ goto out;
+ }
+
+ return handle_mm_fault(mm, vma, addr & PAGE_MASK, flags);
+
+check_stack:
+ if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
+ goto good_area;
+out:
+ return fault;
+}
+
+static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
+ struct pt_regs *regs)
+{
+ struct task_struct *tsk;
+ struct mm_struct *mm;
+ int fault, sig, code;
+ int write = esr & ESR_WRITE;
+ unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
+ (write ? FAULT_FLAG_WRITE : 0);
+
+ tsk = current;
+ mm = tsk->mm;
+
+ /* Enable interrupts if they were enabled in the parent context. */
+ if (interrupts_enabled(regs))
+ local_irq_enable();
+
+ /*
+ * If we're in an interrupt or have no user context, we must not take
+ * the fault.
+ */
+ if (in_atomic() || !mm)
+ goto no_context;
+
+ /*
+ * As per x86, we may deadlock here. However, since the kernel only
+ * validly references user space from well defined areas of the code,
+ * we can bug out early if this is from code which shouldn't.
+ */
+ if (!down_read_trylock(&mm->mmap_sem)) {
+ if (!user_mode(regs) && !search_exception_tables(regs->pc))
+ goto no_context;
+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();
+#ifdef CONFIG_DEBUG_VM
+ if (!user_mode(regs) && !search_exception_tables(regs->pc))
+ goto no_context;
+#endif
+ }
+
+ fault = __do_page_fault(mm, addr, esr, flags, tsk);
+
+ /*
+ * If we need to retry but a fatal signal is pending, handle the
+ * signal first. We do not need to release the mmap_sem because it
+ * would already be released in __lock_page_or_retry in mm/filemap.c.
+ */
+ if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
+ return 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.
+ */
+
+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
+ if (flags & FAULT_FLAG_ALLOW_RETRY) {
+ if (fault & VM_FAULT_MAJOR) {
+ tsk->maj_flt++;
+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs,
+ addr);
+ } else {
+ tsk->min_flt++;
+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs,
+ addr);
+ }
+ if (fault & VM_FAULT_RETRY) {
+ /*
+ * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk of
+ * starvation.
+ */
+ flags &= ~FAULT_FLAG_ALLOW_RETRY;
+ goto retry;
+ }
+ }
+
+ up_read(&mm->mmap_sem);
+
+ /*
+ * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR
+ */
+ if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP |
+ VM_FAULT_BADACCESS))))
+ return 0;
+
+ if (fault & VM_FAULT_OOM) {
+ /*
+ * We ran out of memory, call the OOM killer, and return to
+ * userspace (which will retry the fault, or kill us if we got
+ * oom-killed).
+ */
+ pagefault_out_of_memory();
+ return 0;
+ }
+
+ /*
+ * If we are in kernel mode at this point, we have no context to
+ * handle this fault with.
+ */
+ if (!user_mode(regs))
+ goto no_context;
+
+ if (fault & VM_FAULT_SIGBUS) {
+ /*
+ * We had some memory, but were unable to successfully fix up
+ * this page fault.
+ */
+ sig = SIGBUS;
+ code = BUS_ADRERR;
+ } else {
+ /*
+ * Something tried to access memory that isn't in our memory
+ * map.
+ */
+ sig = SIGSEGV;
+ code = fault == VM_FAULT_BADACCESS ?
+ SEGV_ACCERR : SEGV_MAPERR;
+ }
+
+ __do_user_fault(tsk, addr, esr, sig, code, regs);
+ return 0;
+
+no_context:
+ __do_kernel_fault(mm, addr, esr, regs);
+ return 0;
+}
+
+/*
+ * First Level Translation Fault Handler
+ *
+ * We enter here because the first level page table doesn't contain a valid
+ * entry for the address.
+ *
+ * If the address is in kernel space (>= TASK_SIZE), then we are probably
+ * faulting in the vmalloc() area.
+ *
+ * If the init_task's first level page tables contains the relevant entry, we
+ * copy the it to this task. If not, we send the process a signal, fixup the
+ * exception, or oops the kernel.
+ *
+ * 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.
+ */
+static int __kprobes do_translation_fault(unsigned long addr,
+ unsigned int esr,
+ struct pt_regs *regs)
+{
+ if (addr < TASK_SIZE)
+ return do_page_fault(addr, esr, regs);
+
+ do_bad_area(addr, esr, regs);
+ return 0;
+}
+
+/*
+ * Some section permission faults need to be handled gracefully. They can
+ * happen due to a __{get,put}_user during an oops.
+ */
+static int do_sect_fault(unsigned long addr, unsigned int esr,
+ struct pt_regs *regs)
+{
+ do_bad_area(addr, esr, regs);
+ return 0;
+}
+
+/*
+ * This abort handler always returns "fault".
+ */
+static int do_bad(unsigned long addr, unsigned int esr, struct pt_regs *regs)
+{
+ return 1;
+}
+
+static struct fault_info {
+ int (*fn)(unsigned long addr, unsigned int esr, struct pt_regs *regs);
+ int sig;
+ int code;
+ const char *name;
+} fault_info[] = {
+ { do_bad, SIGBUS, 0, "ttbr address size fault" },
+ { do_bad, SIGBUS, 0, "level 1 address size fault" },
+ { do_bad, SIGBUS, 0, "level 2 address size fault" },
+ { do_bad, SIGBUS, 0, "level 3 address size fault" },
+ { do_translation_fault, SIGSEGV, SEGV_MAPERR, "input address range fault" },
+ { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 1 translation fault" },
+ { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 2 translation fault" },
+ { do_page_fault, SIGSEGV, SEGV_MAPERR, "level 3 translation fault" },
+ { do_bad, SIGBUS, 0, "reserved access flag fault" },
+ { do_bad, SIGSEGV, SEGV_ACCERR, "level 1 access flag fault" },
+ { do_bad, SIGSEGV, SEGV_ACCERR, "level 2 access flag fault" },
+ { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 access flag fault" },
+ { do_bad, SIGBUS, 0, "reserved permission fault" },
+ { do_bad, SIGSEGV, SEGV_ACCERR, "level 1 permission fault" },
+ { do_sect_fault, SIGSEGV, SEGV_ACCERR, "level 2 permission fault" },
+ { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 permission fault" },
+ { do_bad, SIGBUS, 0, "synchronous external abort" },
+ { do_bad, SIGBUS, 0, "asynchronous external abort" },
+ { do_bad, SIGBUS, 0, "unknown 18" },
+ { do_bad, SIGBUS, 0, "unknown 19" },
+ { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
+ { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
+ { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
+ { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
+ { do_bad, SIGBUS, 0, "synchronous parity error" },
+ { do_bad, SIGBUS, 0, "asynchronous parity error" },
+ { do_bad, SIGBUS, 0, "unknown 26" },
+ { do_bad, SIGBUS, 0, "unknown 27" },
+ { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" },
+ { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" },
+ { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" },
+ { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" },
+ { do_bad, SIGBUS, 0, "unknown 32" },
+ { do_bad, SIGBUS, BUS_ADRALN, "alignment fault" },
+ { do_bad, SIGBUS, 0, "debug event" },
+ { do_bad, SIGBUS, 0, "unknown 35" },
+ { do_bad, SIGBUS, 0, "unknown 36" },
+ { do_bad, SIGBUS, 0, "unknown 37" },
+ { do_bad, SIGBUS, 0, "unknown 38" },
+ { do_bad, SIGBUS, 0, "unknown 39" },
+ { do_bad, SIGBUS, 0, "unknown 40" },
+ { do_bad, SIGBUS, 0, "unknown 41" },
+ { do_bad, SIGBUS, 0, "unknown 42" },
+ { do_bad, SIGBUS, 0, "unknown 43" },
+ { do_bad, SIGBUS, 0, "unknown 44" },
+ { do_bad, SIGBUS, 0, "unknown 45" },
+ { do_bad, SIGBUS, 0, "unknown 46" },
+ { do_bad, SIGBUS, 0, "unknown 47" },
+ { do_bad, SIGBUS, 0, "unknown 48" },
+ { do_bad, SIGBUS, 0, "unknown 49" },
+ { do_bad, SIGBUS, 0, "unknown 50" },
+ { do_bad, SIGBUS, 0, "unknown 51" },
+ { do_bad, SIGBUS, 0, "implementation fault (lockdown abort)" },
+ { do_bad, SIGBUS, 0, "unknown 53" },
+ { do_bad, SIGBUS, 0, "unknown 54" },
+ { do_bad, SIGBUS, 0, "unknown 55" },
+ { do_bad, SIGBUS, 0, "unknown 56" },
+ { do_bad, SIGBUS, 0, "unknown 57" },
+ { do_bad, SIGBUS, 0, "implementation fault (coprocessor abort)" },
+ { do_bad, SIGBUS, 0, "unknown 59" },
+ { do_bad, SIGBUS, 0, "unknown 60" },
+ { do_bad, SIGBUS, 0, "unknown 61" },
+ { do_bad, SIGBUS, 0, "unknown 62" },
+ { do_bad, SIGBUS, 0, "unknown 63" },
+};
+
+/*
+ * Dispatch a data abort to the relevant handler.
+ */
+asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr,
+ struct pt_regs *regs)
+{
+ const struct fault_info *inf = fault_info + (esr & 63);
+ struct siginfo info;
+
+ if (!inf->fn(addr, esr, regs))
+ return;
+
+ pr_alert("Unhandled fault: %s (0x%08x) at 0x%016lx\n",
+ inf->name, esr, addr);
+
+ info.si_signo = inf->sig;
+ info.si_errno = 0;
+ info.si_code = inf->code;
+ info.si_addr = (void __user *)addr;
+ arm64_notify_die("", regs, &info, esr);
+}
+
+/*
+ * Handle stack alignment exceptions.
+ */
+asmlinkage void __exception do_sp_pc_abort(unsigned long addr,
+ unsigned int esr,
+ struct pt_regs *regs)
+{
+ struct siginfo info;
+
+ info.si_signo = SIGBUS;
+ info.si_errno = 0;
+ info.si_code = BUS_ADRALN;
+ info.si_addr = (void __user *)addr;
+ arm64_notify_die("", regs, &info, esr);
+}
+
+static struct fault_info debug_fault_info[] = {
+ { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware breakpoint" },
+ { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware single-step" },
+ { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware watchpoint" },
+ { do_bad, SIGBUS, 0, "unknown 3" },
+ { do_bad, SIGTRAP, TRAP_BRKPT, "aarch32 BKPT" },
+ { do_bad, SIGTRAP, 0, "aarch32 vector catch" },
+ { do_bad, SIGTRAP, TRAP_BRKPT, "aarch64 BRK" },
+ { do_bad, SIGBUS, 0, "unknown 7" },
+};
+
+void __init hook_debug_fault_code(int nr,
+ int (*fn)(unsigned long, unsigned int, struct pt_regs *),
+ int sig, int code, const char *name)
+{
+ BUG_ON(nr < 0 || nr >= ARRAY_SIZE(debug_fault_info));
+
+ debug_fault_info[nr].fn = fn;
+ debug_fault_info[nr].sig = sig;
+ debug_fault_info[nr].code = code;
+ debug_fault_info[nr].name = name;
+}
+
+asmlinkage int __exception do_debug_exception(unsigned long addr,
+ unsigned int esr,
+ struct pt_regs *regs)
+{
+ const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr);
+ struct siginfo info;
+
+ if (!inf->fn(addr, esr, regs))
+ return 1;
+
+ pr_alert("Unhandled debug exception: %s (0x%08x) at 0x%016lx\n",
+ inf->name, esr, addr);
+
+ info.si_signo = inf->sig;
+ info.si_errno = 0;
+ info.si_code = inf->code;
+ info.si_addr = (void __user *)addr;
+ arm64_notify_die("", regs, &info, esr);
+
+ return 0;
+}