e0feb66a2408a9f3f89e2da50e1f74dc4dca5faa
[linux-2.6.git] / 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
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
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
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
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
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, 4) != 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 /*
197  * These symbols are defined by vdso32.S to mark the bounds
198  * of the ELF DSO images included therein.
199  */
200 extern const char vdso32_default_start, vdso32_default_end;
201 extern const char vdso32_sysenter_start, vdso32_sysenter_end;
202 static struct page *vdso32_pages[1];
203
204 #ifdef CONFIG_X86_64
205
206 static int use_sysenter __read_mostly = -1;
207
208 #define vdso32_sysenter()       (use_sysenter > 0)
209
210 /* May not be __init: called during resume */
211 void syscall32_cpu_init(void)
212 {
213         if (use_sysenter < 0)
214                 use_sysenter = (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL);
215
216         /* Load these always in case some future AMD CPU supports
217            SYSENTER from compat mode too. */
218         checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
219         checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
220         checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
221
222         wrmsrl(MSR_CSTAR, ia32_cstar_target);
223 }
224
225 #define compat_uses_vma         1
226
227 static inline void map_compat_vdso(int map)
228 {
229 }
230
231 #else  /* CONFIG_X86_32 */
232
233 #define vdso32_sysenter()       (boot_cpu_has(X86_FEATURE_SEP))
234
235 void enable_sep_cpu(void)
236 {
237         int cpu = get_cpu();
238         struct tss_struct *tss = &per_cpu(init_tss, cpu);
239
240         if (!boot_cpu_has(X86_FEATURE_SEP)) {
241                 put_cpu();
242                 return;
243         }
244
245         tss->x86_tss.ss1 = __KERNEL_CS;
246         tss->x86_tss.sp1 = sizeof(struct tss_struct) + (unsigned long) tss;
247         wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
248         wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0);
249         wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0);
250         put_cpu();      
251 }
252
253 static struct vm_area_struct gate_vma;
254
255 static int __init gate_vma_init(void)
256 {
257         gate_vma.vm_mm = NULL;
258         gate_vma.vm_start = FIXADDR_USER_START;
259         gate_vma.vm_end = FIXADDR_USER_END;
260         gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
261         gate_vma.vm_page_prot = __P101;
262         /*
263          * Make sure the vDSO gets into every core dump.
264          * Dumping its contents makes post-mortem fully interpretable later
265          * without matching up the same kernel and hardware config to see
266          * what PC values meant.
267          */
268         gate_vma.vm_flags |= VM_ALWAYSDUMP;
269         return 0;
270 }
271
272 #define compat_uses_vma         0
273
274 static void map_compat_vdso(int map)
275 {
276         static int vdso_mapped;
277
278         if (map == vdso_mapped)
279                 return;
280
281         vdso_mapped = map;
282
283         __set_fixmap(FIX_VDSO, page_to_pfn(vdso32_pages[0]) << PAGE_SHIFT,
284                      map ? PAGE_READONLY_EXEC : PAGE_NONE);
285
286         /* flush stray tlbs */
287         flush_tlb_all();
288 }
289
290 #endif  /* CONFIG_X86_64 */
291
292 int __init sysenter_setup(void)
293 {
294         void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
295         const void *vsyscall;
296         size_t vsyscall_len;
297
298         vdso32_pages[0] = virt_to_page(syscall_page);
299
300 #ifdef CONFIG_X86_32
301         gate_vma_init();
302
303         printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
304 #endif
305
306         if (!vdso32_sysenter()) {
307                 vsyscall = &vdso32_default_start;
308                 vsyscall_len = &vdso32_default_end - &vdso32_default_start;
309         } else {
310                 vsyscall = &vdso32_sysenter_start;
311                 vsyscall_len = &vdso32_sysenter_end - &vdso32_sysenter_start;
312         }
313
314         memcpy(syscall_page, vsyscall, vsyscall_len);
315         relocate_vdso(syscall_page);
316
317         return 0;
318 }
319
320 /* Setup a VMA at program startup for the vsyscall page */
321 int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
322 {
323         struct mm_struct *mm = current->mm;
324         unsigned long addr;
325         int ret = 0;
326         bool compat;
327
328         down_write(&mm->mmap_sem);
329
330         /* Test compat mode once here, in case someone
331            changes it via sysctl */
332         compat = (vdso_enabled == VDSO_COMPAT);
333
334         map_compat_vdso(compat);
335
336         if (compat)
337                 addr = VDSO_HIGH_BASE;
338         else {
339                 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
340                 if (IS_ERR_VALUE(addr)) {
341                         ret = addr;
342                         goto up_fail;
343                 }
344         }
345
346         if (compat_uses_vma || !compat) {
347                 /*
348                  * MAYWRITE to allow gdb to COW and set breakpoints
349                  *
350                  * Make sure the vDSO gets into every core dump.
351                  * Dumping its contents makes post-mortem fully
352                  * interpretable later without matching up the same
353                  * kernel and hardware config to see what PC values
354                  * meant.
355                  */
356                 ret = install_special_mapping(mm, addr, PAGE_SIZE,
357                                               VM_READ|VM_EXEC|
358                                               VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
359                                               VM_ALWAYSDUMP,
360                                               vdso32_pages);
361
362                 if (ret)
363                         goto up_fail;
364         }
365
366         current->mm->context.vdso = (void *)addr;
367         current_thread_info()->sysenter_return =
368                 VDSO32_SYMBOL(addr, SYSENTER_RETURN);
369
370   up_fail:
371         up_write(&mm->mmap_sem);
372
373         return ret;
374 }
375
376 #ifdef CONFIG_X86_64
377
378 __initcall(sysenter_setup);
379
380 #else  /* CONFIG_X86_32 */
381
382 const char *arch_vma_name(struct vm_area_struct *vma)
383 {
384         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
385                 return "[vdso]";
386         return NULL;
387 }
388
389 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
390 {
391         struct mm_struct *mm = tsk->mm;
392
393         /* Check to see if this task was created in compat vdso mode */
394         if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
395                 return &gate_vma;
396         return NULL;
397 }
398
399 int in_gate_area(struct task_struct *task, unsigned long addr)
400 {
401         const struct vm_area_struct *vma = get_gate_vma(task);
402
403         return vma && addr >= vma->vm_start && addr < vma->vm_end;
404 }
405
406 int in_gate_area_no_task(unsigned long addr)
407 {
408         return 0;
409 }
410
411 #endif  /* CONFIG_X86_64 */