--- /dev/null
+/*
+ * Kernel Probes Jump Optimization (Optprobes)
+ *
+ * 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
+ * Copyright (C) Hitachi Ltd., 2012
+ */
+#include <linux/kprobes.h>
+#include <linux/ptrace.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/hardirq.h>
+#include <linux/preempt.h>
+#include <linux/module.h>
+#include <linux/kdebug.h>
+#include <linux/kallsyms.h>
+#include <linux/ftrace.h>
+
+#include <asm/cacheflush.h>
+#include <asm/desc.h>
+#include <asm/pgtable.h>
+#include <asm/uaccess.h>
+#include <asm/alternative.h>
+#include <asm/insn.h>
+#include <asm/debugreg.h>
+
+#include "common.h"
+
+unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr)
+{
+ struct optimized_kprobe *op;
+ struct kprobe *kp;
+ long offs;
+ int i;
+
+ for (i = 0; i < RELATIVEJUMP_SIZE; i++) {
+ kp = get_kprobe((void *)addr - i);
+ /* This function only handles jump-optimized kprobe */
+ if (kp && kprobe_optimized(kp)) {
+ op = container_of(kp, struct optimized_kprobe, kp);
+ /* If op->list is not empty, op is under optimizing */
+ if (list_empty(&op->list))
+ goto found;
+ }
+ }
+
+ return addr;
+found:
+ /*
+ * If the kprobe can be optimized, original bytes which can be
+ * overwritten by jump destination address. In this case, original
+ * bytes must be recovered from op->optinsn.copied_insn buffer.
+ */
+ memcpy(buf, (void *)addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+ if (addr == (unsigned long)kp->addr) {
+ buf[0] = kp->opcode;
+ memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
+ } else {
+ offs = addr - (unsigned long)kp->addr - 1;
+ memcpy(buf, op->optinsn.copied_insn + offs, RELATIVE_ADDR_SIZE - offs);
+ }
+
+ return (unsigned long)buf;
+}
+
+/* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */
+static void synthesize_set_arg1(kprobe_opcode_t *addr, unsigned long val)
+{
+#ifdef CONFIG_X86_64
+ *addr++ = 0x48;
+ *addr++ = 0xbf;
+#else
+ *addr++ = 0xb8;
+#endif
+ *(unsigned long *)addr = val;
+}
+
+asm (
+ ".global optprobe_template_entry\n"
+ "optprobe_template_entry:\n"
+#ifdef CONFIG_X86_64
+ /* We don't bother saving the ss register */
+ " pushq %rsp\n"
+ " pushfq\n"
+ SAVE_REGS_STRING
+ " movq %rsp, %rsi\n"
+ ".global optprobe_template_val\n"
+ "optprobe_template_val:\n"
+ ASM_NOP5
+ ASM_NOP5
+ ".global optprobe_template_call\n"
+ "optprobe_template_call:\n"
+ ASM_NOP5
+ /* Move flags to rsp */
+ " movq 144(%rsp), %rdx\n"
+ " movq %rdx, 152(%rsp)\n"
+ RESTORE_REGS_STRING
+ /* Skip flags entry */
+ " addq $8, %rsp\n"
+ " popfq\n"
+#else /* CONFIG_X86_32 */
+ " pushf\n"
+ SAVE_REGS_STRING
+ " movl %esp, %edx\n"
+ ".global optprobe_template_val\n"
+ "optprobe_template_val:\n"
+ ASM_NOP5
+ ".global optprobe_template_call\n"
+ "optprobe_template_call:\n"
+ ASM_NOP5
+ RESTORE_REGS_STRING
+ " addl $4, %esp\n" /* skip cs */
+ " popf\n"
+#endif
+ ".global optprobe_template_end\n"
+ "optprobe_template_end:\n");
+
+#define TMPL_MOVE_IDX \
+ ((long)&optprobe_template_val - (long)&optprobe_template_entry)
+#define TMPL_CALL_IDX \
+ ((long)&optprobe_template_call - (long)&optprobe_template_entry)
+#define TMPL_END_IDX \
+ ((long)&optprobe_template_end - (long)&optprobe_template_entry)
+
+#define INT3_SIZE sizeof(kprobe_opcode_t)
+
+/* Optimized kprobe call back function: called from optinsn */
+static void
+optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
+{
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+ unsigned long flags;
+
+ /* This is possible if op is under delayed unoptimizing */
+ if (kprobe_disabled(&op->kp))
+ return;
+
+ local_irq_save(flags);
+ if (kprobe_running()) {
+ kprobes_inc_nmissed_count(&op->kp);
+ } else {
+ /* Save skipped registers */
+#ifdef CONFIG_X86_64
+ regs->cs = __KERNEL_CS;
+#else
+ regs->cs = __KERNEL_CS | get_kernel_rpl();
+ regs->gs = 0;
+#endif
+ regs->ip = (unsigned long)op->kp.addr + INT3_SIZE;
+ regs->orig_ax = ~0UL;
+
+ __this_cpu_write(current_kprobe, &op->kp);
+ kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+ opt_pre_handler(&op->kp, regs);
+ __this_cpu_write(current_kprobe, NULL);
+ }
+ local_irq_restore(flags);
+}
+NOKPROBE_SYMBOL(optimized_callback);
+
+static int copy_optimized_instructions(u8 *dest, u8 *src)
+{
+ int len = 0, ret;
+
+ while (len < RELATIVEJUMP_SIZE) {
+ ret = __copy_instruction(dest + len, src + len);
+ if (!ret || !can_boost(dest + len))
+ return -EINVAL;
+ len += ret;
+ }
+ /* Check whether the address range is reserved */
+ if (ftrace_text_reserved(src, src + len - 1) ||
+ alternatives_text_reserved(src, src + len - 1) ||
+ jump_label_text_reserved(src, src + len - 1))
+ return -EBUSY;
+
+ return len;
+}
+
+/* Check whether insn is indirect jump */
+static int insn_is_indirect_jump(struct insn *insn)
+{
+ return ((insn->opcode.bytes[0] == 0xff &&
+ (X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
+ insn->opcode.bytes[0] == 0xea); /* Segment based jump */
+}
+
+/* Check whether insn jumps into specified address range */
+static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
+{
+ unsigned long target = 0;
+
+ switch (insn->opcode.bytes[0]) {
+ case 0xe0: /* loopne */
+ case 0xe1: /* loope */
+ case 0xe2: /* loop */
+ case 0xe3: /* jcxz */
+ case 0xe9: /* near relative jump */
+ case 0xeb: /* short relative jump */
+ break;
+ case 0x0f:
+ if ((insn->opcode.bytes[1] & 0xf0) == 0x80) /* jcc near */
+ break;
+ return 0;
+ default:
+ if ((insn->opcode.bytes[0] & 0xf0) == 0x70) /* jcc short */
+ break;
+ return 0;
+ }
+ target = (unsigned long)insn->next_byte + insn->immediate.value;
+
+ return (start <= target && target <= start + len);
+}
+
+/* Decode whole function to ensure any instructions don't jump into target */
+static int can_optimize(unsigned long paddr)
+{
+ unsigned long addr, size = 0, offset = 0;
+ struct insn insn;
+ kprobe_opcode_t buf[MAX_INSN_SIZE];
+
+ /* Lookup symbol including addr */
+ if (!kallsyms_lookup_size_offset(paddr, &size, &offset))
+ return 0;
+
+ /*
+ * Do not optimize in the entry code due to the unstable
+ * stack handling.
+ */
+ if ((paddr >= (unsigned long)__entry_text_start) &&
+ (paddr < (unsigned long)__entry_text_end))
+ return 0;
+
+ /* Check there is enough space for a relative jump. */
+ if (size - offset < RELATIVEJUMP_SIZE)
+ return 0;
+
+ /* Decode instructions */
+ addr = paddr - offset;
+ while (addr < paddr - offset + size) { /* Decode until function end */
+ unsigned long recovered_insn;
+ if (search_exception_tables(addr))
+ /*
+ * Since some fixup code will jumps into this function,
+ * we can't optimize kprobe in this function.
+ */
+ return 0;
+ recovered_insn = recover_probed_instruction(buf, addr);
+ if (!recovered_insn)
+ return 0;
+ kernel_insn_init(&insn, (void *)recovered_insn, MAX_INSN_SIZE);
+ insn_get_length(&insn);
+ /* Another subsystem puts a breakpoint */
+ if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
+ return 0;
+ /* Recover address */
+ insn.kaddr = (void *)addr;
+ insn.next_byte = (void *)(addr + insn.length);
+ /* Check any instructions don't jump into target */
+ if (insn_is_indirect_jump(&insn) ||
+ insn_jump_into_range(&insn, paddr + INT3_SIZE,
+ RELATIVE_ADDR_SIZE))
+ return 0;
+ addr += insn.length;
+ }
+
+ return 1;
+}
+
+/* Check optimized_kprobe can actually be optimized. */
+int arch_check_optimized_kprobe(struct optimized_kprobe *op)
+{
+ int i;
+ struct kprobe *p;
+
+ for (i = 1; i < op->optinsn.size; i++) {
+ p = get_kprobe(op->kp.addr + i);
+ if (p && !kprobe_disabled(p))
+ return -EEXIST;
+ }
+
+ return 0;
+}
+
+/* Check the addr is within the optimized instructions. */
+int arch_within_optimized_kprobe(struct optimized_kprobe *op,
+ unsigned long addr)
+{
+ return ((unsigned long)op->kp.addr <= addr &&
+ (unsigned long)op->kp.addr + op->optinsn.size > addr);
+}
+
+/* Free optimized instruction slot */
+static
+void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
+{
+ if (op->optinsn.insn) {
+ free_optinsn_slot(op->optinsn.insn, dirty);
+ op->optinsn.insn = NULL;
+ op->optinsn.size = 0;
+ }
+}
+
+void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
+{
+ __arch_remove_optimized_kprobe(op, 1);
+}
+
+/*
+ * Copy replacing target instructions
+ * Target instructions MUST be relocatable (checked inside)
+ * This is called when new aggr(opt)probe is allocated or reused.
+ */
+int arch_prepare_optimized_kprobe(struct optimized_kprobe *op,
+ struct kprobe *__unused)
+{
+ u8 *buf;
+ int ret;
+ long rel;
+
+ if (!can_optimize((unsigned long)op->kp.addr))
+ return -EILSEQ;
+
+ op->optinsn.insn = get_optinsn_slot();
+ if (!op->optinsn.insn)
+ return -ENOMEM;
+
+ /*
+ * Verify if the address gap is in 2GB range, because this uses
+ * a relative jump.
+ */
+ rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE;
+ if (abs(rel) > 0x7fffffff) {
+ __arch_remove_optimized_kprobe(op, 0);
+ return -ERANGE;
+ }
+
+ buf = (u8 *)op->optinsn.insn;
+
+ /* Copy instructions into the out-of-line buffer */
+ ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr);
+ if (ret < 0) {
+ __arch_remove_optimized_kprobe(op, 0);
+ return ret;
+ }
+ op->optinsn.size = ret;
+
+ /* Copy arch-dep-instance from template */
+ memcpy(buf, &optprobe_template_entry, TMPL_END_IDX);
+
+ /* Set probe information */
+ synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op);
+
+ /* Set probe function call */
+ synthesize_relcall(buf + TMPL_CALL_IDX, optimized_callback);
+
+ /* Set returning jmp instruction at the tail of out-of-line buffer */
+ synthesize_reljump(buf + TMPL_END_IDX + op->optinsn.size,
+ (u8 *)op->kp.addr + op->optinsn.size);
+
+ flush_icache_range((unsigned long) buf,
+ (unsigned long) buf + TMPL_END_IDX +
+ op->optinsn.size + RELATIVEJUMP_SIZE);
+ return 0;
+}
+
+/*
+ * Replace breakpoints (int3) with relative jumps.
+ * Caller must call with locking kprobe_mutex and text_mutex.
+ */
+void arch_optimize_kprobes(struct list_head *oplist)
+{
+ struct optimized_kprobe *op, *tmp;
+ u8 insn_buf[RELATIVEJUMP_SIZE];
+
+ list_for_each_entry_safe(op, tmp, oplist, list) {
+ s32 rel = (s32)((long)op->optinsn.insn -
+ ((long)op->kp.addr + RELATIVEJUMP_SIZE));
+
+ WARN_ON(kprobe_disabled(&op->kp));
+
+ /* Backup instructions which will be replaced by jump address */
+ memcpy(op->optinsn.copied_insn, op->kp.addr + INT3_SIZE,
+ RELATIVE_ADDR_SIZE);
+
+ insn_buf[0] = RELATIVEJUMP_OPCODE;
+ *(s32 *)(&insn_buf[1]) = rel;
+
+ text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
+ op->optinsn.insn);
+
+ list_del_init(&op->list);
+ }
+}
+
+/* Replace a relative jump with a breakpoint (int3). */
+void arch_unoptimize_kprobe(struct optimized_kprobe *op)
+{
+ u8 insn_buf[RELATIVEJUMP_SIZE];
+
+ /* Set int3 to first byte for kprobes */
+ insn_buf[0] = BREAKPOINT_INSTRUCTION;
+ memcpy(insn_buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
+ text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
+ op->optinsn.insn);
+}
+
+/*
+ * Recover original instructions and breakpoints from relative jumps.
+ * Caller must call with locking kprobe_mutex.
+ */
+extern void arch_unoptimize_kprobes(struct list_head *oplist,
+ struct list_head *done_list)
+{
+ struct optimized_kprobe *op, *tmp;
+
+ list_for_each_entry_safe(op, tmp, oplist, list) {
+ arch_unoptimize_kprobe(op);
+ list_move(&op->list, done_list);
+ }
+}
+
+int setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter)
+{
+ struct optimized_kprobe *op;
+
+ if (p->flags & KPROBE_FLAG_OPTIMIZED) {
+ /* This kprobe is really able to run optimized path. */
+ op = container_of(p, struct optimized_kprobe, kp);
+ /* Detour through copied instructions */
+ regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
+ if (!reenter)
+ reset_current_kprobe();
+ preempt_enable_no_resched();
+ return 1;
+ }
+ return 0;
+}
+NOKPROBE_SYMBOL(setup_detour_execution);
Code Review / kvmfornfv.git / blobdiff