1 files changed, 385 insertions, 0 deletions

diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
new file mode 100644
index 00000000000..67168165924
--- /dev/null
+++ b/arch/i386/kernel/kprobes.c
@@ -0,0 +1,385 @@
+/*
+ *  Kernel Probes (KProbes)
+ *  arch/i386/kernel/kprobes.c
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * 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.
+ */
+
+#include <linux/config.h>
+#include <linux/kprobes.h>
+#include <linux/ptrace.h>
+#include <linux/spinlock.h>
+#include <linux/preempt.h>
+#include <asm/kdebug.h>
+#include <asm/desc.h>
+
+/* kprobe_status settings */
+#define KPROBE_HIT_ACTIVE	0x00000001
+#define KPROBE_HIT_SS		0x00000002
+
+static struct kprobe *current_kprobe;
+static unsigned long kprobe_status, kprobe_old_eflags, kprobe_saved_eflags;
+static struct pt_regs jprobe_saved_regs;
+static long *jprobe_saved_esp;
+/* copy of the kernel stack at the probe fire time */
+static kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];
+void jprobe_return_end(void);
+
+/*
+ * returns non-zero if opcode modifies the interrupt flag.
+ */
+static inline int is_IF_modifier(kprobe_opcode_t opcode)
+{
+	switch (opcode) {
+	case 0xfa:		/* cli */
+	case 0xfb:		/* sti */
+	case 0xcf:		/* iret/iretd */
+	case 0x9d:		/* popf/popfd */
+		return 1;
+	}
+	return 0;
+}
+
+int arch_prepare_kprobe(struct kprobe *p)
+{
+	return 0;
+}
+
+void arch_copy_kprobe(struct kprobe *p)
+{
+	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+}
+
+void arch_remove_kprobe(struct kprobe *p)
+{
+}
+
+static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs)
+{
+	*p->addr = p->opcode;
+	regs->eip = (unsigned long)p->addr;
+}
+
+static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
+{
+	regs->eflags |= TF_MASK;
+	regs->eflags &= ~IF_MASK;
+	/*single step inline if the instruction is an int3*/
+	if (p->opcode == BREAKPOINT_INSTRUCTION)
+		regs->eip = (unsigned long)p->addr;
+	else
+		regs->eip = (unsigned long)&p->ainsn.insn;
+}
+
+/*
+ * Interrupts are disabled on entry as trap3 is an interrupt gate and they
+ * remain disabled thorough out this function.
+ */
+static int kprobe_handler(struct pt_regs *regs)
+{
+	struct kprobe *p;
+	int ret = 0;
+	kprobe_opcode_t *addr = NULL;
+	unsigned long *lp;
+
+	/* We're in an interrupt, but this is clear and BUG()-safe. */
+	preempt_disable();
+	/* Check if the application is using LDT entry for its code segment and
+	 * calculate the address by reading the base address from the LDT entry.
+	 */
+	if ((regs->xcs & 4) && (current->mm)) {
+		lp = (unsigned long *) ((unsigned long)((regs->xcs >> 3) * 8)
+					+ (char *) current->mm->context.ldt);
+		addr = (kprobe_opcode_t *) (get_desc_base(lp) + regs->eip -
+						sizeof(kprobe_opcode_t));
+	} else {
+		addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
+	}
+	/* Check we're not actually recursing */
+	if (kprobe_running()) {
+		/* We *are* holding lock here, so this is safe.
+		   Disarm the probe we just hit, and ignore it. */
+		p = get_kprobe(addr);
+		if (p) {
+			if (kprobe_status == KPROBE_HIT_SS) {
+				regs->eflags &= ~TF_MASK;
+				regs->eflags |= kprobe_saved_eflags;
+				unlock_kprobes();
+				goto no_kprobe;
+			}
+			disarm_kprobe(p, regs);
+			ret = 1;
+		} else {
+			p = current_kprobe;
+			if (p->break_handler && p->break_handler(p, regs)) {
+				goto ss_probe;
+			}
+		}
+		/* If it's not ours, can't be delete race, (we hold lock). */
+		goto no_kprobe;
+	}
+
+	lock_kprobes();
+	p = get_kprobe(addr);
+	if (!p) {
+		unlock_kprobes();
+		if (regs->eflags & VM_MASK) {
+			/* We are in virtual-8086 mode. Return 0 */
+			goto no_kprobe;
+		}
+
+		if (*addr != BREAKPOINT_INSTRUCTION) {
+			/*
+			 * 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;
+	}
+
+	kprobe_status = KPROBE_HIT_ACTIVE;
+	current_kprobe = p;
+	kprobe_saved_eflags = kprobe_old_eflags
+	    = (regs->eflags & (TF_MASK | IF_MASK));
+	if (is_IF_modifier(p->opcode))
+		kprobe_saved_eflags &= ~IF_MASK;
+
+	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);
+	kprobe_status = KPROBE_HIT_SS;
+	return 1;
+
+no_kprobe:
+	preempt_enable_no_resched();
+	return ret;
+}
+
+/*
+ * Called after single-stepping.  p->addr is the address of the
+ * instruction whose first byte has been replaced by the "int 3"
+ * 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.
+ *
+ * This function prepares to return from the post-single-step
+ * interrupt.  We have to fix up the stack as follows:
+ *
+ * 0) Except in the case of absolute or indirect jump or call instructions,
+ * the new eip is relative to the copied instruction.  We need to make
+ * it relative to the original instruction.
+ *
+ * 1) If the single-stepped instruction was pushfl, then the TF and IF
+ * flags are set in the just-pushed eflags, and may need to be cleared.
+ *
+ * 2) If the single-stepped instruction was a call, the return address
+ * that is atop the stack is the address following the copied instruction.
+ * We need to make it the address following the original instruction.
+ */
+static void resume_execution(struct kprobe *p, struct pt_regs *regs)
+{
+	unsigned long *tos = (unsigned long *)&regs->esp;
+	unsigned long next_eip = 0;
+	unsigned long copy_eip = (unsigned long)&p->ainsn.insn;
+	unsigned long orig_eip = (unsigned long)p->addr;
+
+	switch (p->ainsn.insn[0]) {
+	case 0x9c:		/* pushfl */
+		*tos &= ~(TF_MASK | IF_MASK);
+		*tos |= kprobe_old_eflags;
+		break;
+	case 0xe8:		/* call relative - Fix return addr */
+		*tos = orig_eip + (*tos - copy_eip);
+		break;
+	case 0xff:
+		if ((p->ainsn.insn[1] & 0x30) == 0x10) {
+			/* call absolute, indirect */
+			/* Fix return addr; eip is correct. */
+			next_eip = regs->eip;
+			*tos = orig_eip + (*tos - copy_eip);
+		} else if (((p->ainsn.insn[1] & 0x31) == 0x20) ||	/* jmp near, absolute indirect */
+			   ((p->ainsn.insn[1] & 0x31) == 0x21)) {	/* jmp far, absolute indirect */
+			/* eip is correct. */
+			next_eip = regs->eip;
+		}
+		break;
+	case 0xea:		/* jmp absolute -- eip is correct */
+		next_eip = regs->eip;
+		break;
+	default:
+		break;
+	}
+
+	regs->eflags &= ~TF_MASK;
+	if (next_eip) {
+		regs->eip = next_eip;
+	} else {
+		regs->eip = orig_eip + (regs->eip - copy_eip);
+	}
+}
+
+/*
+ * Interrupts are disabled on entry as trap1 is an interrupt gate and they
+ * remain disabled thoroughout this function.  And we hold kprobe lock.
+ */
+static inline int post_kprobe_handler(struct pt_regs *regs)
+{
+	if (!kprobe_running())
+		return 0;
+
+	if (current_kprobe->post_handler)
+		current_kprobe->post_handler(current_kprobe, regs, 0);
+
+	resume_execution(current_kprobe, regs);
+	regs->eflags |= kprobe_saved_eflags;
+
+	unlock_kprobes();
+	preempt_enable_no_resched();
+
+	/*
+	 * if somebody else is singlestepping across a probe point, eflags
+	 * will have TF set, in which case, continue the remaining processing
+	 * of do_debug, as if this is not a probe hit.
+	 */
+	if (regs->eflags & TF_MASK)
+		return 0;
+
+	return 1;
+}
+
+/* Interrupts disabled, kprobe_lock held. */
+static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
+{
+	if (current_kprobe->fault_handler
+	    && current_kprobe->fault_handler(current_kprobe, regs, trapnr))
+		return 1;
+
+	if (kprobe_status & KPROBE_HIT_SS) {
+		resume_execution(current_kprobe, regs);
+		regs->eflags |= kprobe_old_eflags;
+
+		unlock_kprobes();
+		preempt_enable_no_resched();
+	}
+	return 0;
+}
+
+/*
+ * Wrapper routine to for handling exceptions.
+ */
+int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
+			     void *data)
+{
+	struct die_args *args = (struct die_args *)data;
+	switch (val) {
+	case DIE_INT3:
+		if (kprobe_handler(args->regs))
+			return NOTIFY_STOP;
+		break;
+	case DIE_DEBUG:
+		if (post_kprobe_handler(args->regs))
+			return NOTIFY_STOP;
+		break;
+	case DIE_GPF:
+		if (kprobe_running() &&
+		    kprobe_fault_handler(args->regs, args->trapnr))
+			return NOTIFY_STOP;
+		break;
+	case DIE_PAGE_FAULT:
+		if (kprobe_running() &&
+		    kprobe_fault_handler(args->regs, args->trapnr))
+			return NOTIFY_STOP;
+		break;
+	default:
+		break;
+	}
+	return NOTIFY_DONE;
+}
+
+int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	struct jprobe *jp = container_of(p, struct jprobe, kp);
+	unsigned long addr;
+
+	jprobe_saved_regs = *regs;
+	jprobe_saved_esp = &regs->esp;
+	addr = (unsigned long)jprobe_saved_esp;
+
+	/*
+	 * 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(jprobes_stack, (kprobe_opcode_t *) addr, MIN_STACK_SIZE(addr));
+	regs->eflags &= ~IF_MASK;
+	regs->eip = (unsigned long)(jp->entry);
+	return 1;
+}
+
+void jprobe_return(void)
+{
+	preempt_enable_no_resched();
+	asm volatile ("       xchgl   %%ebx,%%esp     \n"
+		      "       int3			\n"
+		      "       .globl jprobe_return_end	\n"
+		      "       jprobe_return_end:	\n"
+		      "       nop			\n"::"b"
+		      (jprobe_saved_esp):"memory");
+}
+
+int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	u8 *addr = (u8 *) (regs->eip - 1);
+	unsigned long stack_addr = (unsigned long)jprobe_saved_esp;
+	struct jprobe *jp = container_of(p, struct jprobe, kp);
+
+	if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
+		if (&regs->esp != jprobe_saved_esp) {
+			struct pt_regs *saved_regs =
+			    container_of(jprobe_saved_esp, struct pt_regs, esp);
+			printk("current esp %p does not match saved esp %p\n",
+			       &regs->esp, jprobe_saved_esp);
+			printk("Saved registers for jprobe %p\n", jp);
+			show_registers(saved_regs);
+			printk("Current registers\n");
+			show_registers(regs);
+			BUG();
+		}
+		*regs = jprobe_saved_regs;
+		memcpy((kprobe_opcode_t *) stack_addr, jprobes_stack,
+		       MIN_STACK_SIZE(stack_addr));
+		return 1;
+	}
+	return 0;
+}