xref: /linux-6.3-rc2/arch/arm64/kernel/traps.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Based on arch/arm/kernel/traps.c
 *
 * Copyright (C) 1995-2009 Russell King
 * Copyright (C) 2012 ARM Ltd.
 */

#include <linux/bug.h>
#include <linux/context_tracking.h>
#include <linux/signal.h>
#include <linux/kallsyms.h>
#include <linux/kprobes.h>
#include <linux/spinlock.h>
#include <linux/uaccess.h>
#include <linux/hardirq.h>
#include <linux/kdebug.h>
#include <linux/module.h>
#include <linux/kexec.h>
#include <linux/delay.h>
#include <linux/efi.h>
#include <linux/init.h>
#include <linux/sched/signal.h>
#include <linux/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/sizes.h>
#include <linux/syscalls.h>
#include <linux/mm_types.h>
#include <linux/kasan.h>
#include <linux/ubsan.h>
#include <linux/cfi.h>

#include <asm/atomic.h>
#include <asm/bug.h>
#include <asm/cpufeature.h>
#include <asm/daifflags.h>
#include <asm/debug-monitors.h>
#include <asm/efi.h>
#include <asm/esr.h>
#include <asm/exception.h>
#include <asm/extable.h>
#include <asm/insn.h>
#include <asm/kprobes.h>
#include <asm/patching.h>
#include <asm/traps.h>
#include <asm/smp.h>
#include <asm/stack_pointer.h>
#include <asm/stacktrace.h>
#include <asm/system_misc.h>
#include <asm/sysreg.h>

static bool __kprobes __check_eq(unsigned long pstate)
{
	return (pstate & PSR_Z_BIT) != 0;
}

static bool __kprobes __check_ne(unsigned long pstate)
{
	return (pstate & PSR_Z_BIT) == 0;
}

static bool __kprobes __check_cs(unsigned long pstate)
{
	return (pstate & PSR_C_BIT) != 0;
}

static bool __kprobes __check_cc(unsigned long pstate)
{
	return (pstate & PSR_C_BIT) == 0;
}

static bool __kprobes __check_mi(unsigned long pstate)
{
	return (pstate & PSR_N_BIT) != 0;
}

static bool __kprobes __check_pl(unsigned long pstate)
{
	return (pstate & PSR_N_BIT) == 0;
}

static bool __kprobes __check_vs(unsigned long pstate)
{
	return (pstate & PSR_V_BIT) != 0;
}

static bool __kprobes __check_vc(unsigned long pstate)
{
	return (pstate & PSR_V_BIT) == 0;
}

static bool __kprobes __check_hi(unsigned long pstate)
{
	pstate &= ~(pstate >> 1);	/* PSR_C_BIT &= ~PSR_Z_BIT */
	return (pstate & PSR_C_BIT) != 0;
}

static bool __kprobes __check_ls(unsigned long pstate)
{
	pstate &= ~(pstate >> 1);	/* PSR_C_BIT &= ~PSR_Z_BIT */
	return (pstate & PSR_C_BIT) == 0;
}

static bool __kprobes __check_ge(unsigned long pstate)
{
	pstate ^= (pstate << 3);	/* PSR_N_BIT ^= PSR_V_BIT */
	return (pstate & PSR_N_BIT) == 0;
}

static bool __kprobes __check_lt(unsigned long pstate)
{
	pstate ^= (pstate << 3);	/* PSR_N_BIT ^= PSR_V_BIT */
	return (pstate & PSR_N_BIT) != 0;
}

static bool __kprobes __check_gt(unsigned long pstate)
{
	/*PSR_N_BIT ^= PSR_V_BIT */
	unsigned long temp = pstate ^ (pstate << 3);

	temp |= (pstate << 1);	/*PSR_N_BIT |= PSR_Z_BIT */
	return (temp & PSR_N_BIT) == 0;
}

static bool __kprobes __check_le(unsigned long pstate)
{
	/*PSR_N_BIT ^= PSR_V_BIT */
	unsigned long temp = pstate ^ (pstate << 3);

	temp |= (pstate << 1);	/*PSR_N_BIT |= PSR_Z_BIT */
	return (temp & PSR_N_BIT) != 0;
}

static bool __kprobes __check_al(unsigned long pstate)
{
	return true;
}

/*
 * Note that the ARMv8 ARM calls condition code 0b1111 "nv", but states that
 * it behaves identically to 0b1110 ("al").
 */
pstate_check_t * const aarch32_opcode_cond_checks[16] = {
	__check_eq, __check_ne, __check_cs, __check_cc,
	__check_mi, __check_pl, __check_vs, __check_vc,
	__check_hi, __check_ls, __check_ge, __check_lt,
	__check_gt, __check_le, __check_al, __check_al
};

int show_unhandled_signals = 0;

static void dump_kernel_instr(const char *lvl, struct pt_regs *regs)
{
	unsigned long addr = instruction_pointer(regs);
	char str[sizeof("00000000 ") * 5 + 2 + 1], *p = str;
	int i;

	if (user_mode(regs))
		return;

	for (i = -4; i < 1; i++) {
		unsigned int val, bad;

		bad = aarch64_insn_read(&((u32 *)addr)[i], &val);

		if (!bad)
			p += sprintf(p, i == 0 ? "(%08x) " : "%08x ", val);
		else
			p += sprintf(p, i == 0 ? "(????????) " : "???????? ");
	}

	printk("%sCode: %s\n", lvl, str);
}

#ifdef CONFIG_PREEMPT
#define S_PREEMPT " PREEMPT"
#elif defined(CONFIG_PREEMPT_RT)
#define S_PREEMPT " PREEMPT_RT"
#else
#define S_PREEMPT ""
#endif

#define S_SMP " SMP"

static int __die(const char *str, long err, struct pt_regs *regs)
{
	static int die_counter;
	int ret;

	pr_emerg("Internal error: %s: %016lx [#%d]" S_PREEMPT S_SMP "\n",
		 str, err, ++die_counter);

	/* trap and error numbers are mostly meaningless on ARM */
	ret = notify_die(DIE_OOPS, str, regs, err, 0, SIGSEGV);
	if (ret == NOTIFY_STOP)
		return ret;

	print_modules();
	show_regs(regs);

	dump_kernel_instr(KERN_EMERG, regs);

	return ret;
}

static DEFINE_RAW_SPINLOCK(die_lock);

/*
 * This function is protected against re-entrancy.
 */
void die(const char *str, struct pt_regs *regs, long err)
{
	int ret;
	unsigned long flags;

	raw_spin_lock_irqsave(&die_lock, flags);

	oops_enter();

	console_verbose();
	bust_spinlocks(1);
	ret = __die(str, err, regs);

	if (regs && kexec_should_crash(current))
		crash_kexec(regs);

	bust_spinlocks(0);
	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
	oops_exit();

	if (in_interrupt())
		panic("%s: Fatal exception in interrupt", str);
	if (panic_on_oops)
		panic("%s: Fatal exception", str);

	raw_spin_unlock_irqrestore(&die_lock, flags);

	if (ret != NOTIFY_STOP)
		make_task_dead(SIGSEGV);
}

static void arm64_show_signal(int signo, const char *str)
{
	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
				      DEFAULT_RATELIMIT_BURST);
	struct task_struct *tsk = current;
	unsigned long esr = tsk->thread.fault_code;
	struct pt_regs *regs = task_pt_regs(tsk);

	/* Leave if the signal won't be shown */
	if (!show_unhandled_signals ||
	    !unhandled_signal(tsk, signo) ||
	    !__ratelimit(&rs))
		return;

	pr_info("%s[%d]: unhandled exception: ", tsk->comm, task_pid_nr(tsk));
	if (esr)
		pr_cont("%s, ESR 0x%016lx, ", esr_get_class_string(esr), esr);

	pr_cont("%s", str);
	print_vma_addr(KERN_CONT " in ", regs->pc);
	pr_cont("\n");
	__show_regs(regs);
}

void arm64_force_sig_fault(int signo, int code, unsigned long far,
			   const char *str)
{
	arm64_show_signal(signo, str);
	if (signo == SIGKILL)
		force_sig(SIGKILL);
	else
		force_sig_fault(signo, code, (void __user *)far);
}

void arm64_force_sig_mceerr(int code, unsigned long far, short lsb,
			    const char *str)
{
	arm64_show_signal(SIGBUS, str);
	force_sig_mceerr(code, (void __user *)far, lsb);
}

void arm64_force_sig_ptrace_errno_trap(int errno, unsigned long far,
				       const char *str)
{
	arm64_show_signal(SIGTRAP, str);
	force_sig_ptrace_errno_trap(errno, (void __user *)far);
}

void arm64_notify_die(const char *str, struct pt_regs *regs,
		      int signo, int sicode, unsigned long far,
		      unsigned long err)
{
	if (user_mode(regs)) {
		WARN_ON(regs != current_pt_regs());
		current->thread.fault_address = 0;
		current->thread.fault_code = err;

		arm64_force_sig_fault(signo, sicode, far, str);
	} else {
		die(str, regs, err);
	}
}

#ifdef CONFIG_COMPAT
#define PSTATE_IT_1_0_SHIFT	25
#define PSTATE_IT_1_0_MASK	(0x3 << PSTATE_IT_1_0_SHIFT)
#define PSTATE_IT_7_2_SHIFT	10
#define PSTATE_IT_7_2_MASK	(0x3f << PSTATE_IT_7_2_SHIFT)

static u32 compat_get_it_state(struct pt_regs *regs)
{
	u32 it, pstate = regs->pstate;

	it  = (pstate & PSTATE_IT_1_0_MASK) >> PSTATE_IT_1_0_SHIFT;
	it |= ((pstate & PSTATE_IT_7_2_MASK) >> PSTATE_IT_7_2_SHIFT) << 2;

	return it;
}

static void compat_set_it_state(struct pt_regs *regs, u32 it)
{
	u32 pstate_it;

	pstate_it  = (it << PSTATE_IT_1_0_SHIFT) & PSTATE_IT_1_0_MASK;
	pstate_it |= ((it >> 2) << PSTATE_IT_7_2_SHIFT) & PSTATE_IT_7_2_MASK;

	regs->pstate &= ~PSR_AA32_IT_MASK;
	regs->pstate |= pstate_it;
}

static void advance_itstate(struct pt_regs *regs)
{
	u32 it;

	/* ARM mode */
	if (!(regs->pstate & PSR_AA32_T_BIT) ||
	    !(regs->pstate & PSR_AA32_IT_MASK))
		return;

	it  = compat_get_it_state(regs);

	/*
	 * If this is the last instruction of the block, wipe the IT
	 * state. Otherwise advance it.
	 */
	if (!(it & 7))
		it = 0;
	else
		it = (it & 0xe0) | ((it << 1) & 0x1f);

	compat_set_it_state(regs, it);
}
#else
static void advance_itstate(struct pt_regs *regs)
{
}
#endif

void arm64_skip_faulting_instruction(struct pt_regs *regs, unsigned long size)
{
	regs->pc += size;

	/*
	 * If we were single stepping, we want to get the step exception after
	 * we return from the trap.
	 */
	if (user_mode(regs))
		user_fastforward_single_step(current);

	if (compat_user_mode(regs))
		advance_itstate(regs);
	else
		regs->pstate &= ~PSR_BTYPE_MASK;
}

static int user_insn_read(struct pt_regs *regs, u32 *insnp)
{
	u32 instr;
	unsigned long pc = instruction_pointer(regs);

	if (compat_thumb_mode(regs)) {
		/* 16-bit Thumb instruction */
		__le16 instr_le;
		if (get_user(instr_le, (__le16 __user *)pc))
			return -EFAULT;
		instr = le16_to_cpu(instr_le);
		if (aarch32_insn_is_wide(instr)) {
			u32 instr2;

			if (get_user(instr_le, (__le16 __user *)(pc + 2)))
				return -EFAULT;
			instr2 = le16_to_cpu(instr_le);
			instr = (instr << 16) | instr2;
		}
	} else {
		/* 32-bit ARM instruction */
		__le32 instr_le;
		if (get_user(instr_le, (__le32 __user *)pc))
			return -EFAULT;
		instr = le32_to_cpu(instr_le);
	}

	*insnp = instr;
	return 0;
}

void force_signal_inject(int signal, int code, unsigned long address, unsigned long err)
{
	const char *desc;
	struct pt_regs *regs = current_pt_regs();

	if (WARN_ON(!user_mode(regs)))
		return;

	switch (signal) {
	case SIGILL:
		desc = "undefined instruction";
		break;
	case SIGSEGV:
		desc = "illegal memory access";
		break;
	default:
		desc = "unknown or unrecoverable error";
		break;
	}

	/* Force signals we don't understand to SIGKILL */
	if (WARN_ON(signal != SIGKILL &&
		    siginfo_layout(signal, code) != SIL_FAULT)) {
		signal = SIGKILL;
	}

	arm64_notify_die(desc, regs, signal, code, address, err);
}

/*
 * Set up process info to signal segmentation fault - called on access error.
 */
void arm64_notify_segfault(unsigned long addr)
{
	int code;

	mmap_read_lock(current->mm);
	if (find_vma(current->mm, untagged_addr(addr)) == NULL)
		code = SEGV_MAPERR;
	else
		code = SEGV_ACCERR;
	mmap_read_unlock(current->mm);

	force_signal_inject(SIGSEGV, code, addr, 0);
}

void do_el0_undef(struct pt_regs *regs, unsigned long esr)
{
	u32 insn;

	/* check for AArch32 breakpoint instructions */
	if (!aarch32_break_handler(regs))
		return;

	if (user_insn_read(regs, &insn))
		goto out_err;

	if (try_emulate_mrs(regs, insn))
		return;

	if (try_emulate_armv8_deprecated(regs, insn))
		return;

out_err:
	force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc, 0);
}

void do_el1_undef(struct pt_regs *regs, unsigned long esr)
{
	u32 insn;

	if (aarch64_insn_read((void *)regs->pc, &insn))
		goto out_err;

	if (try_emulate_el1_ssbs(regs, insn))
		return;

out_err:
	die("Oops - Undefined instruction", regs, esr);
}

void do_el0_bti(struct pt_regs *regs)
{
	force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc, 0);
}

void do_el1_bti(struct pt_regs *regs, unsigned long esr)
{
	if (efi_runtime_fixup_exception(regs, "BTI violation")) {
		regs->pstate &= ~PSR_BTYPE_MASK;
		return;
	}
	die("Oops - BTI", regs, esr);
}

void do_el0_fpac(struct pt_regs *regs, unsigned long esr)
{
	force_signal_inject(SIGILL, ILL_ILLOPN, regs->pc, esr);
}

void do_el1_fpac(struct pt_regs *regs, unsigned long esr)
{
	/*
	 * Unexpected FPAC exception in the kernel: kill the task before it
	 * does any more harm.
	 */
	die("Oops - FPAC", regs, esr);
}

#define __user_cache_maint(insn, address, res)			\
	if (address >= TASK_SIZE_MAX) {				\
		res = -EFAULT;					\
	} else {						\
		uaccess_ttbr0_enable();				\
		asm volatile (					\
			"1:	" insn ", %1\n"			\
			"	mov	%w0, #0\n"		\
			"2:\n"					\
			_ASM_EXTABLE_UACCESS_ERR(1b, 2b, %w0)	\
			: "=r" (res)				\
			: "r" (address));			\
		uaccess_ttbr0_disable();			\
	}

static void user_cache_maint_handler(unsigned long esr, struct pt_regs *regs)
{
	unsigned long tagged_address, address;
	int rt = ESR_ELx_SYS64_ISS_RT(esr);
	int crm = (esr & ESR_ELx_SYS64_ISS_CRM_MASK) >> ESR_ELx_SYS64_ISS_CRM_SHIFT;
	int ret = 0;

	tagged_address = pt_regs_read_reg(regs, rt);
	address = untagged_addr(tagged_address);

	switch (crm) {
	case ESR_ELx_SYS64_ISS_CRM_DC_CVAU:	/* DC CVAU, gets promoted */
		__user_cache_maint("dc civac", address, ret);
		break;
	case ESR_ELx_SYS64_ISS_CRM_DC_CVAC:	/* DC CVAC, gets promoted */
		__user_cache_maint("dc civac", address, ret);
		break;
	case ESR_ELx_SYS64_ISS_CRM_DC_CVADP:	/* DC CVADP */
		__user_cache_maint("sys 3, c7, c13, 1", address, ret);
		break;
	case ESR_ELx_SYS64_ISS_CRM_DC_CVAP:	/* DC CVAP */
		__user_cache_maint("sys 3, c7, c12, 1", address, ret);
		break;
	case ESR_ELx_SYS64_ISS_CRM_DC_CIVAC:	/* DC CIVAC */
		__user_cache_maint("dc civac", address, ret);
		break;
	case ESR_ELx_SYS64_ISS_CRM_IC_IVAU:	/* IC IVAU */
		__user_cache_maint("ic ivau", address, ret);
		break;
	default:
		force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc, 0);
		return;
	}

	if (ret)
		arm64_notify_segfault(tagged_address);
	else
		arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE);
}

static void ctr_read_handler(unsigned long esr, struct pt_regs *regs)
{
	int rt = ESR_ELx_SYS64_ISS_RT(esr);
	unsigned long val = arm64_ftr_reg_user_value(&arm64_ftr_reg_ctrel0);

	if (cpus_have_const_cap(ARM64_WORKAROUND_1542419)) {
		/* Hide DIC so that we can trap the unnecessary maintenance...*/
		val &= ~BIT(CTR_EL0_DIC_SHIFT);

		/* ... and fake IminLine to reduce the number of traps. */
		val &= ~CTR_EL0_IminLine_MASK;
		val |= (PAGE_SHIFT - 2) & CTR_EL0_IminLine_MASK;
	}

	pt_regs_write_reg(regs, rt, val);

	arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE);
}

static void cntvct_read_handler(unsigned long esr, struct pt_regs *regs)
{
	int rt = ESR_ELx_SYS64_ISS_RT(esr);

	pt_regs_write_reg(regs, rt, arch_timer_read_counter());
	arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE);
}

static void cntfrq_read_handler(unsigned long esr, struct pt_regs *regs)
{
	int rt = ESR_ELx_SYS64_ISS_RT(esr);

	pt_regs_write_reg(regs, rt, arch_timer_get_rate());
	arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE);
}

static void mrs_handler(unsigned long esr, struct pt_regs *regs)
{
	u32 sysreg, rt;

	rt = ESR_ELx_SYS64_ISS_RT(esr);
	sysreg = esr_sys64_to_sysreg(esr);

	if (do_emulate_mrs(regs, sysreg, rt) != 0)
		force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc, 0);
}

static void wfi_handler(unsigned long esr, struct pt_regs *regs)
{
	arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE);
}

struct sys64_hook {
	unsigned long esr_mask;
	unsigned long esr_val;
	void (*handler)(unsigned long esr, struct pt_regs *regs);
};

static const struct sys64_hook sys64_hooks[] = {
	{
		.esr_mask = ESR_ELx_SYS64_ISS_EL0_CACHE_OP_MASK,
		.esr_val = ESR_ELx_SYS64_ISS_EL0_CACHE_OP_VAL,
		.handler = user_cache_maint_handler,
	},
	{
		/* Trap read access to CTR_EL0 */
		.esr_mask = ESR_ELx_SYS64_ISS_SYS_OP_MASK,
		.esr_val = ESR_ELx_SYS64_ISS_SYS_CTR_READ,
		.handler = ctr_read_handler,
	},
	{
		/* Trap read access to CNTVCT_EL0 */
		.esr_mask = ESR_ELx_SYS64_ISS_SYS_OP_MASK,
		.esr_val = ESR_ELx_SYS64_ISS_SYS_CNTVCT,
		.handler = cntvct_read_handler,
	},
	{
		/* Trap read access to CNTVCTSS_EL0 */
		.esr_mask = ESR_ELx_SYS64_ISS_SYS_OP_MASK,
		.esr_val = ESR_ELx_SYS64_ISS_SYS_CNTVCTSS,
		.handler = cntvct_read_handler,
	},
	{
		/* Trap read access to CNTFRQ_EL0 */
		.esr_mask = ESR_ELx_SYS64_ISS_SYS_OP_MASK,
		.esr_val = ESR_ELx_SYS64_ISS_SYS_CNTFRQ,
		.handler = cntfrq_read_handler,
	},
	{
		/* Trap read access to CPUID registers */
		.esr_mask = ESR_ELx_SYS64_ISS_SYS_MRS_OP_MASK,
		.esr_val = ESR_ELx_SYS64_ISS_SYS_MRS_OP_VAL,
		.handler = mrs_handler,
	},
	{
		/* Trap WFI instructions executed in userspace */
		.esr_mask = ESR_ELx_WFx_MASK,
		.esr_val = ESR_ELx_WFx_WFI_VAL,
		.handler = wfi_handler,
	},
	{},
};

#ifdef CONFIG_COMPAT
static bool cp15_cond_valid(unsigned long esr, struct pt_regs *regs)
{
	int cond;

	/* Only a T32 instruction can trap without CV being set */
	if (!(esr & ESR_ELx_CV)) {
		u32 it;

		it = compat_get_it_state(regs);
		if (!it)
			return true;

		cond = it >> 4;
	} else {
		cond = (esr & ESR_ELx_COND_MASK) >> ESR_ELx_COND_SHIFT;
	}

	return aarch32_opcode_cond_checks[cond](regs->pstate);
}

static void compat_cntfrq_read_handler(unsigned long esr, struct pt_regs *regs)
{
	int reg = (esr & ESR_ELx_CP15_32_ISS_RT_MASK) >> ESR_ELx_CP15_32_ISS_RT_SHIFT;

	pt_regs_write_reg(regs, reg, arch_timer_get_rate());
	arm64_skip_faulting_instruction(regs, 4);
}

static const struct sys64_hook cp15_32_hooks[] = {
	{
		.esr_mask = ESR_ELx_CP15_32_ISS_SYS_MASK,
		.esr_val = ESR_ELx_CP15_32_ISS_SYS_CNTFRQ,
		.handler = compat_cntfrq_read_handler,
	},
	{},
};

static void compat_cntvct_read_handler(unsigned long esr, struct pt_regs *regs)
{
	int rt = (esr & ESR_ELx_CP15_64_ISS_RT_MASK) >> ESR_ELx_CP15_64_ISS_RT_SHIFT;
	int rt2 = (esr & ESR_ELx_CP15_64_ISS_RT2_MASK) >> ESR_ELx_CP15_64_ISS_RT2_SHIFT;
	u64 val = arch_timer_read_counter();

	pt_regs_write_reg(regs, rt, lower_32_bits(val));
	pt_regs_write_reg(regs, rt2, upper_32_bits(val));
	arm64_skip_faulting_instruction(regs, 4);
}

static const struct sys64_hook cp15_64_hooks[] = {
	{
		.esr_mask = ESR_ELx_CP15_64_ISS_SYS_MASK,
		.esr_val = ESR_ELx_CP15_64_ISS_SYS_CNTVCT,
		.handler = compat_cntvct_read_handler,
	},
	{
		.esr_mask = ESR_ELx_CP15_64_ISS_SYS_MASK,
		.esr_val = ESR_ELx_CP15_64_ISS_SYS_CNTVCTSS,
		.handler = compat_cntvct_read_handler,
	},
	{},
};

void do_el0_cp15(unsigned long esr, struct pt_regs *regs)
{
	const struct sys64_hook *hook, *hook_base;

	if (!cp15_cond_valid(esr, regs)) {
		/*
		 * There is no T16 variant of a CP access, so we
		 * always advance PC by 4 bytes.
		 */
		arm64_skip_faulting_instruction(regs, 4);
		return;
	}

	switch (ESR_ELx_EC(esr)) {
	case ESR_ELx_EC_CP15_32:
		hook_base = cp15_32_hooks;
		break;
	case ESR_ELx_EC_CP15_64:
		hook_base = cp15_64_hooks;
		break;
	default:
		do_el0_undef(regs, esr);
		return;
	}

	for (hook = hook_base; hook->handler; hook++)
		if ((hook->esr_mask & esr) == hook->esr_val) {
			hook->handler(esr, regs);
			return;
		}

	/*
	 * New cp15 instructions may previously have been undefined at
	 * EL0. Fall back to our usual undefined instruction handler
	 * so that we handle these consistently.
	 */
	do_el0_undef(regs, esr);
}
#endif

void do_el0_sys(unsigned long esr, struct pt_regs *regs)
{
	const struct sys64_hook *hook;

	for (hook = sys64_hooks; hook->handler; hook++)
		if ((hook->esr_mask & esr) == hook->esr_val) {
			hook->handler(esr, regs);
			return;
		}

	/*
	 * New SYS instructions may previously have been undefined at EL0. Fall
	 * back to our usual undefined instruction handler so that we handle
	 * these consistently.
	 */
	do_el0_undef(regs, esr);
}

static const char *esr_class_str[] = {
	[0 ... ESR_ELx_EC_MAX]		= "UNRECOGNIZED EC",
	[ESR_ELx_EC_UNKNOWN]		= "Unknown/Uncategorized",
	[ESR_ELx_EC_WFx]		= "WFI/WFE",
	[ESR_ELx_EC_CP15_32]		= "CP15 MCR/MRC",
	[ESR_ELx_EC_CP15_64]		= "CP15 MCRR/MRRC",
	[ESR_ELx_EC_CP14_MR]		= "CP14 MCR/MRC",
	[ESR_ELx_EC_CP14_LS]		= "CP14 LDC/STC",
	[ESR_ELx_EC_FP_ASIMD]		= "ASIMD",
	[ESR_ELx_EC_CP10_ID]		= "CP10 MRC/VMRS",
	[ESR_ELx_EC_PAC]		= "PAC",
	[ESR_ELx_EC_CP14_64]		= "CP14 MCRR/MRRC",
	[ESR_ELx_EC_BTI]		= "BTI",
	[ESR_ELx_EC_ILL]		= "PSTATE.IL",
	[ESR_ELx_EC_SVC32]		= "SVC (AArch32)",
	[ESR_ELx_EC_HVC32]		= "HVC (AArch32)",
	[ESR_ELx_EC_SMC32]		= "SMC (AArch32)",
	[ESR_ELx_EC_SVC64]		= "SVC (AArch64)",
	[ESR_ELx_EC_HVC64]		= "HVC (AArch64)",
	[ESR_ELx_EC_SMC64]		= "SMC (AArch64)",
	[ESR_ELx_EC_SYS64]		= "MSR/MRS (AArch64)",
	[ESR_ELx_EC_SVE]		= "SVE",
	[ESR_ELx_EC_ERET]		= "ERET/ERETAA/ERETAB",
	[ESR_ELx_EC_FPAC]		= "FPAC",
	[ESR_ELx_EC_SME]		= "SME",
	[ESR_ELx_EC_IMP_DEF]		= "EL3 IMP DEF",
	[ESR_ELx_EC_IABT_LOW]		= "IABT (lower EL)",
	[ESR_ELx_EC_IABT_CUR]		= "IABT (current EL)",
	[ESR_ELx_EC_PC_ALIGN]		= "PC Alignment",
	[ESR_ELx_EC_DABT_LOW]		= "DABT (lower EL)",
	[ESR_ELx_EC_DABT_CUR]		= "DABT (current EL)",
	[ESR_ELx_EC_SP_ALIGN]		= "SP Alignment",
	[ESR_ELx_EC_FP_EXC32]		= "FP (AArch32)",
	[ESR_ELx_EC_FP_EXC64]		= "FP (AArch64)",
	[ESR_ELx_EC_SERROR]		= "SError",
	[ESR_ELx_EC_BREAKPT_LOW]	= "Breakpoint (lower EL)",
	[ESR_ELx_EC_BREAKPT_CUR]	= "Breakpoint (current EL)",
	[ESR_ELx_EC_SOFTSTP_LOW]	= "Software Step (lower EL)",
	[ESR_ELx_EC_SOFTSTP_CUR]	= "Software Step (current EL)",
	[ESR_ELx_EC_WATCHPT_LOW]	= "Watchpoint (lower EL)",
	[ESR_ELx_EC_WATCHPT_CUR]	= "Watchpoint (current EL)",
	[ESR_ELx_EC_BKPT32]		= "BKPT (AArch32)",
	[ESR_ELx_EC_VECTOR32]		= "Vector catch (AArch32)",
	[ESR_ELx_EC_BRK64]		= "BRK (AArch64)",
};

const char *esr_get_class_string(unsigned long esr)
{
	return esr_class_str[ESR_ELx_EC(esr)];
}

/*
 * bad_el0_sync handles unexpected, but potentially recoverable synchronous
 * exceptions taken from EL0.
 */
void bad_el0_sync(struct pt_regs *regs, int reason, unsigned long esr)
{
	unsigned long pc = instruction_pointer(regs);

	current->thread.fault_address = 0;
	current->thread.fault_code = esr;

	arm64_force_sig_fault(SIGILL, ILL_ILLOPC, pc,
			      "Bad EL0 synchronous exception");
}

#ifdef CONFIG_VMAP_STACK

DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack)
	__aligned(16);

void panic_bad_stack(struct pt_regs *regs, unsigned long esr, unsigned long far)
{
	unsigned long tsk_stk = (unsigned long)current->stack;
	unsigned long irq_stk = (unsigned long)this_cpu_read(irq_stack_ptr);
	unsigned long ovf_stk = (unsigned long)this_cpu_ptr(overflow_stack);

	console_verbose();
	pr_emerg("Insufficient stack space to handle exception!");

	pr_emerg("ESR: 0x%016lx -- %s\n", esr, esr_get_class_string(esr));
	pr_emerg("FAR: 0x%016lx\n", far);

	pr_emerg("Task stack:     [0x%016lx..0x%016lx]\n",
		 tsk_stk, tsk_stk + THREAD_SIZE);
	pr_emerg("IRQ stack:      [0x%016lx..0x%016lx]\n",
		 irq_stk, irq_stk + IRQ_STACK_SIZE);
	pr_emerg("Overflow stack: [0x%016lx..0x%016lx]\n",
		 ovf_stk, ovf_stk + OVERFLOW_STACK_SIZE);

	__show_regs(regs);

	/*
	 * We use nmi_panic to limit the potential for recusive overflows, and
	 * to get a better stack trace.
	 */
	nmi_panic(NULL, "kernel stack overflow");
	cpu_park_loop();
}
#endif

void __noreturn arm64_serror_panic(struct pt_regs *regs, unsigned long esr)
{
	console_verbose();

	pr_crit("SError Interrupt on CPU%d, code 0x%016lx -- %s\n",
		smp_processor_id(), esr, esr_get_class_string(esr));
	if (regs)
		__show_regs(regs);

	nmi_panic(regs, "Asynchronous SError Interrupt");

	cpu_park_loop();
	unreachable();
}

bool arm64_is_fatal_ras_serror(struct pt_regs *regs, unsigned long esr)
{
	unsigned long aet = arm64_ras_serror_get_severity(esr);

	switch (aet) {
	case ESR_ELx_AET_CE:	/* corrected error */
	case ESR_ELx_AET_UEO:	/* restartable, not yet consumed */
		/*
		 * The CPU can make progress. We may take UEO again as
		 * a more severe error.
		 */
		return false;

	case ESR_ELx_AET_UEU:	/* Uncorrected Unrecoverable */
	case ESR_ELx_AET_UER:	/* Uncorrected Recoverable */
		/*
		 * The CPU can't make progress. The exception may have
		 * been imprecise.
		 *
		 * Neoverse-N1 #1349291 means a non-KVM SError reported as
		 * Unrecoverable should be treated as Uncontainable. We
		 * call arm64_serror_panic() in both cases.
		 */
		return true;

	case ESR_ELx_AET_UC:	/* Uncontainable or Uncategorized error */
	default:
		/* Error has been silently propagated */
		arm64_serror_panic(regs, esr);
	}
}

void do_serror(struct pt_regs *regs, unsigned long esr)
{
	/* non-RAS errors are not containable */
	if (!arm64_is_ras_serror(esr) || arm64_is_fatal_ras_serror(regs, esr))
		arm64_serror_panic(regs, esr);
}

/* GENERIC_BUG traps */

int is_valid_bugaddr(unsigned long addr)
{
	/*
	 * bug_handler() only called for BRK #BUG_BRK_IMM.
	 * So the answer is trivial -- any spurious instances with no
	 * bug table entry will be rejected by report_bug() and passed
	 * back to the debug-monitors code and handled as a fatal
	 * unexpected debug exception.
	 */
	return 1;
}

static int bug_handler(struct pt_regs *regs, unsigned long esr)
{
	switch (report_bug(regs->pc, regs)) {
	case BUG_TRAP_TYPE_BUG:
		die("Oops - BUG", regs, esr);
		break;

	case BUG_TRAP_TYPE_WARN:
		break;

	default:
		/* unknown/unrecognised bug trap type */
		return DBG_HOOK_ERROR;
	}

	/* If thread survives, skip over the BUG instruction and continue: */
	arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE);
	return DBG_HOOK_HANDLED;
}

static struct break_hook bug_break_hook = {
	.fn = bug_handler,
	.imm = BUG_BRK_IMM,
};

#ifdef CONFIG_CFI_CLANG
static int cfi_handler(struct pt_regs *regs, unsigned long esr)
{
	unsigned long target;
	u32 type;

	target = pt_regs_read_reg(regs, FIELD_GET(CFI_BRK_IMM_TARGET, esr));
	type = (u32)pt_regs_read_reg(regs, FIELD_GET(CFI_BRK_IMM_TYPE, esr));

	switch (report_cfi_failure(regs, regs->pc, &target, type)) {
	case BUG_TRAP_TYPE_BUG:
		die("Oops - CFI", regs, esr);
		break;

	case BUG_TRAP_TYPE_WARN:
		break;

	default:
		return DBG_HOOK_ERROR;
	}

	arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE);
	return DBG_HOOK_HANDLED;
}

static struct break_hook cfi_break_hook = {
	.fn = cfi_handler,
	.imm = CFI_BRK_IMM_BASE,
	.mask = CFI_BRK_IMM_MASK,
};
#endif /* CONFIG_CFI_CLANG */

static int reserved_fault_handler(struct pt_regs *regs, unsigned long esr)
{
	pr_err("%s generated an invalid instruction at %pS!\n",
		"Kernel text patching",
		(void *)instruction_pointer(regs));

	/* We cannot handle this */
	return DBG_HOOK_ERROR;
}

static struct break_hook fault_break_hook = {
	.fn = reserved_fault_handler,
	.imm = FAULT_BRK_IMM,
};

#ifdef CONFIG_KASAN_SW_TAGS

#define KASAN_ESR_RECOVER	0x20
#define KASAN_ESR_WRITE	0x10
#define KASAN_ESR_SIZE_MASK	0x0f
#define KASAN_ESR_SIZE(esr)	(1 << ((esr) & KASAN_ESR_SIZE_MASK))

static int kasan_handler(struct pt_regs *regs, unsigned long esr)
{
	bool recover = esr & KASAN_ESR_RECOVER;
	bool write = esr & KASAN_ESR_WRITE;
	size_t size = KASAN_ESR_SIZE(esr);
	u64 addr = regs->regs[0];
	u64 pc = regs->pc;

	kasan_report(addr, size, write, pc);

	/*
	 * The instrumentation allows to control whether we can proceed after
	 * a crash was detected. This is done by passing the -recover flag to
	 * the compiler. Disabling recovery allows to generate more compact
	 * code.
	 *
	 * Unfortunately disabling recovery doesn't work for the kernel right
	 * now. KASAN reporting is disabled in some contexts (for example when
	 * the allocator accesses slab object metadata; this is controlled by
	 * current->kasan_depth). All these accesses are detected by the tool,
	 * even though the reports for them are not printed.
	 *
	 * This is something that might be fixed at some point in the future.
	 */
	if (!recover)
		die("Oops - KASAN", regs, esr);

	/* If thread survives, skip over the brk instruction and continue: */
	arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE);
	return DBG_HOOK_HANDLED;
}

static struct break_hook kasan_break_hook = {
	.fn	= kasan_handler,
	.imm	= KASAN_BRK_IMM,
	.mask	= KASAN_BRK_MASK,
};
#endif

#ifdef CONFIG_UBSAN_TRAP
static int ubsan_handler(struct pt_regs *regs, unsigned long esr)
{
	die(report_ubsan_failure(regs, esr & UBSAN_BRK_MASK), regs, esr);
	return DBG_HOOK_HANDLED;
}

static struct break_hook ubsan_break_hook = {
	.fn	= ubsan_handler,
	.imm	= UBSAN_BRK_IMM,
	.mask	= UBSAN_BRK_MASK,
};
#endif

#define esr_comment(esr) ((esr) & ESR_ELx_BRK64_ISS_COMMENT_MASK)

/*
 * Initial handler for AArch64 BRK exceptions
 * This handler only used until debug_traps_init().
 */
int __init early_brk64(unsigned long addr, unsigned long esr,
		struct pt_regs *regs)
{
#ifdef CONFIG_CFI_CLANG
	if ((esr_comment(esr) & ~CFI_BRK_IMM_MASK) == CFI_BRK_IMM_BASE)
		return cfi_handler(regs, esr) != DBG_HOOK_HANDLED;
#endif
#ifdef CONFIG_KASAN_SW_TAGS
	if ((esr_comment(esr) & ~KASAN_BRK_MASK) == KASAN_BRK_IMM)
		return kasan_handler(regs, esr) != DBG_HOOK_HANDLED;
#endif
#ifdef CONFIG_UBSAN_TRAP
	if ((esr_comment(esr) & ~UBSAN_BRK_MASK) == UBSAN_BRK_IMM)
		return ubsan_handler(regs, esr) != DBG_HOOK_HANDLED;
#endif
	return bug_handler(regs, esr) != DBG_HOOK_HANDLED;
}

void __init trap_init(void)
{
	register_kernel_break_hook(&bug_break_hook);
#ifdef CONFIG_CFI_CLANG
	register_kernel_break_hook(&cfi_break_hook);
#endif
	register_kernel_break_hook(&fault_break_hook);
#ifdef CONFIG_KASAN_SW_TAGS
	register_kernel_break_hook(&kasan_break_hook);
#endif
#ifdef CONFIG_UBSAN_TRAP
	register_kernel_break_hook(&ubsan_break_hook);
#endif
	debug_traps_init();
}