// SPDX-License-Identifier: GPL-2.0-only
/*
* arch/arm/probes/kprobes/actions-arm.c
*
* Copyright (C) 2006, 2007 Motorola Inc.
*/
/*
* We do not have hardware single-stepping on ARM, This
* effort is further complicated by the ARM not having a
* "next PC" register. Instructions that change the PC
* can't be safely single-stepped in a MP environment, so
* we have a lot of work to do:
*
* In the prepare phase:
* *) If it is an instruction that does anything
* with the CPU mode, we reject it for a kprobe.
* (This is out of laziness rather than need. The
* instructions could be simulated.)
*
* *) Otherwise, decode the instruction rewriting its
* registers to take fixed, ordered registers and
* setting a handler for it to run the instruction.
*
* In the execution phase by an instruction's handler:
*
* *) If the PC is written to by the instruction, the
* instruction must be fully simulated in software.
*
* *) Otherwise, a modified form of the instruction is
* directly executed. Its handler calls the
* instruction in insn[0]. In insn[1] is a
* "mov pc, lr" to return.
*
* Before calling, load up the reordered registers
* from the original instruction's registers. If one
* of the original input registers is the PC, compute
* and adjust the appropriate input register.
*
* After call completes, copy the output registers to
* the original instruction's original registers.
*
* We don't use a real breakpoint instruction since that
* would have us in the kernel go from SVC mode to SVC
* mode losing the link register. Instead we use an
* undefined instruction. To simplify processing, the
* undefined instruction used for kprobes must be reserved
* exclusively for kprobes use.
*
* TODO: ifdef out some instruction decoding based on architecture.
*/
#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include "../decode-arm.h"
#include "core.h"
#include "checkers.h"
#if __LINUX_ARM_ARCH__ >= 6
#define BLX(reg) "blx "reg" \n\t"
#else
#define BLX(reg) "mov lr, pc \n\t" \
"mov pc, "reg" \n\t"
#endif
static void __kprobes
emulate_ldrdstrd(probes_opcode_t insn,
struct arch_probes_insn *asi, struct pt_regs *regs)
{
unsigned long pc = regs->ARM_pc + 4;
int rt = (insn >> 12) & 0xf;
int rn = (insn >> 16) & 0xf;
int rm = insn & 0xf;
register unsigned long rtv asm("r0") = regs->uregs[rt];
register unsigned long rt2v asm("r1") = regs->uregs[rt+1];
register unsigned long rnv asm("r2") = (rn == 15) ? pc
: regs->uregs[rn];
register unsigned long rmv asm("r3") = regs->uregs[rm];
__asm__ __volatile__ (
BLX("%[fn]")
: "=r" (rtv), "=r" (rt2v), "=r" (rnv)
: "0" (rtv), "1" (rt2v), "2" (rnv), "r" (rmv),
[fn] "r" (asi->insn_fn)
: "lr", "memory", "cc"
);
regs->uregs[rt] = rtv;
regs->uregs[rt+1] = rt2v;
if (is_writeback(insn))
regs->uregs[rn] = rnv;
}
static void __kprobes
emulate_ldr(probes_opcode_t insn,
struct arch_probes_insn *asi, struct pt_regs *regs)
{
unsigned long pc = regs->ARM_pc + 4;
int rt = (insn >> 12) & 0xf;
int rn = (insn >> 16) & 0xf;
int rm = insn & 0xf;
register unsigned long rtv asm("r0");
register unsigned long rnv asm("r2") = (rn == 15) ? pc
: regs->uregs[rn];
register unsigned long rmv asm("r3") = regs->uregs[rm];
__asm__ __volatile__ (
BLX("%[fn]")
: "=r" (rtv), "=r" (rnv)
: "1" (rnv), "r" (rmv), [fn] "r" (asi->insn_fn)
: "lr", "memory", "cc"
);
if (rt == 15)
load_write_pc(rtv, regs);
else
regs->uregs[rt] = rtv;
if (is_writeback(insn))
regs->uregs[rn] = rnv;
}
static void __kprobes
emulate_str(probes_opcode_t insn,
struct arch_probes_insn *asi, struct pt_regs *regs)
{
unsigned long rtpc = regs->ARM_pc - 4 + str_pc_offset;
unsigned long rnpc = regs->ARM_pc + 4;
int rt = (insn >> 12) & 0xf;
int rn = (insn >> 16) & 0xf;
int rm = insn & 0xf;
register unsigned long rtv asm("r0") = (rt == 15) ? rtpc
: regs->uregs[rt];
register unsigned long rnv asm("r2") = (rn == 15) ? rnpc
: regs->uregs[rn];
register unsigned long rmv asm("r3") = regs->uregs[rm];
__asm__ __volatile__ (
BLX("%[fn]")
: "=r" (rnv)
: "r" (rtv), "0" (rnv), "r" (rmv), [fn] "r" (asi->insn_fn)
: "lr", "memory", "cc"
);
if (is_writeback(insn))
regs->uregs[rn] = rnv;
}
static void __kprobes
emulate_rd12rn16rm0rs8_rwflags(probes_opcode_t insn,
struct arch_probes_insn *asi, struct pt_regs *regs)
{
unsigned long pc = regs->ARM_pc + 4;
int rd = (insn >> 12) & 0xf;
int rn = (insn >> 16) & 0xf;
int rm = insn & 0xf;
int rs = (insn >> 8) & 0xf;
register unsigned long rdv asm("r0") = regs->uregs[rd];
register unsigned long rnv asm("r2") = (rn == 15) ? pc
: regs->uregs[rn];
register unsigned long rmv asm("r3") = (rm == 15) ? pc
: regs->uregs[rm];
register unsigned long rsv asm("r1") = regs->uregs[rs];
unsigned long cpsr = regs->ARM_cpsr;
__asm__ __volatile__ (
"msr cpsr_fs, %[cpsr] \n\t"
BLX("%[fn]")
"mrs %[cpsr], cpsr \n\t"
: "=r" (rdv), [cpsr] "=r" (cpsr)
: "0" (rdv), "r" (rnv), "r" (rmv), "r" (rsv),
"1" (cpsr), [fn] "r" (asi->insn_fn)
: "lr", "memory", "cc"
);
if (rd == 15)
alu_write_pc(rdv, regs);
else
regs->uregs[rd] = rdv;
regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) | (cpsr & APSR_MASK);
}
static void __kprobes
emulate_rd12rn16rm0_rwflags_nopc(probes_opcode_t insn,
struct arch_probes_insn *asi, struct pt_regs *regs)
{
int rd = (insn >> 12) & 0xf;
int rn = (insn >> 16) & 0xf;
int rm = insn & 0xf;
register unsigned long rdv asm("r0") = regs->uregs[rd];
register unsigned long rnv asm("r2") = regs->uregs[rn];
register unsigned long rmv asm("r3") = regs->uregs[rm];
unsigned long cpsr = regs->ARM_cpsr;
__asm__ __volatile__ (
"msr cpsr_fs, %[cpsr] \n\t"
BLX("%[fn]")
"mrs %[cpsr], cpsr \n\t"
: "=r" (rdv), [cpsr] "=r" (cpsr)
: "0" (rdv), "r" (rnv), "r" (rmv),
"1" (cpsr), [fn] "r" (asi->insn_fn)
: "lr", "memory", "cc"
);
regs->uregs[rd] = rdv;
regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) | (cpsr & APSR_MASK);
}
static void __kprobes
emulate_rd16rn12rm0rs8_rwflags_nopc(probes_opcode_t insn,
struct arch_probes_insn *asi,
struct pt_regs *regs)
{
int rd = (insn >> 16) & 0xf;
int rn = (insn >> 12) & 0xf;
int rm = insn & 0xf;
int rs = (insn >> 8) & 0xf;
register unsigned long rdv asm("r2") = regs->uregs[rd];
register unsigned long rnv asm("r0") = regs->uregs[rn];
register unsigned long rmv asm("r3") = regs->uregs[rm];
register unsigned long rsv asm("r1") = regs->uregs[rs];
unsigned long cpsr = regs->ARM_cpsr;
__asm__ __volatile__ (
"msr cpsr_fs, %[cpsr] \n\t"
BLX("%[fn]")
"mrs %[cpsr], cpsr \n\t"
: "=r" (rdv), [cpsr] "=r" (cpsr)
: "0" (rdv), "r" (rnv), "r" (rmv), "r" (rsv),
"1" (cpsr), [fn] "r" (asi->insn_fn)
: "lr", "memory", "cc"
);
regs->uregs[rd] = rdv;
regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) | (cpsr & APSR_MASK);
}
static void __kprobes
emulate_rd12rm0_noflags_nopc(probes_opcode_t insn,
struct arch_probes_insn *asi, struct pt_regs *regs)
{
int rd = (insn >> 12) & 0xf;
int rm = insn & 0xf;
register unsigned long rdv asm("r0") = regs->uregs[rd];
register unsigned long rmv asm("r3") = regs->uregs[rm];
__asm__ __volatile__ (
BLX("%[fn]")
: "=r" (rdv)
: "0" (rdv), "r" (rmv), [fn] "r" (asi->insn_fn)
: "lr", "memory", "cc"
);
regs->uregs[rd] = rdv;
}
static void __kprobes
emulate_rdlo12rdhi16rn0rm8_rwflags_nopc(probes_opcode_t insn,
struct arch_probes_insn *asi,
struct pt_regs *regs)
{
int rdlo = (insn >> 12) & 0xf;
int rdhi = (insn >> 16) & 0xf;
int rn = insn & 0xf;
int rm = (insn >> 8) & 0xf;
register unsigned long rdlov asm("r0") = regs->uregs[rdlo];
register unsigned long rdhiv asm("r2") = regs->uregs[rdhi];
register unsigned long rnv asm("r3") = regs->uregs[rn];
register unsigned long rmv asm("r1") = regs->uregs[rm];
unsigned long cpsr = regs->ARM_cpsr;
__asm__ __volatile__ (
"msr cpsr_fs, %[cpsr] \n\t"
BLX("%[fn]")
"mrs %[cpsr], cpsr \n\t"
: "=r" (rdlov), "=r" (rdhiv), [cpsr] "=r" (cpsr)
: "0" (rdlov), "1" (rdhiv), "r" (rnv), "r" (rmv),
"2" (cpsr), [fn] "r" (asi->insn_fn)
: "lr", "memory", "cc"
);
regs->uregs[rdlo] = rdlov;
regs->uregs[rdhi] = rdhiv;
regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) | (cpsr & APSR_MASK);
}
const union decode_action kprobes_arm_actions[NUM_PROBES_ARM_ACTIONS] = {
[PROBES_PRELOAD_IMM] = {.handler = probes_simulate_nop},
[PROBES_PRELOAD_REG] = {.handler = probes_simulate_nop},
[PROBES_BRANCH_IMM] = {.handler = simulate_blx1},
[PROBES_MRS] = {.handler = simulate_mrs},
[PROBES_BRANCH_REG] = {.handler = simulate_blx2bx},
[PROBES_CLZ] = {.handler = emulate_rd12rm0_noflags_nopc},
[PROBES_SATURATING_ARITHMETIC] = {
.handler = emulate_rd12rn16rm0_rwflags_nopc},
[PROBES_MUL1] = {.handler = emulate_rdlo12rdhi16rn0rm8_rwflags_nopc},
[PROBES_MUL2] = {.handler = emulate_rd16rn12rm0rs8_rwflags_nopc},
[PROBES_SWP] = {.handler = emulate_rd12rn16rm0_rwflags_nopc},
[PROBES_LDRSTRD] = {.handler = emulate_ldrdstrd},
[PROBES_LOAD_EXTRA] = {.handler = emulate_ldr},
[PROBES_LOAD] = {.handler = emulate_ldr},
[PROBES_STORE_EXTRA] = {.handler = emulate_str},
[PROBES_STORE] = {.handler = emulate_str},
[PROBES_MOV_IP_SP] = {.handler = simulate_mov_ipsp},
[PROBES_DATA_PROCESSING_REG] = {
.handler = emulate_rd12rn16rm0rs8_rwflags},
[PROBES_DATA_PROCESSING_IMM] = {
.handler = emulate_rd12rn16rm0rs8_rwflags},
[PROBES_MOV_HALFWORD] = {.handler = emulate_rd12rm0_noflags_nopc},
[PROBES_SEV] = {.handler = probes_emulate_none},
[PROBES_WFE] = {.handler = probes_simulate_nop},
[PROBES_SATURATE] = {.handler = emulate_rd12rn16rm0_rwflags_nopc},
[PROBES_REV] = {.handler = emulate_rd12rm0_noflags_nopc},
[PROBES_MMI] = {.handler = emulate_rd12rn16rm0_rwflags_nopc},
[PROBES_PACK] = {.handler = emulate_rd12rn16rm0_rwflags_nopc},
[PROBES_EXTEND] = {.handler = emulate_rd12rm0_noflags_nopc},
[PROBES_EXTEND_ADD] = {.handler = emulate_rd12rn16rm0_rwflags_nopc},
[PROBES_MUL_ADD_LONG] = {
.handler = emulate_rdlo12rdhi16rn0rm8_rwflags_nopc},
[PROBES_MUL_ADD] = {.handler = emulate_rd16rn12rm0rs8_rwflags_nopc},
[PROBES_BITFIELD] = {.handler = emulate_rd12rm0_noflags_nopc},
[PROBES_BRANCH] = {.handler = simulate_bbl},
[PROBES_LDMSTM] = {.decoder = kprobe_decode_ldmstm}
};
const struct decode_checker *kprobes_arm_checkers[] = {arm_stack_checker, arm_regs_checker, NULL};