1 files changed, 571 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
new file mode 100644
index 000000000..00fafc8b2
--- /dev/null
+++ b/arch/powerpc/kernel/kprobes.c
@@ -0,0 +1,571 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Kernel Probes (KProbes)
+ *
+ * Copyright (C) IBM Corporation, 2002, 2004
+ *
+ * 2002-Oct	Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
+ *		Probes initial implementation ( includes contributions from
+ *		Rusty Russell).
+ * 2004-July	Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
+ *		interface to access function arguments.
+ * 2004-Nov	Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
+ *		for PPC64
+ */
+
+#include <linux/kprobes.h>
+#include <linux/ptrace.h>
+#include <linux/preempt.h>
+#include <linux/extable.h>
+#include <linux/kdebug.h>
+#include <linux/slab.h>
+#include <asm/code-patching.h>
+#include <asm/cacheflush.h>
+#include <asm/sstep.h>
+#include <asm/sections.h>
+#include <asm/inst.h>
+#include <linux/uaccess.h>
+
+DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
+DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
+
+struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
+
+bool arch_within_kprobe_blacklist(unsigned long addr)
+{
+	return  (addr >= (unsigned long)__kprobes_text_start &&
+		 addr < (unsigned long)__kprobes_text_end) ||
+		(addr >= (unsigned long)_stext &&
+		 addr < (unsigned long)__head_end);
+}
+
+kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
+{
+	kprobe_opcode_t *addr = NULL;
+
+#ifdef PPC64_ELF_ABI_v2
+	/* PPC64 ABIv2 needs local entry point */
+	addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
+	if (addr && !offset) {
+#ifdef CONFIG_KPROBES_ON_FTRACE
+		unsigned long faddr;
+		/*
+		 * Per livepatch.h, ftrace location is always within the first
+		 * 16 bytes of a function on powerpc with -mprofile-kernel.
+		 */
+		faddr = ftrace_location_range((unsigned long)addr,
+					      (unsigned long)addr + 16);
+		if (faddr)
+			addr = (kprobe_opcode_t *)faddr;
+		else
+#endif
+			addr = (kprobe_opcode_t *)ppc_function_entry(addr);
+	}
+#elif defined(PPC64_ELF_ABI_v1)
+	/*
+	 * 64bit powerpc ABIv1 uses function descriptors:
+	 * - Check for the dot variant of the symbol first.
+	 * - If that fails, try looking up the symbol provided.
+	 *
+	 * This ensures we always get to the actual symbol and not
+	 * the descriptor.
+	 *
+	 * Also handle <module:symbol> format.
+	 */
+	char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
+	bool dot_appended = false;
+	const char *c;
+	ssize_t ret = 0;
+	int len = 0;
+
+	if ((c = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
+		c++;
+		len = c - name;
+		memcpy(dot_name, name, len);
+	} else
+		c = name;
+
+	if (*c != '\0' && *c != '.') {
+		dot_name[len++] = '.';
+		dot_appended = true;
+	}
+	ret = strscpy(dot_name + len, c, KSYM_NAME_LEN);
+	if (ret > 0)
+		addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
+
+	/* Fallback to the original non-dot symbol lookup */
+	if (!addr && dot_appended)
+		addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
+#else
+	addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
+#endif
+
+	return addr;
+}
+
+int arch_prepare_kprobe(struct kprobe *p)
+{
+	int ret = 0;
+	struct kprobe *prev;
+	struct ppc_inst insn = ppc_inst_read((struct ppc_inst *)p->addr);
+
+	if ((unsigned long)p->addr & 0x03) {
+		printk("Attempt to register kprobe at an unaligned address\n");
+		ret = -EINVAL;
+	} else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
+		printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
+		ret = -EINVAL;
+	} else if ((unsigned long)p->addr & ~PAGE_MASK &&
+		   ppc_inst_prefixed(ppc_inst_read((struct ppc_inst *)(p->addr - 1)))) {
+		printk("Cannot register a kprobe on the second word of prefixed instruction\n");
+		ret = -EINVAL;
+	}
+	preempt_disable();
+	prev = get_kprobe(p->addr - 1);
+	preempt_enable_no_resched();
+	if (prev &&
+	    ppc_inst_prefixed(ppc_inst_read((struct ppc_inst *)prev->ainsn.insn))) {
+		printk("Cannot register a kprobe on the second word of prefixed instruction\n");
+		ret = -EINVAL;
+	}
+
+	/* insn must be on a special executable page on ppc64.  This is
+	 * not explicitly required on ppc32 (right now), but it doesn't hurt */
+	if (!ret) {
+		p->ainsn.insn = get_insn_slot();
+		if (!p->ainsn.insn)
+			ret = -ENOMEM;
+	}
+
+	if (!ret) {
+		patch_instruction((struct ppc_inst *)p->ainsn.insn, insn);
+		p->opcode = ppc_inst_val(insn);
+	}
+
+	p->ainsn.boostable = 0;
+	return ret;
+}
+NOKPROBE_SYMBOL(arch_prepare_kprobe);
+
+void arch_arm_kprobe(struct kprobe *p)
+{
+	patch_instruction((struct ppc_inst *)p->addr, ppc_inst(BREAKPOINT_INSTRUCTION));
+}
+NOKPROBE_SYMBOL(arch_arm_kprobe);
+
+void arch_disarm_kprobe(struct kprobe *p)
+{
+	patch_instruction((struct ppc_inst *)p->addr, ppc_inst(p->opcode));
+}
+NOKPROBE_SYMBOL(arch_disarm_kprobe);
+
+void arch_remove_kprobe(struct kprobe *p)
+{
+	if (p->ainsn.insn) {
+		free_insn_slot(p->ainsn.insn, 0);
+		p->ainsn.insn = NULL;
+	}
+}
+NOKPROBE_SYMBOL(arch_remove_kprobe);
+
+static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
+{
+	enable_single_step(regs);
+
+	/*
+	 * On powerpc we should single step on the original
+	 * instruction even if the probed insn is a trap
+	 * variant as values in regs could play a part in
+	 * if the trap is taken or not
+	 */
+	regs->nip = (unsigned long)p->ainsn.insn;
+}
+
+static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
+{
+	kcb->prev_kprobe.kp = kprobe_running();
+	kcb->prev_kprobe.status = kcb->kprobe_status;
+	kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
+}
+
+static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
+{
+	__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
+	kcb->kprobe_status = kcb->prev_kprobe.status;
+	kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
+}
+
+static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
+				struct kprobe_ctlblk *kcb)
+{
+	__this_cpu_write(current_kprobe, p);
+	kcb->kprobe_saved_msr = regs->msr;
+}
+
+bool arch_kprobe_on_func_entry(unsigned long offset)
+{
+#ifdef PPC64_ELF_ABI_v2
+#ifdef CONFIG_KPROBES_ON_FTRACE
+	return offset <= 16;
+#else
+	return offset <= 8;
+#endif
+#else
+	return !offset;
+#endif
+}
+
+void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
+{
+	ri->ret_addr = (kprobe_opcode_t *)regs->link;
+	ri->fp = NULL;
+
+	/* Replace the return addr with trampoline addr */
+	regs->link = (unsigned long)kretprobe_trampoline;
+}
+NOKPROBE_SYMBOL(arch_prepare_kretprobe);
+
+static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
+{
+	int ret;
+	struct ppc_inst insn = ppc_inst_read((struct ppc_inst *)p->ainsn.insn);
+
+	/* regs->nip is also adjusted if emulate_step returns 1 */
+	ret = emulate_step(regs, insn);
+	if (ret > 0) {
+		/*
+		 * Once this instruction has been boosted
+		 * successfully, set the boostable flag
+		 */
+		if (unlikely(p->ainsn.boostable == 0))
+			p->ainsn.boostable = 1;
+	} else if (ret < 0) {
+		/*
+		 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
+		 * So, we should never get here... but, its still
+		 * good to catch them, just in case...
+		 */
+		printk("Can't step on instruction %s\n", ppc_inst_as_str(insn));
+		BUG();
+	} else {
+		/*
+		 * If we haven't previously emulated this instruction, then it
+		 * can't be boosted. Note it down so we don't try to do so again.
+		 *
+		 * If, however, we had emulated this instruction in the past,
+		 * then this is just an error with the current run (for
+		 * instance, exceptions due to a load/store). We return 0 so
+		 * that this is now single-stepped, but continue to try
+		 * emulating it in subsequent probe hits.
+		 */
+		if (unlikely(p->ainsn.boostable != 1))
+			p->ainsn.boostable = -1;
+	}
+
+	return ret;
+}
+NOKPROBE_SYMBOL(try_to_emulate);
+
+int kprobe_handler(struct pt_regs *regs)
+{
+	struct kprobe *p;
+	int ret = 0;
+	unsigned int *addr = (unsigned int *)regs->nip;
+	struct kprobe_ctlblk *kcb;
+
+	if (user_mode(regs))
+		return 0;
+
+	if (!IS_ENABLED(CONFIG_BOOKE) &&
+	    (!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR)))
+		return 0;
+
+	/*
+	 * We don't want to be preempted for the entire
+	 * duration of kprobe processing
+	 */
+	preempt_disable();
+	kcb = get_kprobe_ctlblk();
+
+	p = get_kprobe(addr);
+	if (!p) {
+		unsigned int instr;
+
+		if (get_kernel_nofault(instr, addr))
+			goto no_kprobe;
+
+		if (instr != BREAKPOINT_INSTRUCTION) {
+			/*
+			 * PowerPC has multiple variants of the "trap"
+			 * instruction. If the current instruction is a
+			 * trap variant, it could belong to someone else
+			 */
+			if (is_trap(instr))
+				goto no_kprobe;
+			/*
+			 * The breakpoint instruction was removed right
+			 * after we hit it.  Another cpu has removed
+			 * either a probepoint or a debugger breakpoint
+			 * at this address.  In either case, no further
+			 * handling of this interrupt is appropriate.
+			 */
+			ret = 1;
+		}
+		/* Not one of ours: let kernel handle it */
+		goto no_kprobe;
+	}
+
+	/* Check we're not actually recursing */
+	if (kprobe_running()) {
+		kprobe_opcode_t insn = *p->ainsn.insn;
+		if (kcb->kprobe_status == KPROBE_HIT_SS && is_trap(insn)) {
+			/* Turn off 'trace' bits */
+			regs->msr &= ~MSR_SINGLESTEP;
+			regs->msr |= kcb->kprobe_saved_msr;
+			goto no_kprobe;
+		}
+
+		/*
+		 * We have reentered the kprobe_handler(), since another probe
+		 * was hit while within the handler. We here save the original
+		 * kprobes variables and just single step on the instruction of
+		 * the new probe without calling any user handlers.
+		 */
+		save_previous_kprobe(kcb);
+		set_current_kprobe(p, regs, kcb);
+		kprobes_inc_nmissed_count(p);
+		kcb->kprobe_status = KPROBE_REENTER;
+		if (p->ainsn.boostable >= 0) {
+			ret = try_to_emulate(p, regs);
+
+			if (ret > 0) {
+				restore_previous_kprobe(kcb);
+				preempt_enable_no_resched();
+				return 1;
+			}
+		}
+		prepare_singlestep(p, regs);
+		return 1;
+	}
+
+	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+	set_current_kprobe(p, regs, kcb);
+	if (p->pre_handler && p->pre_handler(p, regs)) {
+		/* handler changed execution path, so skip ss setup */
+		reset_current_kprobe();
+		preempt_enable_no_resched();
+		return 1;
+	}
+
+	if (p->ainsn.boostable >= 0) {
+		ret = try_to_emulate(p, regs);
+
+		if (ret > 0) {
+			if (p->post_handler)
+				p->post_handler(p, regs, 0);
+
+			kcb->kprobe_status = KPROBE_HIT_SSDONE;
+			reset_current_kprobe();
+			preempt_enable_no_resched();
+			return 1;
+		}
+	}
+	prepare_singlestep(p, regs);
+	kcb->kprobe_status = KPROBE_HIT_SS;
+	return 1;
+
+no_kprobe:
+	preempt_enable_no_resched();
+	return ret;
+}
+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
+ */
+asm(".global kretprobe_trampoline\n"
+	".type kretprobe_trampoline, @function\n"
+	"kretprobe_trampoline:\n"
+	"nop\n"
+	"blr\n"
+	".size kretprobe_trampoline, .-kretprobe_trampoline\n");
+
+/*
+ * Called when the probe at kretprobe trampoline is hit
+ */
+static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	unsigned long orig_ret_address;
+
+	orig_ret_address = __kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL);
+	/*
+	 * We get here through one of two paths:
+	 * 1. by taking a trap -> kprobe_handler() -> here
+	 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
+	 *
+	 * When going back through (1), we need regs->nip to be setup properly
+	 * as it is used to determine the return address from the trap.
+	 * For (2), since nip is not honoured with optprobes, we instead setup
+	 * the link register properly so that the subsequent 'blr' in
+	 * kretprobe_trampoline jumps back to the right instruction.
+	 *
+	 * For nip, we should set the address to the previous instruction since
+	 * we end up emulating it in kprobe_handler(), which increments the nip
+	 * again.
+	 */
+	regs->nip = orig_ret_address - 4;
+	regs->link = orig_ret_address;
+
+	return 0;
+}
+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.
+ */
+int kprobe_post_handler(struct pt_regs *regs)
+{
+	int len;
+	struct kprobe *cur = kprobe_running();
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+	if (!cur || user_mode(regs))
+		return 0;
+
+	len = ppc_inst_len(ppc_inst_read((struct ppc_inst *)cur->ainsn.insn));
+	/* make sure we got here for instruction we have a kprobe on */
+	if (((unsigned long)cur->ainsn.insn + len) != regs->nip)
+		return 0;
+
+	if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
+		kcb->kprobe_status = KPROBE_HIT_SSDONE;
+		cur->post_handler(cur, regs, 0);
+	}
+
+	/* Adjust nip to after the single-stepped instruction */
+	regs->nip = (unsigned long)cur->addr + len;
+	regs->msr |= kcb->kprobe_saved_msr;
+
+	/*Restore back the original saved kprobes variables and continue. */
+	if (kcb->kprobe_status == KPROBE_REENTER) {
+		restore_previous_kprobe(kcb);
+		goto out;
+	}
+	reset_current_kprobe();
+out:
+	preempt_enable_no_resched();
+
+	/*
+	 * if somebody else is singlestepping across a probe point, msr
+	 * will have DE/SE set, in which case, continue the remaining processing
+	 * of do_debug, as if this is not a probe hit.
+	 */
+	if (regs->msr & MSR_SINGLESTEP)
+		return 0;
+
+	return 1;
+}
+NOKPROBE_SYMBOL(kprobe_post_handler);
+
+int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
+{
+	struct kprobe *cur = kprobe_running();
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+	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.
+		 */
+		regs->nip = (unsigned long)cur->addr;
+		regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
+		regs->msr |= kcb->kprobe_saved_msr;
+		if (kcb->kprobe_status == KPROBE_REENTER)
+			restore_previous_kprobe(kcb);
+		else
+			reset_current_kprobe();
+		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(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 first.
+		 */
+		if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
+			return 1;
+
+		/*
+		 * In case the user-specified fault handler returned
+		 * zero, try to fix up.
+		 */
+		if ((entry = search_exception_tables(regs->nip)) != NULL) {
+			regs->nip = extable_fixup(entry);
+			return 1;
+		}
+
+		/*
+		 * fixup_exception() could not handle it,
+		 * Let do_page_fault() fix it.
+		 */
+		break;
+	default:
+		break;
+	}
+	return 0;
+}
+NOKPROBE_SYMBOL(kprobe_fault_handler);
+
+unsigned long arch_deref_entry_point(void *entry)
+{
+#ifdef PPC64_ELF_ABI_v1
+	if (!kernel_text_address((unsigned long)entry))
+		return ppc_global_function_entry(entry);
+	else
+#endif
+		return (unsigned long)entry;
+}
+NOKPROBE_SYMBOL(arch_deref_entry_point);
+
+static struct kprobe trampoline_p = {
+	.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
+	.pre_handler = trampoline_probe_handler
+};
+
+int __init arch_init_kprobes(void)
+{
+	return register_kprobe(&trampoline_p);
+}
+
+int arch_trampoline_kprobe(struct kprobe *p)
+{
+	if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
+		return 1;
+
+	return 0;
+}
+NOKPROBE_SYMBOL(arch_trampoline_kprobe);