1 files changed, 607 insertions, 0 deletions

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
new file mode 100644
index 000000000..af5177801
--- /dev/null
+++ b/arch/arm/mm/fault.c
@@ -0,0 +1,607 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/arch/arm/mm/fault.c
+ *
+ *  Copyright (C) 1995  Linus Torvalds
+ *  Modifications for ARM processor (c) 1995-2004 Russell King
+ */
+#include <linux/extable.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/signal.h>
+#include <linux/sched/debug.h>
+#include <linux/highmem.h>
+#include <linux/perf_event.h>
+
+#include <asm/system_misc.h>
+#include <asm/system_info.h>
+#include <asm/tlbflush.h>
+
+#include "fault.h"
+
+#ifdef CONFIG_MMU
+
+/*
+ * This is useful to dump out the page tables associated with
+ * 'addr' in mm 'mm'.
+ */
+void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr)
+{
+	pgd_t *pgd;
+
+	if (!mm)
+		mm = &init_mm;
+
+	printk("%spgd = %p\n", lvl, mm->pgd);
+	pgd = pgd_offset(mm, addr);
+	printk("%s[%08lx] *pgd=%08llx", lvl, addr, (long long)pgd_val(*pgd));
+
+	do {
+		p4d_t *p4d;
+		pud_t *pud;
+		pmd_t *pmd;
+		pte_t *pte;
+
+		p4d = p4d_offset(pgd, addr);
+		if (p4d_none(*p4d))
+			break;
+
+		if (p4d_bad(*p4d)) {
+			pr_cont("(bad)");
+			break;
+		}
+
+		pud = pud_offset(p4d, addr);
+		if (PTRS_PER_PUD != 1)
+			pr_cont(", *pud=%08llx", (long long)pud_val(*pud));
+
+		if (pud_none(*pud))
+			break;
+
+		if (pud_bad(*pud)) {
+			pr_cont("(bad)");
+			break;
+		}
+
+		pmd = pmd_offset(pud, addr);
+		if (PTRS_PER_PMD != 1)
+			pr_cont(", *pmd=%08llx", (long long)pmd_val(*pmd));
+
+		if (pmd_none(*pmd))
+			break;
+
+		if (pmd_bad(*pmd)) {
+			pr_cont("(bad)");
+			break;
+		}
+
+		/* We must not map this if we have highmem enabled */
+		if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
+			break;
+
+		pte = pte_offset_map(pmd, addr);
+		pr_cont(", *pte=%08llx", (long long)pte_val(*pte));
+#ifndef CONFIG_ARM_LPAE
+		pr_cont(", *ppte=%08llx",
+		       (long long)pte_val(pte[PTE_HWTABLE_PTRS]));
+#endif
+		pte_unmap(pte);
+	} while(0);
+
+	pr_cont("\n");
+}
+#else					/* CONFIG_MMU */
+void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr)
+{ }
+#endif					/* CONFIG_MMU */
+
+/*
+ * Oops.  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 fsr,
+		  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("8<--- cut here ---\n");
+	pr_alert("Unable to handle kernel %s at virtual address %08lx\n",
+		 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
+		 "paging request", addr);
+
+	show_pte(KERN_ALERT, mm, addr);
+	die("Oops", regs, fsr);
+	bust_spinlocks(0);
+	make_task_dead(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(unsigned long addr, unsigned int fsr, unsigned int sig,
+		int code, struct pt_regs *regs)
+{
+	struct task_struct *tsk = current;
+
+	if (addr > TASK_SIZE)
+		harden_branch_predictor();
+
+#ifdef CONFIG_DEBUG_USER
+	if (((user_debug & UDBG_SEGV) && (sig == SIGSEGV)) ||
+	    ((user_debug & UDBG_BUS)  && (sig == SIGBUS))) {
+		pr_err("8<--- cut here ---\n");
+		pr_err("%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
+		       tsk->comm, sig, addr, fsr);
+		show_pte(KERN_ERR, tsk->mm, addr);
+		show_regs(regs);
+	}
+#endif
+#ifndef CONFIG_KUSER_HELPERS
+	if ((sig == SIGSEGV) && ((addr & PAGE_MASK) == 0xffff0000))
+		printk_ratelimited(KERN_DEBUG
+				   "%s: CONFIG_KUSER_HELPERS disabled at 0x%08lx\n",
+				   tsk->comm, addr);
+#endif
+
+	tsk->thread.address = addr;
+	tsk->thread.error_code = fsr;
+	tsk->thread.trap_no = 14;
+	force_sig_fault(sig, code, (void __user *)addr);
+}
+
+void do_bad_area(unsigned long addr, unsigned int fsr, 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(addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
+	else
+		__do_kernel_fault(mm, addr, fsr, regs);
+}
+
+#ifdef CONFIG_MMU
+#define VM_FAULT_BADMAP		0x010000
+#define VM_FAULT_BADACCESS	0x020000
+
+/*
+ * 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 fsr, struct vm_area_struct *vma)
+{
+	unsigned int mask = VM_ACCESS_FLAGS;
+
+	if ((fsr & FSR_WRITE) && !(fsr & FSR_CM))
+		mask = VM_WRITE;
+	if (fsr & FSR_LNX_PF)
+		mask = VM_EXEC;
+
+	return vma->vm_flags & mask ? false : true;
+}
+
+static vm_fault_t __kprobes
+__do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
+		unsigned int flags, struct task_struct *tsk,
+		struct pt_regs *regs)
+{
+	struct vm_area_struct *vma;
+	vm_fault_t 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(fsr, vma)) {
+		fault = VM_FAULT_BADACCESS;
+		goto out;
+	}
+
+	return handle_mm_fault(vma, addr & PAGE_MASK, flags, regs);
+
+check_stack:
+	/* Don't allow expansion below FIRST_USER_ADDRESS */
+	if (vma->vm_flags & VM_GROWSDOWN &&
+	    addr >= FIRST_USER_ADDRESS && !expand_stack(vma, addr))
+		goto good_area;
+out:
+	return fault;
+}
+
+static int __kprobes
+do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
+{
+	struct task_struct *tsk;
+	struct mm_struct *mm;
+	int sig, code;
+	vm_fault_t fault;
+	unsigned int flags = FAULT_FLAG_DEFAULT;
+
+	if (kprobe_page_fault(regs, fsr))
+		return 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 (faulthandler_disabled() || !mm)
+		goto no_context;
+
+	if (user_mode(regs))
+		flags |= FAULT_FLAG_USER;
+	if ((fsr & FSR_WRITE) && !(fsr & FSR_CM))
+		flags |= FAULT_FLAG_WRITE;
+
+	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
+
+	/*
+	 * 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 (!mmap_read_trylock(mm)) {
+		if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
+			goto no_context;
+retry:
+		mmap_read_lock(mm);
+	} 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->ARM_pc))
+			goto no_context;
+#endif
+	}
+
+	fault = __do_page_fault(mm, addr, fsr, flags, tsk, regs);
+
+	/* If we need to retry but a fatal signal is pending, handle the
+	 * signal first. We do not need to release the mmap_lock because
+	 * it would already be released in __lock_page_or_retry in
+	 * mm/filemap.c. */
+	if (fault_signal_pending(fault, regs)) {
+		if (!user_mode(regs))
+			goto no_context;
+		return 0;
+	}
+
+	if (!(fault & VM_FAULT_ERROR) && flags & FAULT_FLAG_ALLOW_RETRY) {
+		if (fault & VM_FAULT_RETRY) {
+			flags |= FAULT_FLAG_TRIED;
+			goto retry;
+		}
+	}
+
+	mmap_read_unlock(mm);
+
+	/*
+	 * Handle the "normal" case first - VM_FAULT_MAJOR
+	 */
+	if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
+		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_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 (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(addr, fsr, sig, code, regs);
+	return 0;
+
+no_context:
+	__do_kernel_fault(mm, addr, fsr, regs);
+	return 0;
+}
+#else					/* CONFIG_MMU */
+static int
+do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
+{
+	return 0;
+}
+#endif					/* CONFIG_MMU */
+
+/*
+ * 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.
+ */
+#ifdef CONFIG_MMU
+static int __kprobes
+do_translation_fault(unsigned long addr, unsigned int fsr,
+		     struct pt_regs *regs)
+{
+	unsigned int index;
+	pgd_t *pgd, *pgd_k;
+	p4d_t *p4d, *p4d_k;
+	pud_t *pud, *pud_k;
+	pmd_t *pmd, *pmd_k;
+
+	if (addr < TASK_SIZE)
+		return do_page_fault(addr, fsr, regs);
+
+	if (user_mode(regs))
+		goto bad_area;
+
+	index = pgd_index(addr);
+
+	pgd = cpu_get_pgd() + index;
+	pgd_k = init_mm.pgd + index;
+
+	p4d = p4d_offset(pgd, addr);
+	p4d_k = p4d_offset(pgd_k, addr);
+
+	if (p4d_none(*p4d_k))
+		goto bad_area;
+	if (!p4d_present(*p4d))
+		set_p4d(p4d, *p4d_k);
+
+	pud = pud_offset(p4d, addr);
+	pud_k = pud_offset(p4d_k, addr);
+
+	if (pud_none(*pud_k))
+		goto bad_area;
+	if (!pud_present(*pud))
+		set_pud(pud, *pud_k);
+
+	pmd = pmd_offset(pud, addr);
+	pmd_k = pmd_offset(pud_k, addr);
+
+#ifdef CONFIG_ARM_LPAE
+	/*
+	 * Only one hardware entry per PMD with LPAE.
+	 */
+	index = 0;
+#else
+	/*
+	 * On ARM one Linux PGD entry contains two hardware entries (see page
+	 * tables layout in pgtable.h). We normally guarantee that we always
+	 * fill both L1 entries. But create_mapping() doesn't follow the rule.
+	 * It can create inidividual L1 entries, so here we have to call
+	 * pmd_none() check for the entry really corresponded to address, not
+	 * for the first of pair.
+	 */
+	index = (addr >> SECTION_SHIFT) & 1;
+#endif
+	if (pmd_none(pmd_k[index]))
+		goto bad_area;
+
+	copy_pmd(pmd, pmd_k);
+	return 0;
+
+bad_area:
+	do_bad_area(addr, fsr, regs);
+	return 0;
+}
+#else					/* CONFIG_MMU */
+static int
+do_translation_fault(unsigned long addr, unsigned int fsr,
+		     struct pt_regs *regs)
+{
+	return 0;
+}
+#endif					/* CONFIG_MMU */
+
+/*
+ * Some section permission faults need to be handled gracefully.
+ * They can happen due to a __{get,put}_user during an oops.
+ */
+#ifndef CONFIG_ARM_LPAE
+static int
+do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
+{
+	do_bad_area(addr, fsr, regs);
+	return 0;
+}
+#endif /* CONFIG_ARM_LPAE */
+
+/*
+ * This abort handler always returns "fault".
+ */
+static int
+do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
+{
+	return 1;
+}
+
+struct fsr_info {
+	int	(*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
+	int	sig;
+	int	code;
+	const char *name;
+};
+
+/* FSR definition */
+#ifdef CONFIG_ARM_LPAE
+#include "fsr-3level.c"
+#else
+#include "fsr-2level.c"
+#endif
+
+void __init
+hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
+		int sig, int code, const char *name)
+{
+	if (nr < 0 || nr >= ARRAY_SIZE(fsr_info))
+		BUG();
+
+	fsr_info[nr].fn   = fn;
+	fsr_info[nr].sig  = sig;
+	fsr_info[nr].code = code;
+	fsr_info[nr].name = name;
+}
+
+/*
+ * Dispatch a data abort to the relevant handler.
+ */
+asmlinkage void
+do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
+{
+	const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
+
+	if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
+		return;
+
+	pr_alert("8<--- cut here ---\n");
+	pr_alert("Unhandled fault: %s (0x%03x) at 0x%08lx\n",
+		inf->name, fsr, addr);
+	show_pte(KERN_ALERT, current->mm, addr);
+
+	arm_notify_die("", regs, inf->sig, inf->code, (void __user *)addr,
+		       fsr, 0);
+}
+
+void __init
+hook_ifault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
+		 int sig, int code, const char *name)
+{
+	if (nr < 0 || nr >= ARRAY_SIZE(ifsr_info))
+		BUG();
+
+	ifsr_info[nr].fn   = fn;
+	ifsr_info[nr].sig  = sig;
+	ifsr_info[nr].code = code;
+	ifsr_info[nr].name = name;
+}
+
+asmlinkage void
+do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
+{
+	const struct fsr_info *inf = ifsr_info + fsr_fs(ifsr);
+
+	if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
+		return;
+
+	pr_alert("Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
+		inf->name, ifsr, addr);
+
+	arm_notify_die("", regs, inf->sig, inf->code, (void __user *)addr,
+		       ifsr, 0);
+}
+
+/*
+ * Abort handler to be used only during first unmasking of asynchronous aborts
+ * on the boot CPU. This makes sure that the machine will not die if the
+ * firmware/bootloader left an imprecise abort pending for us to trip over.
+ */
+static int __init early_abort_handler(unsigned long addr, unsigned int fsr,
+				      struct pt_regs *regs)
+{
+	pr_warn("Hit pending asynchronous external abort (FSR=0x%08x) during "
+		"first unmask, this is most likely caused by a "
+		"firmware/bootloader bug.\n", fsr);
+
+	return 0;
+}
+
+void __init early_abt_enable(void)
+{
+	fsr_info[FSR_FS_AEA].fn = early_abort_handler;
+	local_abt_enable();
+	fsr_info[FSR_FS_AEA].fn = do_bad;
+}
+
+#ifndef CONFIG_ARM_LPAE
+static int __init exceptions_init(void)
+{
+	if (cpu_architecture() >= CPU_ARCH_ARMv6) {
+		hook_fault_code(4, do_translation_fault, SIGSEGV, SEGV_MAPERR,
+				"I-cache maintenance fault");
+	}
+
+	if (cpu_architecture() >= CPU_ARCH_ARMv7) {
+		/*
+		 * TODO: Access flag faults introduced in ARMv6K.
+		 * Runtime check for 'K' extension is needed
+		 */
+		hook_fault_code(3, do_bad, SIGSEGV, SEGV_MAPERR,
+				"section access flag fault");
+		hook_fault_code(6, do_bad, SIGSEGV, SEGV_MAPERR,
+				"section access flag fault");
+	}
+
+	return 0;
+}
+
+arch_initcall(exceptions_init);
+#endif