1 files changed, 145 insertions, 144 deletions

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index b2eefdefc108..998bd807fc7b 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -7,18 +7,18 @@
 #include <linux/sched.h>		/* test_thread_flag(), ...	*/
 #include <linux/sched/task_stack.h>	/* task_stack_*(), ...		*/
 #include <linux/kdebug.h>		/* oops_begin/end, ...		*/
-#include <linux/extable.h>		/* search_exception_tables	*/
 #include <linux/memblock.h>		/* max_low_pfn			*/
 #include <linux/kfence.h>		/* kfence_handle_page_fault	*/
 #include <linux/kprobes.h>		/* NOKPROBE_SYMBOL, ...		*/
 #include <linux/mmiotrace.h>		/* kmmio_handler, ...		*/
 #include <linux/perf_event.h>		/* perf_sw_event		*/
 #include <linux/hugetlb.h>		/* hstate_index_to_shift	*/
-#include <linux/prefetch.h>		/* prefetchw			*/
 #include <linux/context_tracking.h>	/* exception_enter(), ...	*/
 #include <linux/uaccess.h>		/* faulthandler_disabled()	*/
 #include <linux/efi.h>			/* efi_crash_gracefully_on_page_fault()*/
 #include <linux/mm_types.h>
+#include <linux/mm.h>			/* find_and_lock_vma() */
+#include <linux/vmalloc.h>
 
 #include <asm/cpufeature.h>		/* boot_cpu_has, ...		*/
 #include <asm/traps.h>			/* dotraplinkage, ...		*/
@@ -32,9 +32,12 @@
 #include <asm/pgtable_areas.h>		/* VMALLOC_START, ...		*/
 #include <asm/kvm_para.h>		/* kvm_handle_async_pf		*/
 #include <asm/vdso.h>			/* fixup_vdso_exception()	*/
+#include <asm/irq_stack.h>
+#include <asm/fred.h>
+#include <asm/sev.h>			/* snp_dump_hva_rmpentry()	*/
 
 #define CREATE_TRACE_POINTS
-#include <asm/trace/exceptions.h>
+#include <trace/events/exceptions.h>
 
 /*
  * Returns 0 if mmiotrace is disabled, or if the fault is not
@@ -148,7 +151,7 @@ is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
 		unsigned char opcode;
 
 		if (user_mode(regs)) {
-			if (get_user(opcode, instr))
+			if (get_user(opcode, (unsigned char __user *) instr))
 				break;
 		} else {
 			if (get_kernel_nofault(opcode, instr))
@@ -248,7 +251,7 @@ static noinline int vmalloc_fault(unsigned long address)
 	if (!pmd_k)
 		return -1;
 
-	if (pmd_large(*pmd_k))
+	if (pmd_leaf(*pmd_k))
 		return 0;
 
 	pte_k = pte_offset_kernel(pmd_k, address);
@@ -317,7 +320,7 @@ static void dump_pagetable(unsigned long address)
 	 * And let's rather not kmap-atomic the pte, just in case
 	 * it's allocated already:
 	 */
-	if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
+	if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_leaf(*pmd))
 		goto out;
 
 	pte = pte_offset_kernel(pmd, address);
@@ -366,7 +369,7 @@ static void dump_pagetable(unsigned long address)
 		goto bad;
 
 	pr_cont("P4D %lx ", p4d_val(*p4d));
-	if (!p4d_present(*p4d) || p4d_large(*p4d))
+	if (!p4d_present(*p4d) || p4d_leaf(*p4d))
 		goto out;
 
 	pud = pud_offset(p4d, address);
@@ -374,7 +377,7 @@ static void dump_pagetable(unsigned long address)
 		goto bad;
 
 	pr_cont("PUD %lx ", pud_val(*pud));
-	if (!pud_present(*pud) || pud_large(*pud))
+	if (!pud_present(*pud) || pud_leaf(*pud))
 		goto out;
 
 	pmd = pmd_offset(pud, address);
@@ -382,7 +385,7 @@ static void dump_pagetable(unsigned long address)
 		goto bad;
 
 	pr_cont("PMD %lx ", pmd_val(*pmd));
-	if (!pmd_present(*pmd) || pmd_large(*pmd))
+	if (!pmd_present(*pmd) || pmd_leaf(*pmd))
 		goto out;
 
 	pte = pte_offset_kernel(pmd, address);
@@ -510,18 +513,19 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long ad
 
 	if (error_code & X86_PF_INSTR) {
 		unsigned int level;
+		bool nx, rw;
 		pgd_t *pgd;
 		pte_t *pte;
 
 		pgd = __va(read_cr3_pa());
 		pgd += pgd_index(address);
 
-		pte = lookup_address_in_pgd(pgd, address, &level);
+		pte = lookup_address_in_pgd_attr(pgd, address, &level, &nx, &rw);
 
-		if (pte && pte_present(*pte) && !pte_exec(*pte))
+		if (pte && pte_present(*pte) && (!pte_exec(*pte) || nx))
 			pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n",
 				from_kuid(&init_user_ns, current_uid()));
-		if (pte && pte_present(*pte) && pte_exec(*pte) &&
+		if (pte && pte_present(*pte) && pte_exec(*pte) && !nx &&
 				(pgd_flags(*pgd) & _PAGE_USER) &&
 				(__read_cr4() & X86_CR4_SMEP))
 			pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
@@ -545,6 +549,7 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long ad
 		 !(error_code & X86_PF_PROT) ? "not-present page" :
 		 (error_code & X86_PF_RSVD)  ? "reserved bit violation" :
 		 (error_code & X86_PF_PK)    ? "protection keys violation" :
+		 (error_code & X86_PF_RMP)   ? "RMP violation" :
 					       "permissions violation");
 
 	if (!(error_code & X86_PF_USER) && user_mode(regs)) {
@@ -577,6 +582,9 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long ad
 	}
 
 	dump_pagetable(address);
+
+	if (error_code & X86_PF_RMP)
+		snp_dump_hva_rmpentry(address);
 }
 
 static noinline void
@@ -631,6 +639,9 @@ static noinline void
 page_fault_oops(struct pt_regs *regs, unsigned long error_code,
 		unsigned long address)
 {
+#ifdef CONFIG_VMAP_STACK
+	struct stack_info info;
+#endif
 	unsigned long flags;
 	int sig;
 
@@ -649,9 +660,7 @@ page_fault_oops(struct pt_regs *regs, unsigned long error_code,
 	 * that we're in vmalloc space to avoid this.
 	 */
 	if (is_vmalloc_addr((void *)address) &&
-	    (((unsigned long)current->stack - 1 - address < PAGE_SIZE) ||
-	     address - ((unsigned long)current->stack + THREAD_SIZE) < PAGE_SIZE)) {
-		unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *);
+	    get_stack_guard_info((void *)address, &info)) {
 		/*
 		 * We're likely to be running with very little stack space
 		 * left.  It's plausible that we'd hit this condition but
@@ -662,14 +671,12 @@ page_fault_oops(struct pt_regs *regs, unsigned long error_code,
 		 * and then double-fault, though, because we're likely to
 		 * break the console driver and lose most of the stack dump.
 		 */
-		asm volatile ("movq %[stack], %%rsp\n\t"
-			      "call handle_stack_overflow\n\t"
-			      "1: jmp 1b"
-			      : ASM_CALL_CONSTRAINT
-			      : "D" ("kernel stack overflow (page fault)"),
-				"S" (regs), "d" (address),
-				[stack] "rm" (stack));
-		unreachable();
+		call_on_stack(__this_cpu_ist_top_va(DF) - sizeof(void*),
+			      handle_stack_overflow,
+			      ASM_CALL_ARG3,
+			      , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info));
+
+		BUG();
 	}
 #endif
 
@@ -710,40 +717,14 @@ oops:
 
 static noinline void
 kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
-			 unsigned long address, int signal, int si_code)
+			 unsigned long address, int signal, int si_code,
+			 u32 pkey)
 {
 	WARN_ON_ONCE(user_mode(regs));
 
 	/* Are we prepared to handle this kernel fault? */
-	if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) {
-		/*
-		 * Any interrupt that takes a fault gets the fixup. This makes
-		 * the below recursive fault logic only apply to a faults from
-		 * task context.
-		 */
-		if (in_interrupt())
-			return;
-
-		/*
-		 * Per the above we're !in_interrupt(), aka. task context.
-		 *
-		 * In this case we need to make sure we're not recursively
-		 * faulting through the emulate_vsyscall() logic.
-		 */
-		if (current->thread.sig_on_uaccess_err && signal) {
-			sanitize_error_code(address, &error_code);
-
-			set_signal_archinfo(address, error_code);
-
-			/* XXX: hwpoison faults will set the wrong code. */
-			force_sig_fault(signal, si_code, (void __user *)address);
-		}
-
-		/*
-		 * Barring that, we can do the fixup and be happy.
-		 */
+	if (fixup_exception(regs, X86_TRAP_PF, error_code, address))
 		return;
-	}
 
 	/*
 	 * AMD erratum #91 manifests as a spurious page fault on a PREFETCH
@@ -764,6 +745,8 @@ show_signal_msg(struct pt_regs *regs, unsigned long error_code,
 		unsigned long address, struct task_struct *tsk)
 {
 	const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG;
+	/* This is a racy snapshot, but it's better than nothing. */
+	int cpu = raw_smp_processor_id();
 
 	if (!unhandled_signal(tsk, SIGSEGV))
 		return;
@@ -777,20 +760,19 @@ show_signal_msg(struct pt_regs *regs, unsigned long error_code,
 
 	print_vma_addr(KERN_CONT " in ", regs->ip);
 
+	/*
+	 * Dump the likely CPU where the fatal segfault happened.
+	 * This can help identify faulty hardware.
+	 */
+	printk(KERN_CONT " likely on CPU %d (core %d, socket %d)", cpu,
+	       topology_core_id(cpu), topology_physical_package_id(cpu));
+
+
 	printk(KERN_CONT "\n");
 
 	show_opcodes(regs, loglvl);
 }
 
-/*
- * The (legacy) vsyscall page is the long page in the kernel portion
- * of the address space that has user-accessible permissions.
- */
-static bool is_vsyscall_vaddr(unsigned long vaddr)
-{
-	return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR);
-}
-
 static void
 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 		       unsigned long address, u32 pkey, int si_code)
@@ -798,7 +780,8 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 	struct task_struct *tsk = current;
 
 	if (!user_mode(regs)) {
-		kernelmode_fixup_or_oops(regs, error_code, address, pkey, si_code);
+		kernelmode_fixup_or_oops(regs, error_code, address,
+					 SIGSEGV, si_code, pkey);
 		return;
 	}
 
@@ -851,24 +834,21 @@ bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 
 static void
 __bad_area(struct pt_regs *regs, unsigned long error_code,
-	   unsigned long address, u32 pkey, int si_code)
+	   unsigned long address, struct mm_struct *mm,
+	   struct vm_area_struct *vma, u32 pkey, int si_code)
 {
-	struct mm_struct *mm = current->mm;
 	/*
 	 * 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);
+	if (mm)
+		mmap_read_unlock(mm);
+	else
+		vma_end_read(vma);
 
 	__bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
 }
 
-static noinline void
-bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
-{
-	__bad_area(regs, error_code, address, 0, SEGV_MAPERR);
-}
-
 static inline bool bad_area_access_from_pkeys(unsigned long error_code,
 		struct vm_area_struct *vma)
 {
@@ -888,7 +868,8 @@ static inline bool bad_area_access_from_pkeys(unsigned long error_code,
 
 static noinline void
 bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
-		      unsigned long address, struct vm_area_struct *vma)
+		      unsigned long address, struct mm_struct *mm,
+		      struct vm_area_struct *vma)
 {
 	/*
 	 * This OSPKE check is not strictly necessary at runtime.
@@ -918,9 +899,9 @@ bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
 		 */
 		u32 pkey = vma_pkey(vma);
 
-		__bad_area(regs, error_code, address, pkey, SEGV_PKUERR);
+		__bad_area(regs, error_code, address, mm, vma, pkey, SEGV_PKUERR);
 	} else {
-		__bad_area(regs, error_code, address, 0, SEGV_ACCERR);
+		__bad_area(regs, error_code, address, mm, vma, 0, SEGV_ACCERR);
 	}
 }
 
@@ -930,7 +911,8 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
 {
 	/* Kernel mode? Handle exceptions or die: */
 	if (!user_mode(regs)) {
-		kernelmode_fixup_or_oops(regs, error_code, address, SIGBUS, BUS_ADRERR);
+		kernelmode_fixup_or_oops(regs, error_code, address,
+					 SIGBUS, BUS_ADRERR, ARCH_DEFAULT_PKEY);
 		return;
 	}
 
@@ -1027,21 +1009,21 @@ spurious_kernel_fault(unsigned long error_code, unsigned long address)
 	if (!p4d_present(*p4d))
 		return 0;
 
-	if (p4d_large(*p4d))
+	if (p4d_leaf(*p4d))
 		return spurious_kernel_fault_check(error_code, (pte_t *) p4d);
 
 	pud = pud_offset(p4d, address);
 	if (!pud_present(*pud))
 		return 0;
 
-	if (pud_large(*pud))
+	if (pud_leaf(*pud))
 		return spurious_kernel_fault_check(error_code, (pte_t *) pud);
 
 	pmd = pmd_offset(pud, address);
 	if (!pmd_present(*pmd))
 		return 0;
 
-	if (pmd_large(*pmd))
+	if (pmd_leaf(*pmd))
 		return spurious_kernel_fault_check(error_code, (pte_t *) pmd);
 
 	pte = pte_offset_kernel(pmd, address);
@@ -1100,8 +1082,22 @@ access_error(unsigned long error_code, struct vm_area_struct *vma)
 				       (error_code & X86_PF_INSTR), foreign))
 		return 1;
 
+	/*
+	 * Shadow stack accesses (PF_SHSTK=1) are only permitted to
+	 * shadow stack VMAs. All other accesses result in an error.
+	 */
+	if (error_code & X86_PF_SHSTK) {
+		if (unlikely(!(vma->vm_flags & VM_SHADOW_STACK)))
+			return 1;
+		if (unlikely(!(vma->vm_flags & VM_WRITE)))
+			return 1;
+		return 0;
+	}
+
 	if (error_code & X86_PF_WRITE) {
 		/* write, present and write, not present: */
+		if (unlikely(vma->vm_flags & VM_SHADOW_STACK))
+			return 1;
 		if (unlikely(!(vma->vm_flags & VM_WRITE)))
 			return 1;
 		return 0;
@@ -1276,28 +1272,37 @@ void do_user_addr_fault(struct pt_regs *regs,
 		return;
 	}
 
-	/*
-	 * It's safe to allow irq's after cr2 has been saved and the
-	 * vmalloc fault has been handled.
-	 *
-	 * User-mode registers count as a user access even for any
-	 * potential system fault or CPU buglet:
-	 */
-	if (user_mode(regs)) {
-		local_irq_enable();
-		flags |= FAULT_FLAG_USER;
-	} else {
-		if (regs->flags & X86_EFLAGS_IF)
-			local_irq_enable();
+	/* Legacy check - remove this after verifying that it doesn't trigger */
+	if (WARN_ON_ONCE(!(regs->flags & X86_EFLAGS_IF))) {
+		bad_area_nosemaphore(regs, error_code, address);
+		return;
 	}
 
+	local_irq_enable();
+
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 
+	/*
+	 * Read-only permissions can not be expressed in shadow stack PTEs.
+	 * Treat all shadow stack accesses as WRITE faults. This ensures
+	 * that the MM will prepare everything (e.g., break COW) such that
+	 * maybe_mkwrite() can create a proper shadow stack PTE.
+	 */
+	if (error_code & X86_PF_SHSTK)
+		flags |= FAULT_FLAG_WRITE;
 	if (error_code & X86_PF_WRITE)
 		flags |= FAULT_FLAG_WRITE;
 	if (error_code & X86_PF_INSTR)
 		flags |= FAULT_FLAG_INSTRUCTION;
 
+	/*
+	 * We set FAULT_FLAG_USER based on the register state, not
+	 * based on X86_PF_USER. User space accesses that cause
+	 * system page faults are still user accesses.
+	 */
+	if (user_mode(regs))
+		flags |= FAULT_FLAG_USER;
+
 #ifdef CONFIG_X86_64
 	/*
 	 * Faults in the vsyscall page might need emulation.  The
@@ -1316,51 +1321,44 @@ void do_user_addr_fault(struct pt_regs *regs,
 	}
 #endif
 
-	/*
-	 * Kernel-mode access to the user address space should only occur
-	 * on well-defined single instructions listed in the exception
-	 * tables.  But, an erroneous kernel fault occurring outside one of
-	 * those areas which also holds mmap_lock might deadlock attempting
-	 * to validate the fault against the address space.
-	 *
-	 * Only do the expensive exception table search when we might be at
-	 * risk of a deadlock.  This happens if we
-	 * 1. Failed to acquire mmap_lock, and
-	 * 2. The access did not originate in userspace.
-	 */
-	if (unlikely(!mmap_read_trylock(mm))) {
-		if (!user_mode(regs) && !search_exception_tables(regs->ip)) {
-			/*
-			 * Fault from code in kernel from
-			 * which we do not expect faults.
-			 */
-			bad_area_nosemaphore(regs, error_code, address);
-			return;
-		}
-retry:
-		mmap_read_lock(mm);
-	} else {
-		/*
-		 * The above down_read_trylock() might have succeeded in
-		 * which case we'll have missed the might_sleep() from
-		 * down_read():
-		 */
-		might_sleep();
-	}
+	if (!(flags & FAULT_FLAG_USER))
+		goto lock_mmap;
 
-	vma = find_vma(mm, address);
-	if (unlikely(!vma)) {
-		bad_area(regs, error_code, address);
+	vma = lock_vma_under_rcu(mm, address);
+	if (!vma)
+		goto lock_mmap;
+
+	if (unlikely(access_error(error_code, vma))) {
+		bad_area_access_error(regs, error_code, address, NULL, vma);
+		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
 		return;
 	}
-	if (likely(vma->vm_start <= address))
-		goto good_area;
-	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
-		bad_area(regs, error_code, address);
+	fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
+	if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
+		vma_end_read(vma);
+
+	if (!(fault & VM_FAULT_RETRY)) {
+		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
+		goto done;
+	}
+	count_vm_vma_lock_event(VMA_LOCK_RETRY);
+	if (fault & VM_FAULT_MAJOR)
+		flags |= FAULT_FLAG_TRIED;
+
+	/* Quick path to respond to signals */
+	if (fault_signal_pending(fault, regs)) {
+		if (!user_mode(regs))
+			kernelmode_fixup_or_oops(regs, error_code, address,
+						 SIGBUS, BUS_ADRERR,
+						 ARCH_DEFAULT_PKEY);
 		return;
 	}
-	if (unlikely(expand_stack(vma, address))) {
-		bad_area(regs, error_code, address);
+lock_mmap:
+
+retry:
+	vma = lock_mm_and_find_vma(mm, address, regs);
+	if (unlikely(!vma)) {
+		bad_area_nosemaphore(regs, error_code, address);
 		return;
 	}
 
@@ -1368,9 +1366,8 @@ retry:
 	 * Ok, we have a good vm_area for this memory access, so
 	 * we can handle it..
 	 */
-good_area:
 	if (unlikely(access_error(error_code, vma))) {
-		bad_area_access_error(regs, error_code, address, vma);
+		bad_area_access_error(regs, error_code, address, mm, vma);
 		return;
 	}
 
@@ -1396,27 +1393,33 @@ good_area:
 		 */
 		if (!user_mode(regs))
 			kernelmode_fixup_or_oops(regs, error_code, address,
-						 SIGBUS, BUS_ADRERR);
+						 SIGBUS, BUS_ADRERR,
+						 ARCH_DEFAULT_PKEY);
 		return;
 	}
 
+	/* The fault is fully completed (including releasing mmap lock) */
+	if (fault & VM_FAULT_COMPLETED)
+		return;
+
 	/*
 	 * If we need to retry the mmap_lock has already been released,
 	 * and if there is a fatal signal pending there is no guarantee
 	 * that we made any progress. Handle this case first.
 	 */
-	if (unlikely((fault & VM_FAULT_RETRY) &&
-		     (flags & FAULT_FLAG_ALLOW_RETRY))) {
+	if (unlikely(fault & VM_FAULT_RETRY)) {
 		flags |= FAULT_FLAG_TRIED;
 		goto retry;
 	}
 
 	mmap_read_unlock(mm);
+done:
 	if (likely(!(fault & VM_FAULT_ERROR)))
 		return;
 
 	if (fatal_signal_pending(current) && !user_mode(regs)) {
-		kernelmode_fixup_or_oops(regs, error_code, address, 0, 0);
+		kernelmode_fixup_or_oops(regs, error_code, address,
+					 0, 0, ARCH_DEFAULT_PKEY);
 		return;
 	}
 
@@ -1424,7 +1427,8 @@ good_area:
 		/* Kernel mode? Handle exceptions or die: */
 		if (!user_mode(regs)) {
 			kernelmode_fixup_or_oops(regs, error_code, address,
-						 SIGSEGV, SEGV_MAPERR);
+						 SIGSEGV, SEGV_MAPERR,
+						 ARCH_DEFAULT_PKEY);
 			return;
 		}
 
@@ -1450,9 +1454,6 @@ static __always_inline void
 trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
 			 unsigned long address)
 {
-	if (!trace_pagefault_enabled())
-		return;
-
 	if (user_mode(regs))
 		trace_page_fault_user(address, regs, error_code);
 	else
@@ -1486,10 +1487,10 @@ handle_page_fault(struct pt_regs *regs, unsigned long error_code,
 
 DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
 {
-	unsigned long address = read_cr2();
 	irqentry_state_t state;
+	unsigned long address;
 
-	prefetchw(&current->mm->mmap_lock);
+	address = cpu_feature_enabled(X86_FEATURE_FRED) ? fred_event_data(regs) : read_cr2();
 
 	/*
 	 * KVM uses #PF vector to deliver 'page not present' events to guests
@@ -1517,7 +1518,7 @@ DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
 
 	/*
 	 * Entry handling for valid #PF from kernel mode is slightly
-	 * different: RCU is already watching and rcu_irq_enter() must not
+	 * different: RCU is already watching and ct_irq_enter() must not
 	 * be invoked because a kernel fault on a user space address might
 	 * sleep.
 	 *