1 files changed, 550 insertions, 0 deletions

diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
new file mode 100644
index 000000000..0f7e7a68d
--- /dev/null
+++ b/arch/s390/kernel/kprobes.c
@@ -0,0 +1,550 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ *  Kernel Probes (KProbes)
+ *
+ * Copyright IBM Corp. 2002, 2006
+ *
+ * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
+ */
+
+#include <linux/moduleloader.h>
+#include <linux/kprobes.h>
+#include <linux/ptrace.h>
+#include <linux/preempt.h>
+#include <linux/stop_machine.h>
+#include <linux/kdebug.h>
+#include <linux/uaccess.h>
+#include <linux/extable.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/hardirq.h>
+#include <linux/ftrace.h>
+#include <asm/set_memory.h>
+#include <asm/sections.h>
+#include <asm/dis.h>
+#include "entry.h"
+
+DEFINE_PER_CPU(struct kprobe *, current_kprobe);
+DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
+
+struct kretprobe_blackpoint kretprobe_blacklist[] = { };
+
+DEFINE_INSN_CACHE_OPS(s390_insn);
+
+static int insn_page_in_use;
+
+void *alloc_insn_page(void)
+{
+	void *page;
+
+	page = module_alloc(PAGE_SIZE);
+	if (!page)
+		return NULL;
+	__set_memory((unsigned long) page, 1, SET_MEMORY_RO | SET_MEMORY_X);
+	return page;
+}
+
+void free_insn_page(void *page)
+{
+	module_memfree(page);
+}
+
+static void *alloc_s390_insn_page(void)
+{
+	if (xchg(&insn_page_in_use, 1) == 1)
+		return NULL;
+	return &kprobes_insn_page;
+}
+
+static void free_s390_insn_page(void *page)
+{
+	xchg(&insn_page_in_use, 0);
+}
+
+struct kprobe_insn_cache kprobe_s390_insn_slots = {
+	.mutex = __MUTEX_INITIALIZER(kprobe_s390_insn_slots.mutex),
+	.alloc = alloc_s390_insn_page,
+	.free = free_s390_insn_page,
+	.pages = LIST_HEAD_INIT(kprobe_s390_insn_slots.pages),
+	.insn_size = MAX_INSN_SIZE,
+};
+
+static void copy_instruction(struct kprobe *p)
+{
+	kprobe_opcode_t insn[MAX_INSN_SIZE];
+	s64 disp, new_disp;
+	u64 addr, new_addr;
+	unsigned int len;
+
+	len = insn_length(*p->addr >> 8);
+	memcpy(&insn, p->addr, len);
+	p->opcode = insn[0];
+	if (probe_is_insn_relative_long(&insn[0])) {
+		/*
+		 * For pc-relative instructions in RIL-b or RIL-c format patch
+		 * the RI2 displacement field. We have already made sure that
+		 * the insn slot for the patched instruction is within the same
+		 * 2GB area as the original instruction (either kernel image or
+		 * module area). Therefore the new displacement will always fit.
+		 */
+		disp = *(s32 *)&insn[1];
+		addr = (u64)(unsigned long)p->addr;
+		new_addr = (u64)(unsigned long)p->ainsn.insn;
+		new_disp = ((addr + (disp * 2)) - new_addr) / 2;
+		*(s32 *)&insn[1] = new_disp;
+	}
+	s390_kernel_write(p->ainsn.insn, &insn, len);
+}
+NOKPROBE_SYMBOL(copy_instruction);
+
+static inline int is_kernel_addr(void *addr)
+{
+	return addr < (void *)_end;
+}
+
+static int s390_get_insn_slot(struct kprobe *p)
+{
+	/*
+	 * Get an insn slot that is within the same 2GB area like the original
+	 * instruction. That way instructions with a 32bit signed displacement
+	 * field can be patched and executed within the insn slot.
+	 */
+	p->ainsn.insn = NULL;
+	if (is_kernel_addr(p->addr))
+		p->ainsn.insn = get_s390_insn_slot();
+	else if (is_module_addr(p->addr))
+		p->ainsn.insn = get_insn_slot();
+	return p->ainsn.insn ? 0 : -ENOMEM;
+}
+NOKPROBE_SYMBOL(s390_get_insn_slot);
+
+static void s390_free_insn_slot(struct kprobe *p)
+{
+	if (!p->ainsn.insn)
+		return;
+	if (is_kernel_addr(p->addr))
+		free_s390_insn_slot(p->ainsn.insn, 0);
+	else
+		free_insn_slot(p->ainsn.insn, 0);
+	p->ainsn.insn = NULL;
+}
+NOKPROBE_SYMBOL(s390_free_insn_slot);
+
+int arch_prepare_kprobe(struct kprobe *p)
+{
+	if ((unsigned long) p->addr & 0x01)
+		return -EINVAL;
+	/* Make sure the probe isn't going on a difficult instruction */
+	if (probe_is_prohibited_opcode(p->addr))
+		return -EINVAL;
+	if (s390_get_insn_slot(p))
+		return -ENOMEM;
+	copy_instruction(p);
+	return 0;
+}
+NOKPROBE_SYMBOL(arch_prepare_kprobe);
+
+struct swap_insn_args {
+	struct kprobe *p;
+	unsigned int arm_kprobe : 1;
+};
+
+static int swap_instruction(void *data)
+{
+	struct swap_insn_args *args = data;
+	struct kprobe *p = args->p;
+	u16 opc;
+
+	opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
+	s390_kernel_write(p->addr, &opc, sizeof(opc));
+	return 0;
+}
+NOKPROBE_SYMBOL(swap_instruction);
+
+void arch_arm_kprobe(struct kprobe *p)
+{
+	struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
+
+	stop_machine_cpuslocked(swap_instruction, &args, NULL);
+}
+NOKPROBE_SYMBOL(arch_arm_kprobe);
+
+void arch_disarm_kprobe(struct kprobe *p)
+{
+	struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
+
+	stop_machine_cpuslocked(swap_instruction, &args, NULL);
+}
+NOKPROBE_SYMBOL(arch_disarm_kprobe);
+
+void arch_remove_kprobe(struct kprobe *p)
+{
+	s390_free_insn_slot(p);
+}
+NOKPROBE_SYMBOL(arch_remove_kprobe);
+
+static void enable_singlestep(struct kprobe_ctlblk *kcb,
+			      struct pt_regs *regs,
+			      unsigned long ip)
+{
+	struct per_regs per_kprobe;
+
+	/* Set up the PER control registers %cr9-%cr11 */
+	per_kprobe.control = PER_EVENT_IFETCH;
+	per_kprobe.start = ip;
+	per_kprobe.end = ip;
+
+	/* Save control regs and psw mask */
+	__ctl_store(kcb->kprobe_saved_ctl, 9, 11);
+	kcb->kprobe_saved_imask = regs->psw.mask &
+		(PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
+
+	/* Set PER control regs, turns on single step for the given address */
+	__ctl_load(per_kprobe, 9, 11);
+	regs->psw.mask |= PSW_MASK_PER;
+	regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
+	regs->psw.addr = ip;
+}
+NOKPROBE_SYMBOL(enable_singlestep);
+
+static void disable_singlestep(struct kprobe_ctlblk *kcb,
+			       struct pt_regs *regs,
+			       unsigned long ip)
+{
+	/* Restore control regs and psw mask, set new psw address */
+	__ctl_load(kcb->kprobe_saved_ctl, 9, 11);
+	regs->psw.mask &= ~PSW_MASK_PER;
+	regs->psw.mask |= kcb->kprobe_saved_imask;
+	regs->psw.addr = ip;
+}
+NOKPROBE_SYMBOL(disable_singlestep);
+
+/*
+ * Activate a kprobe by storing its pointer to current_kprobe. The
+ * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
+ * two kprobes can be active, see KPROBE_REENTER.
+ */
+static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
+{
+	kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
+	kcb->prev_kprobe.status = kcb->kprobe_status;
+	__this_cpu_write(current_kprobe, p);
+}
+NOKPROBE_SYMBOL(push_kprobe);
+
+/*
+ * Deactivate a kprobe by backing up to the previous state. If the
+ * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
+ * for any other state prev_kprobe.kp will be NULL.
+ */
+static void pop_kprobe(struct kprobe_ctlblk *kcb)
+{
+	__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
+	kcb->kprobe_status = kcb->prev_kprobe.status;
+	kcb->prev_kprobe.kp = NULL;
+}
+NOKPROBE_SYMBOL(pop_kprobe);
+
+void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
+{
+	ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
+	ri->fp = NULL;
+
+	/* Replace the return addr with trampoline addr */
+	regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
+}
+NOKPROBE_SYMBOL(arch_prepare_kretprobe);
+
+static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
+{
+	switch (kcb->kprobe_status) {
+	case KPROBE_HIT_SSDONE:
+	case KPROBE_HIT_ACTIVE:
+		kprobes_inc_nmissed_count(p);
+		break;
+	case KPROBE_HIT_SS:
+	case KPROBE_REENTER:
+	default:
+		/*
+		 * A kprobe on the code path to single step an instruction
+		 * is a BUG. The code path resides in the .kprobes.text
+		 * section and is executed with interrupts disabled.
+		 */
+		pr_err("Invalid kprobe detected.\n");
+		dump_kprobe(p);
+		BUG();
+	}
+}
+NOKPROBE_SYMBOL(kprobe_reenter_check);
+
+static int kprobe_handler(struct pt_regs *regs)
+{
+	struct kprobe_ctlblk *kcb;
+	struct kprobe *p;
+
+	/*
+	 * We want to disable preemption for the entire duration of kprobe
+	 * processing. That includes the calls to the pre/post handlers
+	 * and single stepping the kprobe instruction.
+	 */
+	preempt_disable();
+	kcb = get_kprobe_ctlblk();
+	p = get_kprobe((void *)(regs->psw.addr - 2));
+
+	if (p) {
+		if (kprobe_running()) {
+			/*
+			 * We have hit a kprobe while another is still
+			 * active. This can happen in the pre and post
+			 * handler. Single step the instruction of the
+			 * new probe but do not call any handler function
+			 * of this secondary kprobe.
+			 * push_kprobe and pop_kprobe saves and restores
+			 * the currently active kprobe.
+			 */
+			kprobe_reenter_check(kcb, p);
+			push_kprobe(kcb, p);
+			kcb->kprobe_status = KPROBE_REENTER;
+		} else {
+			/*
+			 * If we have no pre-handler or it returned 0, we
+			 * continue with single stepping. If we have a
+			 * pre-handler and it returned non-zero, it prepped
+			 * for changing execution path, so get out doing
+			 * nothing more here.
+			 */
+			push_kprobe(kcb, p);
+			kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+			if (p->pre_handler && p->pre_handler(p, regs)) {
+				pop_kprobe(kcb);
+				preempt_enable_no_resched();
+				return 1;
+			}
+			kcb->kprobe_status = KPROBE_HIT_SS;
+		}
+		enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
+		return 1;
+	} /* else:
+	   * No kprobe at this address and no active kprobe. The trap has
+	   * not been caused by a kprobe breakpoint. The race of breakpoint
+	   * vs. kprobe remove does not exist because on s390 as we use
+	   * stop_machine to arm/disarm the breakpoints.
+	   */
+	preempt_enable_no_resched();
+	return 0;
+}
+NOKPROBE_SYMBOL(kprobe_handler);
+
+/*
+ * Function return probe trampoline:
+ *	- init_kprobes() establishes a probepoint here
+ *	- When the probed function returns, this probe
+ *		causes the handlers to fire
+ */
+static void __used kretprobe_trampoline_holder(void)
+{
+	asm volatile(".global kretprobe_trampoline\n"
+		     "kretprobe_trampoline: bcr 0,0\n");
+}
+
+/*
+ * Called when the probe at kretprobe trampoline is hit
+ */
+static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	regs->psw.addr = __kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL);
+	/*
+	 * By returning a non-zero value, we are telling
+	 * kprobe_handler() that we don't want the post_handler
+	 * to run (and have re-enabled preemption)
+	 */
+	return 1;
+}
+NOKPROBE_SYMBOL(trampoline_probe_handler);
+
+/*
+ * Called after single-stepping.  p->addr is the address of the
+ * instruction whose first byte has been replaced by the "breakpoint"
+ * instruction.  To avoid the SMP problems that can occur when we
+ * temporarily put back the original opcode to single-step, we
+ * single-stepped a copy of the instruction.  The address of this
+ * copy is p->ainsn.insn.
+ */
+static void resume_execution(struct kprobe *p, struct pt_regs *regs)
+{
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+	unsigned long ip = regs->psw.addr;
+	int fixup = probe_get_fixup_type(p->ainsn.insn);
+
+	if (fixup & FIXUP_PSW_NORMAL)
+		ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
+
+	if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
+		int ilen = insn_length(p->ainsn.insn[0] >> 8);
+		if (ip - (unsigned long) p->ainsn.insn == ilen)
+			ip = (unsigned long) p->addr + ilen;
+	}
+
+	if (fixup & FIXUP_RETURN_REGISTER) {
+		int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
+		regs->gprs[reg] += (unsigned long) p->addr -
+				   (unsigned long) p->ainsn.insn;
+	}
+
+	disable_singlestep(kcb, regs, ip);
+}
+NOKPROBE_SYMBOL(resume_execution);
+
+static int post_kprobe_handler(struct pt_regs *regs)
+{
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+	struct kprobe *p = kprobe_running();
+
+	if (!p)
+		return 0;
+
+	resume_execution(p, regs);
+	if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
+		kcb->kprobe_status = KPROBE_HIT_SSDONE;
+		p->post_handler(p, regs, 0);
+	}
+	pop_kprobe(kcb);
+	preempt_enable_no_resched();
+
+	/*
+	 * if somebody else is singlestepping across a probe point, psw mask
+	 * will have PER set, in which case, continue the remaining processing
+	 * of do_single_step, as if this is not a probe hit.
+	 */
+	if (regs->psw.mask & PSW_MASK_PER)
+		return 0;
+
+	return 1;
+}
+NOKPROBE_SYMBOL(post_kprobe_handler);
+
+static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
+{
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+	struct kprobe *p = kprobe_running();
+	const struct exception_table_entry *entry;
+
+	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 nip points back to the probe address
+		 * and allow the page fault handler to continue as a
+		 * normal page fault.
+		 */
+		disable_singlestep(kcb, regs, (unsigned long) p->addr);
+		pop_kprobe(kcb);
+		preempt_enable_no_resched();
+		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(p);
+
+		/*
+		 * 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 (p->fault_handler && p->fault_handler(p, regs, trapnr))
+			return 1;
+
+		/*
+		 * In case the user-specified fault handler returned
+		 * zero, try to fix up.
+		 */
+		entry = s390_search_extables(regs->psw.addr);
+		if (entry && ex_handle(entry, regs))
+			return 1;
+
+		/*
+		 * fixup_exception() could not handle it,
+		 * Let do_page_fault() fix it.
+		 */
+		break;
+	default:
+		break;
+	}
+	return 0;
+}
+NOKPROBE_SYMBOL(kprobe_trap_handler);
+
+int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
+{
+	int ret;
+
+	if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
+		local_irq_disable();
+	ret = kprobe_trap_handler(regs, trapnr);
+	if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
+		local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
+	return ret;
+}
+NOKPROBE_SYMBOL(kprobe_fault_handler);
+
+/*
+ * Wrapper routine to for handling exceptions.
+ */
+int kprobe_exceptions_notify(struct notifier_block *self,
+			     unsigned long val, void *data)
+{
+	struct die_args *args = (struct die_args *) data;
+	struct pt_regs *regs = args->regs;
+	int ret = NOTIFY_DONE;
+
+	if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
+		local_irq_disable();
+
+	switch (val) {
+	case DIE_BPT:
+		if (kprobe_handler(regs))
+			ret = NOTIFY_STOP;
+		break;
+	case DIE_SSTEP:
+		if (post_kprobe_handler(regs))
+			ret = NOTIFY_STOP;
+		break;
+	case DIE_TRAP:
+		if (!preemptible() && kprobe_running() &&
+		    kprobe_trap_handler(regs, args->trapnr))
+			ret = NOTIFY_STOP;
+		break;
+	default:
+		break;
+	}
+
+	if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
+		local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
+
+	return ret;
+}
+NOKPROBE_SYMBOL(kprobe_exceptions_notify);
+
+static struct kprobe trampoline = {
+	.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
+	.pre_handler = trampoline_probe_handler
+};
+
+int __init arch_init_kprobes(void)
+{
+	return register_kprobe(&trampoline);
+}
+
+int arch_trampoline_kprobe(struct kprobe *p)
+{
+	return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
+}
+NOKPROBE_SYMBOL(arch_trampoline_kprobe);