arch/powerpc/kernel/optprobes.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Code for Kernel probes Jump optimization.
  *
  * Copyright 2017, Anju T, IBM Corp.
  */

 #include <linux/kprobes.h>
 #include <linux/jump_label.h>
 #include <linux/types.h>
 #include <linux/slab.h>
 #include <linux/list.h>
 #include <asm/kprobes.h>
 #include <asm/ptrace.h>
 #include <asm/cacheflush.h>
 #include <asm/code-patching.h>
 #include <asm/sstep.h>
 #include <asm/ppc-opcode.h>
 #include <asm/inst.h>

 #define TMPL_CALL_HDLR_IDX	(optprobe_template_call_handler - optprobe_template_entry)
 #define TMPL_EMULATE_IDX	(optprobe_template_call_emulate - optprobe_template_entry)
 #define TMPL_RET_IDX		(optprobe_template_ret - optprobe_template_entry)
 #define TMPL_OP_IDX		(optprobe_template_op_address - optprobe_template_entry)
 #define TMPL_INSN_IDX		(optprobe_template_insn - optprobe_template_entry)
 #define TMPL_END_IDX		(optprobe_template_end - optprobe_template_entry)

 static bool insn_page_in_use;

 void *alloc_optinsn_page(void)
 {
 	if (insn_page_in_use)
 		return NULL;
 	insn_page_in_use = true;
 	return &optinsn_slot;
 }

 void free_optinsn_page(void *page)
 {
 	insn_page_in_use = false;
 }

 /*
  * Check if we can optimize this probe. Returns NIP post-emulation if this can
  * be optimized and 0 otherwise.
  */
 static unsigned long can_optimize(struct kprobe *p)
 {
 	struct pt_regs regs;
 	struct instruction_op op;
 	unsigned long nip = 0;
 	unsigned long addr = (unsigned long)p->addr;

 	/*
 	 * kprobe placed for kretprobe during boot time
 	 * has a 'nop' instruction, which can be emulated.
 	 * So further checks can be skipped.
 	 */
 	if (p->addr == (kprobe_opcode_t *)&__kretprobe_trampoline)
 		return addr + sizeof(kprobe_opcode_t);

 	/*
 	 * We only support optimizing kernel addresses, but not
 	 * module addresses.
 	 *
 	 * FIXME: Optimize kprobes placed in module addresses.
 	 */
 	if (!is_kernel_addr(addr))
 		return 0;

 	memset(&regs, 0, sizeof(struct pt_regs));
 	regs.nip = addr;
 	regs.trap = 0x0;
 	regs.msr = MSR_KERNEL;

 	/*
 	 * Kprobe placed in conditional branch instructions are
 	 * not optimized, as we can't predict the nip prior with
 	 * dummy pt_regs and can not ensure that the return branch
 	 * from detour buffer falls in the range of address (i.e 32MB).
 	 * A branch back from trampoline is set up in the detour buffer
 	 * to the nip returned by the analyse_instr() here.
 	 *
 	 * Ensure that the instruction is not a conditional branch,
 	 * and that can be emulated.
 	 */
 	if (!is_conditional_branch(ppc_inst_read(p->ainsn.insn)) &&
 	    analyse_instr(&op, &regs, ppc_inst_read(p->ainsn.insn)) == 1) {
 		emulate_update_regs(&regs, &op);
 		nip = regs.nip;
 	}

 	return nip;
 }

 static void optimized_callback(struct optimized_kprobe *op,
 			       struct pt_regs *regs)
 {
 	/* This is possible if op is under delayed unoptimizing */
 	if (kprobe_disabled(&op->kp))
 		return;

 	preempt_disable();

 	if (kprobe_running()) {
 		kprobes_inc_nmissed_count(&op->kp);
 	} else {
 		__this_cpu_write(current_kprobe, &op->kp);
 		regs_set_return_ip(regs, (unsigned long)op->kp.addr);
 		get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
 		opt_pre_handler(&op->kp, regs);
 		__this_cpu_write(current_kprobe, NULL);
 	}

 	preempt_enable_no_resched();
 }
 NOKPROBE_SYMBOL(optimized_callback);

 void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
 {
 	if (op->optinsn.insn) {
 		free_optinsn_slot(op->optinsn.insn, 1);
 		op->optinsn.insn = NULL;
 	}
 }

 static void patch_imm32_load_insns(unsigned long val, int reg, kprobe_opcode_t *addr)
 {
 	patch_instruction(addr++, ppc_inst(PPC_RAW_LIS(reg, PPC_HI(val))));
 	patch_instruction(addr, ppc_inst(PPC_RAW_ORI(reg, reg, PPC_LO(val))));
 }

 /*
  * Generate instructions to load provided immediate 64-bit value
  * to register 'reg' and patch these instructions at 'addr'.
  */
 static void patch_imm64_load_insns(unsigned long long val, int reg, kprobe_opcode_t *addr)
 {
 	patch_instruction(addr++, ppc_inst(PPC_RAW_LIS(reg, PPC_HIGHEST(val))));
 	patch_instruction(addr++, ppc_inst(PPC_RAW_ORI(reg, reg, PPC_HIGHER(val))));
 	patch_instruction(addr++, ppc_inst(PPC_RAW_SLDI(reg, reg, 32)));
 	patch_instruction(addr++, ppc_inst(PPC_RAW_ORIS(reg, reg, PPC_HI(val))));
 	patch_instruction(addr, ppc_inst(PPC_RAW_ORI(reg, reg, PPC_LO(val))));
 }

 static void patch_imm_load_insns(unsigned long val, int reg, kprobe_opcode_t *addr)
 {
 	if (IS_ENABLED(CONFIG_PPC64))
 		patch_imm64_load_insns(val, reg, addr);
 	else
 		patch_imm32_load_insns(val, reg, addr);
 }

 int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
 {
 	ppc_inst_t branch_op_callback, branch_emulate_step, temp;
 	unsigned long op_callback_addr, emulate_step_addr;
 	kprobe_opcode_t *buff;
 	long b_offset;
 	unsigned long nip, size;
 	int rc, i;

 	nip = can_optimize(p);
 	if (!nip)
 		return -EILSEQ;

 	/* Allocate instruction slot for detour buffer */
 	buff = get_optinsn_slot();
 	if (!buff)
 		return -ENOMEM;

 	/*
 	 * OPTPROBE uses 'b' instruction to branch to optinsn.insn.
 	 *
 	 * The target address has to be relatively nearby, to permit use
 	 * of branch instruction in powerpc, because the address is specified
 	 * in an immediate field in the instruction opcode itself, ie 24 bits
 	 * in the opcode specify the address. Therefore the address should
 	 * be within 32MB on either side of the current instruction.
 	 */
 	b_offset = (unsigned long)buff - (unsigned long)p->addr;
 	if (!is_offset_in_branch_range(b_offset))
 		goto error;

 	/* Check if the return address is also within 32MB range */
 	b_offset = (unsigned long)(buff + TMPL_RET_IDX) - nip;
 	if (!is_offset_in_branch_range(b_offset))
 		goto error;

 	/* Setup template */
 	/* We can optimize this via patch_instruction_window later */
 	size = (TMPL_END_IDX * sizeof(kprobe_opcode_t)) / sizeof(int);
 	pr_devel("Copying template to %p, size %lu\n", buff, size);
 	for (i = 0; i < size; i++) {
 		rc = patch_instruction(buff + i, ppc_inst(*(optprobe_template_entry + i)));
 		if (rc < 0)
 			goto error;
 	}

 	/*
 	 * Fixup the template with instructions to:
 	 * 1. load the address of the actual probepoint
 	 */
 	patch_imm_load_insns((unsigned long)op, 3, buff + TMPL_OP_IDX);

 	/*
 	 * 2. branch to optimized_callback() and emulate_step()
 	 */
 	op_callback_addr = ppc_kallsyms_lookup_name("optimized_callback");
 	emulate_step_addr = ppc_kallsyms_lookup_name("emulate_step");
 	if (!op_callback_addr || !emulate_step_addr) {
 		WARN(1, "Unable to lookup optimized_callback()/emulate_step()\n");
 		goto error;
 	}

 	rc = create_branch(&branch_op_callback, buff + TMPL_CALL_HDLR_IDX,
 			   op_callback_addr, BRANCH_SET_LINK);

 	rc |= create_branch(&branch_emulate_step, buff + TMPL_EMULATE_IDX,
 			    emulate_step_addr, BRANCH_SET_LINK);

 	if (rc)
 		goto error;

 	patch_instruction(buff + TMPL_CALL_HDLR_IDX, branch_op_callback);
 	patch_instruction(buff + TMPL_EMULATE_IDX, branch_emulate_step);

 	/*
 	 * 3. load instruction to be emulated into relevant register, and
 	 */
 	temp = ppc_inst_read(p->ainsn.insn);
 	patch_imm_load_insns(ppc_inst_as_ulong(temp), 4, buff + TMPL_INSN_IDX);

 	/*
 	 * 4. branch back from trampoline
 	 */
 	patch_branch(buff + TMPL_RET_IDX, nip, 0);

 	flush_icache_range((unsigned long)buff, (unsigned long)(&buff[TMPL_END_IDX]));

 	op->optinsn.insn = buff;

 	return 0;

 error:
 	free_optinsn_slot(buff, 0);
 	return -ERANGE;

 }

 int arch_prepared_optinsn(struct arch_optimized_insn *optinsn)
 {
 	return optinsn->insn != NULL;
 }

 /*
  * On powerpc, Optprobes always replaces one instruction (4 bytes
  * aligned and 4 bytes long). It is impossible to encounter another
  * kprobe in this address range. So always return 0.
  */
 int arch_check_optimized_kprobe(struct optimized_kprobe *op)
 {
 	return 0;
 }

 void arch_optimize_kprobes(struct list_head *oplist)
 {
 	ppc_inst_t instr;
 	struct optimized_kprobe *op;
 	struct optimized_kprobe *tmp;

 	list_for_each_entry_safe(op, tmp, oplist, list) {
 		/*
 		 * Backup instructions which will be replaced
 		 * by jump address
 		 */
 		memcpy(op->optinsn.copied_insn, op->kp.addr, RELATIVEJUMP_SIZE);
 		create_branch(&instr, op->kp.addr, (unsigned long)op->optinsn.insn, 0);
 		patch_instruction(op->kp.addr, instr);
 		list_del_init(&op->list);
 	}
 }

 void arch_unoptimize_kprobe(struct optimized_kprobe *op)
 {
 	arch_arm_kprobe(&op->kp);
 }

 void arch_unoptimize_kprobes(struct list_head *oplist, struct list_head *done_list)
 {
 	struct optimized_kprobe *op;
 	struct optimized_kprobe *tmp;

 	list_for_each_entry_safe(op, tmp, oplist, list) {
 		arch_unoptimize_kprobe(op);
 		list_move(&op->list, done_list);
 	}
 }

 int arch_within_optimized_kprobe(struct optimized_kprobe *op, kprobe_opcode_t *addr)
 {
 	return (op->kp.addr <= addr &&
 		op->kp.addr + (RELATIVEJUMP_SIZE / sizeof(kprobe_opcode_t)) > addr);
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* Code for Kernel probes Jump optimization.
	*
	* Copyright 2017, Anju T, IBM Corp.
	*/

	#include <linux/kprobes.h>
	#include <linux/jump_label.h>
	#include <linux/types.h>
	#include <linux/slab.h>
	#include <linux/list.h>
	#include <asm/kprobes.h>
	#include <asm/ptrace.h>
	#include <asm/cacheflush.h>
	#include <asm/code-patching.h>
	#include <asm/sstep.h>
	#include <asm/ppc-opcode.h>
	#include <asm/inst.h>

	#define TMPL_CALL_HDLR_IDX (optprobe_template_call_handler - optprobe_template_entry)
	#define TMPL_EMULATE_IDX (optprobe_template_call_emulate - optprobe_template_entry)
	#define TMPL_RET_IDX (optprobe_template_ret - optprobe_template_entry)
	#define TMPL_OP_IDX (optprobe_template_op_address - optprobe_template_entry)
	#define TMPL_INSN_IDX (optprobe_template_insn - optprobe_template_entry)
	#define TMPL_END_IDX (optprobe_template_end - optprobe_template_entry)

	static bool insn_page_in_use;

	void *alloc_optinsn_page(void)
	{
	if (insn_page_in_use)
	return NULL;
	insn_page_in_use = true;
	return &optinsn_slot;
	}

	void free_optinsn_page(void *page)
	{
	insn_page_in_use = false;
	}

	/*
	* Check if we can optimize this probe. Returns NIP post-emulation if this can
	* be optimized and 0 otherwise.
	*/
	static unsigned long can_optimize(struct kprobe *p)
	{
	struct pt_regs regs;
	struct instruction_op op;
	unsigned long nip = 0;
	unsigned long addr = (unsigned long)p->addr;

	/*
	* kprobe placed for kretprobe during boot time
	* has a 'nop' instruction, which can be emulated.
	* So further checks can be skipped.
	*/
	if (p->addr == (kprobe_opcode_t *)&__kretprobe_trampoline)
	return addr + sizeof(kprobe_opcode_t);

	/*
	* We only support optimizing kernel addresses, but not
	* module addresses.
	*
	* FIXME: Optimize kprobes placed in module addresses.
	*/
	if (!is_kernel_addr(addr))
	return 0;

	memset(&regs, 0, sizeof(struct pt_regs));
	regs.nip = addr;
	regs.trap = 0x0;
	regs.msr = MSR_KERNEL;

	/*
	* Kprobe placed in conditional branch instructions are
	* not optimized, as we can't predict the nip prior with
	* dummy pt_regs and can not ensure that the return branch
	* from detour buffer falls in the range of address (i.e 32MB).
	* A branch back from trampoline is set up in the detour buffer
	* to the nip returned by the analyse_instr() here.
	*
	* Ensure that the instruction is not a conditional branch,
	* and that can be emulated.
	*/
	if (!is_conditional_branch(ppc_inst_read(p->ainsn.insn)) &&
	analyse_instr(&op, &regs, ppc_inst_read(p->ainsn.insn)) == 1) {
	emulate_update_regs(&regs, &op);
	nip = regs.nip;
	}

	return nip;
	}

	static void optimized_callback(struct optimized_kprobe *op,
	struct pt_regs *regs)
	{
	/* This is possible if op is under delayed unoptimizing */
	if (kprobe_disabled(&op->kp))
	return;

	preempt_disable();

	if (kprobe_running()) {
	kprobes_inc_nmissed_count(&op->kp);
	} else {
	__this_cpu_write(current_kprobe, &op->kp);
	regs_set_return_ip(regs, (unsigned long)op->kp.addr);
	get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
	opt_pre_handler(&op->kp, regs);
	__this_cpu_write(current_kprobe, NULL);
	}

	preempt_enable_no_resched();
	}
	NOKPROBE_SYMBOL(optimized_callback);

	void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
	{
	if (op->optinsn.insn) {
	free_optinsn_slot(op->optinsn.insn, 1);
	op->optinsn.insn = NULL;
	}
	}

	static void patch_imm32_load_insns(unsigned long val, int reg, kprobe_opcode_t *addr)
	{
	patch_instruction(addr++, ppc_inst(PPC_RAW_LIS(reg, PPC_HI(val))));
	patch_instruction(addr, ppc_inst(PPC_RAW_ORI(reg, reg, PPC_LO(val))));
	}

	/*
	* Generate instructions to load provided immediate 64-bit value
	* to register 'reg' and patch these instructions at 'addr'.
	*/
	static void patch_imm64_load_insns(unsigned long long val, int reg, kprobe_opcode_t *addr)
	{
	patch_instruction(addr++, ppc_inst(PPC_RAW_LIS(reg, PPC_HIGHEST(val))));
	patch_instruction(addr++, ppc_inst(PPC_RAW_ORI(reg, reg, PPC_HIGHER(val))));
	patch_instruction(addr++, ppc_inst(PPC_RAW_SLDI(reg, reg, 32)));
	patch_instruction(addr++, ppc_inst(PPC_RAW_ORIS(reg, reg, PPC_HI(val))));
	patch_instruction(addr, ppc_inst(PPC_RAW_ORI(reg, reg, PPC_LO(val))));
	}

	static void patch_imm_load_insns(unsigned long val, int reg, kprobe_opcode_t *addr)
	{
	if (IS_ENABLED(CONFIG_PPC64))
	patch_imm64_load_insns(val, reg, addr);
	else
	patch_imm32_load_insns(val, reg, addr);
	}

	int arch_prepare_optimized_kprobe(struct optimized_kprobe op, struct kprobe p)
	{
	ppc_inst_t branch_op_callback, branch_emulate_step, temp;
	unsigned long op_callback_addr, emulate_step_addr;
	kprobe_opcode_t *buff;
	long b_offset;
	unsigned long nip, size;
	int rc, i;

	nip = can_optimize(p);
	if (!nip)
	return -EILSEQ;

	/* Allocate instruction slot for detour buffer */
	buff = get_optinsn_slot();
	if (!buff)
	return -ENOMEM;

	/*
	* OPTPROBE uses 'b' instruction to branch to optinsn.insn.
	*
	* The target address has to be relatively nearby, to permit use
	* of branch instruction in powerpc, because the address is specified
	* in an immediate field in the instruction opcode itself, ie 24 bits
	* in the opcode specify the address. Therefore the address should
	* be within 32MB on either side of the current instruction.
	*/
	b_offset = (unsigned long)buff - (unsigned long)p->addr;
	if (!is_offset_in_branch_range(b_offset))
	goto error;

	/* Check if the return address is also within 32MB range */
	b_offset = (unsigned long)(buff + TMPL_RET_IDX) - nip;
	if (!is_offset_in_branch_range(b_offset))
	goto error;

	/* Setup template */
	/* We can optimize this via patch_instruction_window later */
	size = (TMPL_END_IDX * sizeof(kprobe_opcode_t)) / sizeof(int);
	pr_devel("Copying template to %p, size %lu\n", buff, size);
	for (i = 0; i < size; i++) {
	rc = patch_instruction(buff + i, ppc_inst(*(optprobe_template_entry + i)));
	if (rc < 0)
	goto error;
	}

	/*
	* Fixup the template with instructions to:
	* 1. load the address of the actual probepoint
	*/
	patch_imm_load_insns((unsigned long)op, 3, buff + TMPL_OP_IDX);

	/*
	* 2. branch to optimized_callback() and emulate_step()
	*/
	op_callback_addr = ppc_kallsyms_lookup_name("optimized_callback");
	emulate_step_addr = ppc_kallsyms_lookup_name("emulate_step");
	if (!op_callback_addr \|\| !emulate_step_addr) {
	WARN(1, "Unable to lookup optimized_callback()/emulate_step()\n");
	goto error;
	}

	rc = create_branch(&branch_op_callback, buff + TMPL_CALL_HDLR_IDX,
	op_callback_addr, BRANCH_SET_LINK);

	rc \|= create_branch(&branch_emulate_step, buff + TMPL_EMULATE_IDX,
	emulate_step_addr, BRANCH_SET_LINK);

	if (rc)
	goto error;

	patch_instruction(buff + TMPL_CALL_HDLR_IDX, branch_op_callback);
	patch_instruction(buff + TMPL_EMULATE_IDX, branch_emulate_step);

	/*
	* 3. load instruction to be emulated into relevant register, and
	*/
	temp = ppc_inst_read(p->ainsn.insn);
	patch_imm_load_insns(ppc_inst_as_ulong(temp), 4, buff + TMPL_INSN_IDX);

	/*
	* 4. branch back from trampoline
	*/
	patch_branch(buff + TMPL_RET_IDX, nip, 0);

	flush_icache_range((unsigned long)buff, (unsigned long)(&buff[TMPL_END_IDX]));

	op->optinsn.insn = buff;

	return 0;

	error:
	free_optinsn_slot(buff, 0);
	return -ERANGE;

	}

	int arch_prepared_optinsn(struct arch_optimized_insn *optinsn)
	{
	return optinsn->insn != NULL;
	}

	/*
	* On powerpc, Optprobes always replaces one instruction (4 bytes
	* aligned and 4 bytes long). It is impossible to encounter another
	* kprobe in this address range. So always return 0.
	*/
	int arch_check_optimized_kprobe(struct optimized_kprobe *op)
	{
	return 0;
	}

	void arch_optimize_kprobes(struct list_head *oplist)
	{
	ppc_inst_t instr;
	struct optimized_kprobe *op;
	struct optimized_kprobe *tmp;

	list_for_each_entry_safe(op, tmp, oplist, list) {
	/*
	* Backup instructions which will be replaced
	* by jump address
	*/
	memcpy(op->optinsn.copied_insn, op->kp.addr, RELATIVEJUMP_SIZE);
	create_branch(&instr, op->kp.addr, (unsigned long)op->optinsn.insn, 0);
	patch_instruction(op->kp.addr, instr);
	list_del_init(&op->list);
	}
	}

	void arch_unoptimize_kprobe(struct optimized_kprobe *op)
	{
	arch_arm_kprobe(&op->kp);
	}

	void arch_unoptimize_kprobes(struct list_head oplist, struct list_head done_list)
	{
	struct optimized_kprobe *op;
	struct optimized_kprobe *tmp;

	list_for_each_entry_safe(op, tmp, oplist, list) {
	arch_unoptimize_kprobe(op);
	list_move(&op->list, done_list);
	}
	}

	int arch_within_optimized_kprobe(struct optimized_kprobe op, kprobe_opcode_t addr)
	{
	return (op->kp.addr <= addr &&
	op->kp.addr + (RELATIVEJUMP_SIZE / sizeof(kprobe_opcode_t)) > addr);
	}