traps.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Traps/Non-MMU Exception handling for ARC
 *
 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
 *
 * vineetg: May 2011
 *  -user-space unaligned access emulation
 *
 * Rahul Trivedi: Codito Technologies 2004
 */

#include <linux/sched/signal.h>
#include <linux/kdebug.h>
#include <linux/uaccess.h>
#include <linux/ptrace.h>
#include <linux/kprobes.h>
#include <linux/kgdb.h>
#include <asm/entry.h>
#include <asm/setup.h>
#include <linux/unaligned.h>
#include <asm/kprobes.h>
#include "unaligned.h"

void die(const char *str, struct pt_regs *regs, unsigned long address)
{
	show_kernel_fault_diag(str, regs, address);

	/* DEAD END */
	__asm__("flag 1");
}

/*
 * Helper called for bulk of exceptions NOT needing specific handling
 *  -for user faults enqueues requested signal
 *  -for kernel, chk if due to copy_(to|from)_user, otherwise die()
 */
static noinline int
unhandled_exception(const char *str, struct pt_regs *regs,
		    int signo, int si_code, void __user *addr)
{
	if (user_mode(regs)) {
		struct task_struct *tsk = current;

		tsk->thread.fault_address = (__force unsigned int)addr;

		force_sig_fault(signo, si_code, addr);

	} else {
		/* If not due to copy_(to|from)_user, we are doomed */
		if (fixup_exception(regs))
			return 0;

		die(str, regs, (unsigned long)addr);
	}

	return 1;
}

#define DO_ERROR_INFO(signr, str, name, sicode) \
int name(unsigned long address, struct pt_regs *regs) \
{								\
	return unhandled_exception(str, regs, signr, sicode,	\
				   (void __user *)address);	\
}

/*
 * Entry points for exceptions NOT needing specific handling
 */
DO_ERROR_INFO(SIGILL, "Priv Op/Disabled Extn", do_privilege_fault, ILL_PRVOPC)
DO_ERROR_INFO(SIGILL, "Invalid Extn Insn", do_extension_fault, ILL_ILLOPC)
DO_ERROR_INFO(SIGILL, "Illegal Insn (or Seq)", insterror_is_error, ILL_ILLOPC)
DO_ERROR_INFO(SIGBUS, "Invalid Mem Access", __weak do_memory_error, BUS_ADRERR)
DO_ERROR_INFO(SIGTRAP, "Breakpoint Set", trap_is_brkpt, TRAP_BRKPT)
DO_ERROR_INFO(SIGBUS, "Misaligned Access", do_misaligned_error, BUS_ADRALN)
DO_ERROR_INFO(SIGSEGV, "gcc generated __builtin_trap", do_trap5_error, 0)

/*
 * Entry Point for Misaligned Data access Exception, for emulating in software
 */
int do_misaligned_access(unsigned long address, struct pt_regs *regs,
			 struct callee_regs *cregs)
{
	/* If emulation not enabled, or failed, kill the task */
	if (misaligned_fixup(address, regs, cregs) != 0)
		return do_misaligned_error(address, regs);

	return 0;
}

/*
 * Entry point for miscll errors such as Nested Exceptions
 *  -Duplicate TLB entry is handled separately though
 */
void do_machine_check_fault(unsigned long address, struct pt_regs *regs)
{
	die("Unhandled Machine Check Exception", regs, address);
}


/*
 * Entry point for traps induced by ARCompact TRAP_S <n> insn
 * This is same family as TRAP0/SWI insn (use the same vector).
 * The only difference being SWI insn take no operand, while TRAP_S does
 * which reflects in ECR Reg as 8 bit param.
 * Thus TRAP_S <n> can be used for specific purpose
 *  -1 used for software breakpointing (gdb)
 *  -2 used by kprobes
 *  -5 __builtin_trap() generated by gcc (2018.03 onwards) for toggle such as
 *     -fno-isolate-erroneous-paths-dereference
 */
void do_non_swi_trap(unsigned long address, struct pt_regs *regs)
{
	switch (regs->ecr.param) {
	case 1:
		trap_is_brkpt(address, regs);
		break;

	case 2:
		trap_is_kprobe(address, regs);
		break;

	case 3:
	case 4:
		kgdb_trap(regs);
		break;

	case 5:
		do_trap5_error(address, regs);
		break;
	default:
		break;
	}
}

/*
 * Entry point for Instruction Error Exception
 *  -For a corner case, ARC kprobes implementation resorts to using
 *   this exception, hence the check
 */
void do_insterror_or_kprobe(unsigned long address, struct pt_regs *regs)
{
	int rc;

	/* Check if this exception is caused by kprobes */
	rc = notify_die(DIE_IERR, "kprobe_ierr", regs, address, 0, SIGILL);
	if (rc == NOTIFY_STOP)
		return;

	insterror_is_error(address, regs);
}

/*
 * abort() call generated by older gcc for __builtin_trap()
 */
void abort(void)
{
	__asm__ __volatile__("trap_s  5\n");
}