1 files changed, 485 insertions, 0 deletions

diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c
new file mode 100644
index 000000000..c0ed17289
--- /dev/null
+++ b/arch/arm/probes/kprobes/core.c
@@ -0,0 +1,485 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * arch/arm/kernel/kprobes.c
+ *
+ * Kprobes on ARM
+ *
+ * Abhishek Sagar <sagar.abhishek@gmail.com>
+ * Copyright (C) 2006, 2007 Motorola Inc.
+ *
+ * Nicolas Pitre <nico@marvell.com>
+ * Copyright (C) 2007 Marvell Ltd.
+ */
+
+#include <linux/kernel.h>
+#include <linux/kprobes.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/stop_machine.h>
+#include <linux/sched/debug.h>
+#include <linux/stringify.h>
+#include <asm/traps.h>
+#include <asm/opcodes.h>
+#include <asm/cacheflush.h>
+#include <linux/percpu.h>
+#include <linux/bug.h>
+#include <asm/patch.h>
+#include <asm/sections.h>
+
+#include "../decode-arm.h"
+#include "../decode-thumb.h"
+#include "core.h"
+
+#define MIN_STACK_SIZE(addr) 				\
+	min((unsigned long)MAX_STACK_SIZE,		\
+	    (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
+
+#define flush_insns(addr, size)				\
+	flush_icache_range((unsigned long)(addr),	\
+			   (unsigned long)(addr) +	\
+			   (size))
+
+DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
+DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
+
+
+int __kprobes arch_prepare_kprobe(struct kprobe *p)
+{
+	kprobe_opcode_t insn;
+	kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
+	unsigned long addr = (unsigned long)p->addr;
+	bool thumb;
+	kprobe_decode_insn_t *decode_insn;
+	const union decode_action *actions;
+	int is;
+	const struct decode_checker **checkers;
+
+#ifdef CONFIG_THUMB2_KERNEL
+	thumb = true;
+	addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */
+	insn = __mem_to_opcode_thumb16(((u16 *)addr)[0]);
+	if (is_wide_instruction(insn)) {
+		u16 inst2 = __mem_to_opcode_thumb16(((u16 *)addr)[1]);
+		insn = __opcode_thumb32_compose(insn, inst2);
+		decode_insn = thumb32_probes_decode_insn;
+		actions = kprobes_t32_actions;
+		checkers = kprobes_t32_checkers;
+	} else {
+		decode_insn = thumb16_probes_decode_insn;
+		actions = kprobes_t16_actions;
+		checkers = kprobes_t16_checkers;
+	}
+#else /* !CONFIG_THUMB2_KERNEL */
+	thumb = false;
+	if (addr & 0x3)
+		return -EINVAL;
+	insn = __mem_to_opcode_arm(*p->addr);
+	decode_insn = arm_probes_decode_insn;
+	actions = kprobes_arm_actions;
+	checkers = kprobes_arm_checkers;
+#endif
+
+	p->opcode = insn;
+	p->ainsn.insn = tmp_insn;
+
+	switch ((*decode_insn)(insn, &p->ainsn, true, actions, checkers)) {
+	case INSN_REJECTED:	/* not supported */
+		return -EINVAL;
+
+	case INSN_GOOD:		/* instruction uses slot */
+		p->ainsn.insn = get_insn_slot();
+		if (!p->ainsn.insn)
+			return -ENOMEM;
+		for (is = 0; is < MAX_INSN_SIZE; ++is)
+			p->ainsn.insn[is] = tmp_insn[is];
+		flush_insns(p->ainsn.insn,
+				sizeof(p->ainsn.insn[0]) * MAX_INSN_SIZE);
+		p->ainsn.insn_fn = (probes_insn_fn_t *)
+					((uintptr_t)p->ainsn.insn | thumb);
+		break;
+
+	case INSN_GOOD_NO_SLOT:	/* instruction doesn't need insn slot */
+		p->ainsn.insn = NULL;
+		break;
+	}
+
+	/*
+	 * Never instrument insn like 'str r0, [sp, +/-r1]'. Also, insn likes
+	 * 'str r0, [sp, #-68]' should also be prohibited.
+	 * See __und_svc.
+	 */
+	if ((p->ainsn.stack_space < 0) ||
+			(p->ainsn.stack_space > MAX_STACK_SIZE))
+		return -EINVAL;
+
+	return 0;
+}
+
+void __kprobes arch_arm_kprobe(struct kprobe *p)
+{
+	unsigned int brkp;
+	void *addr;
+
+	if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
+		/* Remove any Thumb flag */
+		addr = (void *)((uintptr_t)p->addr & ~1);
+
+		if (is_wide_instruction(p->opcode))
+			brkp = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION;
+		else
+			brkp = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION;
+	} else {
+		kprobe_opcode_t insn = p->opcode;
+
+		addr = p->addr;
+		brkp = KPROBE_ARM_BREAKPOINT_INSTRUCTION;
+
+		if (insn >= 0xe0000000)
+			brkp |= 0xe0000000;  /* Unconditional instruction */
+		else
+			brkp |= insn & 0xf0000000;  /* Copy condition from insn */
+	}
+
+	patch_text(addr, brkp);
+}
+
+/*
+ * The actual disarming is done here on each CPU and synchronized using
+ * stop_machine. This synchronization is necessary on SMP to avoid removing
+ * a probe between the moment the 'Undefined Instruction' exception is raised
+ * and the moment the exception handler reads the faulting instruction from
+ * memory. It is also needed to atomically set the two half-words of a 32-bit
+ * Thumb breakpoint.
+ */
+struct patch {
+	void *addr;
+	unsigned int insn;
+};
+
+static int __kprobes_remove_breakpoint(void *data)
+{
+	struct patch *p = data;
+	__patch_text(p->addr, p->insn);
+	return 0;
+}
+
+void __kprobes kprobes_remove_breakpoint(void *addr, unsigned int insn)
+{
+	struct patch p = {
+		.addr = addr,
+		.insn = insn,
+	};
+	stop_machine_cpuslocked(__kprobes_remove_breakpoint, &p,
+				cpu_online_mask);
+}
+
+void __kprobes arch_disarm_kprobe(struct kprobe *p)
+{
+	kprobes_remove_breakpoint((void *)((uintptr_t)p->addr & ~1),
+			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);
+}
+
+static void __kprobes
+singlestep_skip(struct kprobe *p, struct pt_regs *regs)
+{
+#ifdef CONFIG_THUMB2_KERNEL
+	regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
+	if (is_wide_instruction(p->opcode))
+		regs->ARM_pc += 4;
+	else
+		regs->ARM_pc += 2;
+#else
+	regs->ARM_pc += 4;
+#endif
+}
+
+static inline void __kprobes
+singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb)
+{
+	p->ainsn.insn_singlestep(p->opcode, &p->ainsn, regs);
+}
+
+/*
+ * Called with IRQs disabled. IRQs must remain disabled from that point
+ * all the way until processing this kprobe is complete.  The current
+ * kprobes implementation cannot process more than one nested level of
+ * kprobe, and that level is reserved for user kprobe handlers, so we can't
+ * risk encountering a new kprobe in an interrupt handler.
+ */
+static void __kprobes kprobe_handler(struct pt_regs *regs)
+{
+	struct kprobe *p, *cur;
+	struct kprobe_ctlblk *kcb;
+
+	kcb = get_kprobe_ctlblk();
+	cur = kprobe_running();
+
+#ifdef CONFIG_THUMB2_KERNEL
+	/*
+	 * First look for a probe which was registered using an address with
+	 * bit 0 set, this is the usual situation for pointers to Thumb code.
+	 * If not found, fallback to looking for one with bit 0 clear.
+	 */
+	p = get_kprobe((kprobe_opcode_t *)(regs->ARM_pc | 1));
+	if (!p)
+		p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
+
+#else /* ! CONFIG_THUMB2_KERNEL */
+	p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
+#endif
+
+	if (p) {
+		if (!p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
+			/*
+			 * Probe hit but conditional execution check failed,
+			 * so just skip the instruction and continue as if
+			 * nothing had happened.
+			 * In this case, we can skip recursing check too.
+			 */
+			singlestep_skip(p, regs);
+		} else if (cur) {
+			/* Kprobe is pending, so we're recursing. */
+			switch (kcb->kprobe_status) {
+			case KPROBE_HIT_ACTIVE:
+			case KPROBE_HIT_SSDONE:
+			case KPROBE_HIT_SS:
+				/* A pre- or post-handler probe got us here. */
+				kprobes_inc_nmissed_count(p);
+				save_previous_kprobe(kcb);
+				set_current_kprobe(p);
+				kcb->kprobe_status = KPROBE_REENTER;
+				singlestep(p, regs, kcb);
+				restore_previous_kprobe(kcb);
+				break;
+			case KPROBE_REENTER:
+				/* A nested probe was hit in FIQ, it is a BUG */
+				pr_warn("Unrecoverable kprobe detected.\n");
+				dump_kprobe(p);
+				fallthrough;
+			default:
+				/* impossible cases */
+				BUG();
+			}
+		} else {
+			/* Probe hit and conditional execution check ok. */
+			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 will
+			 * modify the execution path and no need to single
+			 * stepping. Let's just reset current kprobe and exit.
+			 */
+			if (!p->pre_handler || !p->pre_handler(p, regs)) {
+				kcb->kprobe_status = KPROBE_HIT_SS;
+				singlestep(p, regs, kcb);
+				if (p->post_handler) {
+					kcb->kprobe_status = KPROBE_HIT_SSDONE;
+					p->post_handler(p, regs, 0);
+				}
+			}
+			reset_current_kprobe();
+		}
+	} else {
+		/*
+		 * The probe was removed and a race is in progress.
+		 * There is nothing we can do about it.  Let's restart
+		 * the instruction.  By the time we can restart, the
+		 * real instruction will be there.
+		 */
+	}
+}
+
+static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
+{
+	unsigned long flags;
+	local_irq_save(flags);
+	kprobe_handler(regs);
+	local_irq_restore(flags);
+	return 0;
+}
+
+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 PC to point back to the probe address
+		 * and allow the page fault handler to continue as a
+		 * normal page fault.
+		 */
+		regs->ARM_pc = (long)cur->addr;
+		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.
+		 */
+		if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
+			return 1;
+		break;
+
+	default:
+		break;
+	}
+
+	return 0;
+}
+
+int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
+				       unsigned long val, void *data)
+{
+	/*
+	 * notify_die() is currently never called on ARM,
+	 * so this callback is currently empty.
+	 */
+	return NOTIFY_DONE;
+}
+
+/*
+ * When a retprobed function returns, trampoline_handler() is called,
+ * calling the kretprobe's handler. We construct a struct pt_regs to
+ * give a view of registers r0-r11 to the user return-handler.  This is
+ * not a complete pt_regs structure, but that should be plenty sufficient
+ * for kretprobe handlers which should normally be interested in r0 only
+ * anyway.
+ */
+void __naked __kprobes kretprobe_trampoline(void)
+{
+	__asm__ __volatile__ (
+		"stmdb	sp!, {r0 - r11}		\n\t"
+		"mov	r0, sp			\n\t"
+		"bl	trampoline_handler	\n\t"
+		"mov	lr, r0			\n\t"
+		"ldmia	sp!, {r0 - r11}		\n\t"
+#ifdef CONFIG_THUMB2_KERNEL
+		"bx	lr			\n\t"
+#else
+		"mov	pc, lr			\n\t"
+#endif
+		: : : "memory");
+}
+
+/* Called from kretprobe_trampoline */
+static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
+{
+	return (void *)kretprobe_trampoline_handler(regs, &kretprobe_trampoline,
+						    (void *)regs->ARM_fp);
+}
+
+void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
+				      struct pt_regs *regs)
+{
+	ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
+	ri->fp = (void *)regs->ARM_fp;
+
+	/* Replace the return addr with trampoline addr. */
+	regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
+}
+
+int __kprobes arch_trampoline_kprobe(struct kprobe *p)
+{
+	return 0;
+}
+
+#ifdef CONFIG_THUMB2_KERNEL
+
+static struct undef_hook kprobes_thumb16_break_hook = {
+	.instr_mask	= 0xffff,
+	.instr_val	= KPROBE_THUMB16_BREAKPOINT_INSTRUCTION,
+	.cpsr_mask	= MODE_MASK,
+	.cpsr_val	= SVC_MODE,
+	.fn		= kprobe_trap_handler,
+};
+
+static struct undef_hook kprobes_thumb32_break_hook = {
+	.instr_mask	= 0xffffffff,
+	.instr_val	= KPROBE_THUMB32_BREAKPOINT_INSTRUCTION,
+	.cpsr_mask	= MODE_MASK,
+	.cpsr_val	= SVC_MODE,
+	.fn		= kprobe_trap_handler,
+};
+
+#else  /* !CONFIG_THUMB2_KERNEL */
+
+static struct undef_hook kprobes_arm_break_hook = {
+	.instr_mask	= 0x0fffffff,
+	.instr_val	= KPROBE_ARM_BREAKPOINT_INSTRUCTION,
+	.cpsr_mask	= MODE_MASK,
+	.cpsr_val	= SVC_MODE,
+	.fn		= kprobe_trap_handler,
+};
+
+#endif /* !CONFIG_THUMB2_KERNEL */
+
+int __init arch_init_kprobes(void)
+{
+	arm_probes_decode_init();
+#ifdef CONFIG_THUMB2_KERNEL
+	register_undef_hook(&kprobes_thumb16_break_hook);
+	register_undef_hook(&kprobes_thumb32_break_hook);
+#else
+	register_undef_hook(&kprobes_arm_break_hook);
+#endif
+	return 0;
+}
+
+bool arch_within_kprobe_blacklist(unsigned long addr)
+{
+	void *a = (void *)addr;
+
+	return __in_irqentry_text(addr) ||
+	       in_entry_text(addr) ||
+	       in_idmap_text(addr) ||
+	       memory_contains(__kprobes_text_start, __kprobes_text_end, a, 1);
+}