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/*
* arch/arm/kernel/kprobes-thumb.c
*
* Copyright (C) 2011 Jon Medhurst <tixy@yxit.co.uk>.
*
* 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.
*/
#include <linux/kernel.h>
#include <linux/kprobes.h>
#include "kprobes.h"
/*
* True if current instruction is in an IT block.
*/
#define in_it_block(cpsr) ((cpsr & 0x06000c00) != 0x00000000)
/*
* Return the condition code to check for the currently executing instruction.
* This is in ITSTATE<7:4> which is in CPSR<15:12> but is only valid if
* in_it_block returns true.
*/
#define current_cond(cpsr) ((cpsr >> 12) & 0xf)
/*
* Return the PC value for a probe in thumb code.
* This is the address of the probed instruction plus 4.
* We subtract one because the address will have bit zero set to indicate
* a pointer to thumb code.
*/
static inline unsigned long __kprobes thumb_probe_pc(struct kprobe *p)
{
return (unsigned long)p->addr - 1 + 4;
}
static void __kprobes
t16_simulate_bxblx(struct kprobe *p, struct pt_regs *regs)
{
kprobe_opcode_t insn = p->opcode;
unsigned long pc = thumb_probe_pc(p);
int rm = (insn >> 3) & 0xf;
unsigned long rmv = (rm == 15) ? pc : regs->uregs[rm];
if (insn & (1 << 7)) /* BLX ? */
regs->ARM_lr = (unsigned long)p->addr + 2;
bx_write_pc(rmv, regs);
}
static unsigned long __kprobes
t16_emulate_loregs(struct kprobe *p, struct pt_regs *regs)
{
unsigned long oldcpsr = regs->ARM_cpsr;
unsigned long newcpsr;
__asm__ __volatile__ (
"msr cpsr_fs, %[oldcpsr] \n\t"
"ldmia %[regs], {r0-r7} \n\t"
"blx %[fn] \n\t"
"stmia %[regs], {r0-r7} \n\t"
"mrs %[newcpsr], cpsr \n\t"
: [newcpsr] "=r" (newcpsr)
: [oldcpsr] "r" (oldcpsr), [regs] "r" (regs),
[fn] "r" (p->ainsn.insn_fn)
: "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7",
"lr", "memory", "cc"
);
return (oldcpsr & ~APSR_MASK) | (newcpsr & APSR_MASK);
}
static void __kprobes
t16_emulate_loregs_rwflags(struct kprobe *p, struct pt_regs *regs)
{
regs->ARM_cpsr = t16_emulate_loregs(p, regs);
}
static void __kprobes
t16_emulate_loregs_noitrwflags(struct kprobe *p, struct pt_regs *regs)
{
unsigned long cpsr = t16_emulate_loregs(p, regs);
if (!in_it_block(cpsr))
regs->ARM_cpsr = cpsr;
}
static void __kprobes
t16_emulate_hiregs(struct kprobe *p, struct pt_regs *regs)
{
kprobe_opcode_t insn = p->opcode;
unsigned long pc = thumb_probe_pc(p);
int rdn = (insn & 0x7) | ((insn & 0x80) >> 4);
int rm = (insn >> 3) & 0xf;
register unsigned long rdnv asm("r1");
register unsigned long rmv asm("r0");
unsigned long cpsr = regs->ARM_cpsr;
rdnv = (rdn == 15) ? pc : regs->uregs[rdn];
rmv = (rm == 15) ? pc : regs->uregs[rm];
__asm__ __volatile__ (
"msr cpsr_fs, %[cpsr] \n\t"
"blx %[fn] \n\t"
"mrs %[cpsr], cpsr \n\t"
: "=r" (rdnv), [cpsr] "=r" (cpsr)
: "0" (rdnv), "r" (rmv), "1" (cpsr), [fn] "r" (p->ainsn.insn_fn)
: "lr", "memory", "cc"
);
if (rdn == 15)
rdnv &= ~1;
regs->uregs[rdn] = rdnv;
regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) | (cpsr & APSR_MASK);
}
static enum kprobe_insn __kprobes
t16_decode_hiregs(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
insn &= ~0x00ff;
insn |= 0x001; /* Set Rdn = R1 and Rm = R0 */
((u16 *)asi->insn)[0] = insn;
asi->insn_handler = t16_emulate_hiregs;
return INSN_GOOD;
}
static const union decode_item t16_table_1011[] = {
/* Miscellaneous 16-bit instructions */
/*
* If-Then, and hints
* 1011 1111 xxxx xxxx
*/
/* YIELD 1011 1111 0001 0000 */
DECODE_OR (0xffff, 0xbf10),
/* SEV 1011 1111 0100 0000 */
DECODE_EMULATE (0xffff, 0xbf40, kprobe_emulate_none),
/* NOP 1011 1111 0000 0000 */
/* WFE 1011 1111 0010 0000 */
/* WFI 1011 1111 0011 0000 */
DECODE_SIMULATE (0xffcf, 0xbf00, kprobe_simulate_nop),
/* Unassigned hints 1011 1111 xxxx 0000 */
DECODE_REJECT (0xff0f, 0xbf00),
DECODE_END
};
const union decode_item kprobe_decode_thumb16_table[] = {
/*
* Shift (immediate), add, subtract, move, and compare
* 00xx xxxx xxxx xxxx
*/
/* CMP (immediate) 0010 1xxx xxxx xxxx */
DECODE_EMULATE (0xf800, 0x2800, t16_emulate_loregs_rwflags),
/* ADD (register) 0001 100x xxxx xxxx */
/* SUB (register) 0001 101x xxxx xxxx */
/* LSL (immediate) 0000 0xxx xxxx xxxx */
/* LSR (immediate) 0000 1xxx xxxx xxxx */
/* ASR (immediate) 0001 0xxx xxxx xxxx */
/* ADD (immediate, Thumb) 0001 110x xxxx xxxx */
/* SUB (immediate, Thumb) 0001 111x xxxx xxxx */
/* MOV (immediate) 0010 0xxx xxxx xxxx */
/* ADD (immediate, Thumb) 0011 0xxx xxxx xxxx */
/* SUB (immediate, Thumb) 0011 1xxx xxxx xxxx */
DECODE_EMULATE (0xc000, 0x0000, t16_emulate_loregs_noitrwflags),
/*
* 16-bit Thumb data-processing instructions
* 0100 00xx xxxx xxxx
*/
/* TST (register) 0100 0010 00xx xxxx */
DECODE_EMULATE (0xffc0, 0x4200, t16_emulate_loregs_rwflags),
/* CMP (register) 0100 0010 10xx xxxx */
/* CMN (register) 0100 0010 11xx xxxx */
DECODE_EMULATE (0xff80, 0x4280, t16_emulate_loregs_rwflags),
/* AND (register) 0100 0000 00xx xxxx */
/* EOR (register) 0100 0000 01xx xxxx */
/* LSL (register) 0100 0000 10xx xxxx */
/* LSR (register) 0100 0000 11xx xxxx */
/* ASR (register) 0100 0001 00xx xxxx */
/* ADC (register) 0100 0001 01xx xxxx */
/* SBC (register) 0100 0001 10xx xxxx */
/* ROR (register) 0100 0001 11xx xxxx */
/* RSB (immediate) 0100 0010 01xx xxxx */
/* ORR (register) 0100 0011 00xx xxxx */
/* MUL 0100 0011 00xx xxxx */
/* BIC (register) 0100 0011 10xx xxxx */
/* MVN (register) 0100 0011 10xx xxxx */
DECODE_EMULATE (0xfc00, 0x4000, t16_emulate_loregs_noitrwflags),
/*
* Special data instructions and branch and exchange
* 0100 01xx xxxx xxxx
*/
/* BLX pc 0100 0111 1111 1xxx */
DECODE_REJECT (0xfff8, 0x47f8),
/* BX (register) 0100 0111 0xxx xxxx */
/* BLX (register) 0100 0111 1xxx xxxx */
DECODE_SIMULATE (0xff00, 0x4700, t16_simulate_bxblx),
/* ADD pc, pc 0100 0100 1111 1111 */
DECODE_REJECT (0xffff, 0x44ff),
/* ADD (register) 0100 0100 xxxx xxxx */
/* CMP (register) 0100 0101 xxxx xxxx */
/* MOV (register) 0100 0110 xxxx xxxx */
DECODE_CUSTOM (0xfc00, 0x4400, t16_decode_hiregs),
/*
* Miscellaneous 16-bit instructions
* 1011 xxxx xxxx xxxx
*/
DECODE_TABLE (0xf000, 0xb000, t16_table_1011),
DECODE_END
};
static unsigned long __kprobes thumb_check_cc(unsigned long cpsr)
{
if (unlikely(in_it_block(cpsr)))
return kprobe_condition_checks[current_cond(cpsr)](cpsr);
return true;
}
static void __kprobes thumb16_singlestep(struct kprobe *p, struct pt_regs *regs)
{
regs->ARM_pc += 2;
p->ainsn.insn_handler(p, regs);
regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
}
static void __kprobes thumb32_singlestep(struct kprobe *p, struct pt_regs *regs)
{
regs->ARM_pc += 4;
p->ainsn.insn_handler(p, regs);
regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
}
enum kprobe_insn __kprobes
thumb16_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
asi->insn_singlestep = thumb16_singlestep;
asi->insn_check_cc = thumb_check_cc;
return kprobe_decode_insn(insn, asi, kprobe_decode_thumb16_table, true);
}
enum kprobe_insn __kprobes
thumb32_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
{
asi->insn_singlestep = thumb32_singlestep;
asi->insn_check_cc = thumb_check_cc;
return INSN_REJECTED;
}
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