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-rw-r--r--arch/arm64/kernel/probes/kprobes.c425
1 files changed, 425 insertions, 0 deletions
diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
new file mode 100644
index 0000000000..70b91a8c6b
--- /dev/null
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -0,0 +1,425 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * arch/arm64/kernel/probes/kprobes.c
+ *
+ * Kprobes support for ARM64
+ *
+ * Copyright (C) 2013 Linaro Limited.
+ * Author: Sandeepa Prabhu <sandeepa.prabhu@linaro.org>
+ */
+
+#define pr_fmt(fmt) "kprobes: " fmt
+
+#include <linux/extable.h>
+#include <linux/kasan.h>
+#include <linux/kernel.h>
+#include <linux/kprobes.h>
+#include <linux/sched/debug.h>
+#include <linux/set_memory.h>
+#include <linux/slab.h>
+#include <linux/stop_machine.h>
+#include <linux/stringify.h>
+#include <linux/uaccess.h>
+#include <linux/vmalloc.h>
+
+#include <asm/cacheflush.h>
+#include <asm/daifflags.h>
+#include <asm/debug-monitors.h>
+#include <asm/insn.h>
+#include <asm/irq.h>
+#include <asm/patching.h>
+#include <asm/ptrace.h>
+#include <asm/sections.h>
+#include <asm/system_misc.h>
+#include <asm/traps.h>
+
+#include "decode-insn.h"
+
+DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
+DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
+
+static void __kprobes
+post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *);
+
+static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
+{
+ kprobe_opcode_t *addr = p->ainsn.api.insn;
+
+ /*
+ * Prepare insn slot, Mark Rutland points out it depends on a coupe of
+ * subtleties:
+ *
+ * - That the I-cache maintenance for these instructions is complete
+ * *before* the kprobe BRK is written (and aarch64_insn_patch_text_nosync()
+ * ensures this, but just omits causing a Context-Synchronization-Event
+ * on all CPUS).
+ *
+ * - That the kprobe BRK results in an exception (and consequently a
+ * Context-Synchronoization-Event), which ensures that the CPU will
+ * fetch thesingle-step slot instructions *after* this, ensuring that
+ * the new instructions are used
+ *
+ * It supposes to place ISB after patching to guarantee I-cache maintenance
+ * is observed on all CPUS, however, single-step slot is installed in
+ * the BRK exception handler, so it is unnecessary to generate
+ * Contex-Synchronization-Event via ISB again.
+ */
+ aarch64_insn_patch_text_nosync(addr, p->opcode);
+ aarch64_insn_patch_text_nosync(addr + 1, BRK64_OPCODE_KPROBES_SS);
+
+ /*
+ * Needs restoring of return address after stepping xol.
+ */
+ p->ainsn.api.restore = (unsigned long) p->addr +
+ sizeof(kprobe_opcode_t);
+}
+
+static void __kprobes arch_prepare_simulate(struct kprobe *p)
+{
+ /* This instructions is not executed xol. No need to adjust the PC */
+ p->ainsn.api.restore = 0;
+}
+
+static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
+{
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+ if (p->ainsn.api.handler)
+ p->ainsn.api.handler((u32)p->opcode, (long)p->addr, regs);
+
+ /* single step simulated, now go for post processing */
+ post_kprobe_handler(p, kcb, regs);
+}
+
+int __kprobes arch_prepare_kprobe(struct kprobe *p)
+{
+ unsigned long probe_addr = (unsigned long)p->addr;
+
+ if (probe_addr & 0x3)
+ return -EINVAL;
+
+ /* copy instruction */
+ p->opcode = le32_to_cpu(*p->addr);
+
+ if (search_exception_tables(probe_addr))
+ return -EINVAL;
+
+ /* decode instruction */
+ switch (arm_kprobe_decode_insn(p->addr, &p->ainsn)) {
+ case INSN_REJECTED: /* insn not supported */
+ return -EINVAL;
+
+ case INSN_GOOD_NO_SLOT: /* insn need simulation */
+ p->ainsn.api.insn = NULL;
+ break;
+
+ case INSN_GOOD: /* instruction uses slot */
+ p->ainsn.api.insn = get_insn_slot();
+ if (!p->ainsn.api.insn)
+ return -ENOMEM;
+ break;
+ }
+
+ /* prepare the instruction */
+ if (p->ainsn.api.insn)
+ arch_prepare_ss_slot(p);
+ else
+ arch_prepare_simulate(p);
+
+ return 0;
+}
+
+void *alloc_insn_page(void)
+{
+ return __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END,
+ GFP_KERNEL, PAGE_KERNEL_ROX, VM_FLUSH_RESET_PERMS,
+ NUMA_NO_NODE, __builtin_return_address(0));
+}
+
+/* arm kprobe: install breakpoint in text */
+void __kprobes arch_arm_kprobe(struct kprobe *p)
+{
+ void *addr = p->addr;
+ u32 insn = BRK64_OPCODE_KPROBES;
+
+ aarch64_insn_patch_text(&addr, &insn, 1);
+}
+
+/* disarm kprobe: remove breakpoint from text */
+void __kprobes arch_disarm_kprobe(struct kprobe *p)
+{
+ void *addr = p->addr;
+
+ aarch64_insn_patch_text(&addr, &p->opcode, 1);
+}
+
+void __kprobes arch_remove_kprobe(struct kprobe *p)
+{
+ if (p->ainsn.api.insn) {
+ free_insn_slot(p->ainsn.api.insn, 0);
+ p->ainsn.api.insn = NULL;
+ }
+}
+
+static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
+{
+ kcb->prev_kprobe.kp = kprobe_running();
+ kcb->prev_kprobe.status = kcb->kprobe_status;
+}
+
+static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
+{
+ __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
+ kcb->kprobe_status = kcb->prev_kprobe.status;
+}
+
+static void __kprobes set_current_kprobe(struct kprobe *p)
+{
+ __this_cpu_write(current_kprobe, p);
+}
+
+/*
+ * Mask all of DAIF while executing the instruction out-of-line, to keep things
+ * simple and avoid nesting exceptions. Interrupts do have to be disabled since
+ * the kprobe state is per-CPU and doesn't get migrated.
+ */
+static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
+ struct pt_regs *regs)
+{
+ kcb->saved_irqflag = regs->pstate & DAIF_MASK;
+ regs->pstate |= DAIF_MASK;
+}
+
+static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
+ struct pt_regs *regs)
+{
+ regs->pstate &= ~DAIF_MASK;
+ regs->pstate |= kcb->saved_irqflag;
+}
+
+static void __kprobes setup_singlestep(struct kprobe *p,
+ struct pt_regs *regs,
+ struct kprobe_ctlblk *kcb, int reenter)
+{
+ unsigned long slot;
+
+ if (reenter) {
+ save_previous_kprobe(kcb);
+ set_current_kprobe(p);
+ kcb->kprobe_status = KPROBE_REENTER;
+ } else {
+ kcb->kprobe_status = KPROBE_HIT_SS;
+ }
+
+
+ if (p->ainsn.api.insn) {
+ /* prepare for single stepping */
+ slot = (unsigned long)p->ainsn.api.insn;
+
+ kprobes_save_local_irqflag(kcb, regs);
+ instruction_pointer_set(regs, slot);
+ } else {
+ /* insn simulation */
+ arch_simulate_insn(p, regs);
+ }
+}
+
+static int __kprobes reenter_kprobe(struct kprobe *p,
+ struct pt_regs *regs,
+ struct kprobe_ctlblk *kcb)
+{
+ switch (kcb->kprobe_status) {
+ case KPROBE_HIT_SSDONE:
+ case KPROBE_HIT_ACTIVE:
+ kprobes_inc_nmissed_count(p);
+ setup_singlestep(p, regs, kcb, 1);
+ break;
+ case KPROBE_HIT_SS:
+ case KPROBE_REENTER:
+ pr_warn("Failed to recover from reentered kprobes.\n");
+ dump_kprobe(p);
+ BUG();
+ break;
+ default:
+ WARN_ON(1);
+ return 0;
+ }
+
+ return 1;
+}
+
+static void __kprobes
+post_kprobe_handler(struct kprobe *cur, struct kprobe_ctlblk *kcb, struct pt_regs *regs)
+{
+ /* return addr restore if non-branching insn */
+ if (cur->ainsn.api.restore != 0)
+ instruction_pointer_set(regs, cur->ainsn.api.restore);
+
+ /* restore back original saved kprobe variables and continue */
+ if (kcb->kprobe_status == KPROBE_REENTER) {
+ restore_previous_kprobe(kcb);
+ return;
+ }
+ /* call post handler */
+ kcb->kprobe_status = KPROBE_HIT_SSDONE;
+ if (cur->post_handler)
+ cur->post_handler(cur, regs, 0);
+
+ reset_current_kprobe();
+}
+
+int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
+{
+ struct kprobe *cur = kprobe_running();
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+ 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 ip points back to the probe address
+ * and allow the page fault handler to continue as a
+ * normal page fault.
+ */
+ instruction_pointer_set(regs, (unsigned long) cur->addr);
+ BUG_ON(!instruction_pointer(regs));
+
+ if (kcb->kprobe_status == KPROBE_REENTER) {
+ restore_previous_kprobe(kcb);
+ } else {
+ kprobes_restore_local_irqflag(kcb, regs);
+ reset_current_kprobe();
+ }
+
+ break;
+ }
+ return 0;
+}
+
+static int __kprobes
+kprobe_breakpoint_handler(struct pt_regs *regs, unsigned long esr)
+{
+ struct kprobe *p, *cur_kprobe;
+ struct kprobe_ctlblk *kcb;
+ unsigned long addr = instruction_pointer(regs);
+
+ kcb = get_kprobe_ctlblk();
+ cur_kprobe = kprobe_running();
+
+ p = get_kprobe((kprobe_opcode_t *) addr);
+ if (WARN_ON_ONCE(!p)) {
+ /*
+ * Something went wrong. This BRK used an immediate reserved
+ * for kprobes, but we couldn't find any corresponding probe.
+ */
+ return DBG_HOOK_ERROR;
+ }
+
+ if (cur_kprobe) {
+ /* Hit a kprobe inside another kprobe */
+ if (!reenter_kprobe(p, regs, kcb))
+ return DBG_HOOK_ERROR;
+ } else {
+ /* Probe hit */
+ set_current_kprobe(p);
+ kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+
+ /*
+ * If we have no pre-handler or it returned 0, we
+ * continue with normal processing. If we have a
+ * pre-handler and it returned non-zero, it will
+ * modify the execution path and not need to single-step
+ * Let's just reset current kprobe and exit.
+ */
+ if (!p->pre_handler || !p->pre_handler(p, regs))
+ setup_singlestep(p, regs, kcb, 0);
+ else
+ reset_current_kprobe();
+ }
+
+ return DBG_HOOK_HANDLED;
+}
+
+static struct break_hook kprobes_break_hook = {
+ .imm = KPROBES_BRK_IMM,
+ .fn = kprobe_breakpoint_handler,
+};
+
+static int __kprobes
+kprobe_breakpoint_ss_handler(struct pt_regs *regs, unsigned long esr)
+{
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+ unsigned long addr = instruction_pointer(regs);
+ struct kprobe *cur = kprobe_running();
+
+ if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) &&
+ ((unsigned long)&cur->ainsn.api.insn[1] == addr)) {
+ kprobes_restore_local_irqflag(kcb, regs);
+ post_kprobe_handler(cur, kcb, regs);
+
+ return DBG_HOOK_HANDLED;
+ }
+
+ /* not ours, kprobes should ignore it */
+ return DBG_HOOK_ERROR;
+}
+
+static struct break_hook kprobes_break_ss_hook = {
+ .imm = KPROBES_BRK_SS_IMM,
+ .fn = kprobe_breakpoint_ss_handler,
+};
+
+/*
+ * Provide a blacklist of symbols identifying ranges which cannot be kprobed.
+ * This blacklist is exposed to userspace via debugfs (kprobes/blacklist).
+ */
+int __init arch_populate_kprobe_blacklist(void)
+{
+ int ret;
+
+ ret = kprobe_add_area_blacklist((unsigned long)__entry_text_start,
+ (unsigned long)__entry_text_end);
+ if (ret)
+ return ret;
+ ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
+ (unsigned long)__irqentry_text_end);
+ if (ret)
+ return ret;
+ ret = kprobe_add_area_blacklist((unsigned long)__hyp_text_start,
+ (unsigned long)__hyp_text_end);
+ if (ret || is_kernel_in_hyp_mode())
+ return ret;
+ ret = kprobe_add_area_blacklist((unsigned long)__hyp_idmap_text_start,
+ (unsigned long)__hyp_idmap_text_end);
+ return ret;
+}
+
+void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
+{
+ return (void *)kretprobe_trampoline_handler(regs, (void *)regs->regs[29]);
+}
+
+void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
+ struct pt_regs *regs)
+{
+ ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
+ ri->fp = (void *)regs->regs[29];
+
+ /* replace return addr (x30) with trampoline */
+ regs->regs[30] = (long)&__kretprobe_trampoline;
+}
+
+int __kprobes arch_trampoline_kprobe(struct kprobe *p)
+{
+ return 0;
+}
+
+int __init arch_init_kprobes(void)
+{
+ register_kernel_break_hook(&kprobes_break_hook);
+ register_kernel_break_hook(&kprobes_break_ss_hook);
+
+ return 0;
+}