/*
* Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp.
* <benh@kernel.crashing.org>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/slab.h>
#include <linux/user.h>
#include <linux/elf.h>
#include <linux/security.h>
#include <linux/bootmem.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/processor.h>
#include <asm/mmu.h>
#include <asm/mmu_context.h>
#include <asm/lmb.h>
#include <asm/machdep.h>
#include <asm/cputable.h>
#include <asm/sections.h>
#include <asm/firmware.h>
#include <asm/vdso.h>
#include <asm/vdso_datapage.h>
#include "setup.h"
#undef DEBUG
#ifdef DEBUG
#define DBG(fmt...) printk(fmt)
#else
#define DBG(fmt...)
#endif
/* Max supported size for symbol names */
#define MAX_SYMNAME 64
extern char vdso32_start, vdso32_end;
static void *vdso32_kbase = &vdso32_start;
unsigned int vdso32_pages;
unsigned long vdso32_sigtramp;
unsigned long vdso32_rt_sigtramp;
#ifdef CONFIG_PPC64
extern char vdso64_start, vdso64_end;
static void *vdso64_kbase = &vdso64_start;
unsigned int vdso64_pages;
unsigned long vdso64_rt_sigtramp;
#endif /* CONFIG_PPC64 */
/*
* The vdso data page (aka. systemcfg for old ppc64 fans) is here.
* Once the early boot kernel code no longer needs to muck around
* with it, it will become dynamically allocated
*/
static union {
struct vdso_data data;
u8 page[PAGE_SIZE];
} vdso_data_store __attribute__((__section__(".data.page_aligned")));
struct vdso_data *vdso_data = &vdso_data_store.data;
/* Format of the patch table */
struct vdso_patch_def
{
unsigned long ftr_mask, ftr_value;
const char *gen_name;
const char *fix_name;
};
/* Table of functions to patch based on the CPU type/revision
*
* Currently, we only change sync_dicache to do nothing on processors
* with a coherent icache
*/
static struct vdso_patch_def vdso_patches[] = {
{
CPU_FTR_COHERENT_ICACHE, CPU_FTR_COHERENT_ICACHE,
"__kernel_sync_dicache", "__kernel_sync_dicache_p5"
},
{
CPU_FTR_USE_TB, 0,
"__kernel_gettimeofday", NULL
},
};
/*
* Some infos carried around for each of them during parsing at
* boot time.
*/
struct lib32_elfinfo
{
Elf32_Ehdr *hdr; /* ptr to ELF */
Elf32_Sym *dynsym; /* ptr to .dynsym section */
unsigned long dynsymsize; /* size of .dynsym section */
char *dynstr; /* ptr to .dynstr section */
unsigned long text; /* offset of .text section in .so */
};
struct lib64_elfinfo
{
Elf64_Ehdr *hdr;
Elf64_Sym *dynsym;
unsigned long dynsymsize;
char *dynstr;
unsigned long text;
};
#ifdef __DEBUG
static void dump_one_vdso_page(struct page *pg, struct page *upg)
{
printk("kpg: %p (c:%d,f:%08lx)", __va(page_to_pfn(pg) << PAGE_SHIFT),
page_count(pg),
pg->flags);
if (upg/* && pg != upg*/) {
printk(" upg: %p (c:%d,f:%08lx)", __va(page_to_pfn(upg)
<< PAGE_SHIFT),
page_count(upg),
upg->flags);
}
printk("\n");
}
static void dump_vdso_pages(struct vm_area_struct * vma)
{
int i;
if (!vma || test_thread_flag(TIF_32BIT)) {
printk("vDSO32 @ %016lx:\n", (unsigned long)vdso32_kbase);
for (i=0; i<vdso32_pages; i++) {
struct page *pg = virt_to_page(vdso32_kbase +
i*PAGE_SIZE);
struct page *upg = (vma && vma->vm_mm) ?
follow_page(vma, vma->vm_start + i*PAGE_SIZE, 0)
: NULL;
dump_one_vdso_page(pg, upg);
}
}
if (!vma || !test_thread_flag(TIF_32BIT)) {
printk("vDSO64 @ %016lx:\n", (unsigned long)vdso64_kbase);
for (i=0; i<vdso64_pages; i++) {
struct page *pg = virt_to_page(vdso64_kbase +
i*PAGE_SIZE);
struct page *upg = (vma && vma->vm_mm) ?
follow_page(vma, vma->vm_start + i*PAGE_SIZE, 0)
: NULL;
dump_one_vdso_page(pg, upg);
}
}
}
#endif /* DEBUG */
/*
* Keep a dummy vma_close for now, it will prevent VMA merging.
*/
static void vdso_vma_close(struct vm_area_struct * vma)
{
}
/*
* Our nopage() function, maps in the actual vDSO kernel pages, they will
* be mapped read-only by do_no_page(), and eventually COW'ed, either
* right away for an initial write access, or by do_wp_page().
*/
static struct page * vdso_vma_nopage(struct vm_area_struct * vma,
unsigned long address, int *type)
{
unsigned long offset = address - vma->vm_start;
struct page *pg;
#ifdef CONFIG_PPC64
void *vbase = (vma->vm_mm->task_size > TASK_SIZE_USER32) ?
vdso64_kbase : vdso32_kbase;
#else
void *vbase = vdso32_kbase;
#endif
DBG("vdso_vma_nopage(current: %s, address: %016lx, off: %lx)\n",
current->comm, address, offset);
if (address < vma->vm_start || address > vma->vm_end)
return NOPAGE_SIGBUS;
/*
* Last page is systemcfg.
*/
if ((vma->vm_end - address) <= PAGE_SIZE)
pg = virt_to_page(vdso_data);
else
pg = virt_to_page(vbase + offset);
get_page(pg);
DBG(" ->page count: %d\n", page_count(pg));
return pg;
}
static struct vm_operations_struct vdso_vmops = {
.close = vdso_vma_close,
.nopage = vdso_vma_nopage,
};
/*
* This is called from binfmt_elf, we create the special vma for the
* vDSO and insert it into the mm struct tree
*/
int arch_setup_additional_pages(struct linux_binprm *bprm,
int executable_stack)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
unsigned long vdso_pages;
unsigned long vdso_base;
int rc;
#ifdef CONFIG_PPC64
if (test_thread_flag(TIF_32BIT)) {
vdso_pages = vdso32_pages;
vdso_base = VDSO32_MBASE;
} else {
vdso_pages = vdso64_pages;
vdso_base = VDSO64_MBASE;
}
#else
vdso_pages = vdso32_pages;
vdso_base = VDSO32_MBASE;
#endif
current->mm->context.vdso_base = 0;
/* vDSO has a problem and was disabled, just don't "enable" it for the
* process
*/
if (vdso_pages == 0)
return 0;
/* Add a page to the vdso size for the data page */
vdso_pages ++;
/*
* pick a base address for the vDSO in process space. We try to put it
* at vdso_base which is the "natural" base for it, but we might fail
* and end up putting it elsewhere.
*/
down_write(&mm->mmap_sem);
vdso_base = get_unmapped_area(NULL, vdso_base,
vdso_pages << PAGE_SHIFT, 0, 0);
if (IS_ERR_VALUE(vdso_base)) {
rc = vdso_base;
goto fail_mmapsem;
}
/* Allocate a VMA structure and fill it up */
vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
if (vma == NULL) {
rc = -ENOMEM;
goto fail_mmapsem;
}
vma->vm_mm = mm;
vma->vm_start = vdso_base;
vma->vm_end = vma->vm_start + (vdso_pages << PAGE_SHIFT);
/*
* our vma flags don't have VM_WRITE so by default, the process isn't
* allowed to write those pages.
* gdb can break that with ptrace interface, and thus trigger COW on
* those pages but it's then your responsibility to never do that on
* the "data" page of the vDSO or you'll stop getting kernel updates
* and your nice userland gettimeofday will be totally dead.
* It's fine to use that for setting breakpoints in the vDSO code
* pages though
*/
vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC;
/*
* Make sure the vDSO gets into every core dump.
* Dumping its contents makes post-mortem fully interpretable later
* without matching up the same kernel and hardware config to see
* what PC values meant.
*/
vma->vm_flags |= VM_ALWAYSDUMP;
vma->vm_flags |= mm->def_flags;
vma->vm_page_prot = protection_map[vma->vm_flags & 0x7];
vma->vm_ops = &vdso_vmops;
/* Insert new VMA */
rc = insert_vm_struct(mm, vma);
if (rc)
goto fail_vma;
/* Put vDSO base into mm struct and account for memory usage */
current->mm->context.vdso_base = vdso_base;
mm->total_vm += (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
up_write(&mm->mmap_sem);
return 0;
fail_vma:
kmem_cache_free(vm_area_cachep, vma);
fail_mmapsem:
up_write(&mm->mmap_sem);
return rc;
}
const char *arch_vma_name(struct vm_area_struct *vma)
{
if (vma->vm_mm && vma->vm_start == vma->vm_mm->context.vdso_base)
return "[vdso]";
return NULL;
}
static void * __init find_section32(Elf32_Ehdr *ehdr, const char *secname,
unsigned long *size)
{
Elf32_Shdr *sechdrs;
unsigned int i;
char *secnames;
/* Grab section headers and strings so we can tell who is who */
sechdrs = (void *)ehdr + ehdr->e_shoff;
secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
/* Find the section they want */
for (i = 1; i < ehdr->e_shnum; i++) {
if (strcmp(secnames+sechdrs[i].sh_name, secname) == 0) {
if (size)
*size = sechdrs[i].sh_size;
return (void *)ehdr + sechdrs[i].sh_offset;
}
}
*size = 0;
return NULL;
}
static Elf32_Sym * __init find_symbol32(struct lib32_elfinfo *lib,
const char *symname)
{
unsigned int i;
char name[MAX_SYMNAME], *c;
for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) {
if (lib->dynsym[i].st_name == 0)
continue;
strlcpy(name, lib->dynstr + lib->dynsym[i].st_name,
MAX_SYMNAME);
c = strchr(name, '@');
if (c)
*c = 0;
if (strcmp(symname, name) == 0)
return &lib->dynsym[i];
}
return NULL;
}
/* Note that we assume the section is .text and the symbol is relative to
* the library base
*/
static unsigned long __init find_function32(struct lib32_elfinfo *lib,
const char *symname)
{
Elf32_Sym *sym = find_symbol32(lib, symname);
if (sym == NULL) {
printk(KERN_WARNING "vDSO32: function %s not found !\n",
symname);
return 0;
}
return sym->st_value - VDSO32_LBASE;
}
static int vdso_do_func_patch32(struct lib32_elfinfo *v32,
struct lib64_elfinfo *v64,
const char *orig, const char *fix)
{
Elf32_Sym *sym32_gen, *sym32_fix;
sym32_gen = find_symbol32(v32, orig);
if (sym32_gen == NULL) {
printk(KERN_ERR "vDSO32: Can't find symbol %s !\n", orig);
return -1;
}
if (fix == NULL) {
sym32_gen->st_name = 0;
return 0;
}
sym32_fix = find_symbol32(v32, fix);
if (sym32_fix == NULL) {
printk(KERN_ERR "vDSO32: Can't find symbol %s !\n", fix);
return -1;
}
sym32_gen->st_value = sym32_fix->st_value;
sym32_gen->st_size = sym32_fix->st_size;
sym32_gen->st_info = sym32_fix->st_info;
sym32_gen->st_other = sym32_fix->st_other;
sym32_gen->st_shndx = sym32_fix->st_shndx;
return 0;
}
#ifdef CONFIG_PPC64
static void * __init find_section64(Elf64_Ehdr *ehdr, const char *secname,
unsigned long *size)
{
Elf64_Shdr *sechdrs;
unsigned int i;
char *secnames;
/* Grab section headers and strings so we can tell who is who */
sechdrs = (void *)ehdr + ehdr->e_shoff;
secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
/* Find the section they want */
for (i = 1; i < ehdr->e_shnum; i++) {
if (strcmp(secnames+sechdrs[i].sh_name, secname) == 0) {
if (size)
*size = sechdrs[i].sh_size;
return (void *)ehdr + sechdrs[i].sh_offset;
}
}
if (size)
*size = 0;
return NULL;
}
static Elf64_Sym * __init find_symbol64(struct lib64_elfinfo *lib,
const char *symname)
{
unsigned int i;
char name[MAX_SYMNAME], *c;
for (i = 0; i < (lib->dynsymsize / sizeof(Elf64_Sym)); i++) {
if (lib->dynsym[i].st_name == 0)
continue;
strlcpy(name, lib->dynstr + lib->dynsym[i].st_name,
MAX_SYMNAME);
c = strchr(name, '@');
if (c)
*c = 0;
if (strcmp(symname, name) == 0)
return &lib->dynsym[i];
}
return NULL;
}
/* Note that we assume the section is .text and the symbol is relative to
* the library base
*/
static unsigned long __init find_function64(struct lib64_elfinfo *lib,
const char *symname)
{
Elf64_Sym *sym = find_symbol64(lib, symname);
if (sym == NULL) {
printk(KERN_WARNING "vDSO64: function %s not found !\n",
symname);
return 0;
}
#ifdef VDS64_HAS_DESCRIPTORS
return *((u64 *)(vdso64_kbase + sym->st_value - VDSO64_LBASE)) -
VDSO64_LBASE;
#else
return sym->st_value - VDSO64_LBASE;
#endif
}
static int vdso_do_func_patch64(struct lib32_elfinfo *v32,
struct lib64_elfinfo *v64,
const char *orig, const char *fix)
{
Elf64_Sym *sym64_gen, *sym64_fix;
sym64_gen = find_symbol64(v64, orig);
if (sym64_gen == NULL) {
printk(KERN_ERR "vDSO64: Can't find symbol %s !\n", orig);
return -1;
}
if (fix == NULL) {
sym64_gen->st_name = 0;
return 0;
}
sym64_fix = find_symbol64(v64, fix);
if (sym64_fix == NULL) {
printk(KERN_ERR "vDSO64: Can't find symbol %s !\n", fix);
return -1;
}
sym64_gen->st_value = sym64_fix->st_value;
sym64_gen->st_size = sym64_fix->st_size;
sym64_gen->st_info = sym64_fix->st_info;
sym64_gen->st_other = sym64_fix->st_other;
sym64_gen->st_shndx = sym64_fix->st_shndx;
return 0;
}
#endif /* CONFIG_PPC64 */
static __init int vdso_do_find_sections(struct lib32_elfinfo *v32,
struct lib64_elfinfo *v64)
{
void *sect;
/*
* Locate symbol tables & text section
*/
v32->dynsym = find_section32(v32->hdr, ".dynsym", &v32->dynsymsize);
v32->dynstr = find_section32(v32->hdr, ".dynstr", NULL);
if (v32->dynsym == NULL || v32->dynstr == NULL) {
printk(KERN_ERR "vDSO32: required symbol section not found\n");
return -1;
}
sect = find_section32(v32->hdr, ".text", NULL);
if (sect == NULL) {
printk(KERN_ERR "vDSO32: the .text section was not found\n");
return -1;
}
v32->text = sect - vdso32_kbase;
#ifdef CONFIG_PPC64
v64->dynsym = find_section64(v64->hdr, ".dynsym", &v64->dynsymsize);
v64->dynstr = find_section64(v64->hdr, ".dynstr", NULL);
if (v64->dynsym == NULL || v64->dynstr == NULL) {
printk(KERN_ERR "vDSO64: required symbol section not found\n");
return -1;
}
sect = find_section64(v64->hdr, ".text", NULL);
if (sect == NULL) {
printk(KERN_ERR "vDSO64: the .text section was not found\n");
return -1;
}
v64->text = sect - vdso64_kbase;
#endif /* CONFIG_PPC64 */
return 0;
}
static __init void vdso_setup_trampolines(struct lib32_elfinfo *v32,
struct lib64_elfinfo *v64)
{
/*
* Find signal trampolines
*/
#ifdef CONFIG_PPC64
vdso64_rt_sigtramp = find_function64(v64, "__kernel_sigtramp_rt64");
#endif
vdso32_sigtramp = find_function32(v32, "__kernel_sigtramp32");
vdso32_rt_sigtramp = find_function32(v32, "__kernel_sigtramp_rt32");
}
static __init int vdso_fixup_datapage(struct lib32_elfinfo *v32,
struct lib64_elfinfo *v64)
{
Elf32_Sym *sym32;
#ifdef CONFIG_PPC64
Elf64_Sym *sym64;
sym64 = find_symbol64(v64, "__kernel_datapage_offset");
if (sym64 == NULL) {
printk(KERN_ERR "vDSO64: Can't find symbol "
"__kernel_datapage_offset !\n");
return -1;
}
*((int *)(vdso64_kbase + sym64->st_value - VDSO64_LBASE)) =
(vdso64_pages << PAGE_SHIFT) -
(sym64->st_value - VDSO64_LBASE);
#endif /* CONFIG_PPC64 */
sym32 = find_symbol32(v32, "__kernel_datapage_offset");
if (sym32 == NULL) {
printk(KERN_ERR "vDSO32: Can't find symbol "
"__kernel_datapage_offset !\n");
return -1;
}
*((int *)(vdso32_kbase + (sym32->st_value - VDSO32_LBASE))) =
(vdso32_pages << PAGE_SHIFT) -
(sym32->st_value - VDSO32_LBASE);
return 0;
}
static __init int vdso_fixup_features(struct lib32_elfinfo *v32,
struct lib64_elfinfo *v64)
{
void *start32;
unsigned long size32;
#ifdef CONFIG_PPC64
void *start64;
unsigned long size64;
start64 = find_section64(v64->hdr, "__ftr_fixup", &size64);
if (start64)
do_feature_fixups(cur_cpu_spec->cpu_features,
start64, start64 + size64);
start64 = find_section64(v64->hdr, "__fw_ftr_fixup", &size64);
if (start64)
do_feature_fixups(powerpc_firmware_features,
start64, start64 + size64);
#endif /* CONFIG_PPC64 */
start32 = find_section32(v32->hdr, "__ftr_fixup", &size32);
if (start32)
do_feature_fixups(cur_cpu_spec->cpu_features,
start32, start32 + size32);
#ifdef CONFIG_PPC64
start32 = find_section32(v32->hdr, "__fw_ftr_fixup", &size32);
if (start32)
do_feature_fixups(powerpc_firmware_features,
start32, start32 + size32);
#endif /* CONFIG_PPC64 */
return 0;
}
static __init int vdso_fixup_alt_funcs(struct lib32_elfinfo *v32,
struct lib64_elfinfo *v64)
{
int i;
for (i = 0; i < ARRAY_SIZE(vdso_patches); i++) {
struct vdso_patch_def *patch = &vdso_patches[i];
int match = (cur_cpu_spec->cpu_features & patch->ftr_mask)
== patch->ftr_value;
if (!match)
continue;
DBG("replacing %s with %s...\n", patch->gen_name,
patch->fix_name ? "NONE" : patch->fix_name);
/*
* Patch the 32 bits and 64 bits symbols. Note that we do not
* patch the "." symbol on 64 bits.
* It would be easy to do, but doesn't seem to be necessary,
* patching the OPD symbol is enough.
*/
vdso_do_func_patch32(v32, v64, patch->gen_name,
patch->fix_name);
#ifdef CONFIG_PPC64
vdso_do_func_patch64(v32, v64, patch->gen_name,
patch->fix_name);
#endif /* CONFIG_PPC64 */
}
return 0;
}
static __init int vdso_setup(void)
{
struct lib32_elfinfo v32;
struct lib64_elfinfo v64;
v32.hdr = vdso32_kbase;
#ifdef CONFIG_PPC64
v64.hdr = vdso64_kbase;
#endif
if (vdso_do_find_sections(&v32, &v64))
return -1;
if (vdso_fixup_datapage(&v32, &v64))
return -1;
if (vdso_fixup_features(&v32, &v64))
return -1;
if (vdso_fixup_alt_funcs(&v32, &v64))
return -1;
vdso_setup_trampolines(&v32, &v64);
return 0;
}
/*
* Called from setup_arch to initialize the bitmap of available
* syscalls in the systemcfg page
*/
static void __init vdso_setup_syscall_map(void)
{
unsigned int i;
extern unsigned long *sys_call_table;
extern unsigned long sys_ni_syscall;
for (i = 0; i < __NR_syscalls; i++) {
#ifdef CONFIG_PPC64
if (sys_call_table[i*2] != sys_ni_syscall)
vdso_data->syscall_map_64[i >> 5] |=
0x80000000UL >> (i & 0x1f);
if (sys_call_table[i*2+1] != sys_ni_syscall)
vdso_data->syscall_map_32[i >> 5] |=
0x80000000UL >> (i & 0x1f);
#else /* CONFIG_PPC64 */
if (sys_call_table[i] != sys_ni_syscall)
vdso_data->syscall_map_32[i >> 5] |=
0x80000000UL >> (i & 0x1f);
#endif /* CONFIG_PPC64 */
}
}
void __init vdso_init(void)
{
int i;
#ifdef CONFIG_PPC64
/*
* Fill up the "systemcfg" stuff for backward compatiblity
*/
strcpy(vdso_data->eye_catcher, "SYSTEMCFG:PPC64");
vdso_data->version.major = SYSTEMCFG_MAJOR;
vdso_data->version.minor = SYSTEMCFG_MINOR;
vdso_data->processor = mfspr(SPRN_PVR);
/*
* Fake the old platform number for pSeries and iSeries and add
* in LPAR bit if necessary
*/
vdso_data->platform = machine_is(iseries) ? 0x200 : 0x100;
if (firmware_has_feature(FW_FEATURE_LPAR))
vdso_data->platform |= 1;
vdso_data->physicalMemorySize = lmb_phys_mem_size();
vdso_data->dcache_size = ppc64_caches.dsize;
vdso_data->dcache_line_size = ppc64_caches.dline_size;
vdso_data->icache_size = ppc64_caches.isize;
vdso_data->icache_line_size = ppc64_caches.iline_size;
/*
* Calculate the size of the 64 bits vDSO
*/
vdso64_pages = (&vdso64_end - &vdso64_start) >> PAGE_SHIFT;
DBG("vdso64_kbase: %p, 0x%x pages\n", vdso64_kbase, vdso64_pages);
#endif /* CONFIG_PPC64 */
/*
* Calculate the size of the 32 bits vDSO
*/
vdso32_pages = (&vdso32_end - &vdso32_start) >> PAGE_SHIFT;
DBG("vdso32_kbase: %p, 0x%x pages\n", vdso32_kbase, vdso32_pages);
/*
* Setup the syscall map in the vDOS
*/
vdso_setup_syscall_map();
/*
* Initialize the vDSO images in memory, that is do necessary
* fixups of vDSO symbols, locate trampolines, etc...
*/
if (vdso_setup()) {
printk(KERN_ERR "vDSO setup failure, not enabled !\n");
vdso32_pages = 0;
#ifdef CONFIG_PPC64
vdso64_pages = 0;
#endif
return;
}
/* Make sure pages are in the correct state */
for (i = 0; i < vdso32_pages; i++) {
struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
ClearPageReserved(pg);
get_page(pg);
}
#ifdef CONFIG_PPC64
for (i = 0; i < vdso64_pages; i++) {
struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
ClearPageReserved(pg);
get_page(pg);
}
#endif /* CONFIG_PPC64 */
get_page(virt_to_page(vdso_data));
}
int in_gate_area_no_task(unsigned long addr)
{
return 0;
}
int in_gate_area(struct task_struct *task, unsigned long addr)
{
return 0;
}
struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
{
return NULL;
}
