cregit-Linux how code gets into the kernel

Release 4.14 arch/arm64/kernel/probes/simulate-insn.c

/*
 * arch/arm64/kernel/probes/simulate-insn.c
 *
 * Copyright (C) 2013 Linaro Limited.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * 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.
 */

#include <linux/bitops.h>
#include <linux/kernel.h>
#include <linux/kprobes.h>

#include <asm/ptrace.h>

#include "simulate-insn.h"


#define bbl_displacement(insn)		\
	sign_extend32(((insn) & 0x3ffffff) << 2, 27)


#define bcond_displacement(insn)	\
	sign_extend32(((insn >> 5) & 0x7ffff) << 2, 20)


#define cbz_displacement(insn)	\
	sign_extend32(((insn >> 5) & 0x7ffff) << 2, 20)


#define tbz_displacement(insn)	\
	sign_extend32(((insn >> 5) & 0x3fff) << 2, 15)


#define ldr_displacement(insn)	\
	sign_extend32(((insn >> 5) & 0x7ffff) << 2, 20)


static inline void set_x_reg(struct pt_regs *regs, int reg, u64 val) { pt_regs_write_reg(regs, reg, val); }

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static inline void set_w_reg(struct pt_regs *regs, int reg, u64 val) { pt_regs_write_reg(regs, reg, lower_32_bits(val)); }

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static inline u64 get_x_reg(struct pt_regs *regs, int reg) { return pt_regs_read_reg(regs, reg); }

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static inline u32 get_w_reg(struct pt_regs *regs, int reg) { return lower_32_bits(pt_regs_read_reg(regs, reg)); }

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static bool __kprobes check_cbz(u32 opcode, struct pt_regs *regs) { int xn = opcode & 0x1f; return (opcode & (1 << 31)) ? (get_x_reg(regs, xn) == 0) : (get_w_reg(regs, xn) == 0); }

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static bool __kprobes check_cbnz(u32 opcode, struct pt_regs *regs) { int xn = opcode & 0x1f; return (opcode & (1 << 31)) ? (get_x_reg(regs, xn) != 0) : (get_w_reg(regs, xn) != 0); }

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static bool __kprobes check_tbz(u32 opcode, struct pt_regs *regs) { int xn = opcode & 0x1f; int bit_pos = ((opcode & (1 << 31)) >> 26) | ((opcode >> 19) & 0x1f); return ((get_x_reg(regs, xn) >> bit_pos) & 0x1) == 0; }

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static bool __kprobes check_tbnz(u32 opcode, struct pt_regs *regs) { int xn = opcode & 0x1f; int bit_pos = ((opcode & (1 << 31)) >> 26) | ((opcode >> 19) & 0x1f); return ((get_x_reg(regs, xn) >> bit_pos) & 0x1) != 0; }

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/* * instruction simulation functions */
void __kprobes simulate_adr_adrp(u32 opcode, long addr, struct pt_regs *regs) { long imm, xn, val; xn = opcode & 0x1f; imm = ((opcode >> 3) & 0x1ffffc) | ((opcode >> 29) & 0x3); imm = sign_extend64(imm, 20); if (opcode & 0x80000000) val = (imm<<12) + (addr & 0xfffffffffffff000); else val = imm + addr; set_x_reg(regs, xn, val); instruction_pointer_set(regs, instruction_pointer(regs) + 4); }

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void __kprobes simulate_b_bl(u32 opcode, long addr, struct pt_regs *regs) { int disp = bbl_displacement(opcode); /* Link register is x30 */ if (opcode & (1 << 31)) set_x_reg(regs, 30, addr + 4); instruction_pointer_set(regs, addr + disp); }

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void __kprobes simulate_b_cond(u32 opcode, long addr, struct pt_regs *regs) { int disp = 4; if (aarch32_opcode_cond_checks[opcode & 0xf](regs->pstate & 0xffffffff)) disp = bcond_displacement(opcode); instruction_pointer_set(regs, addr + disp); }

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void __kprobes simulate_br_blr_ret(u32 opcode, long addr, struct pt_regs *regs) { int xn = (opcode >> 5) & 0x1f; /* update pc first in case we're doing a "blr lr" */ instruction_pointer_set(regs, get_x_reg(regs, xn)); /* Link register is x30 */ if (((opcode >> 21) & 0x3) == 1) set_x_reg(regs, 30, addr + 4); }

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void __kprobes simulate_cbz_cbnz(u32 opcode, long addr, struct pt_regs *regs) { int disp = 4; if (opcode & (1 << 24)) { if (check_cbnz(opcode, regs)) disp = cbz_displacement(opcode); } else { if (check_cbz(opcode, regs)) disp = cbz_displacement(opcode); } instruction_pointer_set(regs, addr + disp); }

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void __kprobes simulate_tbz_tbnz(u32 opcode, long addr, struct pt_regs *regs) { int disp = 4; if (opcode & (1 << 24)) { if (check_tbnz(opcode, regs)) disp = tbz_displacement(opcode); } else { if (check_tbz(opcode, regs)) disp = tbz_displacement(opcode); } instruction_pointer_set(regs, addr + disp); }

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void __kprobes simulate_ldr_literal(u32 opcode, long addr, struct pt_regs *regs) { u64 *load_addr; int xn = opcode & 0x1f; int disp; disp = ldr_displacement(opcode); load_addr = (u64 *) (addr + disp); if (opcode & (1 << 30)) /* x0-x30 */ set_x_reg(regs, xn, *load_addr); else /* w0-w30 */ set_w_reg(regs, xn, *load_addr); instruction_pointer_set(regs, instruction_pointer(regs) + 4); }

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void __kprobes simulate_ldrsw_literal(u32 opcode, long addr, struct pt_regs *regs) { s32 *load_addr; int xn = opcode & 0x1f; int disp; disp = ldr_displacement(opcode); load_addr = (s32 *) (addr + disp); set_x_reg(regs, xn, *load_addr); instruction_pointer_set(regs, instruction_pointer(regs) + 4); }

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Mark Rutland212.07%133.33%
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