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/*
* 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/kernel.h>
#include <linux/kprobes.h>
#include "simulate-insn.h"
#define sign_extend(x, signbit) \
((x) | (0 - ((x) & (1 << (signbit)))))
#define bbl_displacement(insn) \
sign_extend(((insn) & 0x3ffffff) << 2, 27)
#define bcond_displacement(insn) \
sign_extend(((insn >> 5) & 0x7ffff) << 2, 20)
#define cbz_displacement(insn) \
sign_extend(((insn >> 5) & 0x7ffff) << 2, 20)
#define tbz_displacement(insn) \
sign_extend(((insn >> 5) & 0x3fff) << 2, 15)
#define ldr_displacement(insn) \
sign_extend(((insn >> 5) & 0x7ffff) << 2, 20)
static inline void set_x_reg(struct pt_regs *regs, int reg, u64 val)
{
if (reg < 31)
regs->regs[reg] = val;
}
static inline void set_w_reg(struct pt_regs *regs, int reg, u64 val)
{
if (reg < 31)
regs->regs[reg] = lower_32_bits(val);
}
static inline u64 get_x_reg(struct pt_regs *regs, int reg)
{
if (reg < 31)
return regs->regs[reg];
else
return 0;
}
static inline u32 get_w_reg(struct pt_regs *regs, int reg)
{
if (reg < 31)
return lower_32_bits(regs->regs[reg]);
else
return 0;
}
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);
}
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);
}
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;
}
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;
}
/*
* 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_extend(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);
}
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);
}
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);
}
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);
}
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);
}
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);
}
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);
}
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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