arch/ia64/mm/fault.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * MMU fault handling support.
  *
  * Copyright (C) 1998-2002 Hewlett-Packard Co
  *	David Mosberger-Tang <davidm@hpl.hp.com>
  */
 #include <linux/sched/signal.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/extable.h>
 #include <linux/interrupt.h>
 #include <linux/kprobes.h>
 #include <linux/kdebug.h>
 #include <linux/prefetch.h>
 #include <linux/uaccess.h>
 #include <linux/perf_event.h>

 #include <asm/processor.h>
 #include <asm/exception.h>

 extern int die(char *, struct pt_regs *, long);

 /*
  * Return TRUE if ADDRESS points at a page in the kernel's mapped segment
  * (inside region 5, on ia64) and that page is present.
  */
 static int
 mapped_kernel_page_is_present (unsigned long address)
 {
 	pgd_t *pgd;
 	p4d_t *p4d;
 	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *ptep, pte;

 	pgd = pgd_offset_k(address);
 	if (pgd_none(*pgd) || pgd_bad(*pgd))
 		return 0;

 	p4d = p4d_offset(pgd, address);
 	if (p4d_none(*p4d) || p4d_bad(*p4d))
 		return 0;

 	pud = pud_offset(p4d, address);
 	if (pud_none(*pud) || pud_bad(*pud))
 		return 0;

 	pmd = pmd_offset(pud, address);
 	if (pmd_none(*pmd) || pmd_bad(*pmd))
 		return 0;

 	ptep = pte_offset_kernel(pmd, address);
 	if (!ptep)
 		return 0;

 	pte = *ptep;
 	return pte_present(pte);
 }

 #	define VM_READ_BIT	0
 #	define VM_WRITE_BIT	1
 #	define VM_EXEC_BIT	2

 void __kprobes
 ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs)
 {
 	int signal = SIGSEGV, code = SEGV_MAPERR;
 	struct vm_area_struct *vma, *prev_vma;
 	struct mm_struct *mm = current->mm;
 	unsigned long mask;
 	vm_fault_t fault;
 	unsigned int flags = FAULT_FLAG_DEFAULT;

 	mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
 		| (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));

 	/* mmap_lock is performance critical.... */
 	prefetchw(&mm->mmap_lock);

 	/*
 	 * If we're in an interrupt or have no user context, we must not take the fault..
 	 */
 	if (faulthandler_disabled() || !mm)
 		goto no_context;

 	/*
 	 * This is to handle the kprobes on user space access instructions
 	 */
 	if (kprobe_page_fault(regs, TRAP_BRKPT))
 		return;

 	if (user_mode(regs))
 		flags |= FAULT_FLAG_USER;
 	if (mask & VM_WRITE)
 		flags |= FAULT_FLAG_WRITE;

 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 retry:
 	mmap_read_lock(mm);

 	vma = find_vma_prev(mm, address, &prev_vma);
 	if (!vma && !prev_vma )
 		goto bad_area;

         /*
          * find_vma_prev() returns vma such that address < vma->vm_end or NULL
          *
          * May find no vma, but could be that the last vm area is the
          * register backing store that needs to expand upwards, in
          * this case vma will be null, but prev_vma will ne non-null
          */
         if (( !vma && prev_vma ) || (address < vma->vm_start) )
 		goto check_expansion;

   good_area:
 	code = SEGV_ACCERR;

 	/* OK, we've got a good vm_area for this memory area.  Check the access permissions: */

 #	if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \
 	    || (1 << VM_EXEC_BIT) != VM_EXEC)
 #		error File is out of sync with <linux/mm.h>.  Please update.
 #	endif

 	if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE))))
 		goto bad_area;

 	if ((vma->vm_flags & mask) != mask)
 		goto bad_area;

 	/*
 	 * 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, regs);

 	if (fault_signal_pending(fault, regs)) {
 		if (!user_mode(regs))
 			goto no_context;
 		return;
 	}

 	/* The fault is fully completed (including releasing mmap lock) */
 	if (fault & VM_FAULT_COMPLETED)
 		return;

 	if (unlikely(fault & VM_FAULT_ERROR)) {
 		/*
 		 * We ran out of memory, or some other thing happened
 		 * to us that made us unable to handle the page fault
 		 * gracefully.
 		 */
 		if (fault & VM_FAULT_OOM) {
 			goto out_of_memory;
 		} else if (fault & VM_FAULT_SIGSEGV) {
 			goto bad_area;
 		} else if (fault & VM_FAULT_SIGBUS) {
 			signal = SIGBUS;
 			goto bad_area;
 		}
 		BUG();
 	}

 	if (fault & VM_FAULT_RETRY) {
 		flags |= FAULT_FLAG_TRIED;

 		/* No need to mmap_read_unlock(mm) as we would
 		 * have already released it in __lock_page_or_retry
 		 * in mm/filemap.c.
 		 */

 		goto retry;
 	}

 	mmap_read_unlock(mm);
 	return;

   check_expansion:
 	if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) {
 		if (!vma)
 			goto bad_area;
 		if (!(vma->vm_flags & VM_GROWSDOWN))
 			goto bad_area;
 		if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
 		    || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
 			goto bad_area;
 		if (expand_stack(vma, address))
 			goto bad_area;
 	} else {
 		vma = prev_vma;
 		if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
 		    || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
 			goto bad_area;
 		/*
 		 * Since the register backing store is accessed sequentially,
 		 * we disallow growing it by more than a page at a time.
 		 */
 		if (address > vma->vm_end + PAGE_SIZE - sizeof(long))
 			goto bad_area;
 		if (expand_upwards(vma, address))
 			goto bad_area;
 	}
 	goto good_area;

   bad_area:
 	mmap_read_unlock(mm);
 	if ((isr & IA64_ISR_SP)
 	    || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
 	{
 		/*
 		 * This fault was due to a speculative load or lfetch.fault, set the "ed"
 		 * bit in the psr to ensure forward progress.  (Target register will get a
 		 * NaT for ld.s, lfetch will be canceled.)
 		 */
 		ia64_psr(regs)->ed = 1;
 		return;
 	}
 	if (user_mode(regs)) {
 		force_sig_fault(signal, code, (void __user *) address,
 				0, __ISR_VALID, isr);
 		return;
 	}

   no_context:
 	if ((isr & IA64_ISR_SP)
 	    || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
 	{
 		/*
 		 * This fault was due to a speculative load or lfetch.fault, set the "ed"
 		 * bit in the psr to ensure forward progress.  (Target register will get a
 		 * NaT for ld.s, lfetch will be canceled.)
 		 */
 		ia64_psr(regs)->ed = 1;
 		return;
 	}

 	/*
 	 * Since we have no vma's for region 5, we might get here even if the address is
 	 * valid, due to the VHPT walker inserting a non present translation that becomes
 	 * stale. If that happens, the non present fault handler already purged the stale
 	 * translation, which fixed the problem. So, we check to see if the translation is
 	 * valid, and return if it is.
 	 */
 	if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address))
 		return;

 	if (ia64_done_with_exception(regs))
 		return;

 	/*
 	 * Oops. The kernel tried to access some bad page. We'll have to terminate things
 	 * with extreme prejudice.
 	 */
 	bust_spinlocks(1);

 	if (address < PAGE_SIZE)
 		printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address);
 	else
 		printk(KERN_ALERT "Unable to handle kernel paging request at "
 		       "virtual address %016lx\n", address);
 	if (die("Oops", regs, isr))
 		regs = NULL;
 	bust_spinlocks(0);
 	if (regs)
 		make_task_dead(SIGKILL);
 	return;

   out_of_memory:
 	mmap_read_unlock(mm);
 	if (!user_mode(regs))
 		goto no_context;
 	pagefault_out_of_memory();
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* MMU fault handling support.
	*
	* Copyright (C) 1998-2002 Hewlett-Packard Co
	* David Mosberger-Tang <davidm@hpl.hp.com>
	*/
	#include <linux/sched/signal.h>
	#include <linux/kernel.h>
	#include <linux/mm.h>
	#include <linux/extable.h>
	#include <linux/interrupt.h>
	#include <linux/kprobes.h>
	#include <linux/kdebug.h>
	#include <linux/prefetch.h>
	#include <linux/uaccess.h>
	#include <linux/perf_event.h>

	#include <asm/processor.h>
	#include <asm/exception.h>

	extern int die(char , struct pt_regs , long);

	/*
	* Return TRUE if ADDRESS points at a page in the kernel's mapped segment
	* (inside region 5, on ia64) and that page is present.
	*/
	static int
	mapped_kernel_page_is_present (unsigned long address)
	{
	pgd_t *pgd;
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *ptep, pte;

	pgd = pgd_offset_k(address);
	if (pgd_none(pgd) \|\| pgd_bad(pgd))
	return 0;

	p4d = p4d_offset(pgd, address);
	if (p4d_none(p4d) \|\| p4d_bad(p4d))
	return 0;

	pud = pud_offset(p4d, address);
	if (pud_none(pud) \|\| pud_bad(pud))
	return 0;

	pmd = pmd_offset(pud, address);
	if (pmd_none(pmd) \|\| pmd_bad(pmd))
	return 0;

	ptep = pte_offset_kernel(pmd, address);
	if (!ptep)
	return 0;

	pte = *ptep;
	return pte_present(pte);
	}

	# define VM_READ_BIT 0
	# define VM_WRITE_BIT 1
	# define VM_EXEC_BIT 2

	void __kprobes
	ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs)
	{
	int signal = SIGSEGV, code = SEGV_MAPERR;
	struct vm_area_struct vma, prev_vma;
	struct mm_struct *mm = current->mm;
	unsigned long mask;
	vm_fault_t fault;
	unsigned int flags = FAULT_FLAG_DEFAULT;

	mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
	\| (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));

	/* mmap_lock is performance critical.... */
	prefetchw(&mm->mmap_lock);

	/*
	* If we're in an interrupt or have no user context, we must not take the fault..
	*/
	if (faulthandler_disabled() \|\| !mm)
	goto no_context;

	/*
	* This is to handle the kprobes on user space access instructions
	*/
	if (kprobe_page_fault(regs, TRAP_BRKPT))
	return;

	if (user_mode(regs))
	flags \|= FAULT_FLAG_USER;
	if (mask & VM_WRITE)
	flags \|= FAULT_FLAG_WRITE;

	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
	retry:
	mmap_read_lock(mm);

	vma = find_vma_prev(mm, address, &prev_vma);
	if (!vma && !prev_vma )
	goto bad_area;

	/*
	* find_vma_prev() returns vma such that address < vma->vm_end or NULL
	*
	* May find no vma, but could be that the last vm area is the
	* register backing store that needs to expand upwards, in
	* this case vma will be null, but prev_vma will ne non-null
	*/
	if (( !vma && prev_vma ) \|\| (address < vma->vm_start) )
	goto check_expansion;

	good_area:
	code = SEGV_ACCERR;

	/* OK, we've got a good vm_area for this memory area. Check the access permissions: */

	# if (((1 << VM_READ_BIT) != VM_READ \|\| (1 << VM_WRITE_BIT) != VM_WRITE) \
	\|\| (1 << VM_EXEC_BIT) != VM_EXEC)
	# error File is out of sync with <linux/mm.h>. Please update.
	# endif

	if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ \| VM_WRITE))))
	goto bad_area;

	if ((vma->vm_flags & mask) != mask)
	goto bad_area;

	/*
	* 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, regs);

	if (fault_signal_pending(fault, regs)) {
	if (!user_mode(regs))
	goto no_context;
	return;
	}

	/* The fault is fully completed (including releasing mmap lock) */
	if (fault & VM_FAULT_COMPLETED)
	return;

	if (unlikely(fault & VM_FAULT_ERROR)) {
	/*
	* We ran out of memory, or some other thing happened
	* to us that made us unable to handle the page fault
	* gracefully.
	*/
	if (fault & VM_FAULT_OOM) {
	goto out_of_memory;
	} else if (fault & VM_FAULT_SIGSEGV) {
	goto bad_area;
	} else if (fault & VM_FAULT_SIGBUS) {
	signal = SIGBUS;
	goto bad_area;
	}
	BUG();
	}

	if (fault & VM_FAULT_RETRY) {
	flags \|= FAULT_FLAG_TRIED;

	/* No need to mmap_read_unlock(mm) as we would
	* have already released it in __lock_page_or_retry
	* in mm/filemap.c.
	*/

	goto retry;
	}

	mmap_read_unlock(mm);
	return;

	check_expansion:
	if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) {
	if (!vma)
	goto bad_area;
	if (!(vma->vm_flags & VM_GROWSDOWN))
	goto bad_area;
	if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
	\|\| REGION_OFFSET(address) >= RGN_MAP_LIMIT)
	goto bad_area;
	if (expand_stack(vma, address))
	goto bad_area;
	} else {
	vma = prev_vma;
	if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
	\|\| REGION_OFFSET(address) >= RGN_MAP_LIMIT)
	goto bad_area;
	/*
	* Since the register backing store is accessed sequentially,
	* we disallow growing it by more than a page at a time.
	*/
	if (address > vma->vm_end + PAGE_SIZE - sizeof(long))
	goto bad_area;
	if (expand_upwards(vma, address))
	goto bad_area;
	}
	goto good_area;

	bad_area:
	mmap_read_unlock(mm);
	if ((isr & IA64_ISR_SP)
	\|\| ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
	{
	/*
	* This fault was due to a speculative load or lfetch.fault, set the "ed"
	* bit in the psr to ensure forward progress. (Target register will get a
	* NaT for ld.s, lfetch will be canceled.)
	*/
	ia64_psr(regs)->ed = 1;
	return;
	}
	if (user_mode(regs)) {
	force_sig_fault(signal, code, (void __user *) address,
	0, __ISR_VALID, isr);
	return;
	}

	no_context:
	if ((isr & IA64_ISR_SP)
	\|\| ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
	{
	/*
	* This fault was due to a speculative load or lfetch.fault, set the "ed"
	* bit in the psr to ensure forward progress. (Target register will get a
	* NaT for ld.s, lfetch will be canceled.)
	*/
	ia64_psr(regs)->ed = 1;
	return;
	}

	/*
	* Since we have no vma's for region 5, we might get here even if the address is
	* valid, due to the VHPT walker inserting a non present translation that becomes
	* stale. If that happens, the non present fault handler already purged the stale
	* translation, which fixed the problem. So, we check to see if the translation is
	* valid, and return if it is.
	*/
	if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address))
	return;

	if (ia64_done_with_exception(regs))
	return;

	/*
	* Oops. The kernel tried to access some bad page. We'll have to terminate things
	* with extreme prejudice.
	*/
	bust_spinlocks(1);

	if (address < PAGE_SIZE)
	printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address);
	else
	printk(KERN_ALERT "Unable to handle kernel paging request at "
	"virtual address %016lx\n", address);
	if (die("Oops", regs, isr))
	regs = NULL;
	bust_spinlocks(0);
	if (regs)
	make_task_dead(SIGKILL);
	return;

	out_of_memory:
	mmap_read_unlock(mm);
	if (!user_mode(regs))
	goto no_context;
	pagefault_out_of_memory();
	}