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
29 enum {
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 */
57 unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;
58
vdso_setup(char * s)59 static 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
76 EXPORT_SYMBOL_GPL(vdso_enabled);
77 #endif
78
reloc_symtab(Elf32_Ehdr * ehdr,unsigned offset,unsigned size)79 static __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
reloc_dyn(Elf32_Ehdr * ehdr,unsigned offset)107 static __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
relocate_vdso(Elf32_Ehdr * ehdr)159 static __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
196 static 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 */
syscall32_cpu_init(void)204 void 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
map_compat_vdso(int map)217 static 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
enable_sep_cpu(void)226 void 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
244 static struct vm_area_struct gate_vma;
245
gate_vma_init(void)246 static 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
map_compat_vdso(int map)265 static 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
sysenter_setup(void)283 int __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 */
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)313 int 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
377 subsys_initcall(sysenter_setup);
378
379 #ifdef CONFIG_SYSCTL
380 /* Register vsyscall32 into the ABI table */
381 #include <linux/sysctl.h>
382
383 static 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
394 static ctl_table abi_root_table2[] = {
395 {
396 .procname = "abi",
397 .mode = 0555,
398 .child = abi_table2
399 },
400 {}
401 };
402
ia32_binfmt_init(void)403 static __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
arch_vma_name(struct vm_area_struct * vma)413 const 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
get_gate_vma(struct mm_struct * mm)420 struct 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
in_gate_area(struct mm_struct * mm,unsigned long addr)431 int 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
in_gate_area_no_mm(unsigned long addr)438 int in_gate_area_no_mm(unsigned long addr)
439 {
440 return 0;
441 }
442
443 #endif /* CONFIG_X86_64 */
444