arch/alpha/mm/fault.c

Source file repositories/reference/linux-study-clean/arch/alpha/mm/fault.c

File Facts

System
Linux kernel
Corpus path
arch/alpha/mm/fault.c
Extension
.c
Size
6169 bytes
Lines
249
Domain
Architecture Layer
Bucket
arch/alpha
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

* and the problem, and then passes it off to handle_mm_fault().
 *
 * mmcsr:
 *	0 = translation not valid
 *	1 = access violation
 *	2 = fault-on-read
 *	3 = fault-on-execute
 *	4 = fault-on-write
 *
 * cause:
 *	-1 = instruction fetch
 *	0 = load
 *	1 = store
 *
 * Registers $9 through $15 are saved in a block just prior to `regs' and
 * are saved and restored around the call to allow exception code to
 * modify them.
 */

/* Macro for exception fixup code to access integer registers.  */
#define dpf_reg(r)							\
	(((unsigned long *)regs)[(r) <= 8 ? (r) : (r) <= 15 ? (r)-17 :	\
				 (r) <= 18 ? (r)+11 : (r)-10])

asmlinkage void
do_page_fault(unsigned long address, unsigned long mmcsr,
	      long cause, struct pt_regs *regs)
{
	struct vm_area_struct * vma;
	struct mm_struct *mm = current->mm;
	const struct exception_table_entry *fixup;
	int si_code = SEGV_MAPERR;
	vm_fault_t fault;
	unsigned int flags = FAULT_FLAG_DEFAULT;

	/* As of EV6, a load into $31/$f31 is a prefetch, and never faults
	   (or is suppressed by the PALcode).  Support that for older CPUs
	   by ignoring such an instruction.  */
	if (cause == 0) {
		unsigned int insn;
		__get_user(insn, (unsigned int __user *)regs->pc);
		if ((insn >> 21 & 0x1f) == 0x1f &&
		    /* ldq ldl ldt lds ldg ldf ldwu ldbu */
		    (1ul << (insn >> 26) & 0x30f00001400ul)) {
			regs->pc += 4;
			return;
		}
	}

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

#ifdef CONFIG_ALPHA_LARGE_VMALLOC
	if (address >= TASK_SIZE)
		goto vmalloc_fault;
#endif
	if (user_mode(regs))
		flags |= FAULT_FLAG_USER;
	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
retry:
	vma = lock_mm_and_find_vma(mm, address, regs);
	if (!vma)
		goto bad_area_nosemaphore;

	/* Ok, we have a good vm_area for this memory access, so
	   we can handle it.  */
	si_code = SEGV_ACCERR;
	if (cause < 0) {
		if (!(vma->vm_flags & VM_EXEC))
			goto bad_area;
	} else if (!cause) {
		/* Allow reads even for write-only mappings */
		if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
			goto bad_area;
	} else {
		if (!(vma->vm_flags & VM_WRITE))
			goto bad_area;
		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, regs);

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

Annotation

Implementation Notes