void do_page_fault()

in mm/fault.c [260:427]

• 117 lines of code
• 33 McCabe index (conditional complexity)

void do_page_fault(struct pt_regs *regs, unsigned long code,
			      unsigned long address)
{
	struct vm_area_struct *vma, *prev_vma;
	struct task_struct *tsk;
	struct mm_struct *mm;
	unsigned long acc_type;
	vm_fault_t fault = 0;
	unsigned int flags;
	char *msg;

	tsk = current;
	mm = tsk->mm;
	if (!mm) {
		msg = "Page fault: no context";
		goto no_context;
	}

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

	acc_type = parisc_acctyp(code, regs->iir);
	if (acc_type & 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 || address < vma->vm_start)
		goto check_expansion;
/*
 * Ok, we have a good vm_area for this memory access. We still need to
 * check the access permissions.
 */

good_area:

	if ((vma->vm_flags & acc_type) != acc_type)
		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))
		return;

	if (unlikely(fault & VM_FAULT_ERROR)) {
		/*
		 * We hit a shared mapping outside of the file, 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|VM_FAULT_HWPOISON|
				  VM_FAULT_HWPOISON_LARGE))
			goto bad_area;
		BUG();
	}
	if (fault & VM_FAULT_RETRY) {
		/*
		 * No need to mmap_read_unlock(mm) as we would
		 * have already released it in __lock_page_or_retry
		 * in mm/filemap.c.
		 */
		flags |= FAULT_FLAG_TRIED;
		goto retry;
	}
	mmap_read_unlock(mm);
	return;

check_expansion:
	vma = prev_vma;
	if (vma && (expand_stack(vma, address) == 0))
		goto good_area;

/*
 * Something tried to access memory that isn't in our memory map..
 */
bad_area:
	mmap_read_unlock(mm);

	if (user_mode(regs)) {
		int signo, si_code;

		switch (code) {
		case 15:	/* Data TLB miss fault/Data page fault */
			/* send SIGSEGV when outside of vma */
			if (!vma ||
			    address < vma->vm_start || address >= vma->vm_end) {
				signo = SIGSEGV;
				si_code = SEGV_MAPERR;
				break;
			}

			/* send SIGSEGV for wrong permissions */
			if ((vma->vm_flags & acc_type) != acc_type) {
				signo = SIGSEGV;
				si_code = SEGV_ACCERR;
				break;
			}

			/* probably address is outside of mapped file */
			fallthrough;
		case 17:	/* NA data TLB miss / page fault */
		case 18:	/* Unaligned access - PCXS only */
			signo = SIGBUS;
			si_code = (code == 18) ? BUS_ADRALN : BUS_ADRERR;
			break;
		case 16:	/* Non-access instruction TLB miss fault */
		case 26:	/* PCXL: Data memory access rights trap */
		default:
			signo = SIGSEGV;
			si_code = (code == 26) ? SEGV_ACCERR : SEGV_MAPERR;
			break;
		}
#ifdef CONFIG_MEMORY_FAILURE
		if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
			unsigned int lsb = 0;
			printk(KERN_ERR
	"MCE: Killing %s:%d due to hardware memory corruption fault at %08lx\n",
			tsk->comm, tsk->pid, address);
			/*
			 * Either small page or large page may be poisoned.
			 * In other words, VM_FAULT_HWPOISON_LARGE and
			 * VM_FAULT_HWPOISON are mutually exclusive.
			 */
			if (fault & VM_FAULT_HWPOISON_LARGE)
				lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
			else if (fault & VM_FAULT_HWPOISON)
				lsb = PAGE_SHIFT;

			force_sig_mceerr(BUS_MCEERR_AR, (void __user *) address,
					 lsb);
			return;
		}
#endif
		show_signal_msg(regs, code, address, tsk, vma);

		force_sig_fault(signo, si_code, (void __user *) address);
		return;
	}
	msg = "Page fault: bad address";

no_context:

	if (!user_mode(regs) && fixup_exception(regs)) {
		return;
	}

	parisc_terminate(msg, regs, code, address);

out_of_memory:
	mmap_read_unlock(mm);
	if (!user_mode(regs)) {
		msg = "Page fault: out of memory";
		goto no_context;
	}
	pagefault_out_of_memory();
}