1 files changed, 364 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
new file mode 100644
index 000000000..69bfe9688
--- /dev/null
+++ b/arch/powerpc/kernel/optprobes.c
@@ -0,0 +1,364 @@
+// 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)
+
+DEFINE_INSN_CACHE_OPS(ppc_optinsn);
+
+static bool insn_page_in_use;
+
+static void *__ppc_alloc_insn_page(void)
+{
+	if (insn_page_in_use)
+		return NULL;
+	insn_page_in_use = true;
+	return &optinsn_slot;
+}
+
+static void __ppc_free_insn_page(void *page __maybe_unused)
+{
+	insn_page_in_use = false;
+}
+
+struct kprobe_insn_cache kprobe_ppc_optinsn_slots = {
+	.mutex = __MUTEX_INITIALIZER(kprobe_ppc_optinsn_slots.mutex),
+	.pages = LIST_HEAD_INIT(kprobe_ppc_optinsn_slots.pages),
+	/* insn_size initialized later */
+	.alloc = __ppc_alloc_insn_page,
+	.free = __ppc_free_insn_page,
+	.nr_garbage = 0,
+};
+
+/*
+ * 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;
+
+	/*
+	 * 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 (unsigned long)p->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((unsigned long)p->addr))
+		return 0;
+
+	memset(&regs, 0, sizeof(struct pt_regs));
+	regs.nip = (unsigned long)p->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((struct ppc_inst *)p->ainsn.insn)) &&
+	    analyse_instr(&op, &regs,
+			  ppc_inst_read((struct ppc_inst *)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->nip = (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_ppc_optinsn_slot(op->optinsn.insn, 1);
+		op->optinsn.insn = NULL;
+	}
+}
+
+/*
+ * emulate_step() requires insn to be emulated as
+ * second parameter. Load register 'r4' with the
+ * instruction.
+ */
+void patch_imm32_load_insns(unsigned int val, kprobe_opcode_t *addr)
+{
+	/* addis r4,0,(insn)@h */
+	patch_instruction((struct ppc_inst *)addr,
+			  ppc_inst(PPC_INST_ADDIS | ___PPC_RT(4) |
+				   ((val >> 16) & 0xffff)));
+	addr++;
+
+	/* ori r4,r4,(insn)@l */
+	patch_instruction((struct ppc_inst *)addr,
+			  ppc_inst(PPC_INST_ORI | ___PPC_RA(4) |
+				   ___PPC_RS(4) | (val & 0xffff)));
+}
+
+/*
+ * Generate instructions to load provided immediate 64-bit value
+ * to register 'reg' and patch these instructions at 'addr'.
+ */
+void patch_imm64_load_insns(unsigned long val, int reg, kprobe_opcode_t *addr)
+{
+	/* lis reg,(op)@highest */
+	patch_instruction((struct ppc_inst *)addr,
+			  ppc_inst(PPC_INST_ADDIS | ___PPC_RT(reg) |
+				   ((val >> 48) & 0xffff)));
+	addr++;
+
+	/* ori reg,reg,(op)@higher */
+	patch_instruction((struct ppc_inst *)addr,
+			  ppc_inst(PPC_INST_ORI | ___PPC_RA(reg) |
+				   ___PPC_RS(reg) | ((val >> 32) & 0xffff)));
+	addr++;
+
+	/* rldicr reg,reg,32,31 */
+	patch_instruction((struct ppc_inst *)addr,
+			  ppc_inst(PPC_INST_RLDICR | ___PPC_RA(reg) |
+				   ___PPC_RS(reg) | __PPC_SH64(32) | __PPC_ME64(31)));
+	addr++;
+
+	/* oris reg,reg,(op)@h */
+	patch_instruction((struct ppc_inst *)addr,
+			  ppc_inst(PPC_INST_ORIS | ___PPC_RA(reg) |
+				   ___PPC_RS(reg) | ((val >> 16) & 0xffff)));
+	addr++;
+
+	/* ori reg,reg,(op)@l */
+	patch_instruction((struct ppc_inst *)addr,
+			  ppc_inst(PPC_INST_ORI | ___PPC_RA(reg) |
+				   ___PPC_RS(reg) | (val & 0xffff)));
+}
+
+int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
+{
+	struct ppc_inst branch_op_callback, branch_emulate_step, temp;
+	kprobe_opcode_t *op_callback_addr, *emulate_step_addr, *buff;
+	long b_offset;
+	unsigned long nip, size;
+	int rc, i;
+
+	kprobe_ppc_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
+
+	nip = can_optimize(p);
+	if (!nip)
+		return -EILSEQ;
+
+	/* Allocate instruction slot for detour buffer */
+	buff = get_ppc_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) -
+			(unsigned long)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((struct ppc_inst *)(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_imm64_load_insns((unsigned long)op, 3, buff + TMPL_OP_IDX);
+
+	/*
+	 * 2. branch to optimized_callback() and emulate_step()
+	 */
+	op_callback_addr = (kprobe_opcode_t *)ppc_kallsyms_lookup_name("optimized_callback");
+	emulate_step_addr = (kprobe_opcode_t *)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,
+			   (struct ppc_inst *)(buff + TMPL_CALL_HDLR_IDX),
+			   (unsigned long)op_callback_addr,
+			   BRANCH_SET_LINK);
+
+	rc |= create_branch(&branch_emulate_step,
+			    (struct ppc_inst *)(buff + TMPL_EMULATE_IDX),
+			    (unsigned long)emulate_step_addr,
+			    BRANCH_SET_LINK);
+
+	if (rc)
+		goto error;
+
+	patch_instruction((struct ppc_inst *)(buff + TMPL_CALL_HDLR_IDX),
+			  branch_op_callback);
+	patch_instruction((struct ppc_inst *)(buff + TMPL_EMULATE_IDX),
+			  branch_emulate_step);
+
+	/*
+	 * 3. load instruction to be emulated into relevant register, and
+	 */
+	temp = ppc_inst_read((struct ppc_inst *)p->ainsn.insn);
+	patch_imm64_load_insns(ppc_inst_as_u64(temp), 4, buff + TMPL_INSN_IDX);
+
+	/*
+	 * 4. branch back from trampoline
+	 */
+	patch_branch((struct ppc_inst *)(buff + TMPL_RET_IDX), (unsigned long)nip, 0);
+
+	flush_icache_range((unsigned long)buff,
+			   (unsigned long)(&buff[TMPL_END_IDX]));
+
+	op->optinsn.insn = buff;
+
+	return 0;
+
+error:
+	free_ppc_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)
+{
+	struct ppc_inst 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,
+			      (struct ppc_inst *)op->kp.addr,
+			      (unsigned long)op->optinsn.insn, 0);
+		patch_instruction((struct ppc_inst *)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,
+				 unsigned long addr)
+{
+	return ((unsigned long)op->kp.addr <= addr &&
+		(unsigned long)op->kp.addr + RELATIVEJUMP_SIZE > addr);
+}