summaryrefslogtreecommitdiffstats
path: root/arch/powerpc/kernel/kprobes.c
diff options
context:
space:
mode:
Diffstat (limited to 'arch/powerpc/kernel/kprobes.c')
-rw-r--r--arch/powerpc/kernel/kprobes.c629
1 files changed, 629 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
new file mode 100644
index 000000000..ccf16bccc
--- /dev/null
+++ b/arch/powerpc/kernel/kprobes.c
@@ -0,0 +1,629 @@
+/*
+ * Kernel Probes (KProbes)
+ *
+ * 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-Nov Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
+ * for PPC64
+ */
+
+#include <linux/kprobes.h>
+#include <linux/ptrace.h>
+#include <linux/preempt.h>
+#include <linux/extable.h>
+#include <linux/kdebug.h>
+#include <linux/slab.h>
+#include <asm/code-patching.h>
+#include <asm/cacheflush.h>
+#include <asm/sstep.h>
+#include <asm/sections.h>
+#include <linux/uaccess.h>
+
+DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
+DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
+
+struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
+
+bool arch_within_kprobe_blacklist(unsigned long addr)
+{
+ return (addr >= (unsigned long)__kprobes_text_start &&
+ addr < (unsigned long)__kprobes_text_end) ||
+ (addr >= (unsigned long)_stext &&
+ addr < (unsigned long)__head_end);
+}
+
+kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
+{
+ kprobe_opcode_t *addr = NULL;
+
+#ifdef PPC64_ELF_ABI_v2
+ /* PPC64 ABIv2 needs local entry point */
+ addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
+ if (addr && !offset) {
+#ifdef CONFIG_KPROBES_ON_FTRACE
+ unsigned long faddr;
+ /*
+ * Per livepatch.h, ftrace location is always within the first
+ * 16 bytes of a function on powerpc with -mprofile-kernel.
+ */
+ faddr = ftrace_location_range((unsigned long)addr,
+ (unsigned long)addr + 16);
+ if (faddr)
+ addr = (kprobe_opcode_t *)faddr;
+ else
+#endif
+ addr = (kprobe_opcode_t *)ppc_function_entry(addr);
+ }
+#elif defined(PPC64_ELF_ABI_v1)
+ /*
+ * 64bit powerpc ABIv1 uses function descriptors:
+ * - Check for the dot variant of the symbol first.
+ * - If that fails, try looking up the symbol provided.
+ *
+ * This ensures we always get to the actual symbol and not
+ * the descriptor.
+ *
+ * Also handle <module:symbol> format.
+ */
+ char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
+ bool dot_appended = false;
+ const char *c;
+ ssize_t ret = 0;
+ int len = 0;
+
+ if ((c = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
+ c++;
+ len = c - name;
+ memcpy(dot_name, name, len);
+ } else
+ c = name;
+
+ if (*c != '\0' && *c != '.') {
+ dot_name[len++] = '.';
+ dot_appended = true;
+ }
+ ret = strscpy(dot_name + len, c, KSYM_NAME_LEN);
+ if (ret > 0)
+ addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
+
+ /* Fallback to the original non-dot symbol lookup */
+ if (!addr && dot_appended)
+ addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
+#else
+ addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
+#endif
+
+ return addr;
+}
+
+int arch_prepare_kprobe(struct kprobe *p)
+{
+ int ret = 0;
+ kprobe_opcode_t insn = *p->addr;
+
+ if ((unsigned long)p->addr & 0x03) {
+ printk("Attempt to register kprobe at an unaligned address\n");
+ ret = -EINVAL;
+ } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
+ printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
+ ret = -EINVAL;
+ }
+
+ /* insn must be on a special executable page on ppc64. This is
+ * not explicitly required on ppc32 (right now), but it doesn't hurt */
+ if (!ret) {
+ p->ainsn.insn = get_insn_slot();
+ if (!p->ainsn.insn)
+ ret = -ENOMEM;
+ }
+
+ if (!ret) {
+ memcpy(p->ainsn.insn, p->addr,
+ MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+ p->opcode = *p->addr;
+ flush_icache_range((unsigned long)p->ainsn.insn,
+ (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
+ }
+
+ p->ainsn.boostable = 0;
+ return ret;
+}
+NOKPROBE_SYMBOL(arch_prepare_kprobe);
+
+void arch_arm_kprobe(struct kprobe *p)
+{
+ patch_instruction(p->addr, BREAKPOINT_INSTRUCTION);
+}
+NOKPROBE_SYMBOL(arch_arm_kprobe);
+
+void arch_disarm_kprobe(struct kprobe *p)
+{
+ patch_instruction(p->addr, p->opcode);
+}
+NOKPROBE_SYMBOL(arch_disarm_kprobe);
+
+void arch_remove_kprobe(struct kprobe *p)
+{
+ if (p->ainsn.insn) {
+ free_insn_slot(p->ainsn.insn, 0);
+ p->ainsn.insn = NULL;
+ }
+}
+NOKPROBE_SYMBOL(arch_remove_kprobe);
+
+static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
+{
+ enable_single_step(regs);
+
+ /*
+ * On powerpc we should single step on the original
+ * instruction even if the probed insn is a trap
+ * variant as values in regs could play a part in
+ * if the trap is taken or not
+ */
+ regs->nip = (unsigned long)p->ainsn.insn;
+}
+
+static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
+{
+ kcb->prev_kprobe.kp = kprobe_running();
+ kcb->prev_kprobe.status = kcb->kprobe_status;
+ kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
+}
+
+static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
+{
+ __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
+ kcb->kprobe_status = kcb->prev_kprobe.status;
+ kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
+}
+
+static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
+ struct kprobe_ctlblk *kcb)
+{
+ __this_cpu_write(current_kprobe, p);
+ kcb->kprobe_saved_msr = regs->msr;
+}
+
+bool arch_kprobe_on_func_entry(unsigned long offset)
+{
+#ifdef PPC64_ELF_ABI_v2
+#ifdef CONFIG_KPROBES_ON_FTRACE
+ return offset <= 16;
+#else
+ return offset <= 8;
+#endif
+#else
+ return !offset;
+#endif
+}
+
+void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
+{
+ ri->ret_addr = (kprobe_opcode_t *)regs->link;
+
+ /* Replace the return addr with trampoline addr */
+ regs->link = (unsigned long)kretprobe_trampoline;
+}
+NOKPROBE_SYMBOL(arch_prepare_kretprobe);
+
+static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
+{
+ int ret;
+ unsigned int insn = *p->ainsn.insn;
+
+ /* regs->nip is also adjusted if emulate_step returns 1 */
+ ret = emulate_step(regs, insn);
+ if (ret > 0) {
+ /*
+ * Once this instruction has been boosted
+ * successfully, set the boostable flag
+ */
+ if (unlikely(p->ainsn.boostable == 0))
+ p->ainsn.boostable = 1;
+ } else if (ret < 0) {
+ /*
+ * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
+ * So, we should never get here... but, its still
+ * good to catch them, just in case...
+ */
+ printk("Can't step on instruction %x\n", insn);
+ BUG();
+ } else {
+ /*
+ * If we haven't previously emulated this instruction, then it
+ * can't be boosted. Note it down so we don't try to do so again.
+ *
+ * If, however, we had emulated this instruction in the past,
+ * then this is just an error with the current run (for
+ * instance, exceptions due to a load/store). We return 0 so
+ * that this is now single-stepped, but continue to try
+ * emulating it in subsequent probe hits.
+ */
+ if (unlikely(p->ainsn.boostable != 1))
+ p->ainsn.boostable = -1;
+ }
+
+ return ret;
+}
+NOKPROBE_SYMBOL(try_to_emulate);
+
+int kprobe_handler(struct pt_regs *regs)
+{
+ struct kprobe *p;
+ int ret = 0;
+ unsigned int *addr = (unsigned int *)regs->nip;
+ struct kprobe_ctlblk *kcb;
+
+ if (user_mode(regs))
+ return 0;
+
+ if (!IS_ENABLED(CONFIG_BOOKE) &&
+ (!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR)))
+ return 0;
+
+ /*
+ * We don't want to be preempted for the entire
+ * duration of kprobe processing
+ */
+ preempt_disable();
+ kcb = get_kprobe_ctlblk();
+
+ /* Check we're not actually recursing */
+ if (kprobe_running()) {
+ p = get_kprobe(addr);
+ if (p) {
+ kprobe_opcode_t insn = *p->ainsn.insn;
+ if (kcb->kprobe_status == KPROBE_HIT_SS &&
+ is_trap(insn)) {
+ /* Turn off 'trace' bits */
+ regs->msr &= ~MSR_SINGLESTEP;
+ regs->msr |= kcb->kprobe_saved_msr;
+ 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);
+ kcb->kprobe_status = KPROBE_REENTER;
+ if (p->ainsn.boostable >= 0) {
+ ret = try_to_emulate(p, regs);
+
+ if (ret > 0) {
+ restore_previous_kprobe(kcb);
+ preempt_enable_no_resched();
+ return 1;
+ }
+ }
+ prepare_singlestep(p, regs);
+ return 1;
+ } else if (*addr != BREAKPOINT_INSTRUCTION) {
+ /* If trap variant, then it belongs not to us */
+ kprobe_opcode_t cur_insn = *addr;
+
+ if (is_trap(cur_insn))
+ goto no_kprobe;
+ /* The breakpoint instruction was removed by
+ * another cpu right after we hit, no further
+ * handling of this interrupt is appropriate
+ */
+ ret = 1;
+ }
+ goto no_kprobe;
+ }
+
+ p = get_kprobe(addr);
+ if (!p) {
+ if (*addr != BREAKPOINT_INSTRUCTION) {
+ /*
+ * PowerPC has multiple variants of the "trap"
+ * instruction. If the current instruction is a
+ * trap variant, it could belong to someone else
+ */
+ kprobe_opcode_t cur_insn = *addr;
+ if (is_trap(cur_insn))
+ goto no_kprobe;
+ /*
+ * 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;
+ }
+
+ kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+ set_current_kprobe(p, regs, kcb);
+ if (p->pre_handler && p->pre_handler(p, regs)) {
+ /* handler changed execution path, so skip ss setup */
+ reset_current_kprobe();
+ preempt_enable_no_resched();
+ return 1;
+ }
+
+ if (p->ainsn.boostable >= 0) {
+ ret = try_to_emulate(p, regs);
+
+ if (ret > 0) {
+ if (p->post_handler)
+ p->post_handler(p, regs, 0);
+
+ kcb->kprobe_status = KPROBE_HIT_SSDONE;
+ reset_current_kprobe();
+ preempt_enable_no_resched();
+ return 1;
+ }
+ }
+ prepare_singlestep(p, regs);
+ kcb->kprobe_status = KPROBE_HIT_SS;
+ return 1;
+
+no_kprobe:
+ preempt_enable_no_resched();
+ return ret;
+}
+NOKPROBE_SYMBOL(kprobe_handler);
+
+/*
+ * Function return probe trampoline:
+ * - init_kprobes() establishes a probepoint here
+ * - When the probed function returns, this probe
+ * causes the handlers to fire
+ */
+asm(".global kretprobe_trampoline\n"
+ ".type kretprobe_trampoline, @function\n"
+ "kretprobe_trampoline:\n"
+ "nop\n"
+ "blr\n"
+ ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
+
+/*
+ * Called when the probe at kretprobe trampoline is hit
+ */
+static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
+{
+ struct kretprobe_instance *ri = NULL;
+ struct hlist_head *head, empty_rp;
+ struct hlist_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 than 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, tmp, head, hlist) {
+ if (ri->task != current)
+ /* another task is sharing our hash bucket */
+ continue;
+
+ if (ri->rp && ri->rp->handler)
+ ri->rp->handler(ri, regs);
+
+ 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);
+
+ /*
+ * We get here through one of two paths:
+ * 1. by taking a trap -> kprobe_handler() -> here
+ * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
+ *
+ * When going back through (1), we need regs->nip to be setup properly
+ * as it is used to determine the return address from the trap.
+ * For (2), since nip is not honoured with optprobes, we instead setup
+ * the link register properly so that the subsequent 'blr' in
+ * kretprobe_trampoline jumps back to the right instruction.
+ *
+ * For nip, we should set the address to the previous instruction since
+ * we end up emulating it in kprobe_handler(), which increments the nip
+ * again.
+ */
+ regs->nip = orig_ret_address - 4;
+ regs->link = orig_ret_address;
+
+ kretprobe_hash_unlock(current, &flags);
+
+ hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
+ hlist_del(&ri->hlist);
+ kfree(ri);
+ }
+
+ return 0;
+}
+NOKPROBE_SYMBOL(trampoline_probe_handler);
+
+/*
+ * Called after single-stepping. p->addr is the address of the
+ * instruction whose first byte has been replaced by the "breakpoint"
+ * 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.
+ */
+int kprobe_post_handler(struct pt_regs *regs)
+{
+ struct kprobe *cur = kprobe_running();
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+ if (!cur || user_mode(regs))
+ return 0;
+
+ /* make sure we got here for instruction we have a kprobe on */
+ if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
+ return 0;
+
+ if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
+ kcb->kprobe_status = KPROBE_HIT_SSDONE;
+ cur->post_handler(cur, regs, 0);
+ }
+
+ /* Adjust nip to after the single-stepped instruction */
+ regs->nip = (unsigned long)cur->addr + 4;
+ regs->msr |= kcb->kprobe_saved_msr;
+
+ /*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();
+
+ /*
+ * if somebody else is singlestepping across a probe point, msr
+ * will have DE/SE set, in which case, continue the remaining processing
+ * of do_debug, as if this is not a probe hit.
+ */
+ if (regs->msr & MSR_SINGLESTEP)
+ return 0;
+
+ return 1;
+}
+NOKPROBE_SYMBOL(kprobe_post_handler);
+
+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 and the nip points back to the probe address
+ * and allow the page fault handler to continue as a
+ * normal page fault.
+ */
+ regs->nip = (unsigned long)cur->addr;
+ regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
+ regs->msr |= kcb->kprobe_saved_msr;
+ 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->nip)) != NULL) {
+ regs->nip = extable_fixup(entry);
+ return 1;
+ }
+
+ /*
+ * fixup_exception() could not handle it,
+ * Let do_page_fault() fix it.
+ */
+ break;
+ default:
+ break;
+ }
+ return 0;
+}
+NOKPROBE_SYMBOL(kprobe_fault_handler);
+
+unsigned long arch_deref_entry_point(void *entry)
+{
+#ifdef PPC64_ELF_ABI_v1
+ if (!kernel_text_address((unsigned long)entry))
+ return ppc_global_function_entry(entry);
+ else
+#endif
+ return (unsigned long)entry;
+}
+NOKPROBE_SYMBOL(arch_deref_entry_point);
+
+static struct kprobe trampoline_p = {
+ .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
+ .pre_handler = trampoline_probe_handler
+};
+
+int __init arch_init_kprobes(void)
+{
+ return register_kprobe(&trampoline_p);
+}
+
+int arch_trampoline_kprobe(struct kprobe *p)
+{
+ if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
+ return 1;
+
+ return 0;
+}
+NOKPROBE_SYMBOL(arch_trampoline_kprobe);
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-26 16:11:42 +0000