1 files changed, 555 insertions, 0 deletions

diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
new file mode 100644
index 000000000..517821b48
--- /dev/null
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -0,0 +1,555 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Kernel Probes Jump Optimization (Optprobes)
+ *
+ * Copyright (C) IBM Corporation, 2002, 2004
+ * Copyright (C) Hitachi Ltd., 2012
+ */
+#include <linux/kprobes.h>
+#include <linux/perf_event.h>
+#include <linux/ptrace.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/hardirq.h>
+#include <linux/preempt.h>
+#include <linux/extable.h>
+#include <linux/kdebug.h>
+#include <linux/kallsyms.h>
+#include <linux/kgdb.h>
+#include <linux/ftrace.h>
+#include <linux/objtool.h>
+#include <linux/pgtable.h>
+#include <linux/static_call.h>
+
+#include <asm/text-patching.h>
+#include <asm/cacheflush.h>
+#include <asm/desc.h>
+#include <linux/uaccess.h>
+#include <asm/alternative.h>
+#include <asm/insn.h>
+#include <asm/debugreg.h>
+#include <asm/set_memory.h>
+#include <asm/sections.h>
+#include <asm/nospec-branch.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 < JMP32_INSN_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 is optimized or under unoptimizing */
+			if (list_empty(&op->list) || optprobe_queued_unopt(op))
+				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.
+	 */
+	if (copy_from_kernel_nofault(buf, (void *)addr,
+		MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
+		return 0UL;
+
+	if (addr == (unsigned long)kp->addr) {
+		buf[0] = kp->opcode;
+		memcpy(buf + 1, op->optinsn.copied_insn, DISP32_SIZE);
+	} else {
+		offs = addr - (unsigned long)kp->addr - 1;
+		memcpy(buf, op->optinsn.copied_insn + offs, DISP32_SIZE - offs);
+	}
+
+	return (unsigned long)buf;
+}
+
+static void synthesize_clac(kprobe_opcode_t *addr)
+{
+	/*
+	 * Can't be static_cpu_has() due to how objtool treats this feature bit.
+	 * This isn't a fast path anyway.
+	 */
+	if (!boot_cpu_has(X86_FEATURE_SMAP))
+		return;
+
+	/* Replace the NOP3 with CLAC */
+	addr[0] = 0x0f;
+	addr[1] = 0x01;
+	addr[2] = 0xca;
+}
+
+/* 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 (
+			".pushsection .rodata\n"
+			"optprobe_template_func:\n"
+			".global optprobe_template_entry\n"
+			"optprobe_template_entry:\n"
+#ifdef CONFIG_X86_64
+			"       pushq $" __stringify(__KERNEL_DS) "\n"
+			/* Save the 'sp - 8', this will be fixed later. */
+			"	pushq %rsp\n"
+			"	pushfq\n"
+			".global optprobe_template_clac\n"
+			"optprobe_template_clac:\n"
+			ASM_NOP3
+			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
+			/* Copy 'regs->flags' into 'regs->ss'. */
+			"	movq 18*8(%rsp), %rdx\n"
+			"	movq %rdx, 20*8(%rsp)\n"
+			RESTORE_REGS_STRING
+			/* Skip 'regs->flags' and 'regs->sp'. */
+			"	addq $16, %rsp\n"
+			/* And pop flags register from 'regs->ss'. */
+			"	popfq\n"
+#else /* CONFIG_X86_32 */
+			"	pushl %ss\n"
+			/* Save the 'sp - 4', this will be fixed later. */
+			"	pushl %esp\n"
+			"	pushfl\n"
+			".global optprobe_template_clac\n"
+			"optprobe_template_clac:\n"
+			ASM_NOP3
+			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
+			/* Copy 'regs->flags' into 'regs->ss'. */
+			"	movl 14*4(%esp), %edx\n"
+			"	movl %edx, 16*4(%esp)\n"
+			RESTORE_REGS_STRING
+			/* Skip 'regs->flags' and 'regs->sp'. */
+			"	addl $8, %esp\n"
+			/* And pop flags register from 'regs->ss'. */
+			"	popfl\n"
+#endif
+			".global optprobe_template_end\n"
+			"optprobe_template_end:\n"
+			".popsection\n");
+
+void optprobe_template_func(void);
+STACK_FRAME_NON_STANDARD(optprobe_template_func);
+
+#define TMPL_CLAC_IDX \
+	((long)optprobe_template_clac - (long)optprobe_template_entry)
+#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)
+
+/* Optimized kprobe call back function: called from optinsn */
+static void
+optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
+{
+	/* This is possible if op is under delayed unoptimizing */
+	if (kprobe_disabled(&op->kp))
+		return;
+
+	preempt_disable();
+	if (kprobe_running()) {
+		kprobes_inc_nmissed_count(&op->kp);
+	} else {
+		struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+		/* Adjust stack pointer */
+		regs->sp += sizeof(long);
+		/* Save skipped registers */
+		regs->cs = __KERNEL_CS;
+#ifdef CONFIG_X86_32
+		regs->gs = 0;
+#endif
+		regs->ip = (unsigned long)op->kp.addr + INT3_INSN_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);
+	}
+	preempt_enable();
+}
+NOKPROBE_SYMBOL(optimized_callback);
+
+static int copy_optimized_instructions(u8 *dest, u8 *src, u8 *real)
+{
+	struct insn insn;
+	int len = 0, ret;
+
+	while (len < JMP32_INSN_SIZE) {
+		ret = __copy_instruction(dest + len, src + len, real + len, &insn);
+		if (!ret || !can_boost(&insn, src + 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) ||
+	    static_call_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 and registers setup.
+	 */
+	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 < JMP32_INSN_SIZE)
+		return 0;
+
+	/* Decode instructions */
+	addr = paddr - offset;
+	while (addr < paddr - offset + size) { /* Decode until function end */
+		unsigned long recovered_insn;
+		int ret;
+
+		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;
+
+		ret = insn_decode_kernel(&insn, (void *)recovered_insn);
+		if (ret < 0)
+			return 0;
+#ifdef CONFIG_KGDB
+		/*
+		 * If there is a dynamically installed kgdb sw breakpoint,
+		 * this function should not be probed.
+		 */
+		if (insn.opcode.bytes[0] == INT3_INSN_OPCODE &&
+		    kgdb_has_hit_break(addr))
+			return 0;
+#endif
+		/* Recover address */
+		insn.kaddr = (void *)addr;
+		insn.next_byte = (void *)(addr + insn.length);
+		/*
+		 * Check any instructions don't jump into target, indirectly or
+		 * directly.
+		 *
+		 * The indirect case is present to handle a code with jump
+		 * tables. When the kernel uses retpolines, the check should in
+		 * theory additionally look for jumps to indirect thunks.
+		 * However, the kernel built with retpolines or IBT has jump
+		 * tables disabled so the check can be skipped altogether.
+		 */
+		if (!IS_ENABLED(CONFIG_RETPOLINE) &&
+		    !IS_ENABLED(CONFIG_X86_KERNEL_IBT) &&
+		    insn_is_indirect_jump(&insn))
+			return 0;
+		if (insn_jump_into_range(&insn, paddr + INT3_INSN_SIZE,
+					 DISP32_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_disarmed(p))
+			return -EEXIST;
+	}
+
+	return 0;
+}
+
+/* Check the addr is within the optimized instructions. */
+int arch_within_optimized_kprobe(struct optimized_kprobe *op,
+				 kprobe_opcode_t *addr)
+{
+	return (op->kp.addr <= addr &&
+		op->kp.addr + op->optinsn.size > addr);
+}
+
+/* Free optimized instruction slot */
+static
+void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
+{
+	u8 *slot = op->optinsn.insn;
+	if (slot) {
+		int len = TMPL_END_IDX + op->optinsn.size + JMP32_INSN_SIZE;
+
+		/* Record the perf event before freeing the slot */
+		if (dirty)
+			perf_event_text_poke(slot, slot, len, NULL, 0);
+
+		free_optinsn_slot(slot, 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 = NULL, *slot;
+	int ret, len;
+	long rel;
+
+	if (!can_optimize((unsigned long)op->kp.addr))
+		return -EILSEQ;
+
+	buf = kzalloc(MAX_OPTINSN_SIZE, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	op->optinsn.insn = slot = get_optinsn_slot();
+	if (!slot) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/*
+	 * Verify if the address gap is in 2GB range, because this uses
+	 * a relative jump.
+	 */
+	rel = (long)slot - (long)op->kp.addr + JMP32_INSN_SIZE;
+	if (abs(rel) > 0x7fffffff) {
+		ret = -ERANGE;
+		goto err;
+	}
+
+	/* Copy arch-dep-instance from template */
+	memcpy(buf, optprobe_template_entry, TMPL_END_IDX);
+
+	/* Copy instructions into the out-of-line buffer */
+	ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr,
+					  slot + TMPL_END_IDX);
+	if (ret < 0)
+		goto err;
+	op->optinsn.size = ret;
+	len = TMPL_END_IDX + op->optinsn.size;
+
+	synthesize_clac(buf + TMPL_CLAC_IDX);
+
+	/* Set probe information */
+	synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op);
+
+	/* Set probe function call */
+	synthesize_relcall(buf + TMPL_CALL_IDX,
+			   slot + TMPL_CALL_IDX, optimized_callback);
+
+	/* Set returning jmp instruction at the tail of out-of-line buffer */
+	synthesize_reljump(buf + len, slot + len,
+			   (u8 *)op->kp.addr + op->optinsn.size);
+	len += JMP32_INSN_SIZE;
+
+	/*
+	 * Note	len = TMPL_END_IDX + op->optinsn.size + JMP32_INSN_SIZE is also
+	 * used in __arch_remove_optimized_kprobe().
+	 */
+
+	/* We have to use text_poke() for instruction buffer because it is RO */
+	perf_event_text_poke(slot, NULL, 0, buf, len);
+	text_poke(slot, buf, len);
+
+	ret = 0;
+out:
+	kfree(buf);
+	return ret;
+
+err:
+	__arch_remove_optimized_kprobe(op, 0);
+	goto out;
+}
+
+/*
+ * Replace breakpoints (INT3) with relative jumps (JMP.d32).
+ * Caller must call with locking kprobe_mutex and text_mutex.
+ *
+ * The caller will have installed a regular kprobe and after that issued
+ * syncrhonize_rcu_tasks(), this ensures that the instruction(s) that live in
+ * the 4 bytes after the INT3 are unused and can now be overwritten.
+ */
+void arch_optimize_kprobes(struct list_head *oplist)
+{
+	struct optimized_kprobe *op, *tmp;
+	u8 insn_buff[JMP32_INSN_SIZE];
+
+	list_for_each_entry_safe(op, tmp, oplist, list) {
+		s32 rel = (s32)((long)op->optinsn.insn -
+			((long)op->kp.addr + JMP32_INSN_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_INSN_SIZE,
+		       DISP32_SIZE);
+
+		insn_buff[0] = JMP32_INSN_OPCODE;
+		*(s32 *)(&insn_buff[1]) = rel;
+
+		text_poke_bp(op->kp.addr, insn_buff, JMP32_INSN_SIZE, NULL);
+
+		list_del_init(&op->list);
+	}
+}
+
+/*
+ * Replace a relative jump (JMP.d32) with a breakpoint (INT3).
+ *
+ * After that, we can restore the 4 bytes after the INT3 to undo what
+ * arch_optimize_kprobes() scribbled. This is safe since those bytes will be
+ * unused once the INT3 lands.
+ */
+void arch_unoptimize_kprobe(struct optimized_kprobe *op)
+{
+	u8 new[JMP32_INSN_SIZE] = { INT3_INSN_OPCODE, };
+	u8 old[JMP32_INSN_SIZE];
+	u8 *addr = op->kp.addr;
+
+	memcpy(old, op->kp.addr, JMP32_INSN_SIZE);
+	memcpy(new + INT3_INSN_SIZE,
+	       op->optinsn.copied_insn,
+	       JMP32_INSN_SIZE - INT3_INSN_SIZE);
+
+	text_poke(addr, new, INT3_INSN_SIZE);
+	text_poke_sync();
+	text_poke(addr + INT3_INSN_SIZE,
+		  new + INT3_INSN_SIZE,
+		  JMP32_INSN_SIZE - INT3_INSN_SIZE);
+	text_poke_sync();
+
+	perf_event_text_poke(op->kp.addr, old, JMP32_INSN_SIZE, new, JMP32_INSN_SIZE);
+}
+
+/*
+ * 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();
+		return 1;
+	}
+	return 0;
+}
+NOKPROBE_SYMBOL(setup_detour_execution);