From 9999e48639b3cecb08ffb37358bcba3b48161b29 Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Fri, 10 May 2024 08:50:17 +0000
Subject: [PATCH] add ax88772_rst
---
kernel/arch/x86/mm/fault.c | 1010 ++++++++++++++++++++++++++++++----------------------------
1 files changed, 521 insertions(+), 489 deletions(-)
diff --git a/kernel/arch/x86/mm/fault.c b/kernel/arch/x86/mm/fault.c
index c61acf6..e9afbf8 100644
--- a/kernel/arch/x86/mm/fault.c
+++ b/kernel/arch/x86/mm/fault.c
@@ -8,7 +8,8 @@
#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/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 */
@@ -16,15 +17,20 @@
#include <linux/prefetch.h> /* prefetchw */
#include <linux/context_tracking.h> /* exception_enter(), ... */
#include <linux/uaccess.h> /* faulthandler_disabled() */
+#include <linux/efi.h> /* efi_recover_from_page_fault()*/
#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() */
+#include <asm/efi.h> /* efi_recover_from_page_fault()*/
+#include <asm/desc.h> /* store_idt(), ... */
+#include <asm/cpu_entry_area.h> /* exception stack */
+#include <asm/pgtable_areas.h> /* VMALLOC_START, ... */
+#include <asm/kvm_para.h> /* kvm_handle_async_pf */
#define CREATE_TRACE_POINTS
#include <asm/trace/exceptions.h>
@@ -42,28 +48,13 @@
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.
+ * Check that here and ignore it. This is AMD erratum #91.
*
* 64-bit mode:
*
@@ -92,11 +83,7 @@
#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.
+ * In 64-bit mode 0x40..0x4F are valid REX prefixes
*/
return (!user_mode(regs) || user_64bit_mode(regs));
#endif
@@ -108,7 +95,7 @@
return !instr_lo || (instr_lo>>1) == 1;
case 0x00:
/* Prefetch instruction is 0x0F0D or 0x0F18 */
- if (probe_kernel_address(instr, opcode))
+ if (get_kernel_nofault(opcode, instr))
return 0;
*prefetch = (instr_lo == 0xF) &&
@@ -136,94 +123,32 @@
instr = (void *)convert_ip_to_linear(current, regs);
max_instr = instr + 15;
- if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
- return 0;
+ /*
+ * This code has historically always bailed out if IP points to a
+ * not-present page (e.g. due to a race). No one has ever
+ * complained about this.
+ */
+ pagefault_disable();
while (instr < max_instr) {
unsigned char opcode;
- if (probe_kernel_address(instr, opcode))
- break;
+ if (user_mode(regs)) {
+ if (get_user(opcode, instr))
+ break;
+ } else {
+ if (get_kernel_nofault(opcode, instr))
+ break;
+ }
instr++;
if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
break;
}
+
+ pagefault_enable();
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);
@@ -273,47 +198,19 @@
return pmd_k;
}
-static void vmalloc_sync(void)
-{
- unsigned long address;
-
- if (SHARED_KERNEL_PMD)
- return;
-
- for (address = VMALLOC_START & PMD_MASK;
- address >= TASK_SIZE_MAX && address < VMALLOC_END;
- address += PMD_SIZE) {
- struct page *page;
-
- spin_lock(&pgd_lock);
- list_for_each_entry(page, &pgd_list, lru) {
- spinlock_t *pgt_lock;
-
- /* the pgt_lock only for Xen */
- pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
-
- spin_lock(pgt_lock);
- vmalloc_sync_one(page_address(page), address);
- spin_unlock(pgt_lock);
- }
- spin_unlock(&pgd_lock);
- }
-}
-
-void vmalloc_sync_mappings(void)
-{
- vmalloc_sync();
-}
-
-void vmalloc_sync_unmappings(void)
-{
- vmalloc_sync();
-}
-
/*
- * 32-bit:
- *
* Handle a fault on the vmalloc or module mapping area
+ *
+ * This is needed because there is a race condition between the time
+ * when the vmalloc mapping code updates the PMD to the point in time
+ * where it synchronizes this update with the other page-tables in the
+ * system.
+ *
+ * In this race window another thread/CPU can map an area on the same
+ * PMD, finds it already present and does not synchronize it with the
+ * rest of the system yet. As a result v[mz]alloc might return areas
+ * which are not mapped in every page-table in the system, causing an
+ * unhandled page-fault when they are accessed.
*/
static noinline int vmalloc_fault(unsigned long address)
{
@@ -347,6 +244,30 @@
return 0;
}
NOKPROBE_SYMBOL(vmalloc_fault);
+
+void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
+{
+ unsigned long addr;
+
+ for (addr = start & PMD_MASK;
+ addr >= TASK_SIZE_MAX && addr < VMALLOC_END;
+ addr += PMD_SIZE) {
+ struct page *page;
+
+ spin_lock(&pgd_lock);
+ list_for_each_entry(page, &pgd_list, lru) {
+ spinlock_t *pgt_lock;
+
+ /* the pgt_lock only for Xen */
+ pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
+
+ spin_lock(pgt_lock);
+ vmalloc_sync_one(page_address(page), addr);
+ spin_unlock(pgt_lock);
+ }
+ spin_unlock(&pgd_lock);
+ }
+}
/*
* Did it hit the DOS screen memory VA from vm86 mode?
@@ -412,96 +333,6 @@
#else /* CONFIG_X86_64: */
-void vmalloc_sync_mappings(void)
-{
- /*
- * 64-bit mappings might allocate new p4d/pud pages
- * that need to be propagated to all tasks' PGDs.
- */
- sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
-}
-
-void vmalloc_sync_unmappings(void)
-{
- /*
- * Unmappings never allocate or free p4d/pud pages.
- * No work is required here.
- */
-}
-
-/*
- * 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;
-
- /*
- * 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
@@ -524,7 +355,7 @@
{
unsigned long dummy;
- return probe_kernel_address((unsigned long *)p, dummy);
+ return get_kernel_nofault(dummy, (unsigned long *)p);
}
static void dump_pagetable(unsigned long address)
@@ -637,29 +468,51 @@
return 0;
}
+/* Pentium F0 0F C7 C8 bug workaround: */
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;
- }
+ if (boot_cpu_has_bug(X86_BUG_F00F) && idt_is_f00f_address(address)) {
+ handle_invalid_op(regs);
+ return 1;
}
#endif
return 0;
}
+static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index)
+{
+ u32 offset = (index >> 3) * sizeof(struct desc_struct);
+ unsigned long addr;
+ struct ldttss_desc desc;
+
+ if (index == 0) {
+ pr_alert("%s: NULL\n", name);
+ return;
+ }
+
+ if (offset + sizeof(struct ldttss_desc) >= gdt->size) {
+ pr_alert("%s: 0x%hx -- out of bounds\n", name, index);
+ return;
+ }
+
+ if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset),
+ sizeof(struct ldttss_desc))) {
+ pr_alert("%s: 0x%hx -- GDT entry is not readable\n",
+ name, index);
+ return;
+ }
+
+ addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24);
+#ifdef CONFIG_X86_64
+ addr |= ((u64)desc.base3 << 32);
+#endif
+ pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n",
+ name, index, addr, (desc.limit0 | (desc.limit1 << 16)));
+}
+
static void
-show_fault_oops(struct pt_regs *regs, unsigned long error_code,
- unsigned long address)
+show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address)
{
if (!oops_may_print())
return;
@@ -684,9 +537,53 @@
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);
+ if (address < PAGE_SIZE && !user_mode(regs))
+ pr_alert("BUG: kernel NULL pointer dereference, address: %px\n",
+ (void *)address);
+ else
+ pr_alert("BUG: unable to handle page fault for address: %px\n",
+ (void *)address);
+
+ pr_alert("#PF: %s %s in %s mode\n",
+ (error_code & X86_PF_USER) ? "user" : "supervisor",
+ (error_code & X86_PF_INSTR) ? "instruction fetch" :
+ (error_code & X86_PF_WRITE) ? "write access" :
+ "read access",
+ user_mode(regs) ? "user" : "kernel");
+ pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code,
+ !(error_code & X86_PF_PROT) ? "not-present page" :
+ (error_code & X86_PF_RSVD) ? "reserved bit violation" :
+ (error_code & X86_PF_PK) ? "protection keys violation" :
+ "permissions violation");
+
+ if (!(error_code & X86_PF_USER) && user_mode(regs)) {
+ struct desc_ptr idt, gdt;
+ u16 ldtr, tr;
+
+ /*
+ * This can happen for quite a few reasons. The more obvious
+ * ones are faults accessing the GDT, or LDT. Perhaps
+ * surprisingly, if the CPU tries to deliver a benign or
+ * contributory exception from user code and gets a page fault
+ * during delivery, the page fault can be delivered as though
+ * it originated directly from user code. This could happen
+ * due to wrong permissions on the IDT, GDT, LDT, TSS, or
+ * kernel or IST stack.
+ */
+ store_idt(&idt);
+
+ /* Usable even on Xen PV -- it's just slow. */
+ native_store_gdt(&gdt);
+
+ pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n",
+ idt.address, idt.size, gdt.address, gdt.size);
+
+ store_ldt(ldtr);
+ show_ldttss(&gdt, "LDTR", ldtr);
+
+ store_tr(tr);
+ show_ldttss(&gdt, "TR", tr);
+ }
dump_pagetable(address);
}
@@ -707,14 +604,32 @@
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 void set_signal_archinfo(unsigned long address,
+ unsigned long error_code)
+{
+ struct task_struct *tsk = current;
+
+ /*
+ * To avoid leaking information about the kernel page
+ * table layout, pretend that user-mode accesses to
+ * kernel addresses are always protection faults.
+ *
+ * NB: This means that failed vsyscalls with vsyscall=none
+ * will have the PROT bit. This doesn't leak any
+ * information and does not appear to cause any problems.
+ */
+ if (address >= TASK_SIZE_MAX)
+ error_code |= X86_PF_PROT;
+
+ tsk->thread.trap_nr = X86_TRAP_PF;
+ tsk->thread.error_code = error_code | X86_PF_USER;
+ tsk->thread.cr2 = address;
}
static noinline void
@@ -725,8 +640,17 @@
unsigned long flags;
int sig;
+ if (user_mode(regs)) {
+ /*
+ * This is an implicit supervisor-mode access from user
+ * mode. Bypass all the kernel-mode recovery code and just
+ * OOPS.
+ */
+ goto oops;
+ }
+
/* Are we prepared to handle this kernel fault? */
- if (fixup_exception(regs, X86_TRAP_PF)) {
+ 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
@@ -742,13 +666,10 @@
* 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;
+ set_signal_archinfo(address, error_code);
/* XXX: hwpoison faults will set the wrong code. */
- force_sig_info_fault(signal, si_code, address,
- tsk, NULL, 0);
+ force_sig_fault(signal, si_code, (void __user *)address);
}
/*
@@ -766,7 +687,7 @@
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 *);
+ unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *);
/*
* We're likely to be running with very little stack space
* left. It's plausible that we'd hit this condition but
@@ -806,6 +727,19 @@
return;
/*
+ * Buggy firmware could access regions which might page fault, try to
+ * recover from such faults.
+ */
+ if (IS_ENABLED(CONFIG_EFI))
+ efi_recover_from_page_fault(address);
+
+ /* Only not-present faults should be handled by KFENCE. */
+ if (!(error_code & X86_PF_PROT) &&
+ kfence_handle_page_fault(address, error_code & X86_PF_WRITE, regs))
+ return;
+
+oops:
+ /*
* Oops. The kernel tried to access some bad page. We'll have to
* terminate things with extreme prejudice:
*/
@@ -815,10 +749,6 @@
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))
@@ -857,14 +787,23 @@
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)
+ 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) {
+ if (user_mode(regs) && (error_code & X86_PF_USER)) {
/*
* It's possible to have interrupts off here:
*/
@@ -880,18 +819,6 @@
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
@@ -903,11 +830,14 @@
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;
+ set_signal_archinfo(address, error_code);
- force_sig_info_fault(SIGSEGV, si_code, address, tsk, pkey, 0);
+ if (si_code == SEGV_PKUERR)
+ force_sig_pkuerr((void __user *)address, pkey);
+
+ force_sig_fault(SIGSEGV, si_code, (void __user *)address);
+
+ local_irq_disable();
return;
}
@@ -920,35 +850,29 @@
static noinline void
bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
- unsigned long address, u32 *pkey)
+ unsigned long address)
{
- __bad_area_nosemaphore(regs, error_code, address, pkey, SEGV_MAPERR);
+ __bad_area_nosemaphore(regs, error_code, address, 0, 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)
+ unsigned long address, u32 pkey, 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);
+ mmap_read_unlock(mm);
- __bad_area_nosemaphore(regs, error_code, address,
- (vma) ? &pkey : NULL, si_code);
+ __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, NULL, SEGV_MAPERR);
+ __bad_area(regs, error_code, address, 0, SEGV_MAPERR);
}
static inline bool bad_area_access_from_pkeys(unsigned long error_code,
@@ -977,19 +901,39 @@
* 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);
+ if (bad_area_access_from_pkeys(error_code, vma)) {
+ /*
+ * 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. This function captures the pkey from
+ * the vma and passes it to userspace 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_lock, etc...
+ * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
+ * faulted on a pte with its pkey=4.
+ */
+ u32 pkey = vma_pkey(vma);
+
+ __bad_area(regs, error_code, address, pkey, SEGV_PKUERR);
+ } else {
+ __bad_area(regs, error_code, address, 0, SEGV_ACCERR);
+ }
}
static void
do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
- u32 *pkey, unsigned int fault)
+ vm_fault_t 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);
@@ -1000,24 +944,30 @@
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;
+ set_signal_archinfo(address, error_code);
#ifdef CONFIG_MEMORY_FAILURE
if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
- printk(KERN_ERR
+ struct task_struct *tsk = current;
+ unsigned lsb = 0;
+
+ pr_err(
"MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
tsk->comm, tsk->pid, address);
- code = BUS_MCEERR_AR;
+ if (fault & VM_FAULT_HWPOISON_LARGE)
+ lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
+ if (fault & VM_FAULT_HWPOISON)
+ lsb = PAGE_SHIFT;
+ force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
+ return;
}
#endif
- force_sig_info_fault(SIGBUS, code, address, tsk, pkey, fault);
+ force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
}
static noinline void
mm_fault_error(struct pt_regs *regs, unsigned long error_code,
- unsigned long address, u32 *pkey, vm_fault_t fault)
+ unsigned long address, vm_fault_t fault)
{
if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) {
no_context(regs, error_code, address, 0, 0);
@@ -1041,27 +991,21 @@
} else {
if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
VM_FAULT_HWPOISON_LARGE))
- do_sigbus(regs, error_code, address, pkey, fault);
+ do_sigbus(regs, error_code, address, fault);
else if (fault & VM_FAULT_SIGSEGV)
- bad_area_nosemaphore(regs, error_code, address, pkey);
+ bad_area_nosemaphore(regs, error_code, address);
else
BUG();
}
}
-static int spurious_fault_check(unsigned long error_code, pte_t *pte)
+static int spurious_kernel_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;
}
@@ -1088,7 +1032,7 @@
* (Optional Invalidation).
*/
static noinline int
-spurious_fault(unsigned long error_code, unsigned long address)
+spurious_kernel_fault(unsigned long error_code, unsigned long address)
{
pgd_t *pgd;
p4d_t *p4d;
@@ -1119,27 +1063,27 @@
return 0;
if (p4d_large(*p4d))
- return spurious_fault_check(error_code, (pte_t *) 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))
- return spurious_fault_check(error_code, (pte_t *) 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))
- return spurious_fault_check(error_code, (pte_t *) pmd);
+ return spurious_kernel_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);
+ ret = spurious_kernel_fault_check(error_code, pte);
if (!ret)
return 0;
@@ -1147,12 +1091,12 @@
* 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);
+ ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd);
WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
return ret;
}
-NOKPROBE_SYMBOL(spurious_fault);
+NOKPROBE_SYMBOL(spurious_kernel_fault);
int show_unhandled_signals = 1;
@@ -1191,60 +1135,44 @@
return 1;
/* read, not present: */
- if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
+ if (unlikely(!vma_is_accessible(vma)))
return 1;
return 0;
}
-static int fault_in_kernel_space(unsigned long address)
+bool fault_in_kernel_space(unsigned long address)
{
+ /*
+ * On 64-bit systems, the vsyscall page is at an address above
+ * TASK_SIZE_MAX, but is not considered part of the kernel
+ * address space.
+ */
+ if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address))
+ return false;
+
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.
+ * Called for all faults where 'address' is part of the kernel address
+ * space. Might get called for faults that originate from *code* that
+ * ran in userspace or the kernel.
*/
-static noinline void
-__do_page_fault(struct pt_regs *regs, unsigned long error_code,
- unsigned long address)
+static void
+do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_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
+ * Protection keys exceptions only happen on user pages. We
+ * have no user pages in the kernel portion of the address
+ * space, so do not expect them here.
+ */
+ WARN_ON_ONCE(hw_error_code & X86_PF_PK);
+
+#ifdef CONFIG_X86_32
+ /*
+ * We can 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
@@ -1252,41 +1180,85 @@
* 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.
+ * Before doing this on-demand faulting, ensure that the
+ * fault is not any of the following:
+ * 1. A fault on a PTE with a reserved bit set.
+ * 2. A fault caused by a user-mode access. (Do not demand-
+ * fault kernel memory due to user-mode accesses).
+ * 3. A fault caused by a page-level protection violation.
+ * (A demand fault would be on a non-present page which
+ * would have X86_PF_PROT==0).
+ *
+ * This is only needed to close a race condition on x86-32 in
+ * the vmalloc mapping/unmapping code. See the comment above
+ * vmalloc_fault() for details. On x86-64 the race does not
+ * exist as the vmalloc mappings don't need to be synchronized
+ * there.
*/
- 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))
+ if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) {
+ if (vmalloc_fault(address) >= 0)
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;
}
+#endif
+
+ /* Was the fault spurious, caused by lazy TLB invalidation? */
+ if (spurious_kernel_fault(hw_error_code, address))
+ return;
/* kprobes don't want to hook the spurious faults: */
- if (unlikely(kprobes_fault(regs)))
+ if (kprobe_page_fault(regs, X86_TRAP_PF))
return;
- if (unlikely(error_code & X86_PF_RSVD))
- pgtable_bad(regs, error_code, address);
+ /*
+ * Note, despite being a "bad area", there are quite a few
+ * acceptable reasons to get here, such as erratum fixups
+ * and handling kernel code that can fault, like get_user().
+ *
+ * Don't take the mm semaphore here. If we fixup a prefetch
+ * fault we could otherwise deadlock:
+ */
+ bad_area_nosemaphore(regs, hw_error_code, address);
+}
+NOKPROBE_SYMBOL(do_kern_addr_fault);
- if (unlikely(smap_violation(error_code, regs))) {
- bad_area_nosemaphore(regs, error_code, address, NULL);
+/* Handle faults in the user portion of the address space */
+static inline
+void do_user_addr_fault(struct pt_regs *regs,
+ unsigned long hw_error_code,
+ unsigned long address)
+{
+ struct vm_area_struct *vma = NULL;
+ struct task_struct *tsk;
+ struct mm_struct *mm;
+ vm_fault_t fault;
+ unsigned int flags = FAULT_FLAG_DEFAULT;
+
+ tsk = current;
+ mm = tsk->mm;
+
+ /* kprobes don't want to hook the spurious faults: */
+ if (unlikely(kprobe_page_fault(regs, X86_TRAP_PF)))
+ return;
+
+ /*
+ * Reserved bits are never expected to be set on
+ * entries in the user portion of the page tables.
+ */
+ if (unlikely(hw_error_code & X86_PF_RSVD))
+ pgtable_bad(regs, hw_error_code, address);
+
+ /*
+ * If SMAP is on, check for invalid kernel (supervisor) access to user
+ * pages in the user address space. The odd case here is WRUSS,
+ * which, according to the preliminary documentation, does not respect
+ * SMAP and will have the USER bit set so, in all cases, SMAP
+ * enforcement appears to be consistent with the USER bit.
+ */
+ if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) &&
+ !(hw_error_code & X86_PF_USER) &&
+ !(regs->flags & X86_EFLAGS_AC)))
+ {
+ bad_area_nosemaphore(regs, hw_error_code, address);
return;
}
@@ -1295,7 +1267,7 @@
* 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);
+ bad_area_nosemaphore(regs, hw_error_code, address);
return;
}
@@ -1308,7 +1280,6 @@
*/
if (user_mode(regs)) {
local_irq_enable();
- error_code |= X86_PF_USER;
flags |= FAULT_FLAG_USER;
} else {
if (regs->flags & X86_EFLAGS_IF)
@@ -1317,35 +1288,62 @@
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
- if (error_code & X86_PF_WRITE)
+ if (hw_error_code & X86_PF_WRITE)
flags |= FAULT_FLAG_WRITE;
- if (error_code & X86_PF_INSTR)
+ if (hw_error_code & X86_PF_INSTR)
flags |= FAULT_FLAG_INSTRUCTION;
+#ifdef CONFIG_X86_64
/*
- * 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.
+ * Faults in the vsyscall page might need emulation. The
+ * vsyscall page is at a high address (>PAGE_OFFSET), but is
+ * considered to be part of the user address space.
*
- * 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:
+ * The vsyscall page does not have a "real" VMA, so do this
+ * emulation before we go searching for VMAs.
+ *
+ * PKRU never rejects instruction fetches, so we don't need
+ * to consider the PF_PK bit.
*/
- 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);
+ if (is_vsyscall_vaddr(address)) {
+ if (emulate_vsyscall(hw_error_code, regs, address))
+ return;
+ }
+#endif
+
+ /*
+ * Do not try to do a speculative page fault if the fault was due to
+ * protection keys since it can't be resolved.
+ */
+ if (!(hw_error_code & X86_PF_PK)) {
+ fault = handle_speculative_fault(mm, address, flags, &vma, regs);
+ if (fault != VM_FAULT_RETRY)
+ goto done;
+ }
+
+ /*
+ * 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, hw_error_code, address);
return;
}
retry:
- down_read(&mm->mmap_sem);
+ mmap_read_lock(mm);
} else {
/*
* The above down_read_trylock() might have succeeded in
@@ -1355,31 +1353,20 @@
might_sleep();
}
- vma = find_vma(mm, address);
+ if (!vma || !can_reuse_spf_vma(vma, address))
+ vma = find_vma(mm, address);
if (unlikely(!vma)) {
- bad_area(regs, error_code, address);
+ bad_area(regs, hw_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);
+ bad_area(regs, hw_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);
+ bad_area(regs, hw_error_code, address);
return;
}
@@ -1388,8 +1375,8 @@
* we can handle it..
*/
good_area:
- if (unlikely(access_error(error_code, vma))) {
- bad_area_access_error(regs, error_code, address, vma);
+ if (unlikely(access_error(hw_error_code, vma))) {
+ bad_area_access_error(regs, hw_error_code, address, vma);
return;
}
@@ -1397,94 +1384,139 @@
* 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.
+ * we get VM_FAULT_RETRY back, the mmap_lock has been unlocked.
*
- * Note that handle_userfault() may also release and reacquire mmap_sem
+ * Note that handle_userfault() may also release and reacquire mmap_lock
* (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;
+ fault = handle_mm_fault(vma, address, flags, regs);
+
+ /* Quick path to respond to signals */
+ if (fault_signal_pending(fault, regs)) {
+ if (!user_mode(regs))
+ no_context(regs, hw_error_code, address, SIGBUS,
+ BUS_ADRERR);
+ return;
+ }
/*
- * If we need to retry the mmap_sem has already been released,
+ * 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)) {
- /* 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;
- }
+ if (unlikely((fault & VM_FAULT_RETRY) &&
+ (flags & FAULT_FLAG_ALLOW_RETRY))) {
+ flags |= FAULT_FLAG_TRIED;
- /* User mode? Just return to handle the fatal exception */
- if (flags & FAULT_FLAG_USER)
- return;
+ /*
+ * Do not try to reuse this vma and fetch it
+ * again since we will release the mmap_sem.
+ */
+ vma = NULL;
- /* Not returning to user mode? Handle exceptions or die: */
- no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
- return;
+ goto retry;
}
- up_read(&mm->mmap_sem);
+ mmap_read_unlock(mm);
+
+done:
if (unlikely(fault & VM_FAULT_ERROR)) {
- mm_fault_error(regs, error_code, address, &pkey, fault);
+ mm_fault_error(regs, hw_error_code, address, 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);
+NOKPROBE_SYMBOL(do_user_addr_fault);
-static nokprobe_inline void
-trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
- unsigned long error_code)
+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
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)
+static __always_inline void
+handle_page_fault(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address)
{
- unsigned long address = read_cr2(); /* Get the faulting address */
- enum ctx_state prev_state;
+ trace_page_fault_entries(regs, error_code, address);
- prev_state = exception_enter();
- if (trace_pagefault_enabled())
- trace_page_fault_entries(address, regs, error_code);
+ if (unlikely(kmmio_fault(regs, address)))
+ return;
- __do_page_fault(regs, error_code, address);
- exception_exit(prev_state);
+ /* Was the fault on kernel-controlled part of the address space? */
+ if (unlikely(fault_in_kernel_space(address))) {
+ do_kern_addr_fault(regs, error_code, address);
+ } else {
+ do_user_addr_fault(regs, error_code, address);
+ /*
+ * User address page fault handling might have reenabled
+ * interrupts. Fixing up all potential exit points of
+ * do_user_addr_fault() and its leaf functions is just not
+ * doable w/o creating an unholy mess or turning the code
+ * upside down.
+ */
+ local_irq_disable();
+ }
}
-NOKPROBE_SYMBOL(do_page_fault);
+
+DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
+{
+ unsigned long address = read_cr2();
+ irqentry_state_t state;
+
+ prefetchw(¤t->mm->mmap_lock);
+
+ /*
+ * KVM uses #PF vector to deliver 'page not present' events to guests
+ * (asynchronous page fault mechanism). The event happens when a
+ * userspace task is trying to access some valid (from guest's point of
+ * view) memory which is not currently mapped by the host (e.g. the
+ * memory is swapped out). Note, the corresponding "page ready" event
+ * which is injected when the memory becomes available, is delived via
+ * an interrupt mechanism and not a #PF exception
+ * (see arch/x86/kernel/kvm.c: sysvec_kvm_asyncpf_interrupt()).
+ *
+ * We are relying on the interrupted context being sane (valid RSP,
+ * relevant locks not held, etc.), which is fine as long as the
+ * interrupted context had IF=1. We are also relying on the KVM
+ * async pf type field and CR2 being read consistently instead of
+ * getting values from real and async page faults mixed up.
+ *
+ * Fingers crossed.
+ *
+ * The async #PF handling code takes care of idtentry handling
+ * itself.
+ */
+ if (kvm_handle_async_pf(regs, (u32)address))
+ return;
+
+ /*
+ * Entry handling for valid #PF from kernel mode is slightly
+ * different: RCU is already watching and rcu_irq_enter() must not
+ * be invoked because a kernel fault on a user space address might
+ * sleep.
+ *
+ * In case the fault hit a RCU idle region the conditional entry
+ * code reenabled RCU to avoid subsequent wreckage which helps
+ * debugability.
+ */
+ state = irqentry_enter(regs);
+
+ instrumentation_begin();
+ handle_page_fault(regs, error_code, address);
+ instrumentation_end();
+
+ irqentry_exit(regs, state);
+}
--
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