blob: dd6ce86d4332be4c0cff75f52ac88e366f05754a [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2014 ARM Limited
*/
#include <linux/cpu.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/perf_event.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/sysctl.h>
#include <linux/uaccess.h>
#include <asm/cpufeature.h>
#include <asm/insn.h>
#include <asm/sysreg.h>
#include <asm/system_misc.h>
#include <asm/traps.h>
#define CREATE_TRACE_POINTS
#include "trace-events-emulation.h"
/*
* The runtime support for deprecated instruction support can be in one of
* following three states -
*
* 0 = undef
* 1 = emulate (software emulation)
* 2 = hw (supported in hardware)
*/
enum insn_emulation_mode {
INSN_UNDEF,
INSN_EMULATE,
INSN_HW,
};
enum legacy_insn_status {
INSN_DEPRECATED,
INSN_OBSOLETE,
INSN_UNAVAILABLE,
};
struct insn_emulation {
const char *name;
enum legacy_insn_status status;
bool (*try_emulate)(struct pt_regs *regs,
u32 insn);
int (*set_hw_mode)(bool enable);
int current_mode;
int min;
int max;
/* sysctl for this emulation */
struct ctl_table sysctl;
};
#define ARM_OPCODE_CONDTEST_FAIL 0
#define ARM_OPCODE_CONDTEST_PASS 1
#define ARM_OPCODE_CONDTEST_UNCOND 2
#define ARM_OPCODE_CONDITION_UNCOND 0xf
static unsigned int __maybe_unused aarch32_check_condition(u32 opcode, u32 psr)
{
u32 cc_bits = opcode >> 28;
if (cc_bits != ARM_OPCODE_CONDITION_UNCOND) {
if ((*aarch32_opcode_cond_checks[cc_bits])(psr))
return ARM_OPCODE_CONDTEST_PASS;
else
return ARM_OPCODE_CONDTEST_FAIL;
}
return ARM_OPCODE_CONDTEST_UNCOND;
}
#ifdef CONFIG_SWP_EMULATION
/*
* Implement emulation of the SWP/SWPB instructions using load-exclusive and
* store-exclusive.
*
* Syntax of SWP{B} instruction: SWP{B}<c> <Rt>, <Rt2>, [<Rn>]
* Where: Rt = destination
* Rt2 = source
* Rn = address
*/
/*
* Error-checking SWP macros implemented using ldxr{b}/stxr{b}
*/
/* Arbitrary constant to ensure forward-progress of the LL/SC loop */
#define __SWP_LL_SC_LOOPS 4
#define __user_swpX_asm(data, addr, res, temp, temp2, B) \
do { \
uaccess_enable_privileged(); \
__asm__ __volatile__( \
" mov %w3, %w6\n" \
"0: ldxr"B" %w2, [%4]\n" \
"1: stxr"B" %w0, %w1, [%4]\n" \
" cbz %w0, 2f\n" \
" sub %w3, %w3, #1\n" \
" cbnz %w3, 0b\n" \
" mov %w0, %w5\n" \
" b 3f\n" \
"2:\n" \
" mov %w1, %w2\n" \
"3:\n" \
_ASM_EXTABLE_UACCESS_ERR(0b, 3b, %w0) \
_ASM_EXTABLE_UACCESS_ERR(1b, 3b, %w0) \
: "=&r" (res), "+r" (data), "=&r" (temp), "=&r" (temp2) \
: "r" ((unsigned long)addr), "i" (-EAGAIN), \
"i" (__SWP_LL_SC_LOOPS) \
: "memory"); \
uaccess_disable_privileged(); \
} while (0)
#define __user_swp_asm(data, addr, res, temp, temp2) \
__user_swpX_asm(data, addr, res, temp, temp2, "")
#define __user_swpb_asm(data, addr, res, temp, temp2) \
__user_swpX_asm(data, addr, res, temp, temp2, "b")
/*
* Bit 22 of the instruction encoding distinguishes between
* the SWP and SWPB variants (bit set means SWPB).
*/
#define TYPE_SWPB (1 << 22)
static int emulate_swpX(unsigned int address, unsigned int *data,
unsigned int type)
{
unsigned int res = 0;
if ((type != TYPE_SWPB) && (address & 0x3)) {
/* SWP to unaligned address not permitted */
pr_debug("SWP instruction on unaligned pointer!\n");
return -EFAULT;
}
while (1) {
unsigned long temp, temp2;
if (type == TYPE_SWPB)
__user_swpb_asm(*data, address, res, temp, temp2);
else
__user_swp_asm(*data, address, res, temp, temp2);
if (likely(res != -EAGAIN) || signal_pending(current))
break;
cond_resched();
}
return res;
}
/*
* swp_handler logs the id of calling process, dissects the instruction, sanity
* checks the memory location, calls emulate_swpX for the actual operation and
* deals with fixup/error handling before returning
*/
static int swp_handler(struct pt_regs *regs, u32 instr)
{
u32 destreg, data, type, address = 0;
const void __user *user_ptr;
int rn, rt2, res = 0;
perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);
type = instr & TYPE_SWPB;
switch (aarch32_check_condition(instr, regs->pstate)) {
case ARM_OPCODE_CONDTEST_PASS:
break;
case ARM_OPCODE_CONDTEST_FAIL:
/* Condition failed - return to next instruction */
goto ret;
case ARM_OPCODE_CONDTEST_UNCOND:
/* If unconditional encoding - not a SWP, undef */
return -EFAULT;
default:
return -EINVAL;
}
rn = aarch32_insn_extract_reg_num(instr, A32_RN_OFFSET);
rt2 = aarch32_insn_extract_reg_num(instr, A32_RT2_OFFSET);
address = (u32)regs->user_regs.regs[rn];
data = (u32)regs->user_regs.regs[rt2];
destreg = aarch32_insn_extract_reg_num(instr, A32_RT_OFFSET);
pr_debug("addr in r%d->0x%08x, dest is r%d, source in r%d->0x%08x)\n",
rn, address, destreg,
aarch32_insn_extract_reg_num(instr, A32_RT2_OFFSET), data);
/* Check access in reasonable access range for both SWP and SWPB */
user_ptr = (const void __user *)(unsigned long)(address & ~3);
if (!access_ok(user_ptr, 4)) {
pr_debug("SWP{B} emulation: access to 0x%08x not allowed!\n",
address);
goto fault;
}
res = emulate_swpX(address, &data, type);
if (res == -EFAULT)
goto fault;
else if (res == 0)
regs->user_regs.regs[destreg] = data;
ret:
if (type == TYPE_SWPB)
trace_instruction_emulation("swpb", regs->pc);
else
trace_instruction_emulation("swp", regs->pc);
pr_warn_ratelimited("\"%s\" (%ld) uses obsolete SWP{B} instruction at 0x%llx\n",
current->comm, (unsigned long)current->pid, regs->pc);
arm64_skip_faulting_instruction(regs, 4);
return 0;
fault:
pr_debug("SWP{B} emulation: access caused memory abort!\n");
arm64_notify_segfault(address);
return 0;
}
static bool try_emulate_swp(struct pt_regs *regs, u32 insn)
{
/* SWP{B} only exists in ARM state and does not exist in Thumb */
if (!compat_user_mode(regs) || compat_thumb_mode(regs))
return false;
if ((insn & 0x0fb00ff0) != 0x01000090)
return false;
return swp_handler(regs, insn) == 0;
}
static struct insn_emulation insn_swp = {
.name = "swp",
.status = INSN_OBSOLETE,
.try_emulate = try_emulate_swp,
.set_hw_mode = NULL,
};
#endif /* CONFIG_SWP_EMULATION */
#ifdef CONFIG_CP15_BARRIER_EMULATION
static int cp15barrier_handler(struct pt_regs *regs, u32 instr)
{
perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);
switch (aarch32_check_condition(instr, regs->pstate)) {
case ARM_OPCODE_CONDTEST_PASS:
break;
case ARM_OPCODE_CONDTEST_FAIL:
/* Condition failed - return to next instruction */
goto ret;
case ARM_OPCODE_CONDTEST_UNCOND:
/* If unconditional encoding - not a barrier instruction */
return -EFAULT;
default:
return -EINVAL;
}
switch (aarch32_insn_mcr_extract_crm(instr)) {
case 10:
/*
* dmb - mcr p15, 0, Rt, c7, c10, 5
* dsb - mcr p15, 0, Rt, c7, c10, 4
*/
if (aarch32_insn_mcr_extract_opc2(instr) == 5) {
dmb(sy);
trace_instruction_emulation(
"mcr p15, 0, Rt, c7, c10, 5 ; dmb", regs->pc);
} else {
dsb(sy);
trace_instruction_emulation(
"mcr p15, 0, Rt, c7, c10, 4 ; dsb", regs->pc);
}
break;
case 5:
/*
* isb - mcr p15, 0, Rt, c7, c5, 4
*
* Taking an exception or returning from one acts as an
* instruction barrier. So no explicit barrier needed here.
*/
trace_instruction_emulation(
"mcr p15, 0, Rt, c7, c5, 4 ; isb", regs->pc);
break;
}
ret:
pr_warn_ratelimited("\"%s\" (%ld) uses deprecated CP15 Barrier instruction at 0x%llx\n",
current->comm, (unsigned long)current->pid, regs->pc);
arm64_skip_faulting_instruction(regs, 4);
return 0;
}
static int cp15_barrier_set_hw_mode(bool enable)
{
if (enable)
sysreg_clear_set(sctlr_el1, 0, SCTLR_EL1_CP15BEN);
else
sysreg_clear_set(sctlr_el1, SCTLR_EL1_CP15BEN, 0);
return 0;
}
static bool try_emulate_cp15_barrier(struct pt_regs *regs, u32 insn)
{
if (!compat_user_mode(regs) || compat_thumb_mode(regs))
return false;
if ((insn & 0x0fff0fdf) == 0x0e070f9a)
return cp15barrier_handler(regs, insn) == 0;
if ((insn & 0x0fff0fff) == 0x0e070f95)
return cp15barrier_handler(regs, insn) == 0;
return false;
}
static struct insn_emulation insn_cp15_barrier = {
.name = "cp15_barrier",
.status = INSN_DEPRECATED,
.try_emulate = try_emulate_cp15_barrier,
.set_hw_mode = cp15_barrier_set_hw_mode,
};
#endif /* CONFIG_CP15_BARRIER_EMULATION */
#ifdef CONFIG_SETEND_EMULATION
static int setend_set_hw_mode(bool enable)
{
if (!cpu_supports_mixed_endian_el0())
return -EINVAL;
if (enable)
sysreg_clear_set(sctlr_el1, SCTLR_EL1_SED, 0);
else
sysreg_clear_set(sctlr_el1, 0, SCTLR_EL1_SED);
return 0;
}
static int compat_setend_handler(struct pt_regs *regs, u32 big_endian)
{
char *insn;
perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);
if (big_endian) {
insn = "setend be";
regs->pstate |= PSR_AA32_E_BIT;
} else {
insn = "setend le";
regs->pstate &= ~PSR_AA32_E_BIT;
}
trace_instruction_emulation(insn, regs->pc);
pr_warn_ratelimited("\"%s\" (%ld) uses deprecated setend instruction at 0x%llx\n",
current->comm, (unsigned long)current->pid, regs->pc);
return 0;
}
static int a32_setend_handler(struct pt_regs *regs, u32 instr)
{
int rc = compat_setend_handler(regs, (instr >> 9) & 1);
arm64_skip_faulting_instruction(regs, 4);
return rc;
}
static int t16_setend_handler(struct pt_regs *regs, u32 instr)
{
int rc = compat_setend_handler(regs, (instr >> 3) & 1);
arm64_skip_faulting_instruction(regs, 2);
return rc;
}
static bool try_emulate_setend(struct pt_regs *regs, u32 insn)
{
if (compat_thumb_mode(regs) &&
(insn & 0xfffffff7) == 0x0000b650)
return t16_setend_handler(regs, insn) == 0;
if (compat_user_mode(regs) &&
(insn & 0xfffffdff) == 0xf1010000)
return a32_setend_handler(regs, insn) == 0;
return false;
}
static struct insn_emulation insn_setend = {
.name = "setend",
.status = INSN_DEPRECATED,
.try_emulate = try_emulate_setend,
.set_hw_mode = setend_set_hw_mode,
};
#endif /* CONFIG_SETEND_EMULATION */
static struct insn_emulation *insn_emulations[] = {
#ifdef CONFIG_SWP_EMULATION
&insn_swp,
#endif
#ifdef CONFIG_CP15_BARRIER_EMULATION
&insn_cp15_barrier,
#endif
#ifdef CONFIG_SETEND_EMULATION
&insn_setend,
#endif
};
static DEFINE_MUTEX(insn_emulation_mutex);
static void enable_insn_hw_mode(void *data)
{
struct insn_emulation *insn = data;
if (insn->set_hw_mode)
insn->set_hw_mode(true);
}
static void disable_insn_hw_mode(void *data)
{
struct insn_emulation *insn = data;
if (insn->set_hw_mode)
insn->set_hw_mode(false);
}
/* Run set_hw_mode(mode) on all active CPUs */
static int run_all_cpu_set_hw_mode(struct insn_emulation *insn, bool enable)
{
if (!insn->set_hw_mode)
return -EINVAL;
if (enable)
on_each_cpu(enable_insn_hw_mode, (void *)insn, true);
else
on_each_cpu(disable_insn_hw_mode, (void *)insn, true);
return 0;
}
/*
* Run set_hw_mode for all insns on a starting CPU.
* Returns:
* 0 - If all the hooks ran successfully.
* -EINVAL - At least one hook is not supported by the CPU.
*/
static int run_all_insn_set_hw_mode(unsigned int cpu)
{
int rc = 0;
unsigned long flags;
/*
* Disable IRQs to serialize against an IPI from
* run_all_cpu_set_hw_mode(), ensuring the HW is programmed to the most
* recent enablement state if the two race with one another.
*/
local_irq_save(flags);
for (int i = 0; i < ARRAY_SIZE(insn_emulations); i++) {
struct insn_emulation *insn = insn_emulations[i];
bool enable = READ_ONCE(insn->current_mode) == INSN_HW;
if (insn->set_hw_mode && insn->set_hw_mode(enable)) {
pr_warn("CPU[%u] cannot support the emulation of %s",
cpu, insn->name);
rc = -EINVAL;
}
}
local_irq_restore(flags);
return rc;
}
static int update_insn_emulation_mode(struct insn_emulation *insn,
enum insn_emulation_mode prev)
{
int ret = 0;
switch (prev) {
case INSN_UNDEF: /* Nothing to be done */
break;
case INSN_EMULATE:
break;
case INSN_HW:
if (!run_all_cpu_set_hw_mode(insn, false))
pr_notice("Disabled %s support\n", insn->name);
break;
}
switch (insn->current_mode) {
case INSN_UNDEF:
break;
case INSN_EMULATE:
break;
case INSN_HW:
ret = run_all_cpu_set_hw_mode(insn, true);
if (!ret)
pr_notice("Enabled %s support\n", insn->name);
break;
}
return ret;
}
static int emulation_proc_handler(struct ctl_table *table, int write,
void *buffer, size_t *lenp,
loff_t *ppos)
{
int ret = 0;
struct insn_emulation *insn = container_of(table->data, struct insn_emulation, current_mode);
enum insn_emulation_mode prev_mode = insn->current_mode;
mutex_lock(&insn_emulation_mutex);
ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (ret || !write || prev_mode == insn->current_mode)
goto ret;
ret = update_insn_emulation_mode(insn, prev_mode);
if (ret) {
/* Mode change failed, revert to previous mode. */
WRITE_ONCE(insn->current_mode, prev_mode);
update_insn_emulation_mode(insn, INSN_UNDEF);
}
ret:
mutex_unlock(&insn_emulation_mutex);
return ret;
}
static void __init register_insn_emulation(struct insn_emulation *insn)
{
struct ctl_table *sysctl;
insn->min = INSN_UNDEF;
switch (insn->status) {
case INSN_DEPRECATED:
insn->current_mode = INSN_EMULATE;
/* Disable the HW mode if it was turned on at early boot time */
run_all_cpu_set_hw_mode(insn, false);
insn->max = INSN_HW;
break;
case INSN_OBSOLETE:
insn->current_mode = INSN_UNDEF;
insn->max = INSN_EMULATE;
break;
case INSN_UNAVAILABLE:
insn->current_mode = INSN_UNDEF;
insn->max = INSN_UNDEF;
break;
}
/* Program the HW if required */
update_insn_emulation_mode(insn, INSN_UNDEF);
if (insn->status != INSN_UNAVAILABLE) {
sysctl = &insn->sysctl;
sysctl->mode = 0644;
sysctl->maxlen = sizeof(int);
sysctl->procname = insn->name;
sysctl->data = &insn->current_mode;
sysctl->extra1 = &insn->min;
sysctl->extra2 = &insn->max;
sysctl->proc_handler = emulation_proc_handler;
register_sysctl_sz("abi", sysctl, 1);
}
}
bool try_emulate_armv8_deprecated(struct pt_regs *regs, u32 insn)
{
for (int i = 0; i < ARRAY_SIZE(insn_emulations); i++) {
struct insn_emulation *ie = insn_emulations[i];
if (ie->status == INSN_UNAVAILABLE)
continue;
/*
* A trap may race with the mode being changed
* INSN_EMULATE<->INSN_HW. Try to emulate the instruction to
* avoid a spurious UNDEF.
*/
if (READ_ONCE(ie->current_mode) == INSN_UNDEF)
continue;
if (ie->try_emulate(regs, insn))
return true;
}
return false;
}
/*
* Invoked as core_initcall, which guarantees that the instruction
* emulation is ready for userspace.
*/
static int __init armv8_deprecated_init(void)
{
#ifdef CONFIG_SETEND_EMULATION
if (!system_supports_mixed_endian_el0()) {
insn_setend.status = INSN_UNAVAILABLE;
pr_info("setend instruction emulation is not supported on this system\n");
}
#endif
for (int i = 0; i < ARRAY_SIZE(insn_emulations); i++) {
struct insn_emulation *ie = insn_emulations[i];
if (ie->status == INSN_UNAVAILABLE)
continue;
register_insn_emulation(ie);
}
cpuhp_setup_state_nocalls(CPUHP_AP_ARM64_ISNDEP_STARTING,
"arm64/isndep:starting",
run_all_insn_set_hw_mode, NULL);
return 0;
}
core_initcall(armv8_deprecated_init);