Linux-2.6.12-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!
diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
new file mode 100644
index 0000000..4f2a852
--- /dev/null
+++ b/arch/x86_64/kernel/kprobes.c
@@ -0,0 +1,631 @@
+/*
+ * Kernel Probes (KProbes)
+ * arch/x86_64/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.
+ * 2004-Oct Jim Keniston <kenistoj@us.ibm.com> and Prasanna S Panchamukhi
+ * <prasanna@in.ibm.com> adapted for x86_64
+ * 2005-Mar Roland McGrath <roland@redhat.com>
+ * Fixed to handle %rip-relative addressing mode correctly.
+ */
+
+#include <linux/config.h>
+#include <linux/kprobes.h>
+#include <linux/ptrace.h>
+#include <linux/spinlock.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/preempt.h>
+#include <linux/moduleloader.h>
+
+#include <asm/pgtable.h>
+#include <asm/kdebug.h>
+
+static DECLARE_MUTEX(kprobe_mutex);
+
+/* 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_rflags, kprobe_saved_rflags;
+static struct pt_regs jprobe_saved_regs;
+static long *jprobe_saved_rsp;
+static kprobe_opcode_t *get_insn_slot(void);
+static void free_insn_slot(kprobe_opcode_t *slot);
+void jprobe_return_end(void);
+
+/* copy of the kernel stack at the probe fire time */
+static kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];
+
+/*
+ * returns non-zero if opcode modifies the interrupt flag.
+ */
+static inline int is_IF_modifier(kprobe_opcode_t *insn)
+{
+ switch (*insn) {
+ case 0xfa: /* cli */
+ case 0xfb: /* sti */
+ case 0xcf: /* iret/iretd */
+ case 0x9d: /* popf/popfd */
+ return 1;
+ }
+
+ if (*insn >= 0x40 && *insn <= 0x4f && *++insn == 0xcf)
+ return 1;
+ return 0;
+}
+
+int arch_prepare_kprobe(struct kprobe *p)
+{
+ /* insn: must be on special executable page on x86_64. */
+ up(&kprobe_mutex);
+ p->ainsn.insn = get_insn_slot();
+ down(&kprobe_mutex);
+ if (!p->ainsn.insn) {
+ return -ENOMEM;
+ }
+ return 0;
+}
+
+/*
+ * Determine if the instruction uses the %rip-relative addressing mode.
+ * If it does, return the address of the 32-bit displacement word.
+ * If not, return null.
+ */
+static inline s32 *is_riprel(u8 *insn)
+{
+#define W(row,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf) \
+ (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
+ (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \
+ (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \
+ (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \
+ << (row % 64))
+ static const u64 onebyte_has_modrm[256 / 64] = {
+ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
+ /* ------------------------------- */
+ W(0x00, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 00 */
+ W(0x10, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 10 */
+ W(0x20, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 20 */
+ W(0x30, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0), /* 30 */
+ W(0x40, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 40 */
+ W(0x50, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 50 */
+ W(0x60, 0,0,1,1,0,0,0,0,0,1,0,1,0,0,0,0)| /* 60 */
+ W(0x70, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 70 */
+ W(0x80, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 80 */
+ W(0x90, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 90 */
+ W(0xa0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* a0 */
+ W(0xb0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* b0 */
+ W(0xc0, 1,1,0,0,1,1,1,1,0,0,0,0,0,0,0,0)| /* c0 */
+ W(0xd0, 1,1,1,1,0,0,0,0,1,1,1,1,1,1,1,1)| /* d0 */
+ W(0xe0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* e0 */
+ W(0xf0, 0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1) /* f0 */
+ /* ------------------------------- */
+ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
+ };
+ static const u64 twobyte_has_modrm[256 / 64] = {
+ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
+ /* ------------------------------- */
+ W(0x00, 1,1,1,1,0,0,0,0,0,0,0,0,0,1,0,1)| /* 0f */
+ W(0x10, 1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0)| /* 1f */
+ W(0x20, 1,1,1,1,1,0,1,0,1,1,1,1,1,1,1,1)| /* 2f */
+ W(0x30, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 3f */
+ W(0x40, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 4f */
+ W(0x50, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 5f */
+ W(0x60, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 6f */
+ W(0x70, 1,1,1,1,1,1,1,0,0,0,0,0,1,1,1,1), /* 7f */
+ W(0x80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 8f */
+ W(0x90, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 9f */
+ W(0xa0, 0,0,0,1,1,1,1,1,0,0,0,1,1,1,1,1)| /* af */
+ W(0xb0, 1,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1), /* bf */
+ W(0xc0, 1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0)| /* cf */
+ W(0xd0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* df */
+ W(0xe0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* ef */
+ W(0xf0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0) /* ff */
+ /* ------------------------------- */
+ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
+ };
+#undef W
+ int need_modrm;
+
+ /* Skip legacy instruction prefixes. */
+ while (1) {
+ switch (*insn) {
+ case 0x66:
+ case 0x67:
+ case 0x2e:
+ case 0x3e:
+ case 0x26:
+ case 0x64:
+ case 0x65:
+ case 0x36:
+ case 0xf0:
+ case 0xf3:
+ case 0xf2:
+ ++insn;
+ continue;
+ }
+ break;
+ }
+
+ /* Skip REX instruction prefix. */
+ if ((*insn & 0xf0) == 0x40)
+ ++insn;
+
+ if (*insn == 0x0f) { /* Two-byte opcode. */
+ ++insn;
+ need_modrm = test_bit(*insn, twobyte_has_modrm);
+ } else { /* One-byte opcode. */
+ need_modrm = test_bit(*insn, onebyte_has_modrm);
+ }
+
+ if (need_modrm) {
+ u8 modrm = *++insn;
+ if ((modrm & 0xc7) == 0x05) { /* %rip+disp32 addressing mode */
+ /* Displacement follows ModRM byte. */
+ return (s32 *) ++insn;
+ }
+ }
+
+ /* No %rip-relative addressing mode here. */
+ return NULL;
+}
+
+void arch_copy_kprobe(struct kprobe *p)
+{
+ s32 *ripdisp;
+ memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE);
+ ripdisp = is_riprel(p->ainsn.insn);
+ if (ripdisp) {
+ /*
+ * The copied instruction uses the %rip-relative
+ * addressing mode. Adjust the displacement for the
+ * difference between the original location of this
+ * instruction and the location of the copy that will
+ * actually be run. The tricky bit here is making sure
+ * that the sign extension happens correctly in this
+ * calculation, since we need a signed 32-bit result to
+ * be sign-extended to 64 bits when it's added to the
+ * %rip value and yield the same 64-bit result that the
+ * sign-extension of the original signed 32-bit
+ * displacement would have given.
+ */
+ s64 disp = (u8 *) p->addr + *ripdisp - (u8 *) p->ainsn.insn;
+ BUG_ON((s64) (s32) disp != disp); /* Sanity check. */
+ *ripdisp = disp;
+ }
+}
+
+void arch_remove_kprobe(struct kprobe *p)
+{
+ up(&kprobe_mutex);
+ free_insn_slot(p->ainsn.insn);
+ down(&kprobe_mutex);
+}
+
+static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs)
+{
+ *p->addr = p->opcode;
+ regs->rip = (unsigned long)p->addr;
+}
+
+static 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->rip = (unsigned long)p->addr;
+ else
+ regs->rip = (unsigned long)p->ainsn.insn;
+}
+
+/*
+ * Interrupts are disabled on entry as trap3 is an interrupt gate and they
+ * remain disabled thorough out this function.
+ */
+int kprobe_handler(struct pt_regs *regs)
+{
+ struct kprobe *p;
+ int ret = 0;
+ kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t));
+
+ /* We're in an interrupt, but this is clear and BUG()-safe. */
+ preempt_disable();
+
+ /* 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_rflags;
+ 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 (*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_rflags = kprobe_old_rflags
+ = (regs->eflags & (TF_MASK | IF_MASK));
+ if (is_IF_modifier(p->ainsn.insn))
+ kprobe_saved_rflags &= ~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 rip 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->rsp;
+ unsigned long next_rip = 0;
+ unsigned long copy_rip = (unsigned long)p->ainsn.insn;
+ unsigned long orig_rip = (unsigned long)p->addr;
+ kprobe_opcode_t *insn = p->ainsn.insn;
+
+ /*skip the REX prefix*/
+ if (*insn >= 0x40 && *insn <= 0x4f)
+ insn++;
+
+ switch (*insn) {
+ case 0x9c: /* pushfl */
+ *tos &= ~(TF_MASK | IF_MASK);
+ *tos |= kprobe_old_rflags;
+ break;
+ case 0xe8: /* call relative - Fix return addr */
+ *tos = orig_rip + (*tos - copy_rip);
+ break;
+ case 0xff:
+ if ((*insn & 0x30) == 0x10) {
+ /* call absolute, indirect */
+ /* Fix return addr; rip is correct. */
+ next_rip = regs->rip;
+ *tos = orig_rip + (*tos - copy_rip);
+ } else if (((*insn & 0x31) == 0x20) || /* jmp near, absolute indirect */
+ ((*insn & 0x31) == 0x21)) { /* jmp far, absolute indirect */
+ /* rip is correct. */
+ next_rip = regs->rip;
+ }
+ break;
+ case 0xea: /* jmp absolute -- rip is correct */
+ next_rip = regs->rip;
+ break;
+ default:
+ break;
+ }
+
+ regs->eflags &= ~TF_MASK;
+ if (next_rip) {
+ regs->rip = next_rip;
+ } else {
+ regs->rip = orig_rip + (regs->rip - copy_rip);
+ }
+}
+
+/*
+ * Interrupts are disabled on entry as trap1 is an interrupt gate and they
+ * remain disabled thoroughout this function. And we hold kprobe lock.
+ */
+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_rflags;
+
+ 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. */
+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_rflags;
+
+ unlock_kprobes();
+ preempt_enable_no_resched();
+ }
+ return 0;
+}
+
+/*
+ * Wrapper routine 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_rsp = (long *) regs->rsp;
+ addr = (unsigned long)jprobe_saved_rsp;
+ /*
+ * 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->rip = (unsigned long)(jp->entry);
+ return 1;
+}
+
+void jprobe_return(void)
+{
+ preempt_enable_no_resched();
+ asm volatile (" xchg %%rbx,%%rsp \n"
+ " int3 \n"
+ " .globl jprobe_return_end \n"
+ " jprobe_return_end: \n"
+ " nop \n"::"b"
+ (jprobe_saved_rsp):"memory");
+}
+
+int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
+{
+ u8 *addr = (u8 *) (regs->rip - 1);
+ unsigned long stack_addr = (unsigned long)jprobe_saved_rsp;
+ struct jprobe *jp = container_of(p, struct jprobe, kp);
+
+ if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
+ if ((long *)regs->rsp != jprobe_saved_rsp) {
+ struct pt_regs *saved_regs =
+ container_of(jprobe_saved_rsp, struct pt_regs, rsp);
+ printk("current rsp %p does not match saved rsp %p\n",
+ (long *)regs->rsp, jprobe_saved_rsp);
+ 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;
+}
+
+/*
+ * kprobe->ainsn.insn points to the copy of the instruction to be single-stepped.
+ * By default on x86_64, pages we get from kmalloc or vmalloc are not
+ * executable. Single-stepping an instruction on such a page yields an
+ * oops. So instead of storing the instruction copies in their respective
+ * kprobe objects, we allocate a page, map it executable, and store all the
+ * instruction copies there. (We can allocate additional pages if somebody
+ * inserts a huge number of probes.) Each page can hold up to INSNS_PER_PAGE
+ * instruction slots, each of which is MAX_INSN_SIZE*sizeof(kprobe_opcode_t)
+ * bytes.
+ */
+#define INSNS_PER_PAGE (PAGE_SIZE/(MAX_INSN_SIZE*sizeof(kprobe_opcode_t)))
+struct kprobe_insn_page {
+ struct hlist_node hlist;
+ kprobe_opcode_t *insns; /* page of instruction slots */
+ char slot_used[INSNS_PER_PAGE];
+ int nused;
+};
+
+static struct hlist_head kprobe_insn_pages;
+
+/**
+ * get_insn_slot() - Find a slot on an executable page for an instruction.
+ * We allocate an executable page if there's no room on existing ones.
+ */
+static kprobe_opcode_t *get_insn_slot(void)
+{
+ struct kprobe_insn_page *kip;
+ struct hlist_node *pos;
+
+ hlist_for_each(pos, &kprobe_insn_pages) {
+ kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
+ if (kip->nused < INSNS_PER_PAGE) {
+ int i;
+ for (i = 0; i < INSNS_PER_PAGE; i++) {
+ if (!kip->slot_used[i]) {
+ kip->slot_used[i] = 1;
+ kip->nused++;
+ return kip->insns + (i*MAX_INSN_SIZE);
+ }
+ }
+ /* Surprise! No unused slots. Fix kip->nused. */
+ kip->nused = INSNS_PER_PAGE;
+ }
+ }
+
+ /* All out of space. Need to allocate a new page. Use slot 0.*/
+ kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL);
+ if (!kip) {
+ return NULL;
+ }
+
+ /*
+ * For the %rip-relative displacement fixups to be doable, we
+ * need our instruction copy to be within +/- 2GB of any data it
+ * might access via %rip. That is, within 2GB of where the
+ * kernel image and loaded module images reside. So we allocate
+ * a page in the module loading area.
+ */
+ kip->insns = module_alloc(PAGE_SIZE);
+ if (!kip->insns) {
+ kfree(kip);
+ return NULL;
+ }
+ INIT_HLIST_NODE(&kip->hlist);
+ hlist_add_head(&kip->hlist, &kprobe_insn_pages);
+ memset(kip->slot_used, 0, INSNS_PER_PAGE);
+ kip->slot_used[0] = 1;
+ kip->nused = 1;
+ return kip->insns;
+}
+
+/**
+ * free_insn_slot() - Free instruction slot obtained from get_insn_slot().
+ */
+static void free_insn_slot(kprobe_opcode_t *slot)
+{
+ struct kprobe_insn_page *kip;
+ struct hlist_node *pos;
+
+ hlist_for_each(pos, &kprobe_insn_pages) {
+ kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
+ if (kip->insns <= slot
+ && slot < kip->insns+(INSNS_PER_PAGE*MAX_INSN_SIZE)) {
+ int i = (slot - kip->insns) / MAX_INSN_SIZE;
+ kip->slot_used[i] = 0;
+ kip->nused--;
+ if (kip->nused == 0) {
+ /*
+ * Page is no longer in use. Free it unless
+ * it's the last one. We keep the last one
+ * so as not to have to set it up again the
+ * next time somebody inserts a probe.
+ */
+ hlist_del(&kip->hlist);
+ if (hlist_empty(&kprobe_insn_pages)) {
+ INIT_HLIST_NODE(&kip->hlist);
+ hlist_add_head(&kip->hlist,
+ &kprobe_insn_pages);
+ } else {
+ module_free(NULL, kip->insns);
+ kfree(kip);
+ }
+ }
+ return;
+ }
+ }
+}
