6deb159d08e0cf761fe402ed5ab355bcfc9e3d4b
[linux-2.6.git] / arch / i386 / kernel / sysenter.c
1 /*
2  * linux/arch/i386/kernel/sysenter.c
3  *
4  * (C) Copyright 2002 Linus Torvalds
5  * Portions based on the vdso-randomization code from exec-shield:
6  * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
7  *
8  * This file contains the needed initializations to support sysenter.
9  */
10
11 #include <linux/init.h>
12 #include <linux/smp.h>
13 #include <linux/thread_info.h>
14 #include <linux/sched.h>
15 #include <linux/gfp.h>
16 #include <linux/string.h>
17 #include <linux/elf.h>
18 #include <linux/mm.h>
19 #include <linux/module.h>
20
21 #include <asm/cpufeature.h>
22 #include <asm/msr.h>
23 #include <asm/pgtable.h>
24 #include <asm/unistd.h>
25 #include <asm/elf.h>
26 #include <asm/tlbflush.h>
27
28 enum {
29         VDSO_DISABLED = 0,
30         VDSO_ENABLED = 1,
31         VDSO_COMPAT = 2,
32 };
33
34 #ifdef CONFIG_COMPAT_VDSO
35 #define VDSO_DEFAULT    VDSO_COMPAT
36 #else
37 #define VDSO_DEFAULT    VDSO_ENABLED
38 #endif
39
40 /*
41  * Should the kernel map a VDSO page into processes and pass its
42  * address down to glibc upon exec()?
43  */
44 unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;
45
46 EXPORT_SYMBOL_GPL(vdso_enabled);
47
48 static int __init vdso_setup(char *s)
49 {
50         vdso_enabled = simple_strtoul(s, NULL, 0);
51
52         return 1;
53 }
54
55 __setup("vdso=", vdso_setup);
56
57 extern asmlinkage void sysenter_entry(void);
58
59 static __init void reloc_symtab(Elf32_Ehdr *ehdr,
60                                 unsigned offset, unsigned size)
61 {
62         Elf32_Sym *sym = (void *)ehdr + offset;
63         unsigned nsym = size / sizeof(*sym);
64         unsigned i;
65
66         for(i = 0; i < nsym; i++, sym++) {
67                 if (sym->st_shndx == SHN_UNDEF ||
68                     sym->st_shndx == SHN_ABS)
69                         continue;  /* skip */
70
71                 if (sym->st_shndx > SHN_LORESERVE) {
72                         printk(KERN_INFO "VDSO: unexpected st_shndx %x\n",
73                                sym->st_shndx);
74                         continue;
75                 }
76
77                 switch(ELF_ST_TYPE(sym->st_info)) {
78                 case STT_OBJECT:
79                 case STT_FUNC:
80                 case STT_SECTION:
81                 case STT_FILE:
82                         sym->st_value += VDSO_HIGH_BASE;
83                 }
84         }
85 }
86
87 static __init void reloc_dyn(Elf32_Ehdr *ehdr, unsigned offset)
88 {
89         Elf32_Dyn *dyn = (void *)ehdr + offset;
90
91         for(; dyn->d_tag != DT_NULL; dyn++)
92                 switch(dyn->d_tag) {
93                 case DT_PLTGOT:
94                 case DT_HASH:
95                 case DT_STRTAB:
96                 case DT_SYMTAB:
97                 case DT_RELA:
98                 case DT_INIT:
99                 case DT_FINI:
100                 case DT_REL:
101                 case DT_DEBUG:
102                 case DT_JMPREL:
103                 case DT_VERSYM:
104                 case DT_VERDEF:
105                 case DT_VERNEED:
106                 case DT_ADDRRNGLO ... DT_ADDRRNGHI:
107                         /* definitely pointers needing relocation */
108                         dyn->d_un.d_ptr += VDSO_HIGH_BASE;
109                         break;
110
111                 case DT_ENCODING ... OLD_DT_LOOS-1:
112                 case DT_LOOS ... DT_HIOS-1:
113                         /* Tags above DT_ENCODING are pointers if
114                            they're even */
115                         if (dyn->d_tag >= DT_ENCODING &&
116                             (dyn->d_tag & 1) == 0)
117                                 dyn->d_un.d_ptr += VDSO_HIGH_BASE;
118                         break;
119
120                 case DT_VERDEFNUM:
121                 case DT_VERNEEDNUM:
122                 case DT_FLAGS_1:
123                 case DT_RELACOUNT:
124                 case DT_RELCOUNT:
125                 case DT_VALRNGLO ... DT_VALRNGHI:
126                         /* definitely not pointers */
127                         break;
128
129                 case OLD_DT_LOOS ... DT_LOOS-1:
130                 case DT_HIOS ... DT_VALRNGLO-1:
131                 default:
132                         if (dyn->d_tag > DT_ENCODING)
133                                 printk(KERN_INFO "VDSO: unexpected DT_tag %x\n",
134                                        dyn->d_tag);
135                         break;
136                 }
137 }
138
139 static __init void relocate_vdso(Elf32_Ehdr *ehdr)
140 {
141         Elf32_Phdr *phdr;
142         Elf32_Shdr *shdr;
143         int i;
144
145         BUG_ON(memcmp(ehdr->e_ident, ELFMAG, 4) != 0 ||
146                !elf_check_arch(ehdr) ||
147                ehdr->e_type != ET_DYN);
148
149         ehdr->e_entry += VDSO_HIGH_BASE;
150
151         /* rebase phdrs */
152         phdr = (void *)ehdr + ehdr->e_phoff;
153         for (i = 0; i < ehdr->e_phnum; i++) {
154                 phdr[i].p_vaddr += VDSO_HIGH_BASE;
155
156                 /* relocate dynamic stuff */
157                 if (phdr[i].p_type == PT_DYNAMIC)
158                         reloc_dyn(ehdr, phdr[i].p_offset);
159         }
160
161         /* rebase sections */
162         shdr = (void *)ehdr + ehdr->e_shoff;
163         for(i = 0; i < ehdr->e_shnum; i++) {
164                 if (!(shdr[i].sh_flags & SHF_ALLOC))
165                         continue;
166
167                 shdr[i].sh_addr += VDSO_HIGH_BASE;
168
169                 if (shdr[i].sh_type == SHT_SYMTAB ||
170                     shdr[i].sh_type == SHT_DYNSYM)
171                         reloc_symtab(ehdr, shdr[i].sh_offset,
172                                      shdr[i].sh_size);
173         }
174 }
175
176 void enable_sep_cpu(void)
177 {
178         int cpu = get_cpu();
179         struct tss_struct *tss = &per_cpu(init_tss, cpu);
180
181         if (!boot_cpu_has(X86_FEATURE_SEP)) {
182                 put_cpu();
183                 return;
184         }
185
186         tss->x86_tss.ss1 = __KERNEL_CS;
187         tss->x86_tss.esp1 = sizeof(struct tss_struct) + (unsigned long) tss;
188         wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
189         wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.esp1, 0);
190         wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) sysenter_entry, 0);
191         put_cpu();      
192 }
193
194 static struct vm_area_struct gate_vma;
195
196 static int __init gate_vma_init(void)
197 {
198         gate_vma.vm_mm = NULL;
199         gate_vma.vm_start = FIXADDR_USER_START;
200         gate_vma.vm_end = FIXADDR_USER_END;
201         gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
202         gate_vma.vm_page_prot = __P101;
203         /*
204          * Make sure the vDSO gets into every core dump.
205          * Dumping its contents makes post-mortem fully interpretable later
206          * without matching up the same kernel and hardware config to see
207          * what PC values meant.
208          */
209         gate_vma.vm_flags |= VM_ALWAYSDUMP;
210         return 0;
211 }
212
213 /*
214  * These symbols are defined by vsyscall.o to mark the bounds
215  * of the ELF DSO images included therein.
216  */
217 extern const char vsyscall_int80_start, vsyscall_int80_end;
218 extern const char vsyscall_sysenter_start, vsyscall_sysenter_end;
219 static struct page *syscall_pages[1];
220
221 static void map_compat_vdso(int map)
222 {
223         static int vdso_mapped;
224
225         if (map == vdso_mapped)
226                 return;
227
228         vdso_mapped = map;
229
230         __set_fixmap(FIX_VDSO, page_to_pfn(syscall_pages[0]) << PAGE_SHIFT,
231                      map ? PAGE_READONLY_EXEC : PAGE_NONE);
232
233         /* flush stray tlbs */
234         flush_tlb_all();
235 }
236
237 int __init sysenter_setup(void)
238 {
239         void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
240         const void *vsyscall;
241         size_t vsyscall_len;
242
243         syscall_pages[0] = virt_to_page(syscall_page);
244
245         gate_vma_init();
246
247         printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
248
249         if (!boot_cpu_has(X86_FEATURE_SEP)) {
250                 vsyscall = &vsyscall_int80_start;
251                 vsyscall_len = &vsyscall_int80_end - &vsyscall_int80_start;
252         } else {
253                 vsyscall = &vsyscall_sysenter_start;
254                 vsyscall_len = &vsyscall_sysenter_end - &vsyscall_sysenter_start;
255         }
256
257         memcpy(syscall_page, vsyscall, vsyscall_len);
258         relocate_vdso(syscall_page);
259
260         return 0;
261 }
262
263 /* Defined in vsyscall-sysenter.S */
264 extern void SYSENTER_RETURN;
265
266 /* Setup a VMA at program startup for the vsyscall page */
267 int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
268 {
269         struct mm_struct *mm = current->mm;
270         unsigned long addr;
271         int ret = 0;
272         bool compat;
273
274         down_write(&mm->mmap_sem);
275
276         /* Test compat mode once here, in case someone
277            changes it via sysctl */
278         compat = (vdso_enabled == VDSO_COMPAT);
279
280         map_compat_vdso(compat);
281
282         if (compat)
283                 addr = VDSO_HIGH_BASE;
284         else {
285                 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
286                 if (IS_ERR_VALUE(addr)) {
287                         ret = addr;
288                         goto up_fail;
289                 }
290
291                 /*
292                  * MAYWRITE to allow gdb to COW and set breakpoints
293                  *
294                  * Make sure the vDSO gets into every core dump.
295                  * Dumping its contents makes post-mortem fully
296                  * interpretable later without matching up the same
297                  * kernel and hardware config to see what PC values
298                  * meant.
299                  */
300                 ret = install_special_mapping(mm, addr, PAGE_SIZE,
301                                               VM_READ|VM_EXEC|
302                                               VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
303                                               VM_ALWAYSDUMP,
304                                               syscall_pages);
305
306                 if (ret)
307                         goto up_fail;
308         }
309
310         current->mm->context.vdso = (void *)addr;
311         current_thread_info()->sysenter_return =
312                 (void *)VDSO_SYM(&SYSENTER_RETURN);
313
314   up_fail:
315         up_write(&mm->mmap_sem);
316
317         return ret;
318 }
319
320 const char *arch_vma_name(struct vm_area_struct *vma)
321 {
322         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
323                 return "[vdso]";
324         return NULL;
325 }
326
327 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
328 {
329         struct mm_struct *mm = tsk->mm;
330
331         /* Check to see if this task was created in compat vdso mode */
332         if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
333                 return &gate_vma;
334         return NULL;
335 }
336
337 int in_gate_area(struct task_struct *task, unsigned long addr)
338 {
339         const struct vm_area_struct *vma = get_gate_vma(task);
340
341         return vma && addr >= vma->vm_start && addr < vma->vm_end;
342 }
343
344 int in_gate_area_no_task(unsigned long addr)
345 {
346         return 0;
347 }