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Subject[PATCH 4.4 03/37] kaiser: merged update
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dave Hansen <dave.hansen@linux.intel.com>


Merged fixes and cleanups, rebased to 4.4.89 tree (no 5-level paging).

Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/entry/entry_64.S | 106 ++++++++++-
arch/x86/include/asm/kaiser.h | 43 ++--
arch/x86/include/asm/pgtable.h | 18 +
arch/x86/include/asm/pgtable_64.h | 48 ++++-
arch/x86/include/asm/pgtable_types.h | 6
arch/x86/kernel/espfix_64.c | 13 -
arch/x86/kernel/head_64.S | 19 +-
arch/x86/kernel/ldt.c | 27 ++
arch/x86/kernel/tracepoint.c | 2
arch/x86/mm/kaiser.c | 318 +++++++++++++++++++++++++----------
arch/x86/mm/pageattr.c | 63 +++++-
arch/x86/mm/pgtable.c | 40 +---
include/linux/kaiser.h | 26 ++
kernel/fork.c | 9
security/Kconfig | 5
15 files changed, 553 insertions(+), 190 deletions(-)
create mode 100644 include/linux/kaiser.h

--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -212,6 +212,13 @@ entry_SYSCALL_64_fastpath:
movq RIP(%rsp), %rcx
movq EFLAGS(%rsp), %r11
RESTORE_C_REGS_EXCEPT_RCX_R11
+ /*
+ * This opens a window where we have a user CR3, but are
+ * running in the kernel. This makes using the CS
+ * register useless for telling whether or not we need to
+ * switch CR3 in NMIs. Normal interrupts are OK because
+ * they are off here.
+ */
SWITCH_USER_CR3
movq RSP(%rsp), %rsp
/*
@@ -350,11 +357,25 @@ GLOBAL(int_ret_from_sys_call)
syscall_return_via_sysret:
/* rcx and r11 are already restored (see code above) */
RESTORE_C_REGS_EXCEPT_RCX_R11
+ /*
+ * This opens a window where we have a user CR3, but are
+ * running in the kernel. This makes using the CS
+ * register useless for telling whether or not we need to
+ * switch CR3 in NMIs. Normal interrupts are OK because
+ * they are off here.
+ */
SWITCH_USER_CR3
movq RSP(%rsp), %rsp
USERGS_SYSRET64

opportunistic_sysret_failed:
+ /*
+ * This opens a window where we have a user CR3, but are
+ * running in the kernel. This makes using the CS
+ * register useless for telling whether or not we need to
+ * switch CR3 in NMIs. Normal interrupts are OK because
+ * they are off here.
+ */
SWITCH_USER_CR3
SWAPGS
jmp restore_c_regs_and_iret
@@ -1059,6 +1080,13 @@ ENTRY(error_entry)
cld
SAVE_C_REGS 8
SAVE_EXTRA_REGS 8
+ /*
+ * error_entry() always returns with a kernel gsbase and
+ * CR3. We must also have a kernel CR3/gsbase before
+ * calling TRACE_IRQS_*. Just unconditionally switch to
+ * the kernel CR3 here.
+ */
+ SWITCH_KERNEL_CR3
xorl %ebx, %ebx
testb $3, CS+8(%rsp)
jz .Lerror_kernelspace
@@ -1069,7 +1097,6 @@ ENTRY(error_entry)
* from user mode due to an IRET fault.
*/
SWAPGS
- SWITCH_KERNEL_CR3

.Lerror_entry_from_usermode_after_swapgs:
/*
@@ -1122,7 +1149,7 @@ ENTRY(error_entry)
* Switch to kernel gsbase:
*/
SWAPGS
- SWITCH_KERNEL_CR3
+
/*
* Pretend that the exception came from user mode: set up pt_regs
* as if we faulted immediately after IRET and clear EBX so that
@@ -1222,7 +1249,10 @@ ENTRY(nmi)
*/

SWAPGS_UNSAFE_STACK
- SWITCH_KERNEL_CR3_NO_STACK
+ /*
+ * percpu variables are mapped with user CR3, so no need
+ * to switch CR3 here.
+ */
cld
movq %rsp, %rdx
movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
@@ -1256,14 +1286,33 @@ ENTRY(nmi)

movq %rsp, %rdi
movq $-1, %rsi
+#ifdef CONFIG_KAISER
+ /* Unconditionally use kernel CR3 for do_nmi() */
+ /* %rax is saved above, so OK to clobber here */
+ movq %cr3, %rax
+ pushq %rax
+#ifdef CONFIG_KAISER_REAL_SWITCH
+ andq $(~0x1000), %rax
+#endif
+ movq %rax, %cr3
+#endif
call do_nmi
+ /*
+ * Unconditionally restore CR3. I know we return to
+ * kernel code that needs user CR3, but do we ever return
+ * to "user mode" where we need the kernel CR3?
+ */
+#ifdef CONFIG_KAISER
+ popq %rax
+ mov %rax, %cr3
+#endif

/*
* Return back to user mode. We must *not* do the normal exit
- * work, because we don't want to enable interrupts. Fortunately,
- * do_nmi doesn't modify pt_regs.
+ * work, because we don't want to enable interrupts. Do not
+ * switch to user CR3: we might be going back to kernel code
+ * that had a user CR3 set.
*/
- SWITCH_USER_CR3
SWAPGS
jmp restore_c_regs_and_iret

@@ -1459,23 +1508,54 @@ end_repeat_nmi:
ALLOC_PT_GPREGS_ON_STACK

/*
- * Use paranoid_entry to handle SWAPGS, but no need to use paranoid_exit
- * as we should not be calling schedule in NMI context.
- * Even with normal interrupts enabled. An NMI should not be
- * setting NEED_RESCHED or anything that normal interrupts and
- * exceptions might do.
+ * Use the same approach as paranoid_entry to handle SWAPGS, but
+ * without CR3 handling since we do that differently in NMIs. No
+ * need to use paranoid_exit as we should not be calling schedule
+ * in NMI context. Even with normal interrupts enabled. An NMI
+ * should not be setting NEED_RESCHED or anything that normal
+ * interrupts and exceptions might do.
*/
- call paranoid_entry
+ cld
+ SAVE_C_REGS
+ SAVE_EXTRA_REGS
+ movl $1, %ebx
+ movl $MSR_GS_BASE, %ecx
+ rdmsr
+ testl %edx, %edx
+ js 1f /* negative -> in kernel */
+ SWAPGS
+ xorl %ebx, %ebx
+1:
+#ifdef CONFIG_KAISER
+ /* Unconditionally use kernel CR3 for do_nmi() */
+ /* %rax is saved above, so OK to clobber here */
+ movq %cr3, %rax
+ pushq %rax
+#ifdef CONFIG_KAISER_REAL_SWITCH
+ andq $(~0x1000), %rax
+#endif
+ movq %rax, %cr3
+#endif

/* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
movq %rsp, %rdi
+ addq $8, %rdi /* point %rdi at ptregs, fixed up for CR3 */
movq $-1, %rsi
call do_nmi
+ /*
+ * Unconditionally restore CR3. We might be returning to
+ * kernel code that needs user CR3, like just just before
+ * a sysret.
+ */
+#ifdef CONFIG_KAISER
+ popq %rax
+ mov %rax, %cr3
+#endif

testl %ebx, %ebx /* swapgs needed? */
jnz nmi_restore
nmi_swapgs:
- SWITCH_USER_CR3_NO_STACK
+ /* We fixed up CR3 above, so no need to switch it here */
SWAPGS_UNSAFE_STACK
nmi_restore:
RESTORE_EXTRA_REGS
--- a/arch/x86/include/asm/kaiser.h
+++ b/arch/x86/include/asm/kaiser.h
@@ -16,13 +16,17 @@

.macro _SWITCH_TO_KERNEL_CR3 reg
movq %cr3, \reg
+#ifdef CONFIG_KAISER_REAL_SWITCH
andq $(~0x1000), \reg
+#endif
movq \reg, %cr3
.endm

.macro _SWITCH_TO_USER_CR3 reg
movq %cr3, \reg
+#ifdef CONFIG_KAISER_REAL_SWITCH
orq $(0x1000), \reg
+#endif
movq \reg, %cr3
.endm

@@ -65,48 +69,53 @@ movq PER_CPU_VAR(unsafe_stack_register_b
.endm

#endif /* CONFIG_KAISER */
+
#else /* __ASSEMBLY__ */


#ifdef CONFIG_KAISER
-// Upon kernel/user mode switch, it may happen that
-// the address space has to be switched before the registers have been stored.
-// To change the address space, another register is needed.
-// A register therefore has to be stored/restored.
-//
-DECLARE_PER_CPU_USER_MAPPED(unsigned long, unsafe_stack_register_backup);
+/*
+ * Upon kernel/user mode switch, it may happen that the address
+ * space has to be switched before the registers have been
+ * stored. To change the address space, another register is
+ * needed. A register therefore has to be stored/restored.
+*/

-#endif /* CONFIG_KAISER */
+DECLARE_PER_CPU_USER_MAPPED(unsigned long, unsafe_stack_register_backup);

/**
- * shadowmem_add_mapping - map a virtual memory part to the shadow mapping
+ * kaiser_add_mapping - map a virtual memory part to the shadow (user) mapping
* @addr: the start address of the range
* @size: the size of the range
* @flags: The mapping flags of the pages
*
- * the mapping is done on a global scope, so no bigger synchronization has to be done.
- * the pages have to be manually unmapped again when they are not needed any longer.
+ * The mapping is done on a global scope, so no bigger
+ * synchronization has to be done. the pages have to be
+ * manually unmapped again when they are not needed any longer.
*/
-extern void kaiser_add_mapping(unsigned long addr, unsigned long size, unsigned long flags);
+extern int kaiser_add_mapping(unsigned long addr, unsigned long size, unsigned long flags);


/**
- * shadowmem_remove_mapping - unmap a virtual memory part of the shadow mapping
+ * kaiser_remove_mapping - unmap a virtual memory part of the shadow mapping
* @addr: the start address of the range
* @size: the size of the range
*/
extern void kaiser_remove_mapping(unsigned long start, unsigned long size);

/**
- * shadowmem_initialize_mapping - Initalize the shadow mapping
+ * kaiser_initialize_mapping - Initalize the shadow mapping
*
- * most parts of the shadow mapping can be mapped upon boot time.
- * only the thread stacks have to be mapped on runtime.
- * the mapped regions are not unmapped at all.
+ * Most parts of the shadow mapping can be mapped upon boot
+ * time. Only per-process things like the thread stacks
+ * or a new LDT have to be mapped at runtime. These boot-
+ * time mappings are permanent and nevertunmapped.
*/
extern void kaiser_init(void);

-#endif
+#endif /* CONFIG_KAISER */
+
+#endif /* __ASSEMBLY */



--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -653,7 +653,17 @@ static inline pud_t *pud_offset(pgd_t *p

static inline int pgd_bad(pgd_t pgd)
{
- return (pgd_flags(pgd) & ~_PAGE_USER) != _KERNPG_TABLE;
+ pgdval_t ignore_flags = _PAGE_USER;
+ /*
+ * We set NX on KAISER pgds that map userspace memory so
+ * that userspace can not meaningfully use the kernel
+ * page table by accident; it will fault on the first
+ * instruction it tries to run. See native_set_pgd().
+ */
+ if (IS_ENABLED(CONFIG_KAISER))
+ ignore_flags |= _PAGE_NX;
+
+ return (pgd_flags(pgd) & ~ignore_flags) != _KERNPG_TABLE;
}

static inline int pgd_none(pgd_t pgd)
@@ -857,8 +867,10 @@ static inline void clone_pgd_range(pgd_t
{
memcpy(dst, src, count * sizeof(pgd_t));
#ifdef CONFIG_KAISER
- // clone the shadow pgd part as well
- memcpy(native_get_shadow_pgd(dst), native_get_shadow_pgd(src), count * sizeof(pgd_t));
+ /* Clone the shadow pgd part as well */
+ memcpy(native_get_shadow_pgd(dst),
+ native_get_shadow_pgd(src),
+ count * sizeof(pgd_t));
#endif
}

--- a/arch/x86/include/asm/pgtable_64.h
+++ b/arch/x86/include/asm/pgtable_64.h
@@ -107,26 +107,58 @@ static inline void native_pud_clear(pud_
}

#ifdef CONFIG_KAISER
-static inline pgd_t * native_get_shadow_pgd(pgd_t *pgdp) {
+static inline pgd_t * native_get_shadow_pgd(pgd_t *pgdp)
+{
return (pgd_t *)(void*)((unsigned long)(void*)pgdp | (unsigned long)PAGE_SIZE);
}

-static inline pgd_t * native_get_normal_pgd(pgd_t *pgdp) {
+static inline pgd_t * native_get_normal_pgd(pgd_t *pgdp)
+{
return (pgd_t *)(void*)((unsigned long)(void*)pgdp & ~(unsigned long)PAGE_SIZE);
}
+#else
+static inline pgd_t * native_get_shadow_pgd(pgd_t *pgdp)
+{
+ BUILD_BUG_ON(1);
+ return NULL;
+}
+static inline pgd_t * native_get_normal_pgd(pgd_t *pgdp)
+{
+ return pgdp;
+}
#endif /* CONFIG_KAISER */

+/*
+ * Page table pages are page-aligned. The lower half of the top
+ * level is used for userspace and the top half for the kernel.
+ * This returns true for user pages that need to get copied into
+ * both the user and kernel copies of the page tables, and false
+ * for kernel pages that should only be in the kernel copy.
+ */
+static inline bool is_userspace_pgd(void *__ptr)
+{
+ unsigned long ptr = (unsigned long)__ptr;
+
+ return ((ptr % PAGE_SIZE) < (PAGE_SIZE / 2));
+}
+
static inline void native_set_pgd(pgd_t *pgdp, pgd_t pgd)
{
#ifdef CONFIG_KAISER
- // We know that a pgd is page aligned.
- // Therefore the lower indices have to be mapped to user space.
- // These pages are mapped to the shadow mapping.
- if ((((unsigned long)pgdp) % PAGE_SIZE) < (PAGE_SIZE / 2)) {
+ pteval_t extra_kern_pgd_flags = 0;
+ /* Do we need to also populate the shadow pgd? */
+ if (is_userspace_pgd(pgdp)) {
native_get_shadow_pgd(pgdp)->pgd = pgd.pgd;
+ /*
+ * Even if the entry is *mapping* userspace, ensure
+ * that userspace can not use it. This way, if we
+ * get out to userspace running on the kernel CR3,
+ * userspace will crash instead of running.
+ */
+ extra_kern_pgd_flags = _PAGE_NX;
}
-
- pgdp->pgd = pgd.pgd & ~_PAGE_USER;
+ pgdp->pgd = pgd.pgd;
+ pgdp->pgd |= extra_kern_pgd_flags;
#else /* CONFIG_KAISER */
*pgdp = pgd;
#endif
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -42,7 +42,7 @@
#ifdef CONFIG_KAISER
#define _PAGE_GLOBAL (_AT(pteval_t, 0))
#else
-#define _PAGE_GLOBAL (_AT(pteval_t, 1) << _PAGE_BIT_GLOBAL)
+#define _PAGE_GLOBAL (_AT(pteval_t, 1) << _PAGE_BIT_GLOBAL)
#endif
#define _PAGE_SOFTW1 (_AT(pteval_t, 1) << _PAGE_BIT_SOFTW1)
#define _PAGE_SOFTW2 (_AT(pteval_t, 1) << _PAGE_BIT_SOFTW2)
@@ -93,11 +93,7 @@
#define _PAGE_NX (_AT(pteval_t, 0))
#endif

-#ifdef CONFIG_KAISER
-#define _PAGE_PROTNONE (_AT(pteval_t, 0))
-#else
#define _PAGE_PROTNONE (_AT(pteval_t, 1) << _PAGE_BIT_PROTNONE)
-#endif

#define _PAGE_TABLE (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER | \
_PAGE_ACCESSED | _PAGE_DIRTY)
--- a/arch/x86/kernel/espfix_64.c
+++ b/arch/x86/kernel/espfix_64.c
@@ -127,11 +127,14 @@ void __init init_espfix_bsp(void)
/* Install the espfix pud into the kernel page directory */
pgd_p = &init_level4_pgt[pgd_index(ESPFIX_BASE_ADDR)];
pgd_populate(&init_mm, pgd_p, (pud_t *)espfix_pud_page);
-#ifdef CONFIG_KAISER
- // add the esp stack pud to the shadow mapping here.
- // This can be done directly, because the fixup stack has its own pud
- set_pgd(native_get_shadow_pgd(pgd_p), __pgd(_PAGE_TABLE | __pa((pud_t *)espfix_pud_page)));
-#endif
+ /*
+ * Just copy the top-level PGD that is mapping the espfix
+ * area to ensure it is mapped into the shadow user page
+ * tables.
+ */
+ if (IS_ENABLED(CONFIG_KAISER))
+ set_pgd(native_get_shadow_pgd(pgd_p),
+ __pgd(_KERNPG_TABLE | __pa((pud_t *)espfix_pud_page)));

/* Randomize the locations */
init_espfix_random();
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -442,11 +442,24 @@ early_idt_ripmsg:
GLOBAL(name)

#ifdef CONFIG_KAISER
+/*
+ * Each PGD needs to be 8k long and 8k aligned. We do not
+ * ever go out to userspace with these, so we do not
+ * strictly *need* the second page, but this allows us to
+ * have a single set_pgd() implementation that does not
+ * need to worry about whether it has 4k or 8k to work
+ * with.
+ *
+ * This ensures PGDs are 8k long:
+ */
+#define KAISER_USER_PGD_FILL 512
+/* This ensures they are 8k-aligned: */
#define NEXT_PGD_PAGE(name) \
.balign 2 * PAGE_SIZE; \
GLOBAL(name)
#else
#define NEXT_PGD_PAGE(name) NEXT_PAGE(name)
+#define KAISER_USER_PGD_FILL 0
#endif

/* Automate the creation of 1 to 1 mapping pmd entries */
@@ -461,6 +474,7 @@ GLOBAL(name)
NEXT_PGD_PAGE(early_level4_pgt)
.fill 511,8,0
.quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
+ .fill KAISER_USER_PGD_FILL,8,0

NEXT_PAGE(early_dynamic_pgts)
.fill 512*EARLY_DYNAMIC_PAGE_TABLES,8,0
@@ -469,7 +483,8 @@ NEXT_PAGE(early_dynamic_pgts)

#ifndef CONFIG_XEN
NEXT_PGD_PAGE(init_level4_pgt)
- .fill 2*512,8,0
+ .fill 512,8,0
+ .fill KAISER_USER_PGD_FILL,8,0
#else
NEXT_PGD_PAGE(init_level4_pgt)
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
@@ -478,6 +493,7 @@ NEXT_PGD_PAGE(init_level4_pgt)
.org init_level4_pgt + L4_START_KERNEL*8, 0
/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
.quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
+ .fill KAISER_USER_PGD_FILL,8,0

NEXT_PAGE(level3_ident_pgt)
.quad level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
@@ -488,6 +504,7 @@ NEXT_PAGE(level2_ident_pgt)
*/
PMDS(0, __PAGE_KERNEL_IDENT_LARGE_EXEC, PTRS_PER_PMD)
#endif
+ .fill KAISER_USER_PGD_FILL,8,0

NEXT_PAGE(level3_kernel_pgt)
.fill L3_START_KERNEL,8,0
--- a/arch/x86/kernel/ldt.c
+++ b/arch/x86/kernel/ldt.c
@@ -18,6 +18,7 @@
#include <linux/uaccess.h>

#include <asm/ldt.h>
+#include <asm/kaiser.h>
#include <asm/desc.h>
#include <asm/mmu_context.h>
#include <asm/syscalls.h>
@@ -34,11 +35,21 @@ static void flush_ldt(void *current_mm)
set_ldt(pc->ldt->entries, pc->ldt->size);
}

+static void __free_ldt_struct(struct ldt_struct *ldt)
+{
+ if (ldt->size * LDT_ENTRY_SIZE > PAGE_SIZE)
+ vfree(ldt->entries);
+ else
+ free_page((unsigned long)ldt->entries);
+ kfree(ldt);
+}
+
/* The caller must call finalize_ldt_struct on the result. LDT starts zeroed. */
static struct ldt_struct *alloc_ldt_struct(int size)
{
struct ldt_struct *new_ldt;
int alloc_size;
+ int ret = 0;

if (size > LDT_ENTRIES)
return NULL;
@@ -66,6 +77,14 @@ static struct ldt_struct *alloc_ldt_stru
return NULL;
}

+ // FIXME: make kaiser_add_mapping() return an error code
+ // when it fails
+ kaiser_add_mapping((unsigned long)new_ldt->entries, alloc_size,
+ __PAGE_KERNEL);
+ if (ret) {
+ __free_ldt_struct(new_ldt);
+ return NULL;
+ }
new_ldt->size = size;
return new_ldt;
}
@@ -92,12 +111,10 @@ static void free_ldt_struct(struct ldt_s
if (likely(!ldt))
return;

+ kaiser_remove_mapping((unsigned long)ldt->entries,
+ ldt->size * LDT_ENTRY_SIZE);
paravirt_free_ldt(ldt->entries, ldt->size);
- if (ldt->size * LDT_ENTRY_SIZE > PAGE_SIZE)
- vfree(ldt->entries);
- else
- free_page((unsigned long)ldt->entries);
- kfree(ldt);
+ __free_ldt_struct(ldt);
}

/*
--- a/arch/x86/kernel/tracepoint.c
+++ b/arch/x86/kernel/tracepoint.c
@@ -9,10 +9,12 @@
#include <linux/atomic.h>

atomic_t trace_idt_ctr = ATOMIC_INIT(0);
+__aligned(PAGE_SIZE)
struct desc_ptr trace_idt_descr = { NR_VECTORS * 16 - 1,
(unsigned long) trace_idt_table };

/* No need to be aligned, but done to keep all IDTs defined the same way. */
+__aligned(PAGE_SIZE)
gate_desc trace_idt_table[NR_VECTORS] __page_aligned_bss;

static int trace_irq_vector_refcount;
--- a/arch/x86/mm/kaiser.c
+++ b/arch/x86/mm/kaiser.c
@@ -1,160 +1,306 @@
-
-
+#include <linux/bug.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/bug.h>
#include <linux/init.h>
+#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/mm.h>
-
#include <linux/uaccess.h>
+#include <linux/ftrace.h>
+
+#include <asm/kaiser.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/desc.h>
#ifdef CONFIG_KAISER

__visible DEFINE_PER_CPU_USER_MAPPED(unsigned long, unsafe_stack_register_backup);
+/*
+ * At runtime, the only things we map are some things for CPU
+ * hotplug, and stacks for new processes. No two CPUs will ever
+ * be populating the same addresses, so we only need to ensure
+ * that we protect between two CPUs trying to allocate and
+ * populate the same page table page.
+ *
+ * Only take this lock when doing a set_p[4um]d(), but it is not
+ * needed for doing a set_pte(). We assume that only the *owner*
+ * of a given allocation will be doing this for _their_
+ * allocation.
+ *
+ * This ensures that once a system has been running for a while
+ * and there have been stacks all over and these page tables
+ * are fully populated, there will be no further acquisitions of
+ * this lock.
+ */
+static DEFINE_SPINLOCK(shadow_table_allocation_lock);

-/**
- * Get the real ppn from a address in kernel mapping.
- * @param address The virtual adrress
- * @return the physical address
+/*
+ * Returns -1 on error.
*/
-static inline unsigned long get_pa_from_mapping (unsigned long address)
+static inline unsigned long get_pa_from_mapping(unsigned long vaddr)
{
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;

- pgd = pgd_offset_k(address);
- BUG_ON(pgd_none(*pgd) || pgd_large(*pgd));
+ pgd = pgd_offset_k(vaddr);
+ /*
+ * We made all the kernel PGDs present in kaiser_init().
+ * We expect them to stay that way.
+ */
+ BUG_ON(pgd_none(*pgd));
+ /*
+ * PGDs are either 512GB or 128TB on all x86_64
+ * configurations. We don't handle these.
+ */
+ BUG_ON(pgd_large(*pgd));
+
+ pud = pud_offset(pgd, vaddr);
+ if (pud_none(*pud)) {
+ WARN_ON_ONCE(1);
+ return -1;
+ }

- pud = pud_offset(pgd, address);
- BUG_ON(pud_none(*pud));
+ if (pud_large(*pud))
+ return (pud_pfn(*pud) << PAGE_SHIFT) | (vaddr & ~PUD_PAGE_MASK);

- if (pud_large(*pud)) {
- return (pud_pfn(*pud) << PAGE_SHIFT) | (address & ~PUD_PAGE_MASK);
+ pmd = pmd_offset(pud, vaddr);
+ if (pmd_none(*pmd)) {
+ WARN_ON_ONCE(1);
+ return -1;
}

- pmd = pmd_offset(pud, address);
- BUG_ON(pmd_none(*pmd));
+ if (pmd_large(*pmd))
+ return (pmd_pfn(*pmd) << PAGE_SHIFT) | (vaddr & ~PMD_PAGE_MASK);

- if (pmd_large(*pmd)) {
- return (pmd_pfn(*pmd) << PAGE_SHIFT) | (address & ~PMD_PAGE_MASK);
+ pte = pte_offset_kernel(pmd, vaddr);
+ if (pte_none(*pte)) {
+ WARN_ON_ONCE(1);
+ return -1;
}

- pte = pte_offset_kernel(pmd, address);
- BUG_ON(pte_none(*pte));
-
- return (pte_pfn(*pte) << PAGE_SHIFT) | (address & ~PAGE_MASK);
+ return (pte_pfn(*pte) << PAGE_SHIFT) | (vaddr & ~PAGE_MASK);
}

-void _kaiser_copy (unsigned long start_addr, unsigned long size,
- unsigned long flags)
+/*
+ * This is a relatively normal page table walk, except that it
+ * also tries to allocate page tables pages along the way.
+ *
+ * Returns a pointer to a PTE on success, or NULL on failure.
+ */
+static pte_t *kaiser_pagetable_walk(unsigned long address, bool is_atomic)
{
- pgd_t *pgd;
- pud_t *pud;
pmd_t *pmd;
- pte_t *pte;
- unsigned long address;
- unsigned long end_addr = start_addr + size;
- unsigned long target_address;
+ pud_t *pud;
+ pgd_t *pgd = native_get_shadow_pgd(pgd_offset_k(address));
+ gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO);

- for (address = PAGE_ALIGN(start_addr - (PAGE_SIZE - 1));
- address < PAGE_ALIGN(end_addr); address += PAGE_SIZE) {
- target_address = get_pa_from_mapping(address);
+ might_sleep();
+ if (is_atomic) {
+ gfp &= ~GFP_KERNEL;
+ gfp |= __GFP_HIGH | __GFP_ATOMIC;
+ }

- pgd = native_get_shadow_pgd(pgd_offset_k(address));
+ if (pgd_none(*pgd)) {
+ WARN_ONCE(1, "All shadow pgds should have been populated");
+ return NULL;
+ }
+ BUILD_BUG_ON(pgd_large(*pgd) != 0);

- BUG_ON(pgd_none(*pgd) && "All shadow pgds should be mapped at this time\n");
- BUG_ON(pgd_large(*pgd));
+ pud = pud_offset(pgd, address);
+ /* The shadow page tables do not use large mappings: */
+ if (pud_large(*pud)) {
+ WARN_ON(1);
+ return NULL;
+ }
+ if (pud_none(*pud)) {
+ unsigned long new_pmd_page = __get_free_page(gfp);
+ if (!new_pmd_page)
+ return NULL;
+ spin_lock(&shadow_table_allocation_lock);
+ if (pud_none(*pud))
+ set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page)));
+ else
+ free_page(new_pmd_page);
+ spin_unlock(&shadow_table_allocation_lock);
+ }

- pud = pud_offset(pgd, address);
- if (pud_none(*pud)) {
- set_pud(pud, __pud(_PAGE_TABLE | __pa(pmd_alloc_one(0, address))));
- }
- BUG_ON(pud_large(*pud));
+ pmd = pmd_offset(pud, address);
+ /* The shadow page tables do not use large mappings: */
+ if (pmd_large(*pmd)) {
+ WARN_ON(1);
+ return NULL;
+ }
+ if (pmd_none(*pmd)) {
+ unsigned long new_pte_page = __get_free_page(gfp);
+ if (!new_pte_page)
+ return NULL;
+ spin_lock(&shadow_table_allocation_lock);
+ if (pmd_none(*pmd))
+ set_pmd(pmd, __pmd(_KERNPG_TABLE | __pa(new_pte_page)));
+ else
+ free_page(new_pte_page);
+ spin_unlock(&shadow_table_allocation_lock);
+ }

- pmd = pmd_offset(pud, address);
- if (pmd_none(*pmd)) {
- set_pmd(pmd, __pmd(_PAGE_TABLE | __pa(pte_alloc_one_kernel(0, address))));
- }
- BUG_ON(pmd_large(*pmd));
+ return pte_offset_kernel(pmd, address);
+}

- pte = pte_offset_kernel(pmd, address);
+int kaiser_add_user_map(const void *__start_addr, unsigned long size,
+ unsigned long flags)
+{
+ int ret = 0;
+ pte_t *pte;
+ unsigned long start_addr = (unsigned long )__start_addr;
+ unsigned long address = start_addr & PAGE_MASK;
+ unsigned long end_addr = PAGE_ALIGN(start_addr + size);
+ unsigned long target_address;
+
+ for (;address < end_addr; address += PAGE_SIZE) {
+ target_address = get_pa_from_mapping(address);
+ if (target_address == -1) {
+ ret = -EIO;
+ break;
+ }
+ pte = kaiser_pagetable_walk(address, false);
if (pte_none(*pte)) {
set_pte(pte, __pte(flags | target_address));
} else {
- BUG_ON(__pa(pte_page(*pte)) != target_address);
+ pte_t tmp;
+ set_pte(&tmp, __pte(flags | target_address));
+ WARN_ON_ONCE(!pte_same(*pte, tmp));
}
}
+ return ret;
}

-// at first, add a pmd for every pgd entry in the shadowmem-kernel-part of the kernel mapping
-static inline void __init _kaiser_init(void)
+static int kaiser_add_user_map_ptrs(const void *start, const void *end, unsigned long flags)
+{
+ unsigned long size = end - start;
+
+ return kaiser_add_user_map(start, size, flags);
+}
+
+/*
+ * Ensure that the top level of the (shadow) page tables are
+ * entirely populated. This ensures that all processes that get
+ * forked have the same entries. This way, we do not have to
+ * ever go set up new entries in older processes.
+ *
+ * Note: we never free these, so there are no updates to them
+ * after this.
+ */
+static void __init kaiser_init_all_pgds(void)
{
pgd_t *pgd;
int i = 0;

pgd = native_get_shadow_pgd(pgd_offset_k((unsigned long )0));
for (i = PTRS_PER_PGD / 2; i < PTRS_PER_PGD; i++) {
- set_pgd(pgd + i, __pgd(_PAGE_TABLE |__pa(pud_alloc_one(0, 0))));
+ pgd_t new_pgd;
+ pud_t *pud = pud_alloc_one(&init_mm, PAGE_OFFSET + i * PGDIR_SIZE);
+ if (!pud) {
+ WARN_ON(1);
+ break;
+ }
+ new_pgd = __pgd(_KERNPG_TABLE |__pa(pud));
+ /*
+ * Make sure not to stomp on some other pgd entry.
+ */
+ if (!pgd_none(pgd[i])) {
+ WARN_ON(1);
+ continue;
+ }
+ set_pgd(pgd + i, new_pgd);
}
}

+#define kaiser_add_user_map_early(start, size, flags) do { \
+ int __ret = kaiser_add_user_map(start, size, flags); \
+ WARN_ON(__ret); \
+} while (0)
+
+#define kaiser_add_user_map_ptrs_early(start, end, flags) do { \
+ int __ret = kaiser_add_user_map_ptrs(start, end, flags); \
+ WARN_ON(__ret); \
+} while (0)
+
extern char __per_cpu_user_mapped_start[], __per_cpu_user_mapped_end[];
-spinlock_t shadow_table_lock;
+/*
+ * If anything in here fails, we will likely die on one of the
+ * first kernel->user transitions and init will die. But, we
+ * will have most of the kernel up by then and should be able to
+ * get a clean warning out of it. If we BUG_ON() here, we run
+ * the risk of being before we have good console output.
+ */
void __init kaiser_init(void)
{
int cpu;
- spin_lock_init(&shadow_table_lock);
-
- spin_lock(&shadow_table_lock);

- _kaiser_init();
+ kaiser_init_all_pgds();

for_each_possible_cpu(cpu) {
- // map the per cpu user variables
- _kaiser_copy(
- (unsigned long) (__per_cpu_user_mapped_start + per_cpu_offset(cpu)),
- (unsigned long) __per_cpu_user_mapped_end - (unsigned long) __per_cpu_user_mapped_start,
- __PAGE_KERNEL);
- }
-
- // map the entry/exit text section, which is responsible to switch between user- and kernel mode
- _kaiser_copy(
- (unsigned long) __entry_text_start,
- (unsigned long) __entry_text_end - (unsigned long) __entry_text_start,
- __PAGE_KERNEL_RX);
-
- // the fixed map address of the idt_table
- _kaiser_copy(
- (unsigned long) idt_descr.address,
- sizeof(gate_desc) * NR_VECTORS,
- __PAGE_KERNEL_RO);
+ void *percpu_vaddr = __per_cpu_user_mapped_start +
+ per_cpu_offset(cpu);
+ unsigned long percpu_sz = __per_cpu_user_mapped_end -
+ __per_cpu_user_mapped_start;
+ kaiser_add_user_map_early(percpu_vaddr, percpu_sz,
+ __PAGE_KERNEL);
+ }

- spin_unlock(&shadow_table_lock);
+ /*
+ * Map the entry/exit text section, which is needed at
+ * switches from user to and from kernel.
+ */
+ kaiser_add_user_map_ptrs_early(__entry_text_start, __entry_text_end,
+ __PAGE_KERNEL_RX);
+
+#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
+ kaiser_add_user_map_ptrs_early(__irqentry_text_start,
+ __irqentry_text_end,
+ __PAGE_KERNEL_RX);
+#endif
+ kaiser_add_user_map_early((void *)idt_descr.address,
+ sizeof(gate_desc) * NR_VECTORS,
+ __PAGE_KERNEL_RO);
+#ifdef CONFIG_TRACING
+ kaiser_add_user_map_early(&trace_idt_descr,
+ sizeof(trace_idt_descr),
+ __PAGE_KERNEL);
+ kaiser_add_user_map_early(&trace_idt_table,
+ sizeof(gate_desc) * NR_VECTORS,
+ __PAGE_KERNEL);
+#endif
+ kaiser_add_user_map_early(&debug_idt_descr, sizeof(debug_idt_descr),
+ __PAGE_KERNEL);
+ kaiser_add_user_map_early(&debug_idt_table,
+ sizeof(gate_desc) * NR_VECTORS,
+ __PAGE_KERNEL);
}

+extern void unmap_pud_range_nofree(pgd_t *pgd, unsigned long start, unsigned long end);
// add a mapping to the shadow-mapping, and synchronize the mappings
-void kaiser_add_mapping(unsigned long addr, unsigned long size, unsigned long flags)
+int kaiser_add_mapping(unsigned long addr, unsigned long size, unsigned long flags)
{
- spin_lock(&shadow_table_lock);
- _kaiser_copy(addr, size, flags);
- spin_unlock(&shadow_table_lock);
+ return kaiser_add_user_map((const void *)addr, size, flags);
}

-extern void unmap_pud_range(pgd_t *pgd, unsigned long start, unsigned long end);
void kaiser_remove_mapping(unsigned long start, unsigned long size)
{
- pgd_t *pgd = native_get_shadow_pgd(pgd_offset_k(start));
- spin_lock(&shadow_table_lock);
- do {
- unmap_pud_range(pgd, start, start + size);
- } while (pgd++ != native_get_shadow_pgd(pgd_offset_k(start + size)));
- spin_unlock(&shadow_table_lock);
+ unsigned long end = start + size;
+ unsigned long addr;
+
+ for (addr = start; addr < end; addr += PGDIR_SIZE) {
+ pgd_t *pgd = native_get_shadow_pgd(pgd_offset_k(addr));
+ /*
+ * unmap_p4d_range() handles > P4D_SIZE unmaps,
+ * so no need to trim 'end'.
+ */
+ unmap_pud_range_nofree(pgd, addr, end);
+ }
}
#endif /* CONFIG_KAISER */
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -52,6 +52,7 @@ static DEFINE_SPINLOCK(cpa_lock);
#define CPA_FLUSHTLB 1
#define CPA_ARRAY 2
#define CPA_PAGES_ARRAY 4
+#define CPA_FREE_PAGETABLES 8

#ifdef CONFIG_PROC_FS
static unsigned long direct_pages_count[PG_LEVEL_NUM];
@@ -723,10 +724,13 @@ static int split_large_page(struct cpa_d
return 0;
}

-static bool try_to_free_pte_page(pte_t *pte)
+static bool try_to_free_pte_page(struct cpa_data *cpa, pte_t *pte)
{
int i;

+ if (!(cpa->flags & CPA_FREE_PAGETABLES))
+ return false;
+
for (i = 0; i < PTRS_PER_PTE; i++)
if (!pte_none(pte[i]))
return false;
@@ -735,10 +739,13 @@ static bool try_to_free_pte_page(pte_t *
return true;
}

-static bool try_to_free_pmd_page(pmd_t *pmd)
+static bool try_to_free_pmd_page(struct cpa_data *cpa, pmd_t *pmd)
{
int i;

+ if (!(cpa->flags & CPA_FREE_PAGETABLES))
+ return false;
+
for (i = 0; i < PTRS_PER_PMD; i++)
if (!pmd_none(pmd[i]))
return false;
@@ -759,7 +766,9 @@ static bool try_to_free_pud_page(pud_t *
return true;
}

-static bool unmap_pte_range(pmd_t *pmd, unsigned long start, unsigned long end)
+static bool unmap_pte_range(struct cpa_data *cpa, pmd_t *pmd,
+ unsigned long start,
+ unsigned long end)
{
pte_t *pte = pte_offset_kernel(pmd, start);

@@ -770,22 +779,23 @@ static bool unmap_pte_range(pmd_t *pmd,
pte++;
}

- if (try_to_free_pte_page((pte_t *)pmd_page_vaddr(*pmd))) {
+ if (try_to_free_pte_page(cpa, (pte_t *)pmd_page_vaddr(*pmd))) {
pmd_clear(pmd);
return true;
}
return false;
}

-static void __unmap_pmd_range(pud_t *pud, pmd_t *pmd,
+static void __unmap_pmd_range(struct cpa_data *cpa, pud_t *pud, pmd_t *pmd,
unsigned long start, unsigned long end)
{
- if (unmap_pte_range(pmd, start, end))
- if (try_to_free_pmd_page((pmd_t *)pud_page_vaddr(*pud)))
+ if (unmap_pte_range(cpa, pmd, start, end))
+ if (try_to_free_pmd_page(cpa, (pmd_t *)pud_page_vaddr(*pud)))
pud_clear(pud);
}

-static void unmap_pmd_range(pud_t *pud, unsigned long start, unsigned long end)
+static void unmap_pmd_range(struct cpa_data *cpa, pud_t *pud,
+ unsigned long start, unsigned long end)
{
pmd_t *pmd = pmd_offset(pud, start);

@@ -796,7 +806,7 @@ static void unmap_pmd_range(pud_t *pud,
unsigned long next_page = (start + PMD_SIZE) & PMD_MASK;
unsigned long pre_end = min_t(unsigned long, end, next_page);

- __unmap_pmd_range(pud, pmd, start, pre_end);
+ __unmap_pmd_range(cpa, pud, pmd, start, pre_end);

start = pre_end;
pmd++;
@@ -809,7 +819,8 @@ static void unmap_pmd_range(pud_t *pud,
if (pmd_large(*pmd))
pmd_clear(pmd);
else
- __unmap_pmd_range(pud, pmd, start, start + PMD_SIZE);
+ __unmap_pmd_range(cpa, pud, pmd,
+ start, start + PMD_SIZE);

start += PMD_SIZE;
pmd++;
@@ -819,17 +830,19 @@ static void unmap_pmd_range(pud_t *pud,
* 4K leftovers?
*/
if (start < end)
- return __unmap_pmd_range(pud, pmd, start, end);
+ return __unmap_pmd_range(cpa, pud, pmd, start, end);

/*
* Try again to free the PMD page if haven't succeeded above.
*/
if (!pud_none(*pud))
- if (try_to_free_pmd_page((pmd_t *)pud_page_vaddr(*pud)))
+ if (try_to_free_pmd_page(cpa, (pmd_t *)pud_page_vaddr(*pud)))
pud_clear(pud);
}

-void unmap_pud_range(pgd_t *pgd, unsigned long start, unsigned long end)
+static void __unmap_pud_range(struct cpa_data *cpa, pgd_t *pgd,
+ unsigned long start,
+ unsigned long end)
{
pud_t *pud = pud_offset(pgd, start);

@@ -840,7 +853,7 @@ void unmap_pud_range(pgd_t *pgd, unsigne
unsigned long next_page = (start + PUD_SIZE) & PUD_MASK;
unsigned long pre_end = min_t(unsigned long, end, next_page);

- unmap_pmd_range(pud, start, pre_end);
+ unmap_pmd_range(cpa, pud, start, pre_end);

start = pre_end;
pud++;
@@ -854,7 +867,7 @@ void unmap_pud_range(pgd_t *pgd, unsigne
if (pud_large(*pud))
pud_clear(pud);
else
- unmap_pmd_range(pud, start, start + PUD_SIZE);
+ unmap_pmd_range(cpa, pud, start, start + PUD_SIZE);

start += PUD_SIZE;
pud++;
@@ -864,7 +877,7 @@ void unmap_pud_range(pgd_t *pgd, unsigne
* 2M leftovers?
*/
if (start < end)
- unmap_pmd_range(pud, start, end);
+ unmap_pmd_range(cpa, pud, start, end);

/*
* No need to try to free the PUD page because we'll free it in
@@ -872,6 +885,24 @@ void unmap_pud_range(pgd_t *pgd, unsigne
*/
}

+static void unmap_pud_range(pgd_t *pgd, unsigned long start, unsigned long end)
+{
+ struct cpa_data cpa = {
+ .flags = CPA_FREE_PAGETABLES,
+ };
+
+ __unmap_pud_range(&cpa, pgd, start, end);
+}
+
+void unmap_pud_range_nofree(pgd_t *pgd, unsigned long start, unsigned long end)
+{
+ struct cpa_data cpa = {
+ .flags = 0,
+ };
+
+ __unmap_pud_range(&cpa, pgd, start, end);
+}
+
static void unmap_pgd_range(pgd_t *root, unsigned long addr, unsigned long end)
{
pgd_t *pgd_entry = root + pgd_index(addr);
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -340,40 +340,26 @@ static inline void _pgd_free(pgd_t *pgd)
kmem_cache_free(pgd_cache, pgd);
}
#else
-static inline pgd_t *_pgd_alloc(void)
-{
-#ifdef CONFIG_KAISER
- // Instead of one PML4, we aquire two PML4s and, thus, an 8kb-aligned memory
- // block. Therefore, we have to allocate at least 3 pages. However, the
- // __get_free_pages returns us 4 pages. Hence, we store the base pointer at
- // the beginning of the page of our 8kb-aligned memory block in order to
- // correctly free it afterwars.

- unsigned long pages = __get_free_pages(PGALLOC_GFP, get_order(4*PAGE_SIZE));
-
- if(native_get_normal_pgd((pgd_t*) pages) == (pgd_t*) pages)
- {
- *((unsigned long*)(pages + 2 * PAGE_SIZE)) = pages;
- return (pgd_t *) pages;
- }
- else
- {
- *((unsigned long*)(pages + 3 * PAGE_SIZE)) = pages;
- return (pgd_t *) (pages + PAGE_SIZE);
- }
+#ifdef CONFIG_KAISER
+/*
+ * Instead of one pmd, we aquire two pmds. Being order-1, it is
+ * both 8k in size and 8k-aligned. That lets us just flip bit 12
+ * in a pointer to swap between the two 4k halves.
+ */
+#define PGD_ALLOCATION_ORDER 1
#else
- return (pgd_t *)__get_free_page(PGALLOC_GFP);
+#define PGD_ALLOCATION_ORDER 0
#endif
+
+static inline pgd_t *_pgd_alloc(void)
+{
+ return (pgd_t *)__get_free_pages(PGALLOC_GFP, PGD_ALLOCATION_ORDER);
}

static inline void _pgd_free(pgd_t *pgd)
{
-#ifdef CONFIG_KAISER
- unsigned long pages = *((unsigned long*) ((char*) pgd + 2 * PAGE_SIZE));
- free_pages(pages, get_order(4*PAGE_SIZE));
-#else
- free_page((unsigned long)pgd);
-#endif
+ free_pages((unsigned long)pgd, PGD_ALLOCATION_ORDER);
}
#endif /* CONFIG_X86_PAE */

--- /dev/null
+++ b/include/linux/kaiser.h
@@ -0,0 +1,26 @@
+#ifndef _INCLUDE_KAISER_H
+#define _INCLUDE_KAISER_H
+
+#ifdef CONFIG_KAISER
+#include <asm/kaiser.h>
+#else
+
+/*
+ * These stubs are used whenever CONFIG_KAISER is off, which
+ * includes architectures that support KAISER, but have it
+ * disabled.
+ */
+
+static inline void kaiser_init(void)
+{
+}
+static inline void kaiser_remove_mapping(unsigned long start, unsigned long size)
+{
+}
+static inline int kaiser_add_mapping(unsigned long addr, unsigned long size, unsigned long flags)
+{
+ return 0;
+}
+
+#endif /* !CONFIG_KAISER */
+#endif /* _INCLUDE_KAISER_H */
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -58,6 +58,7 @@
#include <linux/tsacct_kern.h>
#include <linux/cn_proc.h>
#include <linux/freezer.h>
+#include <linux/kaiser.h>
#include <linux/delayacct.h>
#include <linux/taskstats_kern.h>
#include <linux/random.h>
@@ -335,7 +336,6 @@ void set_task_stack_end_magic(struct tas
*stackend = STACK_END_MAGIC; /* for overflow detection */
}

-extern void kaiser_add_mapping(unsigned long addr, unsigned long size, unsigned long flags);
static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
{
struct task_struct *tsk;
@@ -357,9 +357,10 @@ static struct task_struct *dup_task_stru
goto free_ti;

tsk->stack = ti;
-#ifdef CONFIG_KAISER
- kaiser_add_mapping((unsigned long)tsk->stack, THREAD_SIZE, __PAGE_KERNEL);
-#endif
+
+ err= kaiser_add_mapping((unsigned long)tsk->stack, THREAD_SIZE, __PAGE_KERNEL);
+ if (err)
+ goto free_ti;
#ifdef CONFIG_SECCOMP
/*
* We must handle setting up seccomp filters once we're under
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -32,12 +32,17 @@ config SECURITY
If you are unsure how to answer this question, answer N.
config KAISER
bool "Remove the kernel mapping in user mode"
+ default y
depends on X86_64
depends on !PARAVIRT
help
This enforces a strict kernel and user space isolation in order to close
hardware side channels on kernel address information.

+config KAISER_REAL_SWITCH
+ bool "KAISER: actually switch page tables"
+ default y
+
config SECURITYFS
bool "Enable the securityfs filesystem"
help

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