summaryrefslogtreecommitdiff
path: root/arch/i386/kernel/kprobes.c
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/i386/kernel/kprobes.c
downloadconfigs-2.6.12-rc2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'arch/i386/kernel/kprobes.c')
-rw-r--r--arch/i386/kernel/kprobes.c385
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;
+}