v4.19.13 snapshot.
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
new file mode 100644
index 0000000..47bebfe
--- /dev/null
+++ b/arch/x86/mm/fault.c
@@ -0,0 +1,1473 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 1995 Linus Torvalds
+ * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
+ * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
+ */
+#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/bootmem.h> /* max_low_pfn */
+#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/mm_types.h>
+
+#include <asm/cpufeature.h> /* boot_cpu_has, ... */
+#include <asm/traps.h> /* dotraplinkage, ... */
+#include <asm/pgalloc.h> /* pgd_*(), ... */
+#include <asm/fixmap.h> /* VSYSCALL_ADDR */
+#include <asm/vsyscall.h> /* emulate_vsyscall */
+#include <asm/vm86.h> /* struct vm86 */
+#include <asm/mmu_context.h> /* vma_pkey() */
+
+#define CREATE_TRACE_POINTS
+#include <asm/trace/exceptions.h>
+
+/*
+ * Returns 0 if mmiotrace is disabled, or if the fault is not
+ * handled by mmiotrace:
+ */
+static nokprobe_inline int
+kmmio_fault(struct pt_regs *regs, unsigned long addr)
+{
+ if (unlikely(is_kmmio_active()))
+ if (kmmio_handler(regs, addr) == 1)
+ return -1;
+ return 0;
+}
+
+static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
+{
+ int ret = 0;
+
+ /* kprobe_running() needs smp_processor_id() */
+ if (kprobes_built_in() && !user_mode(regs)) {
+ preempt_disable();
+ if (kprobe_running() && kprobe_fault_handler(regs, 14))
+ ret = 1;
+ preempt_enable();
+ }
+
+ return ret;
+}
+
+/*
+ * Prefetch quirks:
+ *
+ * 32-bit mode:
+ *
+ * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
+ * Check that here and ignore it.
+ *
+ * 64-bit mode:
+ *
+ * Sometimes the CPU reports invalid exceptions on prefetch.
+ * Check that here and ignore it.
+ *
+ * Opcode checker based on code by Richard Brunner.
+ */
+static inline int
+check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
+ unsigned char opcode, int *prefetch)
+{
+ unsigned char instr_hi = opcode & 0xf0;
+ unsigned char instr_lo = opcode & 0x0f;
+
+ switch (instr_hi) {
+ case 0x20:
+ case 0x30:
+ /*
+ * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
+ * In X86_64 long mode, the CPU will signal invalid
+ * opcode if some of these prefixes are present so
+ * X86_64 will never get here anyway
+ */
+ return ((instr_lo & 7) == 0x6);
+#ifdef CONFIG_X86_64
+ case 0x40:
+ /*
+ * In AMD64 long mode 0x40..0x4F are valid REX prefixes
+ * Need to figure out under what instruction mode the
+ * instruction was issued. Could check the LDT for lm,
+ * but for now it's good enough to assume that long
+ * mode only uses well known segments or kernel.
+ */
+ return (!user_mode(regs) || user_64bit_mode(regs));
+#endif
+ case 0x60:
+ /* 0x64 thru 0x67 are valid prefixes in all modes. */
+ return (instr_lo & 0xC) == 0x4;
+ case 0xF0:
+ /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
+ return !instr_lo || (instr_lo>>1) == 1;
+ case 0x00:
+ /* Prefetch instruction is 0x0F0D or 0x0F18 */
+ if (probe_kernel_address(instr, opcode))
+ return 0;
+
+ *prefetch = (instr_lo == 0xF) &&
+ (opcode == 0x0D || opcode == 0x18);
+ return 0;
+ default:
+ return 0;
+ }
+}
+
+static int
+is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
+{
+ unsigned char *max_instr;
+ unsigned char *instr;
+ int prefetch = 0;
+
+ /*
+ * If it was a exec (instruction fetch) fault on NX page, then
+ * do not ignore the fault:
+ */
+ if (error_code & X86_PF_INSTR)
+ return 0;
+
+ instr = (void *)convert_ip_to_linear(current, regs);
+ max_instr = instr + 15;
+
+ if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
+ return 0;
+
+ while (instr < max_instr) {
+ unsigned char opcode;
+
+ if (probe_kernel_address(instr, opcode))
+ break;
+
+ instr++;
+
+ if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
+ break;
+ }
+ return prefetch;
+}
+
+/*
+ * A protection key fault means that the PKRU value did not allow
+ * access to some PTE. Userspace can figure out what PKRU was
+ * from the XSAVE state, and this function fills out a field in
+ * siginfo so userspace can discover which protection key was set
+ * on the PTE.
+ *
+ * If we get here, we know that the hardware signaled a X86_PF_PK
+ * fault and that there was a VMA once we got in the fault
+ * handler. It does *not* guarantee that the VMA we find here
+ * was the one that we faulted on.
+ *
+ * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
+ * 2. T1 : set PKRU to deny access to pkey=4, touches page
+ * 3. T1 : faults...
+ * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
+ * 5. T1 : enters fault handler, takes mmap_sem, etc...
+ * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
+ * faulted on a pte with its pkey=4.
+ */
+static void fill_sig_info_pkey(int si_signo, int si_code, siginfo_t *info,
+ u32 *pkey)
+{
+ /* This is effectively an #ifdef */
+ if (!boot_cpu_has(X86_FEATURE_OSPKE))
+ return;
+
+ /* Fault not from Protection Keys: nothing to do */
+ if ((si_code != SEGV_PKUERR) || (si_signo != SIGSEGV))
+ return;
+ /*
+ * force_sig_info_fault() is called from a number of
+ * contexts, some of which have a VMA and some of which
+ * do not. The X86_PF_PK handing happens after we have a
+ * valid VMA, so we should never reach this without a
+ * valid VMA.
+ */
+ if (!pkey) {
+ WARN_ONCE(1, "PKU fault with no VMA passed in");
+ info->si_pkey = 0;
+ return;
+ }
+ /*
+ * si_pkey should be thought of as a strong hint, but not
+ * absolutely guranteed to be 100% accurate because of
+ * the race explained above.
+ */
+ info->si_pkey = *pkey;
+}
+
+static void
+force_sig_info_fault(int si_signo, int si_code, unsigned long address,
+ struct task_struct *tsk, u32 *pkey, int fault)
+{
+ unsigned lsb = 0;
+ siginfo_t info;
+
+ clear_siginfo(&info);
+ info.si_signo = si_signo;
+ info.si_errno = 0;
+ info.si_code = si_code;
+ info.si_addr = (void __user *)address;
+ if (fault & VM_FAULT_HWPOISON_LARGE)
+ lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
+ if (fault & VM_FAULT_HWPOISON)
+ lsb = PAGE_SHIFT;
+ info.si_addr_lsb = lsb;
+
+ fill_sig_info_pkey(si_signo, si_code, &info, pkey);
+
+ force_sig_info(si_signo, &info, tsk);
+}
+
+DEFINE_SPINLOCK(pgd_lock);
+LIST_HEAD(pgd_list);
+
+#ifdef CONFIG_X86_32
+static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
+{
+ unsigned index = pgd_index(address);
+ pgd_t *pgd_k;
+ p4d_t *p4d, *p4d_k;
+ pud_t *pud, *pud_k;
+ pmd_t *pmd, *pmd_k;
+
+ pgd += index;
+ pgd_k = init_mm.pgd + index;
+
+ if (!pgd_present(*pgd_k))
+ return NULL;
+
+ /*
+ * set_pgd(pgd, *pgd_k); here would be useless on PAE
+ * and redundant with the set_pmd() on non-PAE. As would
+ * set_p4d/set_pud.
+ */
+ p4d = p4d_offset(pgd, address);
+ p4d_k = p4d_offset(pgd_k, address);
+ if (!p4d_present(*p4d_k))
+ return NULL;
+
+ pud = pud_offset(p4d, address);
+ pud_k = pud_offset(p4d_k, address);
+ if (!pud_present(*pud_k))
+ return NULL;
+
+ pmd = pmd_offset(pud, address);
+ pmd_k = pmd_offset(pud_k, address);
+ if (!pmd_present(*pmd_k))
+ return NULL;
+
+ if (!pmd_present(*pmd))
+ set_pmd(pmd, *pmd_k);
+ else
+ BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
+
+ return pmd_k;
+}
+
+void vmalloc_sync_all(void)
+{
+ unsigned long address;
+
+ if (SHARED_KERNEL_PMD)
+ return;
+
+ for (address = VMALLOC_START & PMD_MASK;
+ address >= TASK_SIZE_MAX && address < FIXADDR_TOP;
+ address += PMD_SIZE) {
+ struct page *page;
+
+ spin_lock(&pgd_lock);
+ list_for_each_entry(page, &pgd_list, lru) {
+ spinlock_t *pgt_lock;
+ pmd_t *ret;
+
+ /* the pgt_lock only for Xen */
+ pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
+
+ spin_lock(pgt_lock);
+ ret = vmalloc_sync_one(page_address(page), address);
+ spin_unlock(pgt_lock);
+
+ if (!ret)
+ break;
+ }
+ spin_unlock(&pgd_lock);
+ }
+}
+
+/*
+ * 32-bit:
+ *
+ * Handle a fault on the vmalloc or module mapping area
+ */
+static noinline int vmalloc_fault(unsigned long address)
+{
+ unsigned long pgd_paddr;
+ pmd_t *pmd_k;
+ pte_t *pte_k;
+
+ /* Make sure we are in vmalloc area: */
+ if (!(address >= VMALLOC_START && address < VMALLOC_END))
+ return -1;
+
+ /*
+ * Synchronize this task's top level page-table
+ * with the 'reference' page table.
+ *
+ * Do _not_ use "current" here. We might be inside
+ * an interrupt in the middle of a task switch..
+ */
+ pgd_paddr = read_cr3_pa();
+ pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
+ if (!pmd_k)
+ return -1;
+
+ if (pmd_large(*pmd_k))
+ return 0;
+
+ pte_k = pte_offset_kernel(pmd_k, address);
+ if (!pte_present(*pte_k))
+ return -1;
+
+ return 0;
+}
+NOKPROBE_SYMBOL(vmalloc_fault);
+
+/*
+ * Did it hit the DOS screen memory VA from vm86 mode?
+ */
+static inline void
+check_v8086_mode(struct pt_regs *regs, unsigned long address,
+ struct task_struct *tsk)
+{
+#ifdef CONFIG_VM86
+ unsigned long bit;
+
+ if (!v8086_mode(regs) || !tsk->thread.vm86)
+ return;
+
+ bit = (address - 0xA0000) >> PAGE_SHIFT;
+ if (bit < 32)
+ tsk->thread.vm86->screen_bitmap |= 1 << bit;
+#endif
+}
+
+static bool low_pfn(unsigned long pfn)
+{
+ return pfn < max_low_pfn;
+}
+
+static void dump_pagetable(unsigned long address)
+{
+ pgd_t *base = __va(read_cr3_pa());
+ pgd_t *pgd = &base[pgd_index(address)];
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *pte;
+
+#ifdef CONFIG_X86_PAE
+ pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
+ if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
+ goto out;
+#define pr_pde pr_cont
+#else
+#define pr_pde pr_info
+#endif
+ p4d = p4d_offset(pgd, address);
+ pud = pud_offset(p4d, address);
+ pmd = pmd_offset(pud, address);
+ pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
+#undef pr_pde
+
+ /*
+ * We must not directly access the pte in the highpte
+ * case if the page table is located in highmem.
+ * 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))
+ goto out;
+
+ pte = pte_offset_kernel(pmd, address);
+ pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
+out:
+ pr_cont("\n");
+}
+
+#else /* CONFIG_X86_64: */
+
+void vmalloc_sync_all(void)
+{
+ sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
+}
+
+/*
+ * 64-bit:
+ *
+ * Handle a fault on the vmalloc area
+ */
+static noinline int vmalloc_fault(unsigned long address)
+{
+ pgd_t *pgd, *pgd_k;
+ p4d_t *p4d, *p4d_k;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *pte;
+
+ /* Make sure we are in vmalloc area: */
+ if (!(address >= VMALLOC_START && address < VMALLOC_END))
+ return -1;
+
+ WARN_ON_ONCE(in_nmi());
+
+ /*
+ * Copy kernel mappings over when needed. This can also
+ * happen within a race in page table update. In the later
+ * case just flush:
+ */
+ pgd = (pgd_t *)__va(read_cr3_pa()) + pgd_index(address);
+ pgd_k = pgd_offset_k(address);
+ if (pgd_none(*pgd_k))
+ return -1;
+
+ if (pgtable_l5_enabled()) {
+ if (pgd_none(*pgd)) {
+ set_pgd(pgd, *pgd_k);
+ arch_flush_lazy_mmu_mode();
+ } else {
+ BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_k));
+ }
+ }
+
+ /* With 4-level paging, copying happens on the p4d level. */
+ p4d = p4d_offset(pgd, address);
+ p4d_k = p4d_offset(pgd_k, address);
+ if (p4d_none(*p4d_k))
+ return -1;
+
+ if (p4d_none(*p4d) && !pgtable_l5_enabled()) {
+ set_p4d(p4d, *p4d_k);
+ arch_flush_lazy_mmu_mode();
+ } else {
+ BUG_ON(p4d_pfn(*p4d) != p4d_pfn(*p4d_k));
+ }
+
+ BUILD_BUG_ON(CONFIG_PGTABLE_LEVELS < 4);
+
+ pud = pud_offset(p4d, address);
+ if (pud_none(*pud))
+ return -1;
+
+ if (pud_large(*pud))
+ return 0;
+
+ pmd = pmd_offset(pud, address);
+ if (pmd_none(*pmd))
+ return -1;
+
+ if (pmd_large(*pmd))
+ return 0;
+
+ pte = pte_offset_kernel(pmd, address);
+ if (!pte_present(*pte))
+ return -1;
+
+ return 0;
+}
+NOKPROBE_SYMBOL(vmalloc_fault);
+
+#ifdef CONFIG_CPU_SUP_AMD
+static const char errata93_warning[] =
+KERN_ERR
+"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
+"******* Working around it, but it may cause SEGVs or burn power.\n"
+"******* Please consider a BIOS update.\n"
+"******* Disabling USB legacy in the BIOS may also help.\n";
+#endif
+
+/*
+ * No vm86 mode in 64-bit mode:
+ */
+static inline void
+check_v8086_mode(struct pt_regs *regs, unsigned long address,
+ struct task_struct *tsk)
+{
+}
+
+static int bad_address(void *p)
+{
+ unsigned long dummy;
+
+ return probe_kernel_address((unsigned long *)p, dummy);
+}
+
+static void dump_pagetable(unsigned long address)
+{
+ pgd_t *base = __va(read_cr3_pa());
+ pgd_t *pgd = base + pgd_index(address);
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *pte;
+
+ if (bad_address(pgd))
+ goto bad;
+
+ pr_info("PGD %lx ", pgd_val(*pgd));
+
+ if (!pgd_present(*pgd))
+ goto out;
+
+ p4d = p4d_offset(pgd, address);
+ if (bad_address(p4d))
+ goto bad;
+
+ pr_cont("P4D %lx ", p4d_val(*p4d));
+ if (!p4d_present(*p4d) || p4d_large(*p4d))
+ goto out;
+
+ pud = pud_offset(p4d, address);
+ if (bad_address(pud))
+ goto bad;
+
+ pr_cont("PUD %lx ", pud_val(*pud));
+ if (!pud_present(*pud) || pud_large(*pud))
+ goto out;
+
+ pmd = pmd_offset(pud, address);
+ if (bad_address(pmd))
+ goto bad;
+
+ pr_cont("PMD %lx ", pmd_val(*pmd));
+ if (!pmd_present(*pmd) || pmd_large(*pmd))
+ goto out;
+
+ pte = pte_offset_kernel(pmd, address);
+ if (bad_address(pte))
+ goto bad;
+
+ pr_cont("PTE %lx", pte_val(*pte));
+out:
+ pr_cont("\n");
+ return;
+bad:
+ pr_info("BAD\n");
+}
+
+#endif /* CONFIG_X86_64 */
+
+/*
+ * Workaround for K8 erratum #93 & buggy BIOS.
+ *
+ * BIOS SMM functions are required to use a specific workaround
+ * to avoid corruption of the 64bit RIP register on C stepping K8.
+ *
+ * A lot of BIOS that didn't get tested properly miss this.
+ *
+ * The OS sees this as a page fault with the upper 32bits of RIP cleared.
+ * Try to work around it here.
+ *
+ * Note we only handle faults in kernel here.
+ * Does nothing on 32-bit.
+ */
+static int is_errata93(struct pt_regs *regs, unsigned long address)
+{
+#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
+ if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
+ || boot_cpu_data.x86 != 0xf)
+ return 0;
+
+ if (address != regs->ip)
+ return 0;
+
+ if ((address >> 32) != 0)
+ return 0;
+
+ address |= 0xffffffffUL << 32;
+ if ((address >= (u64)_stext && address <= (u64)_etext) ||
+ (address >= MODULES_VADDR && address <= MODULES_END)) {
+ printk_once(errata93_warning);
+ regs->ip = address;
+ return 1;
+ }
+#endif
+ return 0;
+}
+
+/*
+ * Work around K8 erratum #100 K8 in compat mode occasionally jumps
+ * to illegal addresses >4GB.
+ *
+ * We catch this in the page fault handler because these addresses
+ * are not reachable. Just detect this case and return. Any code
+ * segment in LDT is compatibility mode.
+ */
+static int is_errata100(struct pt_regs *regs, unsigned long address)
+{
+#ifdef CONFIG_X86_64
+ if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
+ return 1;
+#endif
+ return 0;
+}
+
+static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
+{
+#ifdef CONFIG_X86_F00F_BUG
+ unsigned long nr;
+
+ /*
+ * Pentium F0 0F C7 C8 bug workaround:
+ */
+ if (boot_cpu_has_bug(X86_BUG_F00F)) {
+ nr = (address - idt_descr.address) >> 3;
+
+ if (nr == 6) {
+ do_invalid_op(regs, 0);
+ return 1;
+ }
+ }
+#endif
+ return 0;
+}
+
+static void
+show_fault_oops(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address)
+{
+ if (!oops_may_print())
+ return;
+
+ if (error_code & X86_PF_INSTR) {
+ unsigned int level;
+ pgd_t *pgd;
+ pte_t *pte;
+
+ pgd = __va(read_cr3_pa());
+ pgd += pgd_index(address);
+
+ pte = lookup_address_in_pgd(pgd, address, &level);
+
+ if (pte && pte_present(*pte) && !pte_exec(*pte))
+ 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) &&
+ (pgd_flags(*pgd) & _PAGE_USER) &&
+ (__read_cr4() & X86_CR4_SMEP))
+ pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
+ from_kuid(&init_user_ns, current_uid()));
+ }
+
+ pr_alert("BUG: unable to handle kernel %s at %px\n",
+ address < PAGE_SIZE ? "NULL pointer dereference" : "paging request",
+ (void *)address);
+
+ dump_pagetable(address);
+}
+
+static noinline void
+pgtable_bad(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address)
+{
+ struct task_struct *tsk;
+ unsigned long flags;
+ int sig;
+
+ flags = oops_begin();
+ tsk = current;
+ sig = SIGKILL;
+
+ printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
+ tsk->comm, address);
+ dump_pagetable(address);
+
+ tsk->thread.cr2 = address;
+ tsk->thread.trap_nr = X86_TRAP_PF;
+ tsk->thread.error_code = error_code;
+
+ if (__die("Bad pagetable", regs, error_code))
+ sig = 0;
+
+ oops_end(flags, regs, sig);
+}
+
+static noinline void
+no_context(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address, int signal, int si_code)
+{
+ struct task_struct *tsk = current;
+ unsigned long flags;
+ int sig;
+
+ /* Are we prepared to handle this kernel fault? */
+ if (fixup_exception(regs, X86_TRAP_PF)) {
+ /*
+ * 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) {
+ tsk->thread.trap_nr = X86_TRAP_PF;
+ tsk->thread.error_code = error_code | X86_PF_USER;
+ tsk->thread.cr2 = address;
+
+ /* XXX: hwpoison faults will set the wrong code. */
+ force_sig_info_fault(signal, si_code, address,
+ tsk, NULL, 0);
+ }
+
+ /*
+ * Barring that, we can do the fixup and be happy.
+ */
+ return;
+ }
+
+#ifdef CONFIG_VMAP_STACK
+ /*
+ * Stack overflow? During boot, we can fault near the initial
+ * stack in the direct map, but that's not an overflow -- check
+ * that we're in vmalloc space to avoid this.
+ */
+ if (is_vmalloc_addr((void *)address) &&
+ (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) ||
+ address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) {
+ unsigned long stack = this_cpu_read(orig_ist.ist[DOUBLEFAULT_STACK]) - sizeof(void *);
+ /*
+ * We're likely to be running with very little stack space
+ * left. It's plausible that we'd hit this condition but
+ * double-fault even before we get this far, in which case
+ * we're fine: the double-fault handler will deal with it.
+ *
+ * We don't want to make it all the way into the oops 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();
+ }
+#endif
+
+ /*
+ * 32-bit:
+ *
+ * Valid to do another page fault here, because if this fault
+ * had been triggered by is_prefetch fixup_exception would have
+ * handled it.
+ *
+ * 64-bit:
+ *
+ * Hall of shame of CPU/BIOS bugs.
+ */
+ if (is_prefetch(regs, error_code, address))
+ return;
+
+ if (is_errata93(regs, address))
+ return;
+
+ /*
+ * Oops. The kernel tried to access some bad page. We'll have to
+ * terminate things with extreme prejudice:
+ */
+ flags = oops_begin();
+
+ show_fault_oops(regs, error_code, address);
+
+ if (task_stack_end_corrupted(tsk))
+ printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
+
+ tsk->thread.cr2 = address;
+ tsk->thread.trap_nr = X86_TRAP_PF;
+ tsk->thread.error_code = error_code;
+
+ sig = SIGKILL;
+ if (__die("Oops", regs, error_code))
+ sig = 0;
+
+ /* Executive summary in case the body of the oops scrolled away */
+ printk(KERN_DEFAULT "CR2: %016lx\n", address);
+
+ oops_end(flags, regs, sig);
+}
+
+/*
+ * Print out info about fatal segfaults, if the show_unhandled_signals
+ * sysctl is set:
+ */
+static inline void
+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;
+
+ if (!unhandled_signal(tsk, SIGSEGV))
+ return;
+
+ if (!printk_ratelimit())
+ return;
+
+ printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",
+ loglvl, tsk->comm, task_pid_nr(tsk), address,
+ (void *)regs->ip, (void *)regs->sp, error_code);
+
+ print_vma_addr(KERN_CONT " in ", regs->ip);
+
+ printk(KERN_CONT "\n");
+
+ show_opcodes(regs, loglvl);
+}
+
+static void
+__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address, u32 *pkey, int si_code)
+{
+ struct task_struct *tsk = current;
+
+ /* User mode accesses just cause a SIGSEGV */
+ if (error_code & X86_PF_USER) {
+ /*
+ * It's possible to have interrupts off here:
+ */
+ local_irq_enable();
+
+ /*
+ * Valid to do another page fault here because this one came
+ * from user space:
+ */
+ if (is_prefetch(regs, error_code, address))
+ return;
+
+ if (is_errata100(regs, address))
+ return;
+
+#ifdef CONFIG_X86_64
+ /*
+ * Instruction fetch faults in the vsyscall page might need
+ * emulation.
+ */
+ if (unlikely((error_code & X86_PF_INSTR) &&
+ ((address & ~0xfff) == VSYSCALL_ADDR))) {
+ if (emulate_vsyscall(regs, address))
+ return;
+ }
+#endif
+
+ /*
+ * To avoid leaking information about the kernel page table
+ * layout, pretend that user-mode accesses to kernel addresses
+ * are always protection faults.
+ */
+ if (address >= TASK_SIZE_MAX)
+ error_code |= X86_PF_PROT;
+
+ if (likely(show_unhandled_signals))
+ show_signal_msg(regs, error_code, address, tsk);
+
+ tsk->thread.cr2 = address;
+ tsk->thread.error_code = error_code;
+ tsk->thread.trap_nr = X86_TRAP_PF;
+
+ force_sig_info_fault(SIGSEGV, si_code, address, tsk, pkey, 0);
+
+ return;
+ }
+
+ if (is_f00f_bug(regs, address))
+ return;
+
+ no_context(regs, error_code, address, SIGSEGV, si_code);
+}
+
+static noinline void
+bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address, u32 *pkey)
+{
+ __bad_area_nosemaphore(regs, error_code, address, pkey, SEGV_MAPERR);
+}
+
+static void
+__bad_area(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address, struct vm_area_struct *vma, int si_code)
+{
+ struct mm_struct *mm = current->mm;
+ u32 pkey;
+
+ if (vma)
+ pkey = vma_pkey(vma);
+
+ /*
+ * Something tried to access memory that isn't in our memory map..
+ * Fix it, but check if it's kernel or user first..
+ */
+ up_read(&mm->mmap_sem);
+
+ __bad_area_nosemaphore(regs, error_code, address,
+ (vma) ? &pkey : NULL, si_code);
+}
+
+static noinline void
+bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
+{
+ __bad_area(regs, error_code, address, NULL, SEGV_MAPERR);
+}
+
+static inline bool bad_area_access_from_pkeys(unsigned long error_code,
+ struct vm_area_struct *vma)
+{
+ /* This code is always called on the current mm */
+ bool foreign = false;
+
+ if (!boot_cpu_has(X86_FEATURE_OSPKE))
+ return false;
+ if (error_code & X86_PF_PK)
+ return true;
+ /* this checks permission keys on the VMA: */
+ if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
+ (error_code & X86_PF_INSTR), foreign))
+ return true;
+ return false;
+}
+
+static noinline void
+bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address, struct vm_area_struct *vma)
+{
+ /*
+ * This OSPKE check is not strictly necessary at runtime.
+ * But, doing it this way allows compiler optimizations
+ * if pkeys are compiled out.
+ */
+ if (bad_area_access_from_pkeys(error_code, vma))
+ __bad_area(regs, error_code, address, vma, SEGV_PKUERR);
+ else
+ __bad_area(regs, error_code, address, vma, SEGV_ACCERR);
+}
+
+static void
+do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
+ u32 *pkey, unsigned int fault)
+{
+ struct task_struct *tsk = current;
+ int code = BUS_ADRERR;
+
+ /* Kernel mode? Handle exceptions or die: */
+ if (!(error_code & X86_PF_USER)) {
+ no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
+ return;
+ }
+
+ /* User-space => ok to do another page fault: */
+ if (is_prefetch(regs, error_code, address))
+ return;
+
+ tsk->thread.cr2 = address;
+ tsk->thread.error_code = error_code;
+ tsk->thread.trap_nr = X86_TRAP_PF;
+
+#ifdef CONFIG_MEMORY_FAILURE
+ if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
+ printk(KERN_ERR
+ "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
+ tsk->comm, tsk->pid, address);
+ code = BUS_MCEERR_AR;
+ }
+#endif
+ force_sig_info_fault(SIGBUS, code, address, tsk, pkey, fault);
+}
+
+static noinline void
+mm_fault_error(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address, u32 *pkey, vm_fault_t fault)
+{
+ if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) {
+ no_context(regs, error_code, address, 0, 0);
+ return;
+ }
+
+ if (fault & VM_FAULT_OOM) {
+ /* Kernel mode? Handle exceptions or die: */
+ if (!(error_code & X86_PF_USER)) {
+ no_context(regs, error_code, address,
+ SIGSEGV, SEGV_MAPERR);
+ return;
+ }
+
+ /*
+ * 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):
+ */
+ pagefault_out_of_memory();
+ } else {
+ if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
+ VM_FAULT_HWPOISON_LARGE))
+ do_sigbus(regs, error_code, address, pkey, fault);
+ else if (fault & VM_FAULT_SIGSEGV)
+ bad_area_nosemaphore(regs, error_code, address, pkey);
+ else
+ BUG();
+ }
+}
+
+static int spurious_fault_check(unsigned long error_code, pte_t *pte)
+{
+ if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
+ return 0;
+
+ if ((error_code & X86_PF_INSTR) && !pte_exec(*pte))
+ return 0;
+ /*
+ * Note: We do not do lazy flushing on protection key
+ * changes, so no spurious fault will ever set X86_PF_PK.
+ */
+ if ((error_code & X86_PF_PK))
+ return 1;
+
+ return 1;
+}
+
+/*
+ * Handle a spurious fault caused by a stale TLB entry.
+ *
+ * This allows us to lazily refresh the TLB when increasing the
+ * permissions of a kernel page (RO -> RW or NX -> X). Doing it
+ * eagerly is very expensive since that implies doing a full
+ * cross-processor TLB flush, even if no stale TLB entries exist
+ * on other processors.
+ *
+ * Spurious faults may only occur if the TLB contains an entry with
+ * fewer permission than the page table entry. Non-present (P = 0)
+ * and reserved bit (R = 1) faults are never spurious.
+ *
+ * There are no security implications to leaving a stale TLB when
+ * increasing the permissions on a page.
+ *
+ * Returns non-zero if a spurious fault was handled, zero otherwise.
+ *
+ * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
+ * (Optional Invalidation).
+ */
+static noinline int
+spurious_fault(unsigned long error_code, unsigned long address)
+{
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *pte;
+ int ret;
+
+ /*
+ * Only writes to RO or instruction fetches from NX may cause
+ * spurious faults.
+ *
+ * These could be from user or supervisor accesses but the TLB
+ * is only lazily flushed after a kernel mapping protection
+ * change, so user accesses are not expected to cause spurious
+ * faults.
+ */
+ if (error_code != (X86_PF_WRITE | X86_PF_PROT) &&
+ error_code != (X86_PF_INSTR | X86_PF_PROT))
+ return 0;
+
+ pgd = init_mm.pgd + pgd_index(address);
+ if (!pgd_present(*pgd))
+ return 0;
+
+ p4d = p4d_offset(pgd, address);
+ if (!p4d_present(*p4d))
+ return 0;
+
+ if (p4d_large(*p4d))
+ return spurious_fault_check(error_code, (pte_t *) p4d);
+
+ pud = pud_offset(p4d, address);
+ if (!pud_present(*pud))
+ return 0;
+
+ if (pud_large(*pud))
+ return spurious_fault_check(error_code, (pte_t *) pud);
+
+ pmd = pmd_offset(pud, address);
+ if (!pmd_present(*pmd))
+ return 0;
+
+ if (pmd_large(*pmd))
+ return spurious_fault_check(error_code, (pte_t *) pmd);
+
+ pte = pte_offset_kernel(pmd, address);
+ if (!pte_present(*pte))
+ return 0;
+
+ ret = spurious_fault_check(error_code, pte);
+ if (!ret)
+ return 0;
+
+ /*
+ * Make sure we have permissions in PMD.
+ * If not, then there's a bug in the page tables:
+ */
+ ret = spurious_fault_check(error_code, (pte_t *) pmd);
+ WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
+
+ return ret;
+}
+NOKPROBE_SYMBOL(spurious_fault);
+
+int show_unhandled_signals = 1;
+
+static inline int
+access_error(unsigned long error_code, struct vm_area_struct *vma)
+{
+ /* This is only called for the current mm, so: */
+ bool foreign = false;
+
+ /*
+ * Read or write was blocked by protection keys. This is
+ * always an unconditional error and can never result in
+ * a follow-up action to resolve the fault, like a COW.
+ */
+ if (error_code & X86_PF_PK)
+ return 1;
+
+ /*
+ * Make sure to check the VMA so that we do not perform
+ * faults just to hit a X86_PF_PK as soon as we fill in a
+ * page.
+ */
+ if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
+ (error_code & X86_PF_INSTR), foreign))
+ return 1;
+
+ if (error_code & X86_PF_WRITE) {
+ /* write, present and write, not present: */
+ if (unlikely(!(vma->vm_flags & VM_WRITE)))
+ return 1;
+ return 0;
+ }
+
+ /* read, present: */
+ if (unlikely(error_code & X86_PF_PROT))
+ return 1;
+
+ /* read, not present: */
+ if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
+ return 1;
+
+ return 0;
+}
+
+static int fault_in_kernel_space(unsigned long address)
+{
+ return address >= TASK_SIZE_MAX;
+}
+
+static inline bool smap_violation(int error_code, struct pt_regs *regs)
+{
+ if (!IS_ENABLED(CONFIG_X86_SMAP))
+ return false;
+
+ if (!static_cpu_has(X86_FEATURE_SMAP))
+ return false;
+
+ if (error_code & X86_PF_USER)
+ return false;
+
+ if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC))
+ return false;
+
+ return true;
+}
+
+/*
+ * This routine handles page faults. It determines the address,
+ * and the problem, and then passes it off to one of the appropriate
+ * routines.
+ */
+static noinline void
+__do_page_fault(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address)
+{
+ struct vm_area_struct *vma;
+ struct task_struct *tsk;
+ struct mm_struct *mm;
+ vm_fault_t fault, major = 0;
+ unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
+ u32 pkey;
+
+ tsk = current;
+ mm = tsk->mm;
+
+ prefetchw(&mm->mmap_sem);
+
+ if (unlikely(kmmio_fault(regs, address)))
+ return;
+
+ /*
+ * We 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.
+ *
+ * This verifies that the fault happens in kernel space
+ * (error_code & 4) == 0, and that the fault was not a
+ * protection error (error_code & 9) == 0.
+ */
+ if (unlikely(fault_in_kernel_space(address))) {
+ if (!(error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) {
+ if (vmalloc_fault(address) >= 0)
+ return;
+ }
+
+ /* Can handle a stale RO->RW TLB: */
+ if (spurious_fault(error_code, address))
+ return;
+
+ /* kprobes don't want to hook the spurious faults: */
+ if (kprobes_fault(regs))
+ return;
+ /*
+ * Don't take the mm semaphore here. If we fixup a prefetch
+ * fault we could otherwise deadlock:
+ */
+ bad_area_nosemaphore(regs, error_code, address, NULL);
+
+ return;
+ }
+
+ /* kprobes don't want to hook the spurious faults: */
+ if (unlikely(kprobes_fault(regs)))
+ return;
+
+ if (unlikely(error_code & X86_PF_RSVD))
+ pgtable_bad(regs, error_code, address);
+
+ if (unlikely(smap_violation(error_code, regs))) {
+ bad_area_nosemaphore(regs, error_code, address, NULL);
+ return;
+ }
+
+ /*
+ * If we're in an interrupt, have no user context or are running
+ * in a region with pagefaults disabled then we must not take the fault
+ */
+ if (unlikely(faulthandler_disabled() || !mm)) {
+ bad_area_nosemaphore(regs, error_code, address, NULL);
+ 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();
+ error_code |= X86_PF_USER;
+ flags |= FAULT_FLAG_USER;
+ } else {
+ if (regs->flags & X86_EFLAGS_IF)
+ local_irq_enable();
+ }
+
+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
+
+ if (error_code & X86_PF_WRITE)
+ flags |= FAULT_FLAG_WRITE;
+ if (error_code & X86_PF_INSTR)
+ flags |= FAULT_FLAG_INSTRUCTION;
+
+ /*
+ * When running in the kernel we expect faults to occur only to
+ * addresses in user space. All other faults represent errors in
+ * the kernel and should generate an OOPS. Unfortunately, in the
+ * case of an erroneous fault occurring in a code path which already
+ * holds mmap_sem we will deadlock attempting to validate the fault
+ * against the address space. Luckily the kernel only validly
+ * references user space from well defined areas of code, which are
+ * listed in the exceptions table.
+ *
+ * As the vast majority of faults will be valid we will only perform
+ * the source reference check when there is a possibility of a
+ * deadlock. Attempt to lock the address space, if we cannot we then
+ * validate the source. If this is invalid we can skip the address
+ * space check, thus avoiding the deadlock:
+ */
+ if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
+ if (!(error_code & X86_PF_USER) &&
+ !search_exception_tables(regs->ip)) {
+ bad_area_nosemaphore(regs, error_code, address, NULL);
+ return;
+ }
+retry:
+ down_read(&mm->mmap_sem);
+ } else {
+ /*
+ * The above down_read_trylock() might have succeeded in
+ * which case we'll have missed the might_sleep() from
+ * down_read():
+ */
+ might_sleep();
+ }
+
+ vma = find_vma(mm, address);
+ if (unlikely(!vma)) {
+ bad_area(regs, error_code, address);
+ return;
+ }
+ if (likely(vma->vm_start <= address))
+ goto good_area;
+ if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
+ bad_area(regs, error_code, address);
+ return;
+ }
+ if (error_code & X86_PF_USER) {
+ /*
+ * Accessing the stack below %sp is always a bug.
+ * The large cushion allows instructions like enter
+ * and pusha to work. ("enter $65535, $31" pushes
+ * 32 pointers and then decrements %sp by 65535.)
+ */
+ if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
+ bad_area(regs, error_code, address);
+ return;
+ }
+ }
+ if (unlikely(expand_stack(vma, address))) {
+ bad_area(regs, error_code, address);
+ return;
+ }
+
+ /*
+ * 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);
+ return;
+ }
+
+ /*
+ * If for any reason at all we couldn't handle the fault,
+ * make sure we exit gracefully rather than endlessly redo
+ * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
+ * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
+ *
+ * Note that handle_userfault() may also release and reacquire mmap_sem
+ * (and not return with VM_FAULT_RETRY), when returning to userland to
+ * repeat the page fault later with a VM_FAULT_NOPAGE retval
+ * (potentially after handling any pending signal during the return to
+ * userland). The return to userland is identified whenever
+ * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
+ * Thus we have to be careful about not touching vma after handling the
+ * fault, so we read the pkey beforehand.
+ */
+ pkey = vma_pkey(vma);
+ fault = handle_mm_fault(vma, address, flags);
+ major |= fault & VM_FAULT_MAJOR;
+
+ /*
+ * If we need to retry the mmap_sem 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)) {
+ /* Retry at most once */
+ if (flags & FAULT_FLAG_ALLOW_RETRY) {
+ flags &= ~FAULT_FLAG_ALLOW_RETRY;
+ flags |= FAULT_FLAG_TRIED;
+ if (!fatal_signal_pending(tsk))
+ goto retry;
+ }
+
+ /* User mode? Just return to handle the fatal exception */
+ if (flags & FAULT_FLAG_USER)
+ return;
+
+ /* Not returning to user mode? Handle exceptions or die: */
+ no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
+ return;
+ }
+
+ up_read(&mm->mmap_sem);
+ if (unlikely(fault & VM_FAULT_ERROR)) {
+ mm_fault_error(regs, error_code, address, &pkey, fault);
+ return;
+ }
+
+ /*
+ * Major/minor page fault accounting. If any of the events
+ * returned VM_FAULT_MAJOR, we account it as a major fault.
+ */
+ if (major) {
+ tsk->maj_flt++;
+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
+ } else {
+ tsk->min_flt++;
+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
+ }
+
+ check_v8086_mode(regs, address, tsk);
+}
+NOKPROBE_SYMBOL(__do_page_fault);
+
+static nokprobe_inline void
+trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
+ unsigned long error_code)
+{
+ if (user_mode(regs))
+ trace_page_fault_user(address, regs, error_code);
+ else
+ trace_page_fault_kernel(address, regs, error_code);
+}
+
+/*
+ * We must have this function blacklisted from kprobes, tagged with notrace
+ * and call read_cr2() before calling anything else. To avoid calling any
+ * kind of tracing machinery before we've observed the CR2 value.
+ *
+ * exception_{enter,exit}() contains all sorts of tracepoints.
+ */
+dotraplinkage void notrace
+do_page_fault(struct pt_regs *regs, unsigned long error_code)
+{
+ unsigned long address = read_cr2(); /* Get the faulting address */
+ enum ctx_state prev_state;
+
+ prev_state = exception_enter();
+ if (trace_pagefault_enabled())
+ trace_page_fault_entries(address, regs, error_code);
+
+ __do_page_fault(regs, error_code, address);
+ exception_exit(prev_state);
+}
+NOKPROBE_SYMBOL(do_page_fault);