1 files changed, 525 insertions, 0 deletions

diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
new file mode 100644
index 000000000000..44968019ce0d
--- /dev/null
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -0,0 +1,525 @@
+/*
+ * arch/arm64/kernel/probes/kprobes.c
+ *
+ * Kprobes support for ARM64
+ *
+ * Copyright (C) 2013 Linaro Limited.
+ * Author: Sandeepa Prabhu <sandeepa.prabhu@linaro.org>
+ *
+ * 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.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/kprobes.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/stop_machine.h>
+#include <linux/stringify.h>
+#include <asm/traps.h>
+#include <asm/ptrace.h>
+#include <asm/cacheflush.h>
+#include <asm/debug-monitors.h>
+#include <asm/system_misc.h>
+#include <asm/insn.h>
+#include <asm/uaccess.h>
+#include <asm/irq.h>
+
+#include "decode-insn.h"
+
+#define MIN_STACK_SIZE(addr)	(on_irq_stack(addr, raw_smp_processor_id()) ? \
+	min((unsigned long)IRQ_STACK_SIZE,	\
+	IRQ_STACK_PTR(raw_smp_processor_id()) - (addr)) : \
+	min((unsigned long)MAX_STACK_SIZE,	\
+	(unsigned long)current_thread_info() + THREAD_START_SP - (addr)))
+
+void jprobe_return_break(void);
+
+DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
+DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
+
+static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
+{
+	/* prepare insn slot */
+	p->ainsn.insn[0] = cpu_to_le32(p->opcode);
+
+	flush_icache_range((uintptr_t) (p->ainsn.insn),
+			   (uintptr_t) (p->ainsn.insn) +
+			   MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+
+	/*
+	 * Needs restoring of return address after stepping xol.
+	 */
+	p->ainsn.restore = (unsigned long) p->addr +
+	  sizeof(kprobe_opcode_t);
+}
+
+int __kprobes arch_prepare_kprobe(struct kprobe *p)
+{
+	unsigned long probe_addr = (unsigned long)p->addr;
+	extern char __start_rodata[];
+	extern char __end_rodata[];
+
+	if (probe_addr & 0x3)
+		return -EINVAL;
+
+	/* copy instruction */
+	p->opcode = le32_to_cpu(*p->addr);
+
+	if (in_exception_text(probe_addr))
+		return -EINVAL;
+	if (probe_addr >= (unsigned long) __start_rodata &&
+	    probe_addr <= (unsigned long) __end_rodata)
+		return -EINVAL;
+
+	/* decode instruction */
+	switch (arm_kprobe_decode_insn(p->addr, &p->ainsn)) {
+	case INSN_REJECTED:	/* insn not supported */
+		return -EINVAL;
+
+	case INSN_GOOD:	/* instruction uses slot */
+		p->ainsn.insn = get_insn_slot();
+		if (!p->ainsn.insn)
+			return -ENOMEM;
+		break;
+	};
+
+	/* prepare the instruction */
+	arch_prepare_ss_slot(p);
+
+	return 0;
+}
+
+static int __kprobes patch_text(kprobe_opcode_t *addr, u32 opcode)
+{
+	void *addrs[1];
+	u32 insns[1];
+
+	addrs[0] = (void *)addr;
+	insns[0] = (u32)opcode;
+
+	return aarch64_insn_patch_text(addrs, insns, 1);
+}
+
+/* arm kprobe: install breakpoint in text */
+void __kprobes arch_arm_kprobe(struct kprobe *p)
+{
+	patch_text(p->addr, BRK64_OPCODE_KPROBES);
+}
+
+/* disarm kprobe: remove breakpoint from text */
+void __kprobes arch_disarm_kprobe(struct kprobe *p)
+{
+	patch_text(p->addr, p->opcode);
+}
+
+void __kprobes arch_remove_kprobe(struct kprobe *p)
+{
+	if (p->ainsn.insn) {
+		free_insn_slot(p->ainsn.insn, 0);
+		p->ainsn.insn = NULL;
+	}
+}
+
+static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
+{
+	kcb->prev_kprobe.kp = kprobe_running();
+	kcb->prev_kprobe.status = kcb->kprobe_status;
+}
+
+static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
+{
+	__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
+	kcb->kprobe_status = kcb->prev_kprobe.status;
+}
+
+static void __kprobes set_current_kprobe(struct kprobe *p)
+{
+	__this_cpu_write(current_kprobe, p);
+}
+
+/*
+ * The D-flag (Debug mask) is set (masked) upon debug exception entry.
+ * Kprobes needs to clear (unmask) D-flag -ONLY- in case of recursive
+ * probe i.e. when probe hit from kprobe handler context upon
+ * executing the pre/post handlers. In this case we return with
+ * D-flag clear so that single-stepping can be carried-out.
+ *
+ * Leave D-flag set in all other cases.
+ */
+static void __kprobes
+spsr_set_debug_flag(struct pt_regs *regs, int mask)
+{
+	unsigned long spsr = regs->pstate;
+
+	if (mask)
+		spsr |= PSR_D_BIT;
+	else
+		spsr &= ~PSR_D_BIT;
+
+	regs->pstate = spsr;
+}
+
+/*
+ * Interrupts need to be disabled before single-step mode is set, and not
+ * reenabled until after single-step mode ends.
+ * Without disabling interrupt on local CPU, there is a chance of
+ * interrupt occurrence in the period of exception return and  start of
+ * out-of-line single-step, that result in wrongly single stepping
+ * into the interrupt handler.
+ */
+static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
+						struct pt_regs *regs)
+{
+	kcb->saved_irqflag = regs->pstate;
+	regs->pstate |= PSR_I_BIT;
+}
+
+static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
+						struct pt_regs *regs)
+{
+	if (kcb->saved_irqflag & PSR_I_BIT)
+		regs->pstate |= PSR_I_BIT;
+	else
+		regs->pstate &= ~PSR_I_BIT;
+}
+
+static void __kprobes
+set_ss_context(struct kprobe_ctlblk *kcb, unsigned long addr)
+{
+	kcb->ss_ctx.ss_pending = true;
+	kcb->ss_ctx.match_addr = addr + sizeof(kprobe_opcode_t);
+}
+
+static void __kprobes clear_ss_context(struct kprobe_ctlblk *kcb)
+{
+	kcb->ss_ctx.ss_pending = false;
+	kcb->ss_ctx.match_addr = 0;
+}
+
+static void __kprobes setup_singlestep(struct kprobe *p,
+				       struct pt_regs *regs,
+				       struct kprobe_ctlblk *kcb, int reenter)
+{
+	unsigned long slot;
+
+	if (reenter) {
+		save_previous_kprobe(kcb);
+		set_current_kprobe(p);
+		kcb->kprobe_status = KPROBE_REENTER;
+	} else {
+		kcb->kprobe_status = KPROBE_HIT_SS;
+	}
+
+	BUG_ON(!p->ainsn.insn);
+
+	/* prepare for single stepping */
+	slot = (unsigned long)p->ainsn.insn;
+
+	set_ss_context(kcb, slot);	/* mark pending ss */
+
+	if (kcb->kprobe_status == KPROBE_REENTER)
+		spsr_set_debug_flag(regs, 0);
+
+	/* IRQs and single stepping do not mix well. */
+	kprobes_save_local_irqflag(kcb, regs);
+	kernel_enable_single_step(regs);
+	instruction_pointer_set(regs, slot);
+}
+
+static int __kprobes reenter_kprobe(struct kprobe *p,
+				    struct pt_regs *regs,
+				    struct kprobe_ctlblk *kcb)
+{
+	switch (kcb->kprobe_status) {
+	case KPROBE_HIT_SSDONE:
+	case KPROBE_HIT_ACTIVE:
+		kprobes_inc_nmissed_count(p);
+		setup_singlestep(p, regs, kcb, 1);
+		break;
+	case KPROBE_HIT_SS:
+	case KPROBE_REENTER:
+		pr_warn("Unrecoverable kprobe detected at %p.\n", p->addr);
+		dump_kprobe(p);
+		BUG();
+		break;
+	default:
+		WARN_ON(1);
+		return 0;
+	}
+
+	return 1;
+}
+
+static void __kprobes
+post_kprobe_handler(struct kprobe_ctlblk *kcb, struct pt_regs *regs)
+{
+	struct kprobe *cur = kprobe_running();
+
+	if (!cur)
+		return;
+
+	/* return addr restore if non-branching insn */
+	if (cur->ainsn.restore != 0)
+		instruction_pointer_set(regs, cur->ainsn.restore);
+
+	/* restore back original saved kprobe variables and continue */
+	if (kcb->kprobe_status == KPROBE_REENTER) {
+		restore_previous_kprobe(kcb);
+		return;
+	}
+	/* call post handler */
+	kcb->kprobe_status = KPROBE_HIT_SSDONE;
+	if (cur->post_handler)	{
+		/* post_handler can hit breakpoint and single step
+		 * again, so we enable D-flag for recursive exception.
+		 */
+		cur->post_handler(cur, regs, 0);
+	}
+
+	reset_current_kprobe();
+}
+
+int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
+{
+	struct kprobe *cur = kprobe_running();
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+	switch (kcb->kprobe_status) {
+	case KPROBE_HIT_SS:
+	case KPROBE_REENTER:
+		/*
+		 * We are here because the instruction being single
+		 * stepped caused a page fault. We reset the current
+		 * kprobe and the ip points back to the probe address
+		 * and allow the page fault handler to continue as a
+		 * normal page fault.
+		 */
+		instruction_pointer_set(regs, (unsigned long) cur->addr);
+		if (!instruction_pointer(regs))
+			BUG();
+
+		kernel_disable_single_step();
+		if (kcb->kprobe_status == KPROBE_REENTER)
+			spsr_set_debug_flag(regs, 1);
+
+		if (kcb->kprobe_status == KPROBE_REENTER)
+			restore_previous_kprobe(kcb);
+		else
+			reset_current_kprobe();
+
+		break;
+	case KPROBE_HIT_ACTIVE:
+	case KPROBE_HIT_SSDONE:
+		/*
+		 * We increment the nmissed count for accounting,
+		 * we can also use npre/npostfault count for accounting
+		 * these specific fault cases.
+		 */
+		kprobes_inc_nmissed_count(cur);
+
+		/*
+		 * We come here because instructions in the pre/post
+		 * handler caused the page_fault, this could happen
+		 * if handler tries to access user space by
+		 * copy_from_user(), get_user() etc. Let the
+		 * user-specified handler try to fix it first.
+		 */
+		if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
+			return 1;
+
+		/*
+		 * In case the user-specified fault handler returned
+		 * zero, try to fix up.
+		 */
+		if (fixup_exception(regs))
+			return 1;
+	}
+	return 0;
+}
+
+int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
+				       unsigned long val, void *data)
+{
+	return NOTIFY_DONE;
+}
+
+static void __kprobes kprobe_handler(struct pt_regs *regs)
+{
+	struct kprobe *p, *cur_kprobe;
+	struct kprobe_ctlblk *kcb;
+	unsigned long addr = instruction_pointer(regs);
+
+	kcb = get_kprobe_ctlblk();
+	cur_kprobe = kprobe_running();
+
+	p = get_kprobe((kprobe_opcode_t *) addr);
+
+	if (p) {
+		if (cur_kprobe) {
+			if (reenter_kprobe(p, regs, kcb))
+				return;
+		} else {
+			/* Probe hit */
+			set_current_kprobe(p);
+			kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+
+			/*
+			 * If we have no pre-handler or it returned 0, we
+			 * continue with normal processing.  If we have a
+			 * pre-handler and it returned non-zero, it prepped
+			 * for calling the break_handler below on re-entry,
+			 * so get out doing nothing more here.
+			 *
+			 * pre_handler can hit a breakpoint and can step thru
+			 * before return, keep PSTATE D-flag enabled until
+			 * pre_handler return back.
+			 */
+			if (!p->pre_handler || !p->pre_handler(p, regs)) {
+				setup_singlestep(p, regs, kcb, 0);
+				return;
+			}
+		}
+	} else if ((le32_to_cpu(*(kprobe_opcode_t *) addr) ==
+	    BRK64_OPCODE_KPROBES) && cur_kprobe) {
+		/* We probably hit a jprobe.  Call its break handler. */
+		if (cur_kprobe->break_handler  &&
+		     cur_kprobe->break_handler(cur_kprobe, regs)) {
+			setup_singlestep(cur_kprobe, regs, kcb, 0);
+			return;
+		}
+	}
+	/*
+	 * The breakpoint instruction was removed right
+	 * after we hit it.  Another cpu has removed
+	 * either a probepoint or a debugger breakpoint
+	 * at this address.  In either case, no further
+	 * handling of this interrupt is appropriate.
+	 * Return back to original instruction, and continue.
+	 */
+}
+
+static int __kprobes
+kprobe_ss_hit(struct kprobe_ctlblk *kcb, unsigned long addr)
+{
+	if ((kcb->ss_ctx.ss_pending)
+	    && (kcb->ss_ctx.match_addr == addr)) {
+		clear_ss_context(kcb);	/* clear pending ss */
+		return DBG_HOOK_HANDLED;
+	}
+	/* not ours, kprobes should ignore it */
+	return DBG_HOOK_ERROR;
+}
+
+int __kprobes
+kprobe_single_step_handler(struct pt_regs *regs, unsigned int esr)
+{
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+	int retval;
+
+	/* return error if this is not our step */
+	retval = kprobe_ss_hit(kcb, instruction_pointer(regs));
+
+	if (retval == DBG_HOOK_HANDLED) {
+		kprobes_restore_local_irqflag(kcb, regs);
+		kernel_disable_single_step();
+
+		if (kcb->kprobe_status == KPROBE_REENTER)
+			spsr_set_debug_flag(regs, 1);
+
+		post_kprobe_handler(kcb, regs);
+	}
+
+	return retval;
+}
+
+int __kprobes
+kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr)
+{
+	kprobe_handler(regs);
+	return DBG_HOOK_HANDLED;
+}
+
+int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	struct jprobe *jp = container_of(p, struct jprobe, kp);
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+	long stack_ptr = kernel_stack_pointer(regs);
+
+	kcb->jprobe_saved_regs = *regs;
+	/*
+	 * As Linus pointed out, gcc assumes that the callee
+	 * owns the argument space and could overwrite it, e.g.
+	 * tailcall optimization. So, to be absolutely safe
+	 * we also save and restore enough stack bytes to cover
+	 * the argument area.
+	 */
+	memcpy(kcb->jprobes_stack, (void *)stack_ptr,
+	       MIN_STACK_SIZE(stack_ptr));
+
+	instruction_pointer_set(regs, (unsigned long) jp->entry);
+	preempt_disable();
+	pause_graph_tracing();
+	return 1;
+}
+
+void __kprobes jprobe_return(void)
+{
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+	/*
+	 * Jprobe handler return by entering break exception,
+	 * encoded same as kprobe, but with following conditions
+	 * -a magic number in x0 to identify from rest of other kprobes.
+	 * -restore stack addr to original saved pt_regs
+	 */
+	asm volatile ("ldr x0, [%0]\n\t"
+		      "mov sp, x0\n\t"
+		      ".globl jprobe_return_break\n\t"
+		      "jprobe_return_break:\n\t"
+		      "brk %1\n\t"
+		      :
+		      : "r"(&kcb->jprobe_saved_regs.sp),
+		      "I"(BRK64_ESR_KPROBES)
+		      : "memory");
+}
+
+int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+	long stack_addr = kcb->jprobe_saved_regs.sp;
+	long orig_sp = kernel_stack_pointer(regs);
+	struct jprobe *jp = container_of(p, struct jprobe, kp);
+
+	if (instruction_pointer(regs) != (u64) jprobe_return_break)
+		return 0;
+
+	if (orig_sp != stack_addr) {
+		struct pt_regs *saved_regs =
+		    (struct pt_regs *)kcb->jprobe_saved_regs.sp;
+		pr_err("current sp %lx does not match saved sp %lx\n",
+		       orig_sp, stack_addr);
+		pr_err("Saved registers for jprobe %p\n", jp);
+		show_regs(saved_regs);
+		pr_err("Current registers\n");
+		show_regs(regs);
+		BUG();
+	}
+	unpause_graph_tracing();
+	*regs = kcb->jprobe_saved_regs;
+	memcpy((void *)stack_addr, kcb->jprobes_stack,
+	       MIN_STACK_SIZE(stack_addr));
+	preempt_enable_no_resched();
+	return 1;
+}
+
+int __init arch_init_kprobes(void)
+{
+	return 0;
+}