Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland...
[linux-2.6] / arch / x86 / kernel / sysenter_32.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/err.h>
20 #include <linux/module.h>
21
22 #include <asm/cpufeature.h>
23 #include <asm/msr.h>
24 #include <asm/pgtable.h>
25 #include <asm/unistd.h>
26 #include <asm/elf.h>
27 #include <asm/tlbflush.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 /*
42  * Should the kernel map a VDSO page into processes and pass its
43  * address down to glibc upon exec()?
44  */
45 unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;
46
47 EXPORT_SYMBOL_GPL(vdso_enabled);
48
49 static int __init vdso_setup(char *s)
50 {
51         vdso_enabled = simple_strtoul(s, NULL, 0);
52
53         return 1;
54 }
55
56 __setup("vdso=", vdso_setup);
57
58 extern asmlinkage void sysenter_entry(void);
59
60 static __init void reloc_symtab(Elf32_Ehdr *ehdr,
61                                 unsigned offset, unsigned size)
62 {
63         Elf32_Sym *sym = (void *)ehdr + offset;
64         unsigned nsym = size / sizeof(*sym);
65         unsigned i;
66
67         for(i = 0; i < nsym; i++, sym++) {
68                 if (sym->st_shndx == SHN_UNDEF ||
69                     sym->st_shndx == SHN_ABS)
70                         continue;  /* skip */
71
72                 if (sym->st_shndx > SHN_LORESERVE) {
73                         printk(KERN_INFO "VDSO: unexpected st_shndx %x\n",
74                                sym->st_shndx);
75                         continue;
76                 }
77
78                 switch(ELF_ST_TYPE(sym->st_info)) {
79                 case STT_OBJECT:
80                 case STT_FUNC:
81                 case STT_SECTION:
82                 case STT_FILE:
83                         sym->st_value += VDSO_HIGH_BASE;
84                 }
85         }
86 }
87
88 static __init void reloc_dyn(Elf32_Ehdr *ehdr, unsigned offset)
89 {
90         Elf32_Dyn *dyn = (void *)ehdr + offset;
91
92         for(; dyn->d_tag != DT_NULL; dyn++)
93                 switch(dyn->d_tag) {
94                 case DT_PLTGOT:
95                 case DT_HASH:
96                 case DT_STRTAB:
97                 case DT_SYMTAB:
98                 case DT_RELA:
99                 case DT_INIT:
100                 case DT_FINI:
101                 case DT_REL:
102                 case DT_DEBUG:
103                 case DT_JMPREL:
104                 case DT_VERSYM:
105                 case DT_VERDEF:
106                 case DT_VERNEED:
107                 case DT_ADDRRNGLO ... DT_ADDRRNGHI:
108                         /* definitely pointers needing relocation */
109                         dyn->d_un.d_ptr += VDSO_HIGH_BASE;
110                         break;
111
112                 case DT_ENCODING ... OLD_DT_LOOS-1:
113                 case DT_LOOS ... DT_HIOS-1:
114                         /* Tags above DT_ENCODING are pointers if
115                            they're even */
116                         if (dyn->d_tag >= DT_ENCODING &&
117                             (dyn->d_tag & 1) == 0)
118                                 dyn->d_un.d_ptr += VDSO_HIGH_BASE;
119                         break;
120
121                 case DT_VERDEFNUM:
122                 case DT_VERNEEDNUM:
123                 case DT_FLAGS_1:
124                 case DT_RELACOUNT:
125                 case DT_RELCOUNT:
126                 case DT_VALRNGLO ... DT_VALRNGHI:
127                         /* definitely not pointers */
128                         break;
129
130                 case OLD_DT_LOOS ... DT_LOOS-1:
131                 case DT_HIOS ... DT_VALRNGLO-1:
132                 default:
133                         if (dyn->d_tag > DT_ENCODING)
134                                 printk(KERN_INFO "VDSO: unexpected DT_tag %x\n",
135                                        dyn->d_tag);
136                         break;
137                 }
138 }
139
140 static __init void relocate_vdso(Elf32_Ehdr *ehdr)
141 {
142         Elf32_Phdr *phdr;
143         Elf32_Shdr *shdr;
144         int i;
145
146         BUG_ON(memcmp(ehdr->e_ident, ELFMAG, 4) != 0 ||
147                !elf_check_arch(ehdr) ||
148                ehdr->e_type != ET_DYN);
149
150         ehdr->e_entry += VDSO_HIGH_BASE;
151
152         /* rebase phdrs */
153         phdr = (void *)ehdr + ehdr->e_phoff;
154         for (i = 0; i < ehdr->e_phnum; i++) {
155                 phdr[i].p_vaddr += VDSO_HIGH_BASE;
156
157                 /* relocate dynamic stuff */
158                 if (phdr[i].p_type == PT_DYNAMIC)
159                         reloc_dyn(ehdr, phdr[i].p_offset);
160         }
161
162         /* rebase sections */
163         shdr = (void *)ehdr + ehdr->e_shoff;
164         for(i = 0; i < ehdr->e_shnum; i++) {
165                 if (!(shdr[i].sh_flags & SHF_ALLOC))
166                         continue;
167
168                 shdr[i].sh_addr += VDSO_HIGH_BASE;
169
170                 if (shdr[i].sh_type == SHT_SYMTAB ||
171                     shdr[i].sh_type == SHT_DYNSYM)
172                         reloc_symtab(ehdr, shdr[i].sh_offset,
173                                      shdr[i].sh_size);
174         }
175 }
176
177 void enable_sep_cpu(void)
178 {
179         int cpu = get_cpu();
180         struct tss_struct *tss = &per_cpu(init_tss, cpu);
181
182         if (!boot_cpu_has(X86_FEATURE_SEP)) {
183                 put_cpu();
184                 return;
185         }
186
187         tss->x86_tss.ss1 = __KERNEL_CS;
188         tss->x86_tss.esp1 = sizeof(struct tss_struct) + (unsigned long) tss;
189         wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
190         wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.esp1, 0);
191         wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) sysenter_entry, 0);
192         put_cpu();      
193 }
194
195 static struct vm_area_struct gate_vma;
196
197 static int __init gate_vma_init(void)
198 {
199         gate_vma.vm_mm = NULL;
200         gate_vma.vm_start = FIXADDR_USER_START;
201         gate_vma.vm_end = FIXADDR_USER_END;
202         gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
203         gate_vma.vm_page_prot = __P101;
204         /*
205          * Make sure the vDSO gets into every core dump.
206          * Dumping its contents makes post-mortem fully interpretable later
207          * without matching up the same kernel and hardware config to see
208          * what PC values meant.
209          */
210         gate_vma.vm_flags |= VM_ALWAYSDUMP;
211         return 0;
212 }
213
214 /*
215  * These symbols are defined by vsyscall.o to mark the bounds
216  * of the ELF DSO images included therein.
217  */
218 extern const char vsyscall_int80_start, vsyscall_int80_end;
219 extern const char vsyscall_sysenter_start, vsyscall_sysenter_end;
220 static struct page *syscall_pages[1];
221
222 static void map_compat_vdso(int map)
223 {
224         static int vdso_mapped;
225
226         if (map == vdso_mapped)
227                 return;
228
229         vdso_mapped = map;
230
231         __set_fixmap(FIX_VDSO, page_to_pfn(syscall_pages[0]) << PAGE_SHIFT,
232                      map ? PAGE_READONLY_EXEC : PAGE_NONE);
233
234         /* flush stray tlbs */
235         flush_tlb_all();
236 }
237
238 int __init sysenter_setup(void)
239 {
240         void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
241         const void *vsyscall;
242         size_t vsyscall_len;
243
244         syscall_pages[0] = virt_to_page(syscall_page);
245
246         gate_vma_init();
247
248         printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
249
250         if (!boot_cpu_has(X86_FEATURE_SEP)) {
251                 vsyscall = &vsyscall_int80_start;
252                 vsyscall_len = &vsyscall_int80_end - &vsyscall_int80_start;
253         } else {
254                 vsyscall = &vsyscall_sysenter_start;
255                 vsyscall_len = &vsyscall_sysenter_end - &vsyscall_sysenter_start;
256         }
257
258         memcpy(syscall_page, vsyscall, vsyscall_len);
259         relocate_vdso(syscall_page);
260
261         return 0;
262 }
263
264 /* Defined in vsyscall-sysenter.S */
265 extern void SYSENTER_RETURN;
266
267 /* Setup a VMA at program startup for the vsyscall page */
268 int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
269 {
270         struct mm_struct *mm = current->mm;
271         unsigned long addr;
272         int ret = 0;
273         bool compat;
274
275         down_write(&mm->mmap_sem);
276
277         /* Test compat mode once here, in case someone
278            changes it via sysctl */
279         compat = (vdso_enabled == VDSO_COMPAT);
280
281         map_compat_vdso(compat);
282
283         if (compat)
284                 addr = VDSO_HIGH_BASE;
285         else {
286                 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
287                 if (IS_ERR_VALUE(addr)) {
288                         ret = addr;
289                         goto up_fail;
290                 }
291
292                 /*
293                  * MAYWRITE to allow gdb to COW and set breakpoints
294                  *
295                  * Make sure the vDSO gets into every core dump.
296                  * Dumping its contents makes post-mortem fully
297                  * interpretable later without matching up the same
298                  * kernel and hardware config to see what PC values
299                  * meant.
300                  */
301                 ret = install_special_mapping(mm, addr, PAGE_SIZE,
302                                               VM_READ|VM_EXEC|
303                                               VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
304                                               VM_ALWAYSDUMP,
305                                               syscall_pages);
306
307                 if (ret)
308                         goto up_fail;
309         }
310
311         current->mm->context.vdso = (void *)addr;
312         current_thread_info()->sysenter_return =
313                 (void *)VDSO_SYM(&SYSENTER_RETURN);
314
315   up_fail:
316         up_write(&mm->mmap_sem);
317
318         return ret;
319 }
320
321 const char *arch_vma_name(struct vm_area_struct *vma)
322 {
323         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
324                 return "[vdso]";
325         return NULL;
326 }
327
328 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
329 {
330         struct mm_struct *mm = tsk->mm;
331
332         /* Check to see if this task was created in compat vdso mode */
333         if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
334                 return &gate_vma;
335         return NULL;
336 }
337
338 int in_gate_area(struct task_struct *task, unsigned long addr)
339 {
340         const struct vm_area_struct *vma = get_gate_vma(task);
341
342         return vma && addr >= vma->vm_start && addr < vma->vm_end;
343 }
344
345 int in_gate_area_no_task(unsigned long addr)
346 {
347         return 0;
348 }