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

 /*
  * 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
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, see the file COPYING, or write
  * to the Free Software Foundation, Inc.,
  */


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

 /*
  * 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_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 	int code = SEGV_MAPERR;
 	vm_fault_t fault;

 	cause = regs->scause;
 	addr = regs->sbadaddr;

 	tsk = current;
 	mm = tsk->mm;

 	/*
 	 * 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)))
 		goto vmalloc_fault;

 	/* Enable interrupts if they were enabled in the parent context. */
 	if (likely(regs->sstatus & SR_SPIE))
 		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))
 		goto no_context;

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

 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);

 retry:
 	down_read(&mm->mmap_sem);
 	vma = find_vma(mm, addr);
 	if (unlikely(!vma))
 		goto bad_area;
 	if (likely(vma->vm_start <= addr))
 		goto good_area;
 	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
 		goto bad_area;
 	if (unlikely(expand_stack(vma, addr)))
 		goto bad_area;

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

 	switch (cause) {
 	case EXC_INST_PAGE_FAULT:
 		if (!(vma->vm_flags & VM_EXEC))
 			goto bad_area;
 		break;
 	case EXC_LOAD_PAGE_FAULT:
 		if (!(vma->vm_flags & VM_READ))
 			goto bad_area;
 		break;
 	case EXC_STORE_PAGE_FAULT:
 		if (!(vma->vm_flags & VM_WRITE))
 			goto bad_area;
 		flags |= FAULT_FLAG_WRITE;
 		break;
 	default:
 		panic("%s: unhandled cause %lu", __func__, cause);
 	}

 	/*
 	 * 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);

 	/*
 	 * If we need to retry but a fatal signal is pending, handle the
 	 * signal first. We do not need to release the mmap_sem because it
 	 * would already be released in __lock_page_or_retry in mm/filemap.c.
 	 */
 	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(tsk))
 		return;

 	if (unlikely(fault & VM_FAULT_ERROR)) {
 		if (fault & VM_FAULT_OOM)
 			goto out_of_memory;
 		else if (fault & VM_FAULT_SIGBUS)
 			goto do_sigbus;
 		BUG();
 	}

 	/*
 	 * Major/minor page fault accounting is only done on the
 	 * initial attempt. If we go through a retry, it is extremely
 	 * likely that the page will be found in page cache at that point.
 	 */
 	if (flags & FAULT_FLAG_ALLOW_RETRY) {
 		if (fault & VM_FAULT_MAJOR) {
 			tsk->maj_flt++;
 			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
 				      1, regs, addr);
 		} else {
 			tsk->min_flt++;
 			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN,
 				      1, regs, addr);
 		}
 		if (fault & VM_FAULT_RETRY) {
 			/*
 			 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
 			 * of starvation.
 			 */
 			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);
 	/* User mode accesses just cause a SIGSEGV */
 	if (user_mode(regs)) {
 		do_trap(regs, SIGSEGV, code, addr, tsk);
 		return;
 	}

 no_context:
 	/* 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 %s at virtual address " REG_FMT "\n",
 		(addr < PAGE_SIZE) ? "NULL pointer dereference" :
 		"paging request", addr);
 	die(regs, "Oops");
 	do_exit(SIGKILL);

 	/*
 	 * 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).
 	 */
 out_of_memory:
 	up_read(&mm->mmap_sem);
 	if (!user_mode(regs))
 		goto no_context;
 	pagefault_out_of_memory();
 	return;

 do_sigbus:
 	up_read(&mm->mmap_sem);
 	/* Kernel mode? Handle exceptions or die */
 	if (!user_mode(regs))
 		goto no_context;
 	do_trap(regs, SIGBUS, BUS_ADRERR, addr, tsk);
 	return;

 vmalloc_fault:
 	{
 		pgd_t *pgd, *pgd_k;
 		pud_t *pud, *pud_k;
 		p4d_t *p4d, *p4d_k;
 		pmd_t *pmd, *pmd_k;
 		pte_t *pte_k;
 		int index;

 		if (user_mode(regs))
 			goto bad_area;

 		/*
 		 * 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.
 		 *
 		 * Note: Use the old spbtr name instead of using the current
 		 * satp name to support binutils 2.29 which doesn't know about
 		 * the privileged ISA 1.10 yet.
 		 */
 		index = pgd_index(addr);
 		pgd = (pgd_t *)pfn_to_virt(csr_read(sptbr)) + index;
 		pgd_k = init_mm.pgd + index;

 		if (!pgd_present(*pgd_k))
 			goto no_context;
 		set_pgd(pgd, *pgd_k);

 		p4d = p4d_offset(pgd, addr);
 		p4d_k = p4d_offset(pgd_k, addr);
 		if (!p4d_present(*p4d_k))
 			goto no_context;

 		pud = pud_offset(p4d, addr);
 		pud_k = pud_offset(p4d_k, addr);
 		if (!pud_present(*pud_k))
 			goto no_context;

 		/*
 		 * Since the vmalloc area is global, it is unnecessary
 		 * to copy individual PTEs
 		 */
 		pmd = pmd_offset(pud, addr);
 		pmd_k = pmd_offset(pud_k, addr);
 		if (!pmd_present(*pmd_k))
 			goto no_context;
 		set_pmd(pmd, *pmd_k);

 		/*
 		 * 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))
 			goto no_context;

 		/*
 		 * 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.
 		 * Relying on flush_tlb_fix_spurious_fault would
 		 * suffice, but the extra traps reduce
 		 * performance. So, eagerly SFENCE.VMA.
 		 */
 		local_flush_tlb_page(addr);

 		return;
 	}
 }
	/*
	* 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
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, see the file COPYING, or write
	* to the Free Software Foundation, Inc.,
	*/


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

	/*
	* 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_ALLOW_RETRY \| FAULT_FLAG_KILLABLE;
	int code = SEGV_MAPERR;
	vm_fault_t fault;

	cause = regs->scause;
	addr = regs->sbadaddr;

	tsk = current;
	mm = tsk->mm;

	/*
	* 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)))
	goto vmalloc_fault;

	/* Enable interrupts if they were enabled in the parent context. */
	if (likely(regs->sstatus & SR_SPIE))
	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))
	goto no_context;

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

	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);

	retry:
	down_read(&mm->mmap_sem);
	vma = find_vma(mm, addr);
	if (unlikely(!vma))
	goto bad_area;
	if (likely(vma->vm_start <= addr))
	goto good_area;
	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
	goto bad_area;
	if (unlikely(expand_stack(vma, addr)))
	goto bad_area;

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

	switch (cause) {
	case EXC_INST_PAGE_FAULT:
	if (!(vma->vm_flags & VM_EXEC))
	goto bad_area;
	break;
	case EXC_LOAD_PAGE_FAULT:
	if (!(vma->vm_flags & VM_READ))
	goto bad_area;
	break;
	case EXC_STORE_PAGE_FAULT:
	if (!(vma->vm_flags & VM_WRITE))
	goto bad_area;
	flags \|= FAULT_FLAG_WRITE;
	break;
	default:
	panic("%s: unhandled cause %lu", __func__, cause);
	}

	/*
	* 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);

	/*
	* If we need to retry but a fatal signal is pending, handle the
	* signal first. We do not need to release the mmap_sem because it
	* would already be released in __lock_page_or_retry in mm/filemap.c.
	*/
	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(tsk))
	return;

	if (unlikely(fault & VM_FAULT_ERROR)) {
	if (fault & VM_FAULT_OOM)
	goto out_of_memory;
	else if (fault & VM_FAULT_SIGBUS)
	goto do_sigbus;
	BUG();
	}

	/*
	* Major/minor page fault accounting is only done on the
	* initial attempt. If we go through a retry, it is extremely
	* likely that the page will be found in page cache at that point.
	*/
	if (flags & FAULT_FLAG_ALLOW_RETRY) {
	if (fault & VM_FAULT_MAJOR) {
	tsk->maj_flt++;
	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
	1, regs, addr);
	} else {
	tsk->min_flt++;
	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN,
	1, regs, addr);
	}
	if (fault & VM_FAULT_RETRY) {
	/*
	* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
	* of starvation.
	*/
	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);
	/* User mode accesses just cause a SIGSEGV */
	if (user_mode(regs)) {
	do_trap(regs, SIGSEGV, code, addr, tsk);
	return;
	}

	no_context:
	/* 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 %s at virtual address " REG_FMT "\n",
	(addr < PAGE_SIZE) ? "NULL pointer dereference" :
	"paging request", addr);
	die(regs, "Oops");
	do_exit(SIGKILL);

	/*
	* 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).
	*/
	out_of_memory:
	up_read(&mm->mmap_sem);
	if (!user_mode(regs))
	goto no_context;
	pagefault_out_of_memory();
	return;

	do_sigbus:
	up_read(&mm->mmap_sem);
	/* Kernel mode? Handle exceptions or die */
	if (!user_mode(regs))
	goto no_context;
	do_trap(regs, SIGBUS, BUS_ADRERR, addr, tsk);
	return;

	vmalloc_fault:
	{
	pgd_t pgd, pgd_k;
	pud_t pud, pud_k;
	p4d_t p4d, p4d_k;
	pmd_t pmd, pmd_k;
	pte_t *pte_k;
	int index;

	if (user_mode(regs))
	goto bad_area;

	/*
	* 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.
	*
	* Note: Use the old spbtr name instead of using the current
	* satp name to support binutils 2.29 which doesn't know about
	* the privileged ISA 1.10 yet.
	*/
	index = pgd_index(addr);
	pgd = (pgd_t *)pfn_to_virt(csr_read(sptbr)) + index;
	pgd_k = init_mm.pgd + index;

	if (!pgd_present(*pgd_k))
	goto no_context;
	set_pgd(pgd, *pgd_k);

	p4d = p4d_offset(pgd, addr);
	p4d_k = p4d_offset(pgd_k, addr);
	if (!p4d_present(*p4d_k))
	goto no_context;

	pud = pud_offset(p4d, addr);
	pud_k = pud_offset(p4d_k, addr);
	if (!pud_present(*pud_k))
	goto no_context;

	/*
	* Since the vmalloc area is global, it is unnecessary
	* to copy individual PTEs
	*/
	pmd = pmd_offset(pud, addr);
	pmd_k = pmd_offset(pud_k, addr);
	if (!pmd_present(*pmd_k))
	goto no_context;
	set_pmd(pmd, *pmd_k);

	/*
	* 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))
	goto no_context;

	/*
	* 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.
	* Relying on flush_tlb_fix_spurious_fault would
	* suffice, but the extra traps reduce
	* performance. So, eagerly SFENCE.VMA.
	*/
	local_flush_tlb_page(addr);

	return;
	}
	}