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

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
  *  Lennox Wu <lennox.wu@sunplusct.com>
  *  Chen Liqin <liqin.chen@sunplusct.com>
  * Copyright (C) 2012 Regents of the University of California
  */


 #include <linux/mm.h>
 #include <linux/kernel.h>
 #include <linux/interrupt.h>
 #include <linux/perf_event.h>
 #include <linux/signal.h>
 #include <linux/uaccess.h>
 #include <linux/kprobes.h>
 #include <linux/kfence.h>

 #include <asm/ptrace.h>
 #include <asm/tlbflush.h>

 #include "../kernel/head.h"

 static void die_kernel_fault(const char *msg, unsigned long addr,
 		struct pt_regs *regs)
 {
 	bust_spinlocks(1);

 	pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", msg,
 		addr);

 	bust_spinlocks(0);
 	die(regs, "Oops");
 	make_task_dead(SIGKILL);
 }

 static inline void no_context(struct pt_regs *regs, unsigned long addr)
 {
 	const char *msg;

 	/* Are we prepared to handle this kernel fault? */
 	if (fixup_exception(regs))
 		return;

 	/*
 	 * Oops. The kernel tried to access some bad page. We'll have to
 	 * terminate things with extreme prejudice.
 	 */
 	if (addr < PAGE_SIZE)
 		msg = "NULL pointer dereference";
 	else {
 		if (kfence_handle_page_fault(addr, regs->cause == EXC_STORE_PAGE_FAULT, regs))
 			return;

 		msg = "paging request";
 	}

 	die_kernel_fault(msg, addr, regs);
 }

 static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault)
 {
 	if (fault & VM_FAULT_OOM) {
 		/*
 		 * We ran out of memory, call the OOM killer, and return the userspace
 		 * (which will retry the fault, or kill us if we got oom-killed).
 		 */
 		if (!user_mode(regs)) {
 			no_context(regs, addr);
 			return;
 		}
 		pagefault_out_of_memory();
 		return;
 	} else if (fault & VM_FAULT_SIGBUS) {
 		/* Kernel mode? Handle exceptions or die */
 		if (!user_mode(regs)) {
 			no_context(regs, addr);
 			return;
 		}
 		do_trap(regs, SIGBUS, BUS_ADRERR, addr);
 		return;
 	}
 	BUG();
 }

 static inline void bad_area(struct pt_regs *regs, struct mm_struct *mm, int code, unsigned long addr)
 {
 	/*
 	 * Something tried to access memory that isn't in our memory map.
 	 * Fix it, but check if it's kernel or user first.
 	 */
 	mmap_read_unlock(mm);
 	/* User mode accesses just cause a SIGSEGV */
 	if (user_mode(regs)) {
 		do_trap(regs, SIGSEGV, code, addr);
 		return;
 	}

 	no_context(regs, addr);
 }

 static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr)
 {
 	pgd_t *pgd, *pgd_k;
 	pud_t *pud_k;
 	p4d_t *p4d_k;
 	pmd_t *pmd_k;
 	pte_t *pte_k;
 	int index;
 	unsigned long pfn;

 	/* User mode accesses just cause a SIGSEGV */
 	if (user_mode(regs))
 		return do_trap(regs, SIGSEGV, code, addr);

 	/*
 	 * Synchronize this task's top level page-table
 	 * with the 'reference' page table.
 	 *
 	 * Do _not_ use "tsk->active_mm->pgd" here.
 	 * We might be inside an interrupt in the middle
 	 * of a task switch.
 	 */
 	index = pgd_index(addr);
 	pfn = csr_read(CSR_SATP) & SATP_PPN;
 	pgd = (pgd_t *)pfn_to_virt(pfn) + index;
 	pgd_k = init_mm.pgd + index;

 	if (!pgd_present(*pgd_k)) {
 		no_context(regs, addr);
 		return;
 	}
 	set_pgd(pgd, *pgd_k);

 	p4d_k = p4d_offset(pgd_k, addr);
 	if (!p4d_present(*p4d_k)) {
 		no_context(regs, addr);
 		return;
 	}

 	pud_k = pud_offset(p4d_k, addr);
 	if (!pud_present(*pud_k)) {
 		no_context(regs, addr);
 		return;
 	}

 	/*
 	 * Since the vmalloc area is global, it is unnecessary
 	 * to copy individual PTEs
 	 */
 	pmd_k = pmd_offset(pud_k, addr);
 	if (!pmd_present(*pmd_k)) {
 		no_context(regs, addr);
 		return;
 	}

 	/*
 	 * Make sure the actual PTE exists as well to
 	 * catch kernel vmalloc-area accesses to non-mapped
 	 * addresses. If we don't do this, this will just
 	 * silently loop forever.
 	 */
 	pte_k = pte_offset_kernel(pmd_k, addr);
 	if (!pte_present(*pte_k)) {
 		no_context(regs, addr);
 		return;
 	}

 	/*
 	 * The kernel assumes that TLBs don't cache invalid
 	 * entries, but in RISC-V, SFENCE.VMA specifies an
 	 * ordering constraint, not a cache flush; it is
 	 * necessary even after writing invalid entries.
 	 */
 	local_flush_tlb_page(addr);
 }

 static inline bool access_error(unsigned long cause, struct vm_area_struct *vma)
 {
 	switch (cause) {
 	case EXC_INST_PAGE_FAULT:
 		if (!(vma->vm_flags & VM_EXEC)) {
 			return true;
 		}
 		break;
 	case EXC_LOAD_PAGE_FAULT:
 		/* Write implies read */
 		if (!(vma->vm_flags & (VM_READ | VM_WRITE))) {
 			return true;
 		}
 		break;
 	case EXC_STORE_PAGE_FAULT:
 		if (!(vma->vm_flags & VM_WRITE)) {
 			return true;
 		}
 		break;
 	default:
 		panic("%s: unhandled cause %lu", __func__, cause);
 	}
 	return false;
 }

 /*
  * This routine handles page faults.  It determines the address and the
  * problem, and then passes it off to one of the appropriate routines.
  */
 asmlinkage void do_page_fault(struct pt_regs *regs)
 {
 	struct task_struct *tsk;
 	struct vm_area_struct *vma;
 	struct mm_struct *mm;
 	unsigned long addr, cause;
 	unsigned int flags = FAULT_FLAG_DEFAULT;
 	int code = SEGV_MAPERR;
 	vm_fault_t fault;

 	cause = regs->cause;
 	addr = regs->badaddr;

 	tsk = current;
 	mm = tsk->mm;

 	if (kprobe_page_fault(regs, cause))
 		return;

 	/*
 	 * 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.
 	 */
 	if (unlikely((addr >= VMALLOC_START) && (addr < VMALLOC_END))) {
 		vmalloc_fault(regs, code, addr);
 		return;
 	}

 #ifdef CONFIG_64BIT
 	/*
 	 * Modules in 64bit kernels lie in their own virtual region which is not
 	 * in the vmalloc region, but dealing with page faults in this region
 	 * or the vmalloc region amounts to doing the same thing: checking that
 	 * the mapping exists in init_mm.pgd and updating user page table, so
 	 * just use vmalloc_fault.
 	 */
 	if (unlikely(addr >= MODULES_VADDR && addr < MODULES_END)) {
 		vmalloc_fault(regs, code, addr);
 		return;
 	}
 #endif
 	/* Enable interrupts if they were enabled in the parent context. */
 	if (likely(regs->status & SR_PIE))
 		local_irq_enable();

 	/*
 	 * If we're in an interrupt, have no user context, or are running
 	 * in an atomic region, then we must not take the fault.
 	 */
 	if (unlikely(faulthandler_disabled() || !mm)) {
 		tsk->thread.bad_cause = cause;
 		no_context(regs, addr);
 		return;
 	}

 	if (user_mode(regs))
 		flags |= FAULT_FLAG_USER;

 	if (!user_mode(regs) && addr < TASK_SIZE && unlikely(!(regs->status & SR_SUM))) {
 		if (fixup_exception(regs))
 			return;

 		die_kernel_fault("access to user memory without uaccess routines", addr, regs);
 	}

 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);

 	if (cause == EXC_STORE_PAGE_FAULT)
 		flags |= FAULT_FLAG_WRITE;
 	else if (cause == EXC_INST_PAGE_FAULT)
 		flags |= FAULT_FLAG_INSTRUCTION;
 retry:
 	mmap_read_lock(mm);
 	vma = find_vma(mm, addr);
 	if (unlikely(!vma)) {
 		tsk->thread.bad_cause = cause;
 		bad_area(regs, mm, code, addr);
 		return;
 	}
 	if (likely(vma->vm_start <= addr))
 		goto good_area;
 	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
 		tsk->thread.bad_cause = cause;
 		bad_area(regs, mm, code, addr);
 		return;
 	}
 	if (unlikely(expand_stack(vma, addr))) {
 		tsk->thread.bad_cause = cause;
 		bad_area(regs, mm, code, addr);
 		return;
 	}

 	/*
 	 * Ok, we have a good vm_area for this memory access, so
 	 * we can handle it.
 	 */
 good_area:
 	code = SEGV_ACCERR;

 	if (unlikely(access_error(cause, vma))) {
 		tsk->thread.bad_cause = cause;
 		bad_area(regs, mm, code, addr);
 		return;
 	}

 	/*
 	 * If for any reason at all we could not handle the fault,
 	 * make sure we exit gracefully rather than endlessly redo
 	 * the fault.
 	 */
 	fault = handle_mm_fault(vma, addr, flags, regs);

 	/*
 	 * If we need to retry but a fatal signal is pending, handle the
 	 * signal first. We do not need to release the mmap_lock because it
 	 * would already be released in __lock_page_or_retry in mm/filemap.c.
 	 */
 	if (fault_signal_pending(fault, regs)) {
 		if (!user_mode(regs))
 			no_context(regs, addr);
 		return;
 	}

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

 	if (unlikely(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);

 	if (unlikely(fault & VM_FAULT_ERROR)) {
 		tsk->thread.bad_cause = cause;
 		mm_fault_error(regs, addr, fault);
 		return;
 	}
 	return;
 }
 NOKPROBE_SYMBOL(do_page_fault);
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
	* Lennox Wu <lennox.wu@sunplusct.com>
	* Chen Liqin <liqin.chen@sunplusct.com>
	* Copyright (C) 2012 Regents of the University of California
	*/


	#include <linux/mm.h>
	#include <linux/kernel.h>
	#include <linux/interrupt.h>
	#include <linux/perf_event.h>
	#include <linux/signal.h>
	#include <linux/uaccess.h>
	#include <linux/kprobes.h>
	#include <linux/kfence.h>

	#include <asm/ptrace.h>
	#include <asm/tlbflush.h>

	#include "../kernel/head.h"

	static void die_kernel_fault(const char *msg, unsigned long addr,
	struct pt_regs *regs)
	{
	bust_spinlocks(1);

	pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", msg,
	addr);

	bust_spinlocks(0);
	die(regs, "Oops");
	make_task_dead(SIGKILL);
	}

	static inline void no_context(struct pt_regs *regs, unsigned long addr)
	{
	const char *msg;

	/* Are we prepared to handle this kernel fault? */
	if (fixup_exception(regs))
	return;

	/*
	* Oops. The kernel tried to access some bad page. We'll have to
	* terminate things with extreme prejudice.
	*/
	if (addr < PAGE_SIZE)
	msg = "NULL pointer dereference";
	else {
	if (kfence_handle_page_fault(addr, regs->cause == EXC_STORE_PAGE_FAULT, regs))
	return;

	msg = "paging request";
	}

	die_kernel_fault(msg, addr, regs);
	}

	static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault)
	{
	if (fault & VM_FAULT_OOM) {
	/*
	* We ran out of memory, call the OOM killer, and return the userspace
	* (which will retry the fault, or kill us if we got oom-killed).
	*/
	if (!user_mode(regs)) {
	no_context(regs, addr);
	return;
	}
	pagefault_out_of_memory();
	return;
	} else if (fault & VM_FAULT_SIGBUS) {
	/* Kernel mode? Handle exceptions or die */
	if (!user_mode(regs)) {
	no_context(regs, addr);
	return;
	}
	do_trap(regs, SIGBUS, BUS_ADRERR, addr);
	return;
	}
	BUG();
	}

	static inline void bad_area(struct pt_regs regs, struct mm_struct mm, int code, unsigned long addr)
	{
	/*
	* Something tried to access memory that isn't in our memory map.
	* Fix it, but check if it's kernel or user first.
	*/
	mmap_read_unlock(mm);
	/* User mode accesses just cause a SIGSEGV */
	if (user_mode(regs)) {
	do_trap(regs, SIGSEGV, code, addr);
	return;
	}

	no_context(regs, addr);
	}

	static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr)
	{
	pgd_t pgd, pgd_k;
	pud_t *pud_k;
	p4d_t *p4d_k;
	pmd_t *pmd_k;
	pte_t *pte_k;
	int index;
	unsigned long pfn;

	/* User mode accesses just cause a SIGSEGV */
	if (user_mode(regs))
	return do_trap(regs, SIGSEGV, code, addr);

	/*
	* Synchronize this task's top level page-table
	* with the 'reference' page table.
	*
	* Do _not_ use "tsk->active_mm->pgd" here.
	* We might be inside an interrupt in the middle
	* of a task switch.
	*/
	index = pgd_index(addr);
	pfn = csr_read(CSR_SATP) & SATP_PPN;
	pgd = (pgd_t *)pfn_to_virt(pfn) + index;
	pgd_k = init_mm.pgd + index;

	if (!pgd_present(*pgd_k)) {
	no_context(regs, addr);
	return;
	}
	set_pgd(pgd, *pgd_k);

	p4d_k = p4d_offset(pgd_k, addr);
	if (!p4d_present(*p4d_k)) {
	no_context(regs, addr);
	return;
	}

	pud_k = pud_offset(p4d_k, addr);
	if (!pud_present(*pud_k)) {
	no_context(regs, addr);
	return;
	}

	/*
	* Since the vmalloc area is global, it is unnecessary
	* to copy individual PTEs
	*/
	pmd_k = pmd_offset(pud_k, addr);
	if (!pmd_present(*pmd_k)) {
	no_context(regs, addr);
	return;
	}

	/*
	* Make sure the actual PTE exists as well to
	* catch kernel vmalloc-area accesses to non-mapped
	* addresses. If we don't do this, this will just
	* silently loop forever.
	*/
	pte_k = pte_offset_kernel(pmd_k, addr);
	if (!pte_present(*pte_k)) {
	no_context(regs, addr);
	return;
	}

	/*
	* The kernel assumes that TLBs don't cache invalid
	* entries, but in RISC-V, SFENCE.VMA specifies an
	* ordering constraint, not a cache flush; it is
	* necessary even after writing invalid entries.
	*/
	local_flush_tlb_page(addr);
	}

	static inline bool access_error(unsigned long cause, struct vm_area_struct *vma)
	{
	switch (cause) {
	case EXC_INST_PAGE_FAULT:
	if (!(vma->vm_flags & VM_EXEC)) {
	return true;
	}
	break;
	case EXC_LOAD_PAGE_FAULT:
	/* Write implies read */
	if (!(vma->vm_flags & (VM_READ \| VM_WRITE))) {
	return true;
	}
	break;
	case EXC_STORE_PAGE_FAULT:
	if (!(vma->vm_flags & VM_WRITE)) {
	return true;
	}
	break;
	default:
	panic("%s: unhandled cause %lu", __func__, cause);
	}
	return false;
	}

	/*
	* This routine handles page faults. It determines the address and the
	* problem, and then passes it off to one of the appropriate routines.
	*/
	asmlinkage void do_page_fault(struct pt_regs *regs)
	{
	struct task_struct *tsk;
	struct vm_area_struct *vma;
	struct mm_struct *mm;
	unsigned long addr, cause;
	unsigned int flags = FAULT_FLAG_DEFAULT;
	int code = SEGV_MAPERR;
	vm_fault_t fault;

	cause = regs->cause;
	addr = regs->badaddr;

	tsk = current;
	mm = tsk->mm;

	if (kprobe_page_fault(regs, cause))
	return;

	/*
	* 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.
	*/
	if (unlikely((addr >= VMALLOC_START) && (addr < VMALLOC_END))) {
	vmalloc_fault(regs, code, addr);
	return;
	}

	#ifdef CONFIG_64BIT
	/*
	* Modules in 64bit kernels lie in their own virtual region which is not
	* in the vmalloc region, but dealing with page faults in this region
	* or the vmalloc region amounts to doing the same thing: checking that
	* the mapping exists in init_mm.pgd and updating user page table, so
	* just use vmalloc_fault.
	*/
	if (unlikely(addr >= MODULES_VADDR && addr < MODULES_END)) {
	vmalloc_fault(regs, code, addr);
	return;
	}
	#endif
	/* Enable interrupts if they were enabled in the parent context. */
	if (likely(regs->status & SR_PIE))
	local_irq_enable();

	/*
	* If we're in an interrupt, have no user context, or are running
	* in an atomic region, then we must not take the fault.
	*/
	if (unlikely(faulthandler_disabled() \|\| !mm)) {
	tsk->thread.bad_cause = cause;
	no_context(regs, addr);
	return;
	}

	if (user_mode(regs))
	flags \|= FAULT_FLAG_USER;

	if (!user_mode(regs) && addr < TASK_SIZE && unlikely(!(regs->status & SR_SUM))) {
	if (fixup_exception(regs))
	return;

	die_kernel_fault("access to user memory without uaccess routines", addr, regs);
	}

	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);

	if (cause == EXC_STORE_PAGE_FAULT)
	flags \|= FAULT_FLAG_WRITE;
	else if (cause == EXC_INST_PAGE_FAULT)
	flags \|= FAULT_FLAG_INSTRUCTION;
	retry:
	mmap_read_lock(mm);
	vma = find_vma(mm, addr);
	if (unlikely(!vma)) {
	tsk->thread.bad_cause = cause;
	bad_area(regs, mm, code, addr);
	return;
	}
	if (likely(vma->vm_start <= addr))
	goto good_area;
	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
	tsk->thread.bad_cause = cause;
	bad_area(regs, mm, code, addr);
	return;
	}
	if (unlikely(expand_stack(vma, addr))) {
	tsk->thread.bad_cause = cause;
	bad_area(regs, mm, code, addr);
	return;
	}

	/*
	* Ok, we have a good vm_area for this memory access, so
	* we can handle it.
	*/
	good_area:
	code = SEGV_ACCERR;

	if (unlikely(access_error(cause, vma))) {
	tsk->thread.bad_cause = cause;
	bad_area(regs, mm, code, addr);
	return;
	}

	/*
	* If for any reason at all we could not handle the fault,
	* make sure we exit gracefully rather than endlessly redo
	* the fault.
	*/
	fault = handle_mm_fault(vma, addr, flags, regs);

	/*
	* If we need to retry but a fatal signal is pending, handle the
	* signal first. We do not need to release the mmap_lock because it
	* would already be released in __lock_page_or_retry in mm/filemap.c.
	*/
	if (fault_signal_pending(fault, regs)) {
	if (!user_mode(regs))
	no_context(regs, addr);
	return;
	}

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

	if (unlikely(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);

	if (unlikely(fault & VM_FAULT_ERROR)) {
	tsk->thread.bad_cause = cause;
	mm_fault_error(regs, addr, fault);
	return;
	}
	return;
	}
	NOKPROBE_SYMBOL(do_page_fault);