sh: Add kprobes support.

Initial support for kprobes/kretprobes for 32-bit SH platforms.

[ General cleanup and some rework for the kretprobe hash lock. -- PFM ]

Signed-off-by: Chris Smith <chris.smith@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 568 insertions, 0 deletions

diff --git a/arch/sh/kernel/kprobes.c b/arch/sh/kernel/kprobes.c
new file mode 100644
index 000000000000..c4f4a0923eb9
--- /dev/null
+++ b/arch/sh/kernel/kprobes.c
@@ -0,0 +1,568 @@
+/*
+ * Kernel probes (kprobes) for SuperH
+ *
+ * Copyright (C) 2007 Chris Smith <chris.smith@st.com>
+ * Copyright (C) 2006 Lineo Solutions, Inc.
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+#include <linux/kprobes.h>
+#include <linux/module.h>
+#include <linux/ptrace.h>
+#include <linux/preempt.h>
+#include <linux/kdebug.h>
+#include <asm/cacheflush.h>
+#include <asm/uaccess.h>
+
+DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
+DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
+
+static struct kprobe saved_current_opcode;
+static struct kprobe saved_next_opcode;
+static struct kprobe saved_next_opcode2;
+
+#define OPCODE_JMP(x)	(((x) & 0xF0FF) == 0x402b)
+#define OPCODE_JSR(x)	(((x) & 0xF0FF) == 0x400b)
+#define OPCODE_BRA(x)	(((x) & 0xF000) == 0xa000)
+#define OPCODE_BRAF(x)	(((x) & 0xF0FF) == 0x0023)
+#define OPCODE_BSR(x)	(((x) & 0xF000) == 0xb000)
+#define OPCODE_BSRF(x)	(((x) & 0xF0FF) == 0x0003)
+
+#define OPCODE_BF_S(x)	(((x) & 0xFF00) == 0x8f00)
+#define OPCODE_BT_S(x)	(((x) & 0xFF00) == 0x8d00)
+
+#define OPCODE_BF(x)	(((x) & 0xFF00) == 0x8b00)
+#define OPCODE_BT(x)	(((x) & 0xFF00) == 0x8900)
+
+#define OPCODE_RTS(x)	(((x) & 0x000F) == 0x000b)
+#define OPCODE_RTE(x)	(((x) & 0xFFFF) == 0x002b)
+
+int __kprobes arch_prepare_kprobe(struct kprobe *p)
+{
+	kprobe_opcode_t opcode = *(kprobe_opcode_t *) (p->addr);
+
+	if (OPCODE_RTE(opcode))
+		return -EFAULT;	/* Bad breakpoint */
+
+	p->opcode = opcode;
+
+	return 0;
+}
+
+void __kprobes arch_copy_kprobe(struct kprobe *p)
+{
+	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+	p->opcode = *p->addr;
+}
+
+void __kprobes arch_arm_kprobe(struct kprobe *p)
+{
+	*p->addr = BREAKPOINT_INSTRUCTION;
+	flush_icache_range((unsigned long)p->addr,
+			   (unsigned long)p->addr + sizeof(kprobe_opcode_t));
+}
+
+void __kprobes arch_disarm_kprobe(struct kprobe *p)
+{
+	*p->addr = p->opcode;
+	flush_icache_range((unsigned long)p->addr,
+			   (unsigned long)p->addr + sizeof(kprobe_opcode_t));
+}
+
+int __kprobes arch_trampoline_kprobe(struct kprobe *p)
+{
+	if (*p->addr == BREAKPOINT_INSTRUCTION)
+		return 1;
+
+	return 0;
+}
+
+/**
+ * If an illegal slot instruction exception occurs for an address
+ * containing a kprobe, remove the probe.
+ *
+ * Returns 0 if the exception was handled successfully, 1 otherwise.
+ */
+int __kprobes kprobe_handle_illslot(unsigned long pc)
+{
+	struct kprobe *p = get_kprobe((kprobe_opcode_t *) pc + 1);
+
+	if (p != NULL) {
+		printk("Warning: removing kprobe from delay slot: 0x%.8x\n",
+		       (unsigned int)pc + 2);
+		unregister_kprobe(p);
+		return 0;
+	}
+
+	return 1;
+}
+
+void __kprobes arch_remove_kprobe(struct kprobe *p)
+{
+	if (saved_next_opcode.addr != 0x0) {
+		arch_disarm_kprobe(p);
+		arch_disarm_kprobe(&saved_next_opcode);
+		saved_next_opcode.addr = 0x0;
+		saved_next_opcode.opcode = 0x0;
+
+		if (saved_next_opcode2.addr != 0x0) {
+			arch_disarm_kprobe(&saved_next_opcode2);
+			saved_next_opcode2.addr = 0x0;
+			saved_next_opcode2.opcode = 0x0;
+		}
+	}
+}
+
+static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
+{
+	kcb->prev_kprobe.kp = kprobe_running();
+	kcb->prev_kprobe.status = kcb->kprobe_status;
+}
+
+static inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
+{
+	__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
+	kcb->kprobe_status = kcb->prev_kprobe.status;
+}
+
+static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
+				      struct kprobe_ctlblk *kcb)
+{
+	__get_cpu_var(current_kprobe) = p;
+}
+
+/*
+ * Singlestep is implemented by disabling the current kprobe and setting one
+ * on the next instruction, following branches. Two probes are set if the
+ * branch is conditional.
+ */
+static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
+{
+	kprobe_opcode_t *addr = NULL;
+	saved_current_opcode.addr = (kprobe_opcode_t *) (regs->pc);
+	addr = saved_current_opcode.addr;
+
+	if (p != NULL) {
+		arch_disarm_kprobe(p);
+
+		if (OPCODE_JSR(p->opcode) || OPCODE_JMP(p->opcode)) {
+			unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
+			saved_next_opcode.addr =
+			    (kprobe_opcode_t *) regs->regs[reg_nr];
+		} else if (OPCODE_BRA(p->opcode) || OPCODE_BSR(p->opcode)) {
+			unsigned long disp = (p->opcode & 0x0FFF);
+			saved_next_opcode.addr =
+			    (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
+
+		} else if (OPCODE_BRAF(p->opcode) || OPCODE_BSRF(p->opcode)) {
+			unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
+			saved_next_opcode.addr =
+			    (kprobe_opcode_t *) (regs->pc + 4 +
+						 regs->regs[reg_nr]);
+
+		} else if (OPCODE_RTS(p->opcode)) {
+			saved_next_opcode.addr = (kprobe_opcode_t *) regs->pr;
+
+		} else if (OPCODE_BF(p->opcode) || OPCODE_BT(p->opcode)) {
+			unsigned long disp = (p->opcode & 0x00FF);
+			/* case 1 */
+			saved_next_opcode.addr = p->addr + 1;
+			/* case 2 */
+			saved_next_opcode2.addr =
+			    (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
+			saved_next_opcode2.opcode = *(saved_next_opcode2.addr);
+			arch_arm_kprobe(&saved_next_opcode2);
+
+		} else if (OPCODE_BF_S(p->opcode) || OPCODE_BT_S(p->opcode)) {
+			unsigned long disp = (p->opcode & 0x00FF);
+			/* case 1 */
+			saved_next_opcode.addr = p->addr + 2;
+			/* case 2 */
+			saved_next_opcode2.addr =
+			    (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
+			saved_next_opcode2.opcode = *(saved_next_opcode2.addr);
+			arch_arm_kprobe(&saved_next_opcode2);
+
+		} else {
+			saved_next_opcode.addr = p->addr + 1;
+		}
+
+		saved_next_opcode.opcode = *(saved_next_opcode.addr);
+		arch_arm_kprobe(&saved_next_opcode);
+	}
+}
+
+/* Called with kretprobe_lock held */
+void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
+				      struct pt_regs *regs)
+{
+	ri->ret_addr = (kprobe_opcode_t *) regs->pr;
+
+	/* Replace the return addr with trampoline addr */
+	regs->pr = (unsigned long)kretprobe_trampoline;
+}
+
+static int __kprobes kprobe_handler(struct pt_regs *regs)
+{
+	struct kprobe *p;
+	int ret = 0;
+	kprobe_opcode_t *addr = NULL;
+	struct kprobe_ctlblk *kcb;
+
+	/*
+	 * We don't want to be preempted for the entire
+	 * duration of kprobe processing
+	 */
+	preempt_disable();
+	kcb = get_kprobe_ctlblk();
+
+	addr = (kprobe_opcode_t *) (regs->pc);
+
+	/* Check we're not actually recursing */
+	if (kprobe_running()) {
+		p = get_kprobe(addr);
+		if (p) {
+			if (kcb->kprobe_status == KPROBE_HIT_SS &&
+			    *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
+				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);
+			prepare_singlestep(p, regs);
+			kcb->kprobe_status = KPROBE_REENTER;
+			return 1;
+		} else {
+			p = __get_cpu_var(current_kprobe);
+			if (p->break_handler && p->break_handler(p, regs)) {
+				goto ss_probe;
+			}
+		}
+		goto no_kprobe;
+	}
+
+	p = get_kprobe(addr);
+	if (!p) {
+		/* Not one of ours: let kernel handle it */
+		goto no_kprobe;
+	}
+
+	set_current_kprobe(p, regs, kcb);
+	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+
+	if (p->pre_handler && p->pre_handler(p, regs))
+		/* handler has already set things up, so skip ss setup */
+		return 1;
+
+      ss_probe:
+	prepare_singlestep(p, regs);
+	kcb->kprobe_status = KPROBE_HIT_SS;
+	return 1;
+
+      no_kprobe:
+	preempt_enable_no_resched();
+	return ret;
+}
+
+/*
+ * For function-return probes, init_kprobes() establishes a probepoint
+ * here. When a retprobed function returns, this probe is hit and
+ * trampoline_probe_handler() runs, calling the kretprobe's handler.
+ */
+void kretprobe_trampoline_holder(void)
+{
+	asm volatile ("kretprobe_trampoline: \n" "nop\n");
+}
+
+/*
+ * Called when we hit the probe point at kretprobe_trampoline
+ */
+int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	struct kretprobe_instance *ri = NULL;
+	struct hlist_head *head, empty_rp;
+	struct hlist_node *node, *tmp;
+	unsigned long flags, orig_ret_address = 0;
+	unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
+
+	INIT_HLIST_HEAD(&empty_rp);
+	kretprobe_hash_lock(current, &head, &flags);
+
+	/*
+	 * It is possible to have multiple instances associated with a given
+	 * task either because an multiple functions in the call path
+	 * have a return probe installed on them, and/or more then one return
+	 * return probe was registered for a target function.
+	 *
+	 * We can handle this because:
+	 *     - instances are always inserted at the head of the list
+	 *     - when multiple return probes are registered for the same
+	 *       function, the first instance's ret_addr will point to the
+	 *       real return address, and all the rest will point to
+	 *       kretprobe_trampoline
+	 */
+	hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
+		if (ri->task != current)
+			/* another task is sharing our hash bucket */
+			continue;
+
+		if (ri->rp && ri->rp->handler) {
+			__get_cpu_var(current_kprobe) = &ri->rp->kp;
+			ri->rp->handler(ri, regs);
+			__get_cpu_var(current_kprobe) = NULL;
+		}
+
+		orig_ret_address = (unsigned long)ri->ret_addr;
+		recycle_rp_inst(ri, &empty_rp);
+
+		if (orig_ret_address != trampoline_address)
+			/*
+			 * This is the real return address. Any other
+			 * instances associated with this task are for
+			 * other calls deeper on the call stack
+			 */
+			break;
+	}
+
+	kretprobe_assert(ri, orig_ret_address, trampoline_address);
+
+	regs->pc = orig_ret_address;
+	kretprobe_hash_unlock(current, &flags);
+
+	preempt_enable_no_resched();
+
+	hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
+		hlist_del(&ri->hlist);
+		kfree(ri);
+	}
+
+	return orig_ret_address;
+}
+
+static inline int post_kprobe_handler(struct pt_regs *regs)
+{
+	struct kprobe *cur = kprobe_running();
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+	kprobe_opcode_t *addr = NULL;
+	struct kprobe *p = NULL;
+
+	if (!cur)
+		return 0;
+
+	if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
+		kcb->kprobe_status = KPROBE_HIT_SSDONE;
+		cur->post_handler(cur, regs, 0);
+	}
+
+	if (saved_next_opcode.addr != 0x0) {
+		arch_disarm_kprobe(&saved_next_opcode);
+		saved_next_opcode.addr = 0x0;
+		saved_next_opcode.opcode = 0x0;
+
+		addr = saved_current_opcode.addr;
+		saved_current_opcode.addr = 0x0;
+
+		p = get_kprobe(addr);
+		arch_arm_kprobe(p);
+
+		if (saved_next_opcode2.addr != 0x0) {
+			arch_disarm_kprobe(&saved_next_opcode2);
+			saved_next_opcode2.addr = 0x0;
+			saved_next_opcode2.opcode = 0x0;
+		}
+	}
+
+	/*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();
+
+	return 1;
+}
+
+static inline 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, point the pc back to the probe address
+		 * and allow the page fault handler to continue as a
+		 * normal page fault.
+		 */
+		regs->pc = (unsigned long)cur->addr;
+		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->pc)) != NULL) {
+			regs->pc = entry->fixup;
+			return 1;
+		}
+
+		/*
+		 * fixup_exception() could not handle it,
+		 * Let do_page_fault() fix it.
+		 */
+		break;
+	default:
+		break;
+	}
+	return 0;
+}
+
+/*
+ * Wrapper routine to for handling exceptions.
+ */
+int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
+				       unsigned long val, void *data)
+{
+	struct kprobe *p = NULL;
+	struct die_args *args = (struct die_args *)data;
+	int ret = NOTIFY_DONE;
+	kprobe_opcode_t *addr = NULL;
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+	addr = (kprobe_opcode_t *) (args->regs->pc);
+	if (val == DIE_TRAP) {
+		if (!kprobe_running()) {
+			if (kprobe_handler(args->regs)) {
+				ret = NOTIFY_STOP;
+			} else {
+				/* Not a kprobe trap */
+				force_sig(SIGTRAP, current);
+			}
+		} else {
+			p = get_kprobe(addr);
+			if ((kcb->kprobe_status == KPROBE_HIT_SS) ||
+			    (kcb->kprobe_status == KPROBE_REENTER)) {
+				if (post_kprobe_handler(args->regs))
+					ret = NOTIFY_STOP;
+			} else {
+				if (kprobe_handler(args->regs)) {
+					ret = NOTIFY_STOP;
+				} else {
+					p = __get_cpu_var(current_kprobe);
+					if (p->break_handler
+					    && p->break_handler(p, args->regs))
+						ret = NOTIFY_STOP;
+				}
+			}
+		}
+	}
+
+	return ret;
+}
+
+int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	struct jprobe *jp = container_of(p, struct jprobe, kp);
+	unsigned long addr;
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+	kcb->jprobe_saved_regs = *regs;
+	kcb->jprobe_saved_r15 = regs->regs[15];
+	addr = kcb->jprobe_saved_r15;
+
+	/*
+	 * TBD: As Linus pointed out, gcc assumes that the callee
+	 * owns the argument space and could overwrite it, e.g.
+	 * tailcall optimization. So, to be absolutely safe
+	 * we also save and restore enough stack bytes to cover
+	 * the argument area.
+	 */
+	memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
+	       MIN_STACK_SIZE(addr));
+
+	regs->pc = (unsigned long)(jp->entry);
+
+	return 1;
+}
+
+void __kprobes jprobe_return(void)
+{
+	__asm("trapa #-1\n\t" "jprobe_return_end:\n\t" "nop\n\t");
+
+}
+
+int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+	u8 *addr = (u8 *) regs->pc;
+	unsigned long stack_addr = kcb->jprobe_saved_r15;
+
+	if ((addr >= (u8 *) jprobe_return)
+	    && (addr <= (u8 *) jprobe_return_end)) {
+		*regs = kcb->jprobe_saved_regs;
+
+		memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
+		       MIN_STACK_SIZE(stack_addr));
+
+		kcb->kprobe_status = KPROBE_HIT_SS;
+		return 1;
+	}
+	return 0;
+}
+
+static struct kprobe trampoline_p = {
+	.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
+	.pre_handler = trampoline_probe_handler
+};
+
+int __init arch_init_kprobes(void)
+{
+	saved_next_opcode.addr = 0x0;
+	saved_next_opcode.opcode = 0x0;
+
+	saved_current_opcode.addr = 0x0;
+	saved_current_opcode.opcode = 0x0;
+
+	saved_next_opcode2.addr = 0x0;
+	saved_next_opcode2.opcode = 0x0;
+
+	return register_kprobe(&trampoline_p);
+}