arch/csky/mm/fault.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 // Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.

 #include <linux/extable.h>
 #include <linux/kprobes.h>
 #include <linux/mmu_context.h>
 #include <linux/perf_event.h>

 int fixup_exception(struct pt_regs *regs)
 {
 	const struct exception_table_entry *fixup;

 	fixup = search_exception_tables(instruction_pointer(regs));
 	if (fixup) {
 		regs->pc = fixup->fixup;

 		return 1;
 	}

 	return 0;
 }

 static inline bool is_write(struct pt_regs *regs)
 {
 	switch (trap_no(regs)) {
 	case VEC_TLBINVALIDS:
 		return true;
 	case VEC_TLBMODIFIED:
 		return true;
 	}

 	return false;
 }

 #ifdef CONFIG_CPU_HAS_LDSTEX
 static inline void csky_cmpxchg_fixup(struct pt_regs *regs)
 {
 	return;
 }
 #else
 extern unsigned long csky_cmpxchg_ldw;
 extern unsigned long csky_cmpxchg_stw;
 static inline void csky_cmpxchg_fixup(struct pt_regs *regs)
 {
 	if (trap_no(regs) != VEC_TLBMODIFIED)
 		return;

 	if (instruction_pointer(regs) == csky_cmpxchg_stw)
 		instruction_pointer_set(regs, csky_cmpxchg_ldw);
 	return;
 }
 #endif

 static inline void no_context(struct pt_regs *regs, unsigned long addr)
 {
 	current->thread.trap_no = trap_no(regs);

 	/* 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.
 	 */
 	bust_spinlocks(1);
 	pr_alert("Unable to handle kernel paging request at virtual "
 		 "addr 0x%08lx, pc: 0x%08lx\n", addr, regs->pc);
 	die(regs, "Oops");
 	do_exit(SIGKILL);
 }

 static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault)
 {
 	current->thread.trap_no = trap_no(regs);

 	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, *pud_k;
 	pmd_t *pmd, *pmd_k;
 	pte_t *pte_k;
 	int offset;

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

 	/*
 	 * Synchronize this task's top level page-table
 	 * with the 'reference' page table.
 	 *
 	 * Do _not_ use "tsk" here. We might be inside
 	 * an interrupt in the middle of a task switch..
 	 */
 	offset = pgd_index(addr);

 	pgd = get_pgd() + offset;
 	pgd_k = init_mm.pgd + offset;

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

 	pud = (pud_t *)pgd;
 	pud_k = (pud_t *)pgd_k;
 	if (!pud_present(*pud_k)) {
 		no_context(regs, addr);
 		return;
 	}

 	pmd = pmd_offset(pud, addr);
 	pmd_k = pmd_offset(pud_k, addr);
 	if (!pmd_present(*pmd_k)) {
 		no_context(regs, addr);
 		return;
 	}
 	set_pmd(pmd, *pmd_k);

 	pte_k = pte_offset_kernel(pmd_k, addr);
 	if (!pte_present(*pte_k)) {
 		no_context(regs, addr);
 		return;
 	}

 	flush_tlb_one(addr);
 }

 static inline bool access_error(struct pt_regs *regs, struct vm_area_struct *vma)
 {
 	if (is_write(regs)) {
 		if (!(vma->vm_flags & VM_WRITE))
 			return true;
 	} else {
 		if (unlikely(!vma_is_accessible(vma)))
 			return true;
 	}
 	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 = read_mmu_entryhi() & PAGE_MASK;
 	unsigned int flags = FAULT_FLAG_DEFAULT;
 	int code = SEGV_MAPERR;
 	vm_fault_t fault;

 	tsk = current;
 	mm = tsk->mm;

 	csky_cmpxchg_fixup(regs);

 	if (kprobe_page_fault(regs, tsk->thread.trap_no))
 		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;
 	}

 	/* Enable interrupts if they were enabled in the parent context. */
 	if (likely(regs->sr & BIT(6)))
 		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)) {
 		no_context(regs, addr);
 		return;
 	}

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

 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);

 	if (is_write(regs))
 		flags |= FAULT_FLAG_WRITE;
 retry:
 	mmap_read_lock(mm);
 	vma = find_vma(mm, addr);
 	if (unlikely(!vma)) {
 		bad_area(regs, mm, code, addr);
 		return;
 	}
 	if (likely(vma->vm_start <= addr))
 		goto good_area;
 	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
 		bad_area(regs, mm, code, addr);
 		return;
 	}
 	if (unlikely(expand_stack(vma, addr))) {
 		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(regs, vma))) {
 		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;
 	}

 	if (unlikely((fault & VM_FAULT_RETRY) && (flags & FAULT_FLAG_ALLOW_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)) {
 		mm_fault_error(regs, addr, fault);
 		return;
 	}
 	return;
 }
	// SPDX-License-Identifier: GPL-2.0
	// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.

	#include <linux/extable.h>
	#include <linux/kprobes.h>
	#include <linux/mmu_context.h>
	#include <linux/perf_event.h>

	int fixup_exception(struct pt_regs *regs)
	{
	const struct exception_table_entry *fixup;

	fixup = search_exception_tables(instruction_pointer(regs));
	if (fixup) {
	regs->pc = fixup->fixup;

	return 1;
	}

	return 0;
	}

	static inline bool is_write(struct pt_regs *regs)
	{
	switch (trap_no(regs)) {
	case VEC_TLBINVALIDS:
	return true;
	case VEC_TLBMODIFIED:
	return true;
	}

	return false;
	}

	#ifdef CONFIG_CPU_HAS_LDSTEX
	static inline void csky_cmpxchg_fixup(struct pt_regs *regs)
	{
	return;
	}
	#else
	extern unsigned long csky_cmpxchg_ldw;
	extern unsigned long csky_cmpxchg_stw;
	static inline void csky_cmpxchg_fixup(struct pt_regs *regs)
	{
	if (trap_no(regs) != VEC_TLBMODIFIED)
	return;

	if (instruction_pointer(regs) == csky_cmpxchg_stw)
	instruction_pointer_set(regs, csky_cmpxchg_ldw);
	return;
	}
	#endif

	static inline void no_context(struct pt_regs *regs, unsigned long addr)
	{
	current->thread.trap_no = trap_no(regs);

	/* 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.
	*/
	bust_spinlocks(1);
	pr_alert("Unable to handle kernel paging request at virtual "
	"addr 0x%08lx, pc: 0x%08lx\n", addr, regs->pc);
	die(regs, "Oops");
	do_exit(SIGKILL);
	}

	static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault)
	{
	current->thread.trap_no = trap_no(regs);

	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, pud_k;
	pmd_t pmd, pmd_k;
	pte_t *pte_k;
	int offset;

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

	/*
	* Synchronize this task's top level page-table
	* with the 'reference' page table.
	*
	* Do _not_ use "tsk" here. We might be inside
	* an interrupt in the middle of a task switch..
	*/
	offset = pgd_index(addr);

	pgd = get_pgd() + offset;
	pgd_k = init_mm.pgd + offset;

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

	pud = (pud_t *)pgd;
	pud_k = (pud_t *)pgd_k;
	if (!pud_present(*pud_k)) {
	no_context(regs, addr);
	return;
	}

	pmd = pmd_offset(pud, addr);
	pmd_k = pmd_offset(pud_k, addr);
	if (!pmd_present(*pmd_k)) {
	no_context(regs, addr);
	return;
	}
	set_pmd(pmd, *pmd_k);

	pte_k = pte_offset_kernel(pmd_k, addr);
	if (!pte_present(*pte_k)) {
	no_context(regs, addr);
	return;
	}

	flush_tlb_one(addr);
	}

	static inline bool access_error(struct pt_regs regs, struct vm_area_struct vma)
	{
	if (is_write(regs)) {
	if (!(vma->vm_flags & VM_WRITE))
	return true;
	} else {
	if (unlikely(!vma_is_accessible(vma)))
	return true;
	}
	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 = read_mmu_entryhi() & PAGE_MASK;
	unsigned int flags = FAULT_FLAG_DEFAULT;
	int code = SEGV_MAPERR;
	vm_fault_t fault;

	tsk = current;
	mm = tsk->mm;

	csky_cmpxchg_fixup(regs);

	if (kprobe_page_fault(regs, tsk->thread.trap_no))
	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;
	}

	/* Enable interrupts if they were enabled in the parent context. */
	if (likely(regs->sr & BIT(6)))
	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)) {
	no_context(regs, addr);
	return;
	}

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

	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);

	if (is_write(regs))
	flags \|= FAULT_FLAG_WRITE;
	retry:
	mmap_read_lock(mm);
	vma = find_vma(mm, addr);
	if (unlikely(!vma)) {
	bad_area(regs, mm, code, addr);
	return;
	}
	if (likely(vma->vm_start <= addr))
	goto good_area;
	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
	bad_area(regs, mm, code, addr);
	return;
	}
	if (unlikely(expand_stack(vma, addr))) {
	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(regs, vma))) {
	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;
	}

	if (unlikely((fault & VM_FAULT_RETRY) && (flags & FAULT_FLAG_ALLOW_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)) {
	mm_fault_error(regs, addr, fault);
	return;
	}
	return;
	}