path: root/arch/s390/kernel/kprobes.c

// 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/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>

DEFINE_PER_CPU(struct kprobe *, current_kprobe);
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);

struct kretprobe_blackpoint kretprobe_blacklist[] = { };

DEFINE_INSN_CACHE_OPS(dmainsn);

static void *alloc_dmainsn_page(void)
{
	void *page;

	page = (void *) __get_free_page(GFP_KERNEL | GFP_DMA);
	if (page)
		set_memory_x((unsigned long) page, 1);
	return page;
}

static void free_dmainsn_page(void *page)
{
	set_memory_nx((unsigned long) page, 1);
	free_page((unsigned long)page);
}

struct kprobe_insn_cache kprobe_dmainsn_slots = {
	.mutex = __MUTEX_INITIALIZER(kprobe_dmainsn_slots.mutex),
	.alloc = alloc_dmainsn_page,
	.free = free_dmainsn_page,
	.pages = LIST_HEAD_INIT(kprobe_dmainsn_slots.pages),
	.insn_size = MAX_INSN_SIZE,
};

static void copy_instruction(struct kprobe *p)
{
	unsigned long ip = (unsigned long) p->addr;
	s64 disp, new_disp;
	u64 addr, new_addr;

	if (ftrace_location(ip) == ip) {
		/*
		 * If kprobes patches the instruction that is morphed by
		 * ftrace make sure that kprobes always sees the branch
		 * "jg .+24" that skips the mcount block or the "brcl 0,0"
		 * in case of hotpatch.
		 */
		ftrace_generate_nop_insn((struct ftrace_insn *)p->ainsn.insn);
		p->ainsn.is_ftrace_insn = 1;
	} else
		memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));
	p->opcode = p->ainsn.insn[0];
	if (!probe_is_insn_relative_long(p->ainsn.insn))
		return;
	/*
	 * 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 *)&p->ainsn.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 *)&p->ainsn.insn[1] = new_disp;
}
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_dmainsn_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_dmainsn_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);

int arch_check_ftrace_location(struct kprobe *p)
{
	return 0;
}

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 ftrace_insn new_insn, *insn;
	struct kprobe *p = args->p;
	size_t len;

	new_insn.opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
	len = sizeof(new_insn.opc);
	if (!p->ainsn.is_ftrace_insn)
		goto skip_ftrace;
	len = sizeof(new_insn);
	insn = (struct ftrace_insn *) p->addr;
	if (args->arm_kprobe) {
		if (is_ftrace_nop(insn))
			new_insn.disp = KPROBE_ON_FTRACE_NOP;
		else
			new_insn.disp = KPROBE_ON_FTRACE_CALL;
	} else {
		ftrace_generate_call_insn(&new_insn, (unsigned long)p->addr);
		if (insn->disp == KPROBE_ON_FTRACE_NOP)
			ftrace_generate_nop_insn(&new_insn);
	}
skip_ftrace:
	s390_kernel_write(p->addr, &new_insn, len);
	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_