/arch/x86/vdso/vdso32-setup.c

  1/*
  2 * (C) Copyright 2002 Linus Torvalds
  3 * Portions based on the vdso-randomization code from exec-shield:
  4 * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
  5 *
  6 * This file contains the needed initializations to support sysenter.
  7 */
  8
  9#include <linux/init.h>
 10#include <linux/smp.h>
 11#include <linux/thread_info.h>
 12#include <linux/sched.h>
 13#include <linux/gfp.h>
 14#include <linux/string.h>
 15#include <linux/elf.h>
 16#include <linux/mm.h>
 17#include <linux/err.h>
 18#include <linux/module.h>
 19
 20#include <asm/cpufeature.h>
 21#include <asm/msr.h>
 22#include <asm/pgtable.h>
 23#include <asm/unistd.h>
 24#include <asm/elf.h>
 25#include <asm/tlbflush.h>
 26#include <asm/vdso.h>
 27#include <asm/proto.h>
 28
 29enum {
 30	VDSO_DISABLED = 0,
 31	VDSO_ENABLED = 1,
 32	VDSO_COMPAT = 2,
 33};
 34
 35#ifdef CONFIG_COMPAT_VDSO
 36#define VDSO_DEFAULT	VDSO_COMPAT
 37#else
 38#define VDSO_DEFAULT	VDSO_ENABLED
 39#endif
 40
 41#ifdef CONFIG_X86_64
 42#define vdso_enabled			sysctl_vsyscall32
 43#define arch_setup_additional_pages	syscall32_setup_pages
 44#endif
 45
 46/*
 47 * This is the difference between the prelinked addresses in the vDSO images
 48 * and the VDSO_HIGH_BASE address where CONFIG_COMPAT_VDSO places the vDSO
 49 * in the user address space.
 50 */
 51#define VDSO_ADDR_ADJUST	(VDSO_HIGH_BASE - (unsigned long)VDSO32_PRELINK)
 52
 53/*
 54 * Should the kernel map a VDSO page into processes and pass its
 55 * address down to glibc upon exec()?
 56 */
 57unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;
 58
 59static int __init vdso_setup(char *s)
 60{
 61	vdso_enabled = simple_strtoul(s, NULL, 0);
 62
 63	return 1;
 64}
 65
 66/*
 67 * For consistency, the argument vdso32=[012] affects the 32-bit vDSO
 68 * behavior on both 64-bit and 32-bit kernels.
 69 * On 32-bit kernels, vdso=[012] means the same thing.
 70 */
 71__setup("vdso32=", vdso_setup);
 72
 73#ifdef CONFIG_X86_32
 74__setup_param("vdso=", vdso32_setup, vdso_setup, 0);
 75
 76EXPORT_SYMBOL_GPL(vdso_enabled);
 77#endif
 78
 79static __init void reloc_symtab(Elf32_Ehdr *ehdr,
 80				unsigned offset, unsigned size)
 81{
 82	Elf32_Sym *sym = (void *)ehdr + offset;
 83	unsigned nsym = size / sizeof(*sym);
 84	unsigned i;
 85
 86	for(i = 0; i < nsym; i++, sym++) {
 87		if (sym->st_shndx == SHN_UNDEF ||
 88		    sym->st_shndx == SHN_ABS)
 89			continue;  /* skip */
 90
 91		if (sym->st_shndx > SHN_LORESERVE) {
 92			printk(KERN_INFO "VDSO: unexpected st_shndx %x\n",
 93			       sym->st_shndx);
 94			continue;
 95		}
 96
 97		switch(ELF_ST_TYPE(sym->st_info)) {
 98		case STT_OBJECT:
 99		case STT_FUNC:
100		case STT_SECTION:
101		case STT_FILE:
102			sym->st_value += VDSO_ADDR_ADJUST;
103		}
104	}
105}
106
107static __init void reloc_dyn(Elf32_Ehdr *ehdr, unsigned offset)
108{
109	Elf32_Dyn *dyn = (void *)ehdr + offset;
110
111	for(; dyn->d_tag != DT_NULL; dyn++)
112		switch(dyn->d_tag) {
113		case DT_PLTGOT:
114		case DT_HASH:
115		case DT_STRTAB:
116		case DT_SYMTAB:
117		case DT_RELA:
118		case DT_INIT:
119		case DT_FINI:
120		case DT_REL:
121		case DT_DEBUG:
122		case DT_JMPREL:
123		case DT_VERSYM:
124		case DT_VERDEF:
125		case DT_VERNEED:
126		case DT_ADDRRNGLO ... DT_ADDRRNGHI:
127			/* definitely pointers needing relocation */
128			dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
129			break;
130
131		case DT_ENCODING ... OLD_DT_LOOS-1:
132		case DT_LOOS ... DT_HIOS-1:
133			/* Tags above DT_ENCODING are pointers if
134			   they're even */
135			if (dyn->d_tag >= DT_ENCODING &&
136			    (dyn->d_tag & 1) == 0)
137				dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
138			break;
139
140		case DT_VERDEFNUM:
141		case DT_VERNEEDNUM:
142		case DT_FLAGS_1:
143		case DT_RELACOUNT:
144		case DT_RELCOUNT:
145		case DT_VALRNGLO ... DT_VALRNGHI:
146			/* definitely not pointers */
147			break;
148
149		case OLD_DT_LOOS ... DT_LOOS-1:
150		case DT_HIOS ... DT_VALRNGLO-1:
151		default:
152			if (dyn->d_tag > DT_ENCODING)
153				printk(KERN_INFO "VDSO: unexpected DT_tag %x\n",
154				       dyn->d_tag);
155			break;
156		}
157}
158
159static __init void relocate_vdso(Elf32_Ehdr *ehdr)
160{
161	Elf32_Phdr *phdr;
162	Elf32_Shdr *shdr;
163	int i;
164
165	BUG_ON(memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0 ||
166	       !elf_check_arch_ia32(ehdr) ||
167	       ehdr->e_type != ET_DYN);
168
169	ehdr->e_entry += VDSO_ADDR_ADJUST;
170
171	/* rebase phdrs */
172	phdr = (void *)ehdr + ehdr->e_phoff;
173	for (i = 0; i < ehdr->e_phnum; i++) {
174		phdr[i].p_vaddr += VDSO_ADDR_ADJUST;
175
176		/* relocate dynamic stuff */
177		if (phdr[i].p_type == PT_DYNAMIC)
178			reloc_dyn(ehdr, phdr[i].p_offset);
179	}
180
181	/* rebase sections */
182	shdr = (void *)ehdr + ehdr->e_shoff;
183	for(i = 0; i < ehdr->e_shnum; i++) {
184		if (!(shdr[i].sh_flags & SHF_ALLOC))
185			continue;
186
187		shdr[i].sh_addr += VDSO_ADDR_ADJUST;
188
189		if (shdr[i].sh_type == SHT_SYMTAB ||
190		    shdr[i].sh_type == SHT_DYNSYM)
191			reloc_symtab(ehdr, shdr[i].sh_offset,
192				     shdr[i].sh_size);
193	}
194}
195
196static struct page *vdso32_pages[1];
197
198#ifdef CONFIG_X86_64
199
200#define	vdso32_sysenter()	(boot_cpu_has(X86_FEATURE_SYSENTER32))
201#define	vdso32_syscall()	(boot_cpu_has(X86_FEATURE_SYSCALL32))
202
203/* May not be __init: called during resume */
204void syscall32_cpu_init(void)
205{
206	/* Load these always in case some future AMD CPU supports
207	   SYSENTER from compat mode too. */
208	checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
209	checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
210	checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
211
212	wrmsrl(MSR_CSTAR, ia32_cstar_target);
213}
214
215#define compat_uses_vma		1
216
217static inline void map_compat_vdso(int map)
218{
219}
220
221#else  /* CONFIG_X86_32 */
222
223#define vdso32_sysenter()	(boot_cpu_has(X86_FEATURE_SEP))
224#define vdso32_syscall()	(0)
225
226void enable_sep_cpu(void)
227{
228	int cpu = get_cpu();
229	struct tss_struct *tss = &per_cpu(init_tss, cpu);
230
231	if (!boot_cpu_has(X86_FEATURE_SEP)) {
232		put_cpu();
233		return;
234	}
235
236	tss->x86_tss.ss1 = __KERNEL_CS;
237	tss->x86_tss.sp1 = sizeof(struct tss_struct) + (unsigned long) tss;
238	wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
239	wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0);
240	wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0);
241	put_cpu();	
242}
243
244static struct vm_area_struct gate_vma;
245
246static int __init gate_vma_init(void)
247{
248	gate_vma.vm_mm = NULL;
249	gate_vma.vm_start = FIXADDR_USER_START;
250	gate_vma.vm_end = FIXADDR_USER_END;
251	gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
252	gate_vma.vm_page_prot = __P101;
253	/*
254	 * Make sure the vDSO gets into every core dump.
255	 * Dumping its contents makes post-mortem fully interpretable later
256	 * without matching up the same kernel and hardware config to see
257	 * what PC values meant.
258	 */
259	gate_vma.vm_flags |= VM_ALWAYSDUMP;
260	return 0;
261}
262
263#define compat_uses_vma		0
264
265static void map_compat_vdso(int map)
266{
267	static int vdso_mapped;
268
269	if (map == vdso_mapped)
270		return;
271
272	vdso_mapped = map;
273
274	__set_fixmap(FIX_VDSO, page_to_pfn(vdso32_pages[0]) << PAGE_SHIFT,
275		     map ? PAGE_READONLY_EXEC : PAGE_NONE);
276
277	/* flush stray tlbs */
278	flush_tlb_all();
279}
280
281#endif	/* CONFIG_X86_64 */
282
283int __init sysenter_setup(void)
284{
285	void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
286	const void *vsyscall;
287	size_t vsyscall_len;
288
289	vdso32_pages[0] = virt_to_page(syscall_page);
290
291#ifdef CONFIG_X86_32
292	gate_vma_init();
293#endif
294
295	if (vdso32_syscall()) {
296		vsyscall = &vdso32_syscall_start;
297		vsyscall_len = &vdso32_syscall_end - &vdso32_syscall_start;
298	} else if (vdso32_sysenter()){
299		vsyscall = &vdso32_sysenter_start;
300		vsyscall_len = &vdso32_sysenter_end - &vdso32_sysenter_start;
301	} else {
302		vsyscall = &vdso32_int80_start;
303		vsyscall_len = &vdso32_int80_end - &vdso32_int80_start;
304	}
305
306	memcpy(syscall_page, vsyscall, vsyscall_len);
307	relocate_vdso(syscall_page);
308
309	return 0;
310}
311
312/* Setup a VMA at program startup for the vsyscall page */
313int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
314{
315	struct mm_struct *mm = current->mm;
316	unsigned long addr;
317	int ret = 0;
318	bool compat;
319
320	if (vdso_enabled == VDSO_DISABLED)
321		return 0;
322
323	down_write(&mm->mmap_sem);
324
325	/* Test compat mode once here, in case someone
326	   changes it via sysctl */
327	compat = (vdso_enabled == VDSO_COMPAT);
328
329	map_compat_vdso(compat);
330
331	if (compat)
332		addr = VDSO_HIGH_BASE;
333	else {
334		addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
335		if (IS_ERR_VALUE(addr)) {
336			ret = addr;
337			goto up_fail;
338		}
339	}
340
341	current->mm->context.vdso = (void *)addr;
342
343	if (compat_uses_vma || !compat) {
344		/*
345		 * MAYWRITE to allow gdb to COW and set breakpoints
346		 *
347		 * Make sure the vDSO gets into every core dump.
348		 * Dumping its contents makes post-mortem fully
349		 * interpretable later without matching up the same
350		 * kernel and hardware config to see what PC values
351		 * meant.
352		 */
353		ret = install_special_mapping(mm, addr, PAGE_SIZE,
354					      VM_READ|VM_EXEC|
355					      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
356					      VM_ALWAYSDUMP,
357					      vdso32_pages);
358
359		if (ret)
360			goto up_fail;
361	}
362
363	current_thread_info()->sysenter_return =
364		VDSO32_SYMBOL(addr, SYSENTER_RETURN);
365
366  up_fail:
367	if (ret)
368		current->mm->context.vdso = NULL;
369
370	up_write(&mm->mmap_sem);
371
372	return ret;
373}
374
375#ifdef CONFIG_X86_64
376
377subsys_initcall(sysenter_setup);
378
379#ifdef CONFIG_SYSCTL
380/* Register vsyscall32 into the ABI table */
381#include <linux/sysctl.h>
382
383static ctl_table abi_table2[] = {
384	{
385		.procname	= "vsyscall32",
386		.data		= &sysctl_vsyscall32,
387		.maxlen		= sizeof(int),
388		.mode		= 0644,
389		.proc_handler	= proc_dointvec
390	},
391	{}
392};
393
394static ctl_table abi_root_table2[] = {
395	{
396		.procname = "abi",
397		.mode = 0555,
398		.child = abi_table2
399	},
400	{}
401};
402
403static __init int ia32_binfmt_init(void)
404{
405	register_sysctl_table(abi_root_table2);
406	return 0;
407}
408__initcall(ia32_binfmt_init);
409#endif
410
411#else  /* CONFIG_X86_32 */
412
413const char *arch_vma_name(struct vm_area_struct *vma)
414{
415	if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
416		return "[vdso]";
417	return NULL;
418}
419
420struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
421{
422	/*
423	 * Check to see if the corresponding task was created in compat vdso
424	 * mode.
425	 */
426	if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
427		return &gate_vma;
428	return NULL;
429}
430
431int in_gate_area(struct mm_struct *mm, unsigned long addr)
432{
433	const struct vm_area_struct *vma = get_gate_vma(mm);
434
435	return vma && addr >= vma->vm_start && addr < vma->vm_end;
436}
437
438int in_gate_area_no_mm(unsigned long addr)
439{
440	return 0;
441}
442
443#endif	/* CONFIG_X86_64 */