arch/riscv/kernel/traps_misaligned.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2020 Western Digital Corporation or its affiliates.
 */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/perf_event.h>
#include <linux/irq.h>
#include <linux/stringify.h>

#include <asm/processor.h>
#include <asm/ptrace.h>
#include <asm/csr.h>
#include <asm/entry-common.h>
#include <asm/hwprobe.h>
#include <asm/cpufeature.h>
#include <asm/sbi.h>
#include <asm/vector.h>
#include <asm/insn.h>

#ifdef CONFIG_FPU

#define FP_GET_RD(insn)		(insn >> 7 & 0x1F)

extern void put_f32_reg(unsigned long fp_reg, unsigned long value);

static int set_f32_rd(unsigned long insn, struct pt_regs *regs,
		      unsigned long val)
{
	unsigned long fp_reg = FP_GET_RD(insn);

	put_f32_reg(fp_reg, val);
	regs->status |= SR_FS_DIRTY;

	return 0;
}

extern void put_f64_reg(unsigned long fp_reg, unsigned long value);

static int set_f64_rd(unsigned long insn, struct pt_regs *regs, u64 val)
{
	unsigned long fp_reg = FP_GET_RD(insn);
	unsigned long value;

#if __riscv_xlen == 32
	value = (unsigned long) &val;
#else
	value = val;
#endif
	put_f64_reg(fp_reg, value);
	regs->status |= SR_FS_DIRTY;

	return 0;
}

#if __riscv_xlen == 32
extern void get_f64_reg(unsigned long fp_reg, u64 *value);

static u64 get_f64_rs(unsigned long insn, u8 fp_reg_offset,
		      struct pt_regs *regs)
{
	unsigned long fp_reg = (insn >> fp_reg_offset) & 0x1F;
	u64 val;

	get_f64_reg(fp_reg, &val);
	regs->status |= SR_FS_DIRTY;

	return val;
}
#else

extern unsigned long get_f64_reg(unsigned long fp_reg);

static unsigned long get_f64_rs(unsigned long insn, u8 fp_reg_offset,
				struct pt_regs *regs)
{
	unsigned long fp_reg = (insn >> fp_reg_offset) & 0x1F;
	unsigned long val;

	val = get_f64_reg(fp_reg);
	regs->status |= SR_FS_DIRTY;

	return val;
}

#endif

extern unsigned long get_f32_reg(unsigned long fp_reg);

static unsigned long get_f32_rs(unsigned long insn, u8 fp_reg_offset,
				struct pt_regs *regs)
{
	unsigned long fp_reg = (insn >> fp_reg_offset) & 0x1F;
	unsigned long val;

	val = get_f32_reg(fp_reg);
	regs->status |= SR_FS_DIRTY;

	return val;
}

#else /* CONFIG_FPU */
static void set_f32_rd(unsigned long insn, struct pt_regs *regs,
		       unsigned long val) {}

static void set_f64_rd(unsigned long insn, struct pt_regs *regs, u64 val) {}

static unsigned long get_f64_rs(unsigned long insn, u8 fp_reg_offset,
				struct pt_regs *regs)
{
	return 0;
}

static unsigned long get_f32_rs(unsigned long insn, u8 fp_reg_offset,
				struct pt_regs *regs)
{
	return 0;
}

#endif

#define GET_F64_RS2(insn, regs) (get_f64_rs(insn, 20, regs))
#define GET_F64_RS2C(insn, regs) (get_f64_rs(insn, 2, regs))
#define GET_F64_RS2S(insn, regs) (get_f64_rs(RVC_RS2S(insn), 0, regs))

#define GET_F32_RS2(insn, regs) (get_f32_rs(insn, 20, regs))
#define GET_F32_RS2C(insn, regs) (get_f32_rs(insn, 2, regs))
#define GET_F32_RS2S(insn, regs) (get_f32_rs(RVC_RS2S(insn), 0, regs))

#define __read_insn(regs, insn, insn_addr, type)	\
({							\
	int __ret;					\
							\
	if (user_mode(regs)) {				\
		__ret = get_user(insn, (type __user *) insn_addr); \
	} else {					\
		insn = *(type *)insn_addr;		\
		__ret = 0;				\
	}						\
							\
	__ret;						\
})

static inline int get_insn(struct pt_regs *regs, ulong epc, ulong *r_insn)
{
	ulong insn = 0;

	if (epc & 0x2) {
		ulong tmp = 0;

		if (__read_insn(regs, insn, epc, u16))
			return -EFAULT;
		/* __get_user() uses regular "lw" which sign extend the loaded
		 * value make sure to clear higher order bits in case we "or" it
		 * below with the upper 16 bits half.
		 */
		insn &= GENMASK(15, 0);
		if ((insn & __INSN_LENGTH_MASK) != __INSN_LENGTH_32) {
			*r_insn = insn;
			return 0;
		}
		epc += sizeof(u16);
		if (__read_insn(regs, tmp, epc, u16))
			return -EFAULT;
		*r_insn = (tmp << 16) | insn;

		return 0;
	} else {
		if (__read_insn(regs, insn, epc, u32))
			return -EFAULT;
		if ((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32) {
			*r_insn = insn;
			return 0;
		}
		insn &= GENMASK(15, 0);
		*r_insn = insn;

		return 0;
	}
}

union reg_data {
	u8 data_bytes[8];
	ulong data_ulong;
	u64 data_u64;
};

/* sysctl hooks */
int unaligned_enabled __read_mostly = 1;	/* Enabled by default */

#ifdef CONFIG_RISCV_VECTOR_MISALIGNED
static int handle_vector_misaligned_load(struct pt_regs *regs)
{
	unsigned long epc = regs->epc;
	unsigned long insn;

	if (get_insn(regs, epc, &insn))
		return -1;

	/* Only return 0 when in check_vector_unaligned_access_emulated */
	if (*this_cpu_ptr(&vector_misaligned_access) == RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN) {
		*this_cpu_ptr(&vector_misaligned_access) = RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED;
		regs->epc = epc + INSN_LEN(insn);
		return 0;
	}

	/* If vector instruction we don't emulate it yet */
	regs->epc = epc;
	return -1;
}
#else
static int handle_vector_misaligned_load(struct pt_regs *regs)
{
	return -1;
}
#endif

static int handle_scalar_misaligned_load(struct pt_regs *regs)
{
	union reg_data val;
	unsigned long epc = regs->epc;
	unsigned long insn;
	unsigned long addr = regs->badaddr;
	int fp = 0, shift = 0, len = 0;

	perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr);

	*this_cpu_ptr(&misaligned_access_speed) = RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED;

	if (!unaligned_enabled)
		return -1;

	if (user_mode(regs) && (current->thread.align_ctl & PR_UNALIGN_SIGBUS))
		return -1;

	if (get_insn(regs, epc, &insn))
		return -1;

	regs->epc = 0;

	if ((insn & INSN_MASK_LW) == INSN_MATCH_LW) {
		len = 4;
		shift = 8 * (sizeof(unsigned long) - len);
#if defined(CONFIG_64BIT)
	} else if ((insn & INSN_MASK_LD) == INSN_MATCH_LD) {
		len = 8;
		shift = 8 * (sizeof(unsigned long) - len);
	} else if ((insn & INSN_MASK_LWU) == INSN_MATCH_LWU) {
		len = 4;
#endif
	} else if ((insn & INSN_MASK_FLD) == INSN_MATCH_FLD) {
		fp = 1;
		len = 8;
	} else if ((insn & INSN_MASK_FLW) == INSN_MATCH_FLW) {
		fp = 1;
		len = 4;
	} else if ((insn & INSN_MASK_LH) == INSN_MATCH_LH) {
		len = 2;
		shift = 8 * (sizeof(unsigned long) - len);
	} else if ((insn & INSN_MASK_LHU) == INSN_MATCH_LHU) {
		len = 2;
#if defined(CONFIG_64BIT)
	} else if ((insn & INSN_MASK_C_LD) == INSN_MATCH_C_LD) {
		len = 8;
		shift = 8 * (sizeof(unsigned long) - len);
		insn = RVC_RS2S(insn) << SH_RD;
	} else if ((insn & INSN_MASK_C_LDSP) == INSN_MATCH_C_LDSP &&
		   ((insn >> SH_RD) & 0x1f)) {
		len = 8;
		shift = 8 * (sizeof(unsigned long) - len);
#endif
	} else if ((insn & INSN_MASK_C_LW) == INSN_MATCH_C_LW) {
		len = 4;
		shift = 8 * (sizeof(unsigned long) - len);
		insn = RVC_RS2S(insn) << SH_RD;
	} else if ((insn & INSN_MASK_C_LWSP) == INSN_MATCH_C_LWSP &&
		   ((insn >> SH_RD) & 0x1f)) {
		len = 4;
		shift = 8 * (sizeof(unsigned long) - len);
	} else if ((insn & INSN_MASK_C_FLD) == INSN_MATCH_C_FLD) {
		fp = 1;
		len = 8;
		insn = RVC_RS2S(insn) << SH_RD;
	} else if ((insn & INSN_MASK_C_FLDSP) == INSN_MATCH_C_FLDSP) {
		fp = 1;
		len = 8;
#if defined(CONFIG_32BIT)
	} else if ((insn & INSN_MASK_C_FLW) == INSN_MATCH_C_FLW) {
		fp = 1;
		len = 4;
		insn = RVC_RS2S(insn) << SH_RD;
	} else if ((insn & INSN_MASK_C_FLWSP) == INSN_MATCH_C_FLWSP) {
		fp = 1;
		len = 4;
#endif
	} else if ((insn & INSN_MASK_C_LHU) == INSN_MATCH_C_LHU) {
		len = 2;
		insn = RVC_RS2S(insn) << SH_RD;
	} else if ((insn & INSN_MASK_C_LH) == INSN_MATCH_C_LH) {
		len = 2;
		shift = 8 * (sizeof(ulong) - len);
		insn = RVC_RS2S(insn) << SH_RD;
	} else {
		regs->epc = epc;
		return -1;
	}

	if (!IS_ENABLED(CONFIG_FPU) && fp)
		return -EOPNOTSUPP;

	val.data_u64 = 0;
	if (user_mode(regs)) {
		if (copy_from_user(&val, (u8 __user *)addr, len))
			return -1;
	} else {
		memcpy(&val, (u8 *)addr, len);
	}

	if (!fp)
		SET_RD(insn, regs, (long)(val.data_ulong << shift) >> shift);
	else if (len == 8)
		set_f64_rd(insn, regs, val.data_u64);
	else
		set_f32_rd(insn, regs, val.data_ulong);

	regs->epc = epc + INSN_LEN(insn);

	return 0;
}

static int handle_scalar_misaligned_store(struct pt_regs *regs)
{
	union reg_data val;
	unsigned long epc = regs->epc;
	unsigned long insn;
	unsigned long addr = regs->badaddr;
	int len = 0, fp = 0;

	perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr);

	if (!unaligned_enabled)
		return -1;

	if (user_mode(regs) && (current->thread.align_ctl & PR_UNALIGN_SIGBUS))
		return -1;

	if (get_insn(regs, epc, &insn))
		return -1;

	regs->epc = 0;

	val.data_ulong = GET_RS2(insn, regs);

	if ((insn & INSN_MASK_SW) == INSN_MATCH_SW) {
		len = 4;
#if defined(CONFIG_64BIT)
	} else if ((insn & INSN_MASK_SD) == INSN_MATCH_SD) {
		len = 8;
#endif
	} else if ((insn & INSN_MASK_FSD) == INSN_MATCH_FSD) {
		fp = 1;
		len = 8;
		val.data_u64 = GET_F64_RS2(insn, regs);
	} else if ((insn & INSN_MASK_FSW) == INSN_MATCH_FSW) {
		fp = 1;
		len = 4;
		val.data_ulong = GET_F32_RS2(insn, regs);
	} else if ((insn & INSN_MASK_SH) == INSN_MATCH_SH) {
		len = 2;
#if defined(CONFIG_64BIT)
	} else if ((insn & INSN_MASK_C_SD) == INSN_MATCH_C_SD) {
		len = 8;
		val.data_ulong = GET_RS2S(insn, regs);
	} else if ((insn & INSN_MASK_C_SDSP) == INSN_MATCH_C_SDSP) {
		len = 8;
		val.data_ulong = GET_RS2C(insn, regs);
#endif
	} else if ((insn & INSN_MASK_C_SW) == INSN_MATCH_C_SW) {
		len = 4;
		val.data_ulong = GET_RS2S(insn, regs);
	} else if ((insn & INSN_MASK_C_SWSP) == INSN_MATCH_C_SWSP) {
		len = 4;
		val.data_ulong = GET_RS2C(insn, regs);
	} else if ((insn & INSN_MASK_C_FSD) == INSN_MATCH_C_FSD) {
		fp = 1;
		len = 8;
		val.data_u64 = GET_F64_RS2S(insn, regs);
	} else if ((insn & INSN_MASK_C_FSDSP) == INSN_MATCH_C_FSDSP) {
		fp = 1;
		len = 8;
		val.data_u64 = GET_F64_RS2C(insn, regs);
#if !defined(CONFIG_64BIT)
	} else if ((insn & INSN_MASK_C_FSW) == INSN_MATCH_C_FSW) {
		fp = 1;
		len = 4;
		val.data_ulong = GET_F32_RS2S(insn, regs);
	} else if ((insn & INSN_MASK_C_FSWSP) == INSN_MATCH_C_FSWSP) {
		fp = 1;
		len = 4;
		val.data_ulong = GET_F32_RS2C(insn, regs);
#endif
	} else if ((insn & INSN_MASK_C_SH) == INSN_MATCH_C_SH) {
		len = 2;
		val.data_ulong = GET_RS2S(insn, regs);
	} else {
		regs->epc = epc;
		return -1;
	}

	if (!IS_ENABLED(CONFIG_FPU) && fp)
		return -EOPNOTSUPP;

	if (user_mode(regs)) {
		if (copy_to_user((u8 __user *)addr, &val, len))
			return -1;
	} else {
		memcpy((u8 *)addr, &val, len);
	}

	regs->epc = epc + INSN_LEN(insn);

	return 0;
}

int handle_misaligned_load(struct pt_regs *regs)
{
	unsigned long epc = regs->epc;
	unsigned long insn;

	if (IS_ENABLED(CONFIG_RISCV_VECTOR_MISALIGNED)) {
		if (get_insn(regs, epc, &insn))
			return -1;

		if (insn_is_vector(insn))
			return handle_vector_misaligned_load(regs);
	}

	if (IS_ENABLED(CONFIG_RISCV_SCALAR_MISALIGNED))
		return handle_scalar_misaligned_load(regs);

	return -1;
}

int handle_misaligned_store(struct pt_regs *regs)
{
	if (IS_ENABLED(CONFIG_RISCV_SCALAR_MISALIGNED))
		return handle_scalar_misaligned_store(regs);

	return -1;
}

#ifdef CONFIG_RISCV_VECTOR_MISALIGNED
void check_vector_unaligned_access_emulated(struct work_struct *work __always_unused)
{
	long *mas_ptr = this_cpu_ptr(&vector_misaligned_access);
	unsigned long tmp_var;

	*mas_ptr = RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN;

	kernel_vector_begin();
	/*
	 * In pre-13.0.0 versions of GCC, vector registers cannot appear in
	 * the clobber list. This inline asm clobbers v0, but since we do not
	 * currently build the kernel with V enabled, the v0 clobber arg is not
	 * needed (as the compiler will not emit vector code itself). If the kernel
	 * is changed to build with V enabled, the clobber arg will need to be
	 * added here.
	 */
	__asm__ __volatile__ (
		".balign 4\n\t"
		".option push\n\t"
		".option arch, +zve32x\n\t"
		"       vsetivli zero, 1, e16, m1, ta, ma\n\t"	// Vectors of 16b
		"       vle16.v v0, (%[ptr])\n\t"		// Load bytes
		".option pop\n\t"
		: : [ptr] "r" ((u8 *)&tmp_var + 1));
	kernel_vector_end();
}

bool __init check_vector_unaligned_access_emulated_all_cpus(void)
{
	int cpu;

	/*
	 * While being documented as very slow, schedule_on_each_cpu() is used since
	 * kernel_vector_begin() expects irqs to be enabled or it will panic()
	 */
	schedule_on_each_cpu(check_vector_unaligned_access_emulated);

	for_each_online_cpu(cpu)
		if (per_cpu(vector_misaligned_access, cpu)
		    == RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN)
			return false;

	return true;
}
#else
bool __init check_vector_unaligned_access_emulated_all_cpus(void)
{
	return false;
}
#endif

static bool all_cpus_unaligned_scalar_access_emulated(void)
{
	int cpu;

	for_each_online_cpu(cpu)
		if (per_cpu(misaligned_access_speed, cpu) !=
		    RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED)
			return false;

	return true;
}

#ifdef CONFIG_RISCV_SCALAR_MISALIGNED

static bool unaligned_ctl __read_mostly;

static void check_unaligned_access_emulated(void *arg __always_unused)
{
	int cpu = smp_processor_id();
	unsigned long tmp_var, tmp_val;

	if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN)
		return;

	__asm__ __volatile__ (
		"       "REG_L" %[tmp], 1(%[ptr])\n"
		: [tmp] "=r" (tmp_val) : [ptr] "r" (&tmp_var) : "memory");
}

static int cpu_online_check_unaligned_access_emulated(unsigned int cpu)
{
	long *mas_ptr = per_cpu_ptr(&misaligned_access_speed, cpu);

	check_unaligned_access_emulated(NULL);

	/*
	 * If unaligned_ctl is already set, this means that we detected that all
	 * CPUS uses emulated misaligned access at boot time. If that changed
	 * when hotplugging the new cpu, this is something we don't handle.
	 */
	if (unlikely(unaligned_ctl && (*mas_ptr != RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED))) {
		pr_crit("CPU misaligned accesses non homogeneous (expected all emulated)\n");
		return -EINVAL;
	}

	return 0;
}

bool __init check_unaligned_access_emulated_all_cpus(void)
{
	/*
	 * We can only support PR_UNALIGN controls if all CPUs have misaligned
	 * accesses emulated since tasks requesting such control can run on any
	 * CPU.
	 */
	on_each_cpu(check_unaligned_access_emulated, NULL, 1);

	if (!all_cpus_unaligned_scalar_access_emulated())
		return false;

	unaligned_ctl = true;
	return true;
}

bool unaligned_ctl_available(void)
{
	return unaligned_ctl;
}
#else
bool __init check_unaligned_access_emulated_all_cpus(void)
{
	return false;
}
static int cpu_online_check_unaligned_access_emulated(unsigned int cpu)
{
	return 0;
}
#endif

static bool misaligned_traps_delegated;

#if defined(CONFIG_RISCV_SBI_FWFT_DELEGATE_MISALIGNED)

static int cpu_online_sbi_unaligned_setup(unsigned int cpu)
{
	if (sbi_fwft_set(SBI_FWFT_MISALIGNED_EXC_DELEG, 1, 0) &&
	    misaligned_traps_delegated) {
		pr_crit("Misaligned trap delegation non homogeneous (expected delegated)");
		return -EINVAL;
	}

	return 0;
}

void __init unaligned_access_init(void)
{
	int ret;

	ret = sbi_fwft_set_online_cpus(SBI_FWFT_MISALIGNED_EXC_DELEG, 1, 0);
	if (ret)
		return;

	misaligned_traps_delegated = true;
	pr_info("SBI misaligned access exception delegation ok\n");
	/*
	 * Note that we don't have to take any specific action here, if
	 * the delegation is successful, then
	 * check_unaligned_access_emulated() will verify that indeed the
	 * platform traps on misaligned accesses.
	 */
}
#else
void __init unaligned_access_init(void) {}

static int cpu_online_sbi_unaligned_setup(unsigned int cpu __always_unused)
{
	return 0;
}

#endif

int cpu_online_unaligned_access_init(unsigned int cpu)
{
	int ret;

	ret = cpu_online_sbi_unaligned_setup(cpu);
	if (ret)
		return ret;

	return cpu_online_check_unaligned_access_emulated(cpu);
}

bool misaligned_traps_can_delegate(void)
{
	/*
	 * Either we successfully requested misaligned traps delegation for all
	 * CPUs, or the SBI does not implement the FWFT extension but delegated
	 * the exception by default.
	 */
	return misaligned_traps_delegated ||
	       all_cpus_unaligned_scalar_access_emulated();
}
EXPORT_SYMBOL_GPL(misaligned_traps_can_delegate);