Merge branch 'devel-stable' into for-next

This commit is contained in:
Russell King 2014-12-05 16:30:54 +00:00
commit e9f2d6d660
15 changed files with 394 additions and 57 deletions

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@ -41,7 +41,7 @@ fffe8000 fffeffff DTCM mapping area for platforms with
fffe0000 fffe7fff ITCM mapping area for platforms with
ITCM mounted inside the CPU.
ffc00000 ffdfffff Fixmap mapping region. Addresses provided
ffc00000 ffefffff Fixmap mapping region. Addresses provided
by fix_to_virt() will be located here.
fee00000 feffffff Mapping of PCI I/O space. This is a static

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@ -487,6 +487,16 @@ int set_memory_rw(unsigned long addr, int numpages);
int set_memory_x(unsigned long addr, int numpages);
int set_memory_nx(unsigned long addr, int numpages);
#ifdef CONFIG_DEBUG_RODATA
void mark_rodata_ro(void);
void set_kernel_text_rw(void);
void set_kernel_text_ro(void);
#else
static inline void set_kernel_text_rw(void) { }
static inline void set_kernel_text_ro(void) { }
#endif
void flush_uprobe_xol_access(struct page *page, unsigned long uaddr,
void *kaddr, unsigned long len);
#endif

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@ -2,27 +2,24 @@
#define _ASM_FIXMAP_H
#define FIXADDR_START 0xffc00000UL
#define FIXADDR_TOP 0xffe00000UL
#define FIXADDR_SIZE (FIXADDR_TOP - FIXADDR_START)
#define FIXADDR_END 0xfff00000UL
#define FIXADDR_TOP (FIXADDR_END - PAGE_SIZE)
#define FIX_KMAP_NR_PTES (FIXADDR_SIZE >> PAGE_SHIFT)
#include <asm/kmap_types.h>
#define __fix_to_virt(x) (FIXADDR_START + ((x) << PAGE_SHIFT))
#define __virt_to_fix(x) (((x) - FIXADDR_START) >> PAGE_SHIFT)
enum fixed_addresses {
FIX_KMAP_BEGIN,
FIX_KMAP_END = FIX_KMAP_BEGIN + (KM_TYPE_NR * NR_CPUS) - 1,
extern void __this_fixmap_does_not_exist(void);
/* Support writing RO kernel text via kprobes, jump labels, etc. */
FIX_TEXT_POKE0,
FIX_TEXT_POKE1,
static inline unsigned long fix_to_virt(const unsigned int idx)
{
if (idx >= FIX_KMAP_NR_PTES)
__this_fixmap_does_not_exist();
return __fix_to_virt(idx);
}
__end_of_fixed_addresses
};
static inline unsigned int virt_to_fix(const unsigned long vaddr)
{
BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
return __virt_to_fix(vaddr);
}
void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot);
#include <asm-generic/fixmap.h>
#endif

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@ -68,7 +68,7 @@ test-kprobes-objs += kprobes-test-arm.o
endif
obj-$(CONFIG_OABI_COMPAT) += sys_oabi-compat.o
obj-$(CONFIG_ARM_THUMBEE) += thumbee.o
obj-$(CONFIG_KGDB) += kgdb.o
obj-$(CONFIG_KGDB) += kgdb.o patch.o
obj-$(CONFIG_ARM_UNWIND) += unwind.o
obj-$(CONFIG_HAVE_TCM) += tcm.o
obj-$(CONFIG_OF) += devtree.o

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@ -15,6 +15,7 @@
#include <linux/ftrace.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/stop_machine.h>
#include <asm/cacheflush.h>
#include <asm/opcodes.h>
@ -35,6 +36,22 @@
#define OLD_NOP 0xe1a00000 /* mov r0, r0 */
static int __ftrace_modify_code(void *data)
{
int *command = data;
set_kernel_text_rw();
ftrace_modify_all_code(*command);
set_kernel_text_ro();
return 0;
}
void arch_ftrace_update_code(int command)
{
stop_machine(__ftrace_modify_code, &command, NULL);
}
static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
{
return rec->arch.old_mcount ? OLD_NOP : NOP;
@ -73,6 +90,8 @@ int ftrace_arch_code_modify_prepare(void)
int ftrace_arch_code_modify_post_process(void)
{
set_all_modules_text_ro();
/* Make sure any TLB misses during machine stop are cleared. */
flush_tlb_all();
return 0;
}

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@ -19,7 +19,7 @@ static void __arch_jump_label_transform(struct jump_entry *entry,
insn = arm_gen_nop();
if (is_static)
__patch_text(addr, insn);
__patch_text_early(addr, insn);
else
patch_text(addr, insn);
}

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@ -12,8 +12,12 @@
#include <linux/irq.h>
#include <linux/kdebug.h>
#include <linux/kgdb.h>
#include <linux/uaccess.h>
#include <asm/traps.h>
#include "patch.h"
struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] =
{
{ "r0", 4, offsetof(struct pt_regs, ARM_r0)},
@ -244,6 +248,31 @@ void kgdb_arch_exit(void)
unregister_die_notifier(&kgdb_notifier);
}
int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
{
int err;
/* patch_text() only supports int-sized breakpoints */
BUILD_BUG_ON(sizeof(int) != BREAK_INSTR_SIZE);
err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
BREAK_INSTR_SIZE);
if (err)
return err;
patch_text((void *)bpt->bpt_addr,
*(unsigned int *)arch_kgdb_ops.gdb_bpt_instr);
return err;
}
int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
{
patch_text((void *)bpt->bpt_addr, *(unsigned int *)bpt->saved_instr);
return 0;
}
/*
* Register our undef instruction hooks with ARM undef core.
* We regsiter a hook specifically looking for the KGB break inst

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@ -29,6 +29,7 @@ extern unsigned long kexec_boot_atags;
static atomic_t waiting_for_crash_ipi;
static unsigned long dt_mem;
/*
* Provide a dummy crash_notes definition while crash dump arrives to arm.
* This prevents breakage of crash_notes attribute in kernel/ksysfs.c.
@ -64,7 +65,7 @@ int machine_kexec_prepare(struct kimage *image)
return err;
if (be32_to_cpu(header) == OF_DT_HEADER)
kexec_boot_atags = current_segment->mem;
dt_mem = current_segment->mem;
}
return 0;
}
@ -163,12 +164,12 @@ void machine_kexec(struct kimage *image)
reboot_code_buffer = page_address(image->control_code_page);
/* Prepare parameters for reboot_code_buffer*/
set_kernel_text_rw();
kexec_start_address = image->start;
kexec_indirection_page = page_list;
kexec_mach_type = machine_arch_type;
if (!kexec_boot_atags)
kexec_boot_atags = image->start - KEXEC_ARM_ZIMAGE_OFFSET + KEXEC_ARM_ATAGS_OFFSET;
kexec_boot_atags = dt_mem ?: image->start - KEXEC_ARM_ZIMAGE_OFFSET
+ KEXEC_ARM_ATAGS_OFFSET;
/* copy our kernel relocation code to the control code page */
reboot_entry = fncpy(reboot_code_buffer,

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@ -1,8 +1,11 @@
#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/kprobes.h>
#include <linux/mm.h>
#include <linux/stop_machine.h>
#include <asm/cacheflush.h>
#include <asm/fixmap.h>
#include <asm/smp_plat.h>
#include <asm/opcodes.h>
@ -13,21 +16,77 @@ struct patch {
unsigned int insn;
};
void __kprobes __patch_text(void *addr, unsigned int insn)
static DEFINE_SPINLOCK(patch_lock);
static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
__acquires(&patch_lock)
{
unsigned int uintaddr = (uintptr_t) addr;
bool module = !core_kernel_text(uintaddr);
struct page *page;
if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))
page = vmalloc_to_page(addr);
else if (!module && IS_ENABLED(CONFIG_DEBUG_RODATA))
page = virt_to_page(addr);
else
return addr;
if (flags)
spin_lock_irqsave(&patch_lock, *flags);
else
__acquire(&patch_lock);
set_fixmap(fixmap, page_to_phys(page));
return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
}
static void __kprobes patch_unmap(int fixmap, unsigned long *flags)
__releases(&patch_lock)
{
clear_fixmap(fixmap);
if (flags)
spin_unlock_irqrestore(&patch_lock, *flags);
else
__release(&patch_lock);
}
void __kprobes __patch_text_real(void *addr, unsigned int insn, bool remap)
{
bool thumb2 = IS_ENABLED(CONFIG_THUMB2_KERNEL);
unsigned int uintaddr = (uintptr_t) addr;
bool twopage = false;
unsigned long flags;
void *waddr = addr;
int size;
if (remap)
waddr = patch_map(addr, FIX_TEXT_POKE0, &flags);
else
__acquire(&patch_lock);
if (thumb2 && __opcode_is_thumb16(insn)) {
*(u16 *)addr = __opcode_to_mem_thumb16(insn);
*(u16 *)waddr = __opcode_to_mem_thumb16(insn);
size = sizeof(u16);
} else if (thumb2 && ((uintptr_t)addr & 2)) {
} else if (thumb2 && (uintaddr & 2)) {
u16 first = __opcode_thumb32_first(insn);
u16 second = __opcode_thumb32_second(insn);
u16 *addrh = addr;
u16 *addrh0 = waddr;
u16 *addrh1 = waddr + 2;
addrh[0] = __opcode_to_mem_thumb16(first);
addrh[1] = __opcode_to_mem_thumb16(second);
twopage = (uintaddr & ~PAGE_MASK) == PAGE_SIZE - 2;
if (twopage && remap)
addrh1 = patch_map(addr + 2, FIX_TEXT_POKE1, NULL);
*addrh0 = __opcode_to_mem_thumb16(first);
*addrh1 = __opcode_to_mem_thumb16(second);
if (twopage && addrh1 != addr + 2) {
flush_kernel_vmap_range(addrh1, 2);
patch_unmap(FIX_TEXT_POKE1, NULL);
}
size = sizeof(u32);
} else {
@ -36,10 +95,16 @@ void __kprobes __patch_text(void *addr, unsigned int insn)
else
insn = __opcode_to_mem_arm(insn);
*(u32 *)addr = insn;
*(u32 *)waddr = insn;
size = sizeof(u32);
}
if (waddr != addr) {
flush_kernel_vmap_range(waddr, twopage ? size / 2 : size);
patch_unmap(FIX_TEXT_POKE0, &flags);
} else
__release(&patch_lock);
flush_icache_range((uintptr_t)(addr),
(uintptr_t)(addr) + size);
}
@ -60,16 +125,5 @@ void __kprobes patch_text(void *addr, unsigned int insn)
.insn = insn,
};
if (cache_ops_need_broadcast()) {
stop_machine(patch_text_stop_machine, &patch, cpu_online_mask);
} else {
bool straddles_word = IS_ENABLED(CONFIG_THUMB2_KERNEL)
&& __opcode_is_thumb32(insn)
&& ((uintptr_t)addr & 2);
if (straddles_word)
stop_machine(patch_text_stop_machine, &patch, NULL);
else
__patch_text(addr, insn);
}
stop_machine(patch_text_stop_machine, &patch, NULL);
}

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@ -2,6 +2,16 @@
#define _ARM_KERNEL_PATCH_H
void patch_text(void *addr, unsigned int insn);
void __patch_text(void *addr, unsigned int insn);
void __patch_text_real(void *addr, unsigned int insn, bool remap);
static inline void __patch_text(void *addr, unsigned int insn)
{
__patch_text_real(addr, insn, true);
}
static inline void __patch_text_early(void *addr, unsigned int insn)
{
__patch_text_real(addr, insn, false);
}
#endif

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@ -8,6 +8,9 @@
#include <asm/thread_info.h>
#include <asm/memory.h>
#include <asm/page.h>
#ifdef CONFIG_ARM_KERNMEM_PERMS
#include <asm/pgtable.h>
#endif
#define PROC_INFO \
. = ALIGN(4); \
@ -90,6 +93,11 @@ SECTIONS
_text = .;
HEAD_TEXT
}
#ifdef CONFIG_ARM_KERNMEM_PERMS
. = ALIGN(1<<SECTION_SHIFT);
#endif
.text : { /* Real text segment */
_stext = .; /* Text and read-only data */
__exception_text_start = .;
@ -112,6 +120,9 @@ SECTIONS
ARM_CPU_KEEP(PROC_INFO)
}
#ifdef CONFIG_DEBUG_RODATA
. = ALIGN(1<<SECTION_SHIFT);
#endif
RO_DATA(PAGE_SIZE)
. = ALIGN(4);
@ -145,7 +156,11 @@ SECTIONS
_etext = .; /* End of text and rodata section */
#ifndef CONFIG_XIP_KERNEL
# ifdef CONFIG_ARM_KERNMEM_PERMS
. = ALIGN(1<<SECTION_SHIFT);
# else
. = ALIGN(PAGE_SIZE);
# endif
__init_begin = .;
#endif
/*
@ -218,8 +233,12 @@ SECTIONS
#ifdef CONFIG_XIP_KERNEL
__data_loc = ALIGN(4); /* location in binary */
. = PAGE_OFFSET + TEXT_OFFSET;
#else
#ifdef CONFIG_ARM_KERNMEM_PERMS
. = ALIGN(1<<SECTION_SHIFT);
#else
. = ALIGN(THREAD_SIZE);
#endif
__init_end = .;
__data_loc = .;
#endif

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@ -1009,3 +1009,24 @@ config ARCH_SUPPORTS_BIG_ENDIAN
help
This option specifies the architecture can support big endian
operation.
config ARM_KERNMEM_PERMS
bool "Restrict kernel memory permissions"
help
If this is set, kernel memory other than kernel text (and rodata)
will be made non-executable. The tradeoff is that each region is
padded to section-size (1MiB) boundaries (because their permissions
are different and splitting the 1M pages into 4K ones causes TLB
performance problems), wasting memory.
config DEBUG_RODATA
bool "Make kernel text and rodata read-only"
depends on ARM_KERNMEM_PERMS
default y
help
If this is set, kernel text and rodata will be made read-only. This
is to help catch accidental or malicious attempts to change the
kernel's executable code. Additionally splits rodata from kernel
text so it can be made explicitly non-executable. This creates
another section-size padded region, so it can waste more memory
space while gaining the read-only protections.

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@ -18,19 +18,20 @@
#include <asm/tlbflush.h>
#include "mm.h"
pte_t *fixmap_page_table;
static inline void set_fixmap_pte(int idx, pte_t pte)
{
unsigned long vaddr = __fix_to_virt(idx);
set_pte_ext(fixmap_page_table + idx, pte, 0);
pte_t *ptep = pte_offset_kernel(pmd_off_k(vaddr), vaddr);
set_pte_ext(ptep, pte, 0);
local_flush_tlb_kernel_page(vaddr);
}
static inline pte_t get_fixmap_pte(unsigned long vaddr)
{
unsigned long idx = __virt_to_fix(vaddr);
return *(fixmap_page_table + idx);
pte_t *ptep = pte_offset_kernel(pmd_off_k(vaddr), vaddr);
return *ptep;
}
void *kmap(struct page *page)
@ -84,7 +85,7 @@ void *kmap_atomic(struct page *page)
* With debugging enabled, kunmap_atomic forces that entry to 0.
* Make sure it was indeed properly unmapped.
*/
BUG_ON(!pte_none(*(fixmap_page_table + idx)));
BUG_ON(!pte_none(get_fixmap_pte(vaddr)));
#endif
/*
* When debugging is off, kunmap_atomic leaves the previous mapping
@ -137,7 +138,7 @@ void *kmap_atomic_pfn(unsigned long pfn)
idx = type + KM_TYPE_NR * smp_processor_id();
vaddr = __fix_to_virt(idx);
#ifdef CONFIG_DEBUG_HIGHMEM
BUG_ON(!pte_none(*(fixmap_page_table + idx)));
BUG_ON(!pte_none(get_fixmap_pte(vaddr)));
#endif
set_fixmap_pte(idx, pfn_pte(pfn, kmap_prot));

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@ -29,6 +29,7 @@
#include <asm/prom.h>
#include <asm/sections.h>
#include <asm/setup.h>
#include <asm/system_info.h>
#include <asm/tlb.h>
#include <asm/fixmap.h>
@ -570,7 +571,7 @@ void __init mem_init(void)
MLK(DTCM_OFFSET, (unsigned long) dtcm_end),
MLK(ITCM_OFFSET, (unsigned long) itcm_end),
#endif
MLK(FIXADDR_START, FIXADDR_TOP),
MLK(FIXADDR_START, FIXADDR_END),
MLM(VMALLOC_START, VMALLOC_END),
MLM(PAGE_OFFSET, (unsigned long)high_memory),
#ifdef CONFIG_HIGHMEM
@ -615,7 +616,145 @@ void __init mem_init(void)
}
}
void free_initmem(void)
#ifdef CONFIG_ARM_KERNMEM_PERMS
struct section_perm {
unsigned long start;
unsigned long end;
pmdval_t mask;
pmdval_t prot;
pmdval_t clear;
};
static struct section_perm nx_perms[] = {
/* Make pages tables, etc before _stext RW (set NX). */
{
.start = PAGE_OFFSET,
.end = (unsigned long)_stext,
.mask = ~PMD_SECT_XN,
.prot = PMD_SECT_XN,
},
/* Make init RW (set NX). */
{
.start = (unsigned long)__init_begin,
.end = (unsigned long)_sdata,
.mask = ~PMD_SECT_XN,
.prot = PMD_SECT_XN,
},
#ifdef CONFIG_DEBUG_RODATA
/* Make rodata NX (set RO in ro_perms below). */
{
.start = (unsigned long)__start_rodata,
.end = (unsigned long)__init_begin,
.mask = ~PMD_SECT_XN,
.prot = PMD_SECT_XN,
},
#endif
};
#ifdef CONFIG_DEBUG_RODATA
static struct section_perm ro_perms[] = {
/* Make kernel code and rodata RX (set RO). */
{
.start = (unsigned long)_stext,
.end = (unsigned long)__init_begin,
#ifdef CONFIG_ARM_LPAE
.mask = ~PMD_SECT_RDONLY,
.prot = PMD_SECT_RDONLY,
#else
.mask = ~(PMD_SECT_APX | PMD_SECT_AP_WRITE),
.prot = PMD_SECT_APX | PMD_SECT_AP_WRITE,
.clear = PMD_SECT_AP_WRITE,
#endif
},
};
#endif
/*
* Updates section permissions only for the current mm (sections are
* copied into each mm). During startup, this is the init_mm. Is only
* safe to be called with preemption disabled, as under stop_machine().
*/
static inline void section_update(unsigned long addr, pmdval_t mask,
pmdval_t prot)
{
struct mm_struct *mm;
pmd_t *pmd;
mm = current->active_mm;
pmd = pmd_offset(pud_offset(pgd_offset(mm, addr), addr), addr);
#ifdef CONFIG_ARM_LPAE
pmd[0] = __pmd((pmd_val(pmd[0]) & mask) | prot);
#else
if (addr & SECTION_SIZE)
pmd[1] = __pmd((pmd_val(pmd[1]) & mask) | prot);
else
pmd[0] = __pmd((pmd_val(pmd[0]) & mask) | prot);
#endif
flush_pmd_entry(pmd);
local_flush_tlb_kernel_range(addr, addr + SECTION_SIZE);
}
/* Make sure extended page tables are in use. */
static inline bool arch_has_strict_perms(void)
{
if (cpu_architecture() < CPU_ARCH_ARMv6)
return false;
return !!(get_cr() & CR_XP);
}
#define set_section_perms(perms, field) { \
size_t i; \
unsigned long addr; \
\
if (!arch_has_strict_perms()) \
return; \
\
for (i = 0; i < ARRAY_SIZE(perms); i++) { \
if (!IS_ALIGNED(perms[i].start, SECTION_SIZE) || \
!IS_ALIGNED(perms[i].end, SECTION_SIZE)) { \
pr_err("BUG: section %lx-%lx not aligned to %lx\n", \
perms[i].start, perms[i].end, \
SECTION_SIZE); \
continue; \
} \
\
for (addr = perms[i].start; \
addr < perms[i].end; \
addr += SECTION_SIZE) \
section_update(addr, perms[i].mask, \
perms[i].field); \
} \
}
static inline void fix_kernmem_perms(void)
{
set_section_perms(nx_perms, prot);
}
#ifdef CONFIG_DEBUG_RODATA
void mark_rodata_ro(void)
{
set_section_perms(ro_perms, prot);
}
void set_kernel_text_rw(void)
{
set_section_perms(ro_perms, clear);
}
void set_kernel_text_ro(void)
{
set_section_perms(ro_perms, prot);
}
#endif /* CONFIG_DEBUG_RODATA */
#else
static inline void fix_kernmem_perms(void) { }
#endif /* CONFIG_ARM_KERNMEM_PERMS */
void free_tcmmem(void)
{
#ifdef CONFIG_HAVE_TCM
extern char __tcm_start, __tcm_end;
@ -623,6 +762,12 @@ void free_initmem(void)
poison_init_mem(&__tcm_start, &__tcm_end - &__tcm_start);
free_reserved_area(&__tcm_start, &__tcm_end, -1, "TCM link");
#endif
}
void free_initmem(void)
{
fix_kernmem_perms();
free_tcmmem();
poison_init_mem(__init_begin, __init_end - __init_begin);
if (!machine_is_integrator() && !machine_is_cintegrator())

View File

@ -22,6 +22,7 @@
#include <asm/cputype.h>
#include <asm/sections.h>
#include <asm/cachetype.h>
#include <asm/fixmap.h>
#include <asm/sections.h>
#include <asm/setup.h>
#include <asm/smp_plat.h>
@ -356,6 +357,29 @@ const struct mem_type *get_mem_type(unsigned int type)
}
EXPORT_SYMBOL(get_mem_type);
/*
* To avoid TLB flush broadcasts, this uses local_flush_tlb_kernel_range().
* As a result, this can only be called with preemption disabled, as under
* stop_machine().
*/
void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
{
unsigned long vaddr = __fix_to_virt(idx);
pte_t *pte = pte_offset_kernel(pmd_off_k(vaddr), vaddr);
/* Make sure fixmap region does not exceed available allocation. */
BUILD_BUG_ON(FIXADDR_START + (__end_of_fixed_addresses * PAGE_SIZE) >
FIXADDR_END);
BUG_ON(idx >= __end_of_fixed_addresses);
if (pgprot_val(prot))
set_pte_at(NULL, vaddr, pte,
pfn_pte(phys >> PAGE_SHIFT, prot));
else
pte_clear(NULL, vaddr, pte);
local_flush_tlb_kernel_range(vaddr, vaddr + PAGE_SIZE);
}
/*
* Adjust the PMD section entries according to the CPU in use.
*/
@ -1296,10 +1320,10 @@ static void __init kmap_init(void)
#ifdef CONFIG_HIGHMEM
pkmap_page_table = early_pte_alloc(pmd_off_k(PKMAP_BASE),
PKMAP_BASE, _PAGE_KERNEL_TABLE);
fixmap_page_table = early_pte_alloc(pmd_off_k(FIXADDR_START),
FIXADDR_START, _PAGE_KERNEL_TABLE);
#endif
early_pte_alloc(pmd_off_k(FIXADDR_START), FIXADDR_START,
_PAGE_KERNEL_TABLE);
}
static void __init map_lowmem(void)
@ -1319,12 +1343,19 @@ static void __init map_lowmem(void)
if (start >= end)
break;
if (end < kernel_x_start || start >= kernel_x_end) {
if (end < kernel_x_start) {
map.pfn = __phys_to_pfn(start);
map.virtual = __phys_to_virt(start);
map.length = end - start;
map.type = MT_MEMORY_RWX;
create_mapping(&map);
} else if (start >= kernel_x_end) {
map.pfn = __phys_to_pfn(start);
map.virtual = __phys_to_virt(start);
map.length = end - start;
map.type = MT_MEMORY_RW;
create_mapping(&map);
} else {
/* This better cover the entire kernel */