text: // SPDX-License-Identifier: GPL-2.0
  /*
   * fault.c:  Page fault handlers for the Sparc.
   *
   * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
   * Copyright (C) 1996 Eddie C. Dost (ecd@skynet.be)
   * Copyright (C) 1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
   */
  
  #include <asm/head.h>
  
  #include <linux/string.h>
  #include <linux/types.h>
  #include <linux/sched.h>
  #include <linux/ptrace.h>
  #include <linux/mman.h>
  #include <linux/threads.h>
  #include <linux/kernel.h>
  #include <linux/signal.h>
  #include <linux/mm.h>
  #include <linux/smp.h>
  #include <linux/perf_event.h>
  #include <linux/interrupt.h>
  #include <linux/kdebug.h>
  #include <linux/uaccess.h>
  
  #include <asm/page.h>
  #include <asm/pgtable.h>
  #include <asm/openprom.h>
  #include <asm/oplib.h>
  #include <asm/setup.h>
  #include <asm/smp.h>
  #include <asm/traps.h>
  
  #include "mm_32.h"
  
  int show_unhandled_signals = 1;
  
  static void __noreturn unhandled_fault(unsigned long address,
  				       struct task_struct *tsk,
  				       struct pt_regs *regs)
  {
  	if ((unsigned long) address < PAGE_SIZE) {
  		printk(KERN_ALERT
  		    "Unable to handle kernel NULL pointer dereference\n");
  	} else {
  		printk(KERN_ALERT "Unable to handle kernel paging request at virtual address %08lx\n",
  		       address);
  	}
  	printk(KERN_ALERT "tsk->{mm,active_mm}->context = %08lx\n",
  		(tsk->mm ? tsk->mm->context : tsk->active_mm->context));
  	printk(KERN_ALERT "tsk->{mm,active_mm}->pgd = %08lx\n",
  		(tsk->mm ? (unsigned long) tsk->mm->pgd :
  			(unsigned long) tsk->active_mm->pgd));
  	die_if_kernel("Oops", regs);
  }
  
  asmlinkage int lookup_fault(unsigned long pc, unsigned long ret_pc,
  			    unsigned long address)
  {
  	struct pt_regs regs;
  	unsigned long g2;
  	unsigned int insn;
  	int i;
  
  	i = search_extables_range(ret_pc, &g2);
  	switch (i) {
  	case 3:
  		/* load & store will be handled by fixup */
  		return 3;
  
  	case 1:
  		/* store will be handled by fixup, load will bump out */
  		/* for _to_ macros */
  		insn = *((unsigned int *) pc);
  		if ((insn >> 21) & 1)
  			return 1;
  		break;
  
  	case 2:
  		/* load will be handled by fixup, store will bump out */
  		/* for _from_ macros */
  		insn = *((unsigned int *) pc);
  		if (!((insn >> 21) & 1) || ((insn>>19)&0x3f) == 15)
  			return 2;
  		break;
  
  	default:
  		break;
  	}
  
  	memset(&regs, 0, sizeof(regs));
  	regs.pc = pc;
  	regs.npc = pc + 4;
  	__asm__ __volatile__(
  		"rd %%psr, %0\n\t"
  		"nop\n\t"
  		"nop\n\t"
  		"nop\n" : "=r" (regs.psr));
  	unhandled_fault(address, current, &regs);
  
  	/* Not reached */
  	return 0;
  }
  
  static inline void
  show_signal_msg(struct pt_regs *regs, int sig, int code,
  		unsigned long address, struct task_struct *tsk)
  {
  	if (!unhandled_signal(tsk, sig))
  		return;
  
  	if (!printk_ratelimit())
  		return;
  
  	printk("%s%s[%d]: segfault at %lx ip %px (rpc %px) sp %px error %x",
  	       task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
  	       tsk->comm, task_pid_nr(tsk), address,
  	       (void *)regs->pc, (void *)regs->u_regs[UREG_I7],
  	       (void *)regs->u_regs[UREG_FP], code);
  
  	print_vma_addr(KERN_CONT " in ", regs->pc);
  
  	printk(KERN_CONT "\n");
  }
  
  static void __do_fault_siginfo(int code, int sig, struct pt_regs *regs,
  			       unsigned long addr)
  {
  	siginfo_t info;
  
  	info.si_signo = sig;
  	info.si_code = code;
  	info.si_errno = 0;
  	info.si_addr = (void __user *) addr;
  	info.si_trapno = 0;
  
  	if (unlikely(show_unhandled_signals))
  		show_signal_msg(regs, sig, info.si_code,
  				addr, current);
  
  	force_sig_info (sig, &info, current);
  }
  
  static unsigned long compute_si_addr(struct pt_regs *regs, int text_fault)
  {
  	unsigned int insn;
  
  	if (text_fault)
  		return regs->pc;
  
  	if (regs->psr & PSR_PS)
  		insn = *(unsigned int *) regs->pc;
  	else
  		__get_user(insn, (unsigned int *) regs->pc);
  
  	return safe_compute_effective_address(regs, insn);
  }
  
  static noinline void do_fault_siginfo(int code, int sig, struct pt_regs *regs,
  				      int text_fault)
  {
  	unsigned long addr = compute_si_addr(regs, text_fault);
  
  	__do_fault_siginfo(code, sig, regs, addr);
  }
  
  asmlinkage void do_sparc_fault(struct pt_regs *regs, int text_fault, int write,
  			       unsigned long address)
  {
  	struct vm_area_struct *vma;
  	struct task_struct *tsk = current;
  	struct mm_struct *mm = tsk->mm;
  	unsigned int fixup;
  	unsigned long g2;
  	int from_user = !(regs->psr & PSR_PS);
  	int fault, code;
  	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  
  	if (text_fault)
  		address = regs->pc;
  
  	/*
  	 * We fault-in kernel-space virtual memory on-demand. The
  	 * 'reference' page table is init_mm.pgd.
  	 *
  	 * NOTE! We MUST NOT take any locks for this case. We may
  	 * be in an interrupt or a critical region, and should
  	 * only copy the information from the master page table,
  	 * nothing more.
  	 */
  	code = SEGV_MAPERR;
  	if (address >= TASK_SIZE)
  		goto vmalloc_fault;
  
  	/*
  	 * If we're in an interrupt or have no user
  	 * context, we must not take the fault..
  	 */
  	if (pagefault_disabled() || !mm)
  		goto no_context;
  
  	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
  
  retry:
  	down_read(&mm->mmap_sem);
  
  	if (!from_user && address >= PAGE_OFFSET)
  		goto bad_area;
  
  	vma = find_vma(mm, address);
  	if (!vma)
  		goto bad_area;
  	if (vma->vm_start <= address)
  		goto good_area;
  	if (!(vma->vm_flags & VM_GROWSDOWN))
  		goto bad_area;
  	if (expand_stack(vma, address))
  		goto bad_area;
  	/*
  	 * Ok, we have a good vm_area for this memory access, so
  	 * we can handle it..
  	 */
  good_area:
  	code = SEGV_ACCERR;
  	if (write) {
  		if (!(vma->vm_flags & VM_WRITE))
  			goto bad_area;
  	} else {
  		/* Allow reads even for write-only mappings */
  		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
  			goto bad_area;
  	}
  
  	if (from_user)
  		flags |= FAULT_FLAG_USER;
  	if (write)
  		flags |= FAULT_FLAG_WRITE;
  
  	/*
  	 * If for any reason at all we couldn't handle the fault,
  	 * make sure we exit gracefully rather than endlessly redo
  	 * the fault.
  	 */
  	fault = handle_mm_fault(vma, address, flags);
  
  	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
  		return;
  
  	if (unlikely(fault & VM_FAULT_ERROR)) {
  		if (fault & VM_FAULT_OOM)
  			goto out_of_memory;
  		else if (fault & VM_FAULT_SIGSEGV)
  			goto bad_area;
  		else if (fault & VM_FAULT_SIGBUS)
  			goto do_sigbus;
  		BUG();
  	}
  
  	if (flags & FAULT_FLAG_ALLOW_RETRY) {
  		if (fault & VM_FAULT_MAJOR) {
  			current->maj_flt++;
  			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
  				      1, regs, address);
  		} else {
  			current->min_flt++;
  			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN,
  				      1, regs, address);
  		}
  		if (fault & VM_FAULT_RETRY) {
  			flags &= ~FAULT_FLAG_ALLOW_RETRY;
  			flags |= FAULT_FLAG_TRIED;
  
  			/* No need to up_read(&mm->mmap_sem) as we would
  			 * have already released it in __lock_page_or_retry
  			 * in mm/filemap.c.
  			 */
  
  			goto retry;
  		}
  	}
  
  	up_read(&mm->mmap_sem);
  	return;
  
  	/*
  	 * Something tried to access memory that isn't in our memory map..
  	 * Fix it, but check if it's kernel or user first..
  	 */
  bad_area:
  	up_read(&mm->mmap_sem);
  
  bad_area_nosemaphore:
  	/* User mode accesses just cause a SIGSEGV */
  	if (from_user) {
  		do_fault_siginfo(code, SIGSEGV, regs, text_fault);
  		return;
  	}
  
  	/* Is this in ex_table? */
  no_context:
  	g2 = regs->u_regs[UREG_G2];
  	if (!from_user) {
  		fixup = search_extables_range(regs->pc, &g2);
  		/* Values below 10 are reserved for other things */
  		if (fixup > 10) {
  			extern const unsigned int __memset_start[];
  			extern const unsigned int __memset_end[];
  			extern const unsigned int __csum_partial_copy_start[];
  			extern const unsigned int __csum_partial_copy_end[];
  
  #ifdef DEBUG_EXCEPTIONS
  			printk("Exception: PC<%08lx> faddr<%08lx>\n",
  			       regs->pc, address);
  			printk("EX_TABLE: insn<%08lx> fixup<%08x> g2<%08lx>\n",
  				regs->pc, fixup, g2);
  #endif
  			if ((regs->pc >= (unsigned long)__memset_start &&
  			     regs->pc < (unsigned long)__memset_end) ||
  			    (regs->pc >= (unsigned long)__csum_partial_copy_start &&
  			     regs->pc < (unsigned long)__csum_partial_copy_end)) {
  				regs->u_regs[UREG_I4] = address;
  				regs->u_regs[UREG_I5] = regs->pc;
  			}
  			regs->u_regs[UREG_G2] = g2;
  			regs->pc = fixup;
  			regs->npc = regs->pc + 4;
  			return;
  		}
  	}
  
  	unhandled_fault(address, tsk, regs);
  	do_exit(SIGKILL);
  
  /*
   * We ran out of memory, or some other thing happened to us that made
   * us unable to handle the page fault gracefully.
   */
  out_of_memory:
  	up_read(&mm->mmap_sem);
  	if (from_user) {
  		pagefault_out_of_memory();
  		return;
  	}
  	goto no_context;
  
  do_sigbus:
  	up_read(&mm->mmap_sem);
  	do_fault_siginfo(BUS_ADRERR, SIGBUS, regs, text_fault);
  	if (!from_user)
  		goto no_context;
  
  vmalloc_fault:
  	{
  		/*
  		 * Synchronize this task's top level page-table
  		 * with the 'reference' page table.
  		 */
  		int offset = pgd_index(address);
  		pgd_t *pgd, *pgd_k;
  		pmd_t *pmd, *pmd_k;
  
  		pgd = tsk->active_mm->pgd + offset;
  		pgd_k = init_mm.pgd + offset;
  
  		if (!pgd_present(*pgd)) {
  			if (!pgd_present(*pgd_k))
  				goto bad_area_nosemaphore;
  			pgd_val(*pgd) = pgd_val(*pgd_k);
  			return;
  		}
  
  		pmd = pmd_offset(pgd, address);
  		pmd_k = pmd_offset(pgd_k, address);
  
  		if (pmd_present(*pmd) || !pmd_present(*pmd_k))
  			goto bad_area_nosemaphore;
  
  		*pmd = *pmd_k;
  		return;
  	}
  }
  
  /* This always deals with user addresses. */
  static void force_user_fault(unsigned long address, int write)
  {
  	struct vm_area_struct *vma;
  	struct task_struct *tsk = current;
  	struct mm_struct *mm = tsk->mm;
  	unsigned int flags = FAULT_FLAG_USER;
  	int code;
  
  	code = SEGV_MAPERR;
  
  	down_read(&mm->mmap_sem);
  	vma = find_vma(mm, address);
  	if (!vma)
  		goto bad_area;
  	if (vma->vm_start <= address)
  		goto good_area;
  	if (!(vma->vm_flags & VM_GROWSDOWN))
  		goto bad_area;
  	if (expand_stack(vma, address))
  		goto bad_area;
  good_area:
  	code = SEGV_ACCERR;
  	if (write) {
  		if (!(vma->vm_flags & VM_WRITE))
  			goto bad_area;
  		flags |= FAULT_FLAG_WRITE;
  	} else {
  		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
  			goto bad_area;
  	}
  	switch (handle_mm_fault(vma, address, flags)) {
  	case VM_FAULT_SIGBUS:
  	case VM_FAULT_OOM:
  		goto do_sigbus;
  	}
  	up_read(&mm->mmap_sem);
  	return;
  bad_area:
  	up_read(&mm->mmap_sem);
  	__do_fault_siginfo(code, SIGSEGV, tsk->thread.kregs, address);
  	return;
  
  do_sigbus:
  	up_read(&mm->mmap_sem);
  	__do_fault_siginfo(BUS_ADRERR, SIGBUS, tsk->thread.kregs, address);
  }
  
  static void check_stack_aligned(unsigned long sp)
  {
  	if (sp & 0x7UL)
  		force_sig(SIGILL, current);
  }
  
  void window_overflow_fault(void)
  {
  	unsigned long sp;
  
  	sp = current_thread_info()->rwbuf_stkptrs[0];
  	if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
  		force_user_fault(sp + 0x38, 1);
  	force_user_fault(sp, 1);
  
  	check_stack_aligned(sp);
  }
  
  void window_underflow_fault(unsigned long sp)
  {
  	if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
  		force_user_fault(sp + 0x38, 0);
  	force_user_fault(sp, 0);
  
  	check_stack_aligned(sp);
  }
  
  void window_ret_fault(struct pt_regs *regs)
  {
  	unsigned long sp;
  
  	sp = regs->u_regs[UREG_FP];
  	if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
  		force_user_fault(sp + 0x38, 0);
  	force_user_fault(sp, 0);
  
  	check_stack_aligned(sp);
  }
  