1 #include "userprog/addrspace.h"
7 #include "userprog/tss.h"
8 #include "filesys/file.h"
9 #include "filesys/filesys.h"
10 #include "threads/init.h"
11 #include "threads/mmu.h"
12 #include "threads/paging.h"
13 #include "threads/palloc.h"
14 #include "threads/thread.h"
16 /* We load ELF binaries. The following definitions are taken
17 from the ELF specification, [ELF1], more-or-less verbatim. */
19 /* ELF types. See [ELF1] 1-2. */
20 typedef uint32_t Elf32_Word, Elf32_Addr, Elf32_Off;
21 typedef uint16_t Elf32_Half;
23 /* For use with ELF types in printf(). */
24 #define PE32Wx PRIx32 /* Print Elf32_Word in hexadecimal. */
25 #define PE32Ax PRIx32 /* Print Elf32_Addr in hexadecimal. */
26 #define PE32Ox PRIx32 /* Print Elf32_Off in hexadecimal. */
27 #define PE32Hx PRIx16 /* Print Elf32_Half in hexadecimal. */
29 /* Executable header. See [ELF1] 1-4 to 1-8.
30 This appears at the very beginning of an ELF binary. */
33 unsigned char e_ident[16];
42 Elf32_Half e_phentsize;
44 Elf32_Half e_shentsize;
46 Elf32_Half e_shstrndx;
49 /* Program header. See [ELF1] 2-2 to 2-4.
50 There are e_phnum of these, starting at file offset e_phoff
64 /* Values for p_type. See [ELF1] 2-3. */
65 #define PT_NULL 0 /* Ignore. */
66 #define PT_LOAD 1 /* Loadable segment. */
67 #define PT_DYNAMIC 2 /* Dynamic linking info. */
68 #define PT_INTERP 3 /* Name of dynamic loader. */
69 #define PT_NOTE 4 /* Auxiliary info. */
70 #define PT_SHLIB 5 /* Reserved. */
71 #define PT_PHDR 6 /* Program header table. */
72 #define PT_STACK 0x6474e551 /* Stack segment. */
74 /* Flags for p_flags. See [ELF3] 2-3 and 2-4. */
75 #define PF_X 1 /* Executable. */
76 #define PF_W 2 /* Writable. */
77 #define PF_R 4 /* Readable. */
79 static bool load_segment (struct thread *, struct file *,
80 const struct Elf32_Phdr *);
81 static bool setup_stack (struct thread *);
83 /* Aborts loading an executable, with an error message. */
84 #define LOAD_ERROR(MSG) \
86 printf ("addrspace_load: %s: ", filename); \
92 /* Loads an ELF executable from FILENAME into T,
93 and stores the executable's entry point into *START.
94 Returns true if successful, false otherwise. */
96 addrspace_load (struct thread *t, const char *filename, void (**start) (void))
98 struct Elf32_Ehdr ehdr;
100 bool file_open = false;
102 bool success = false;
105 /* Allocate page directory. */
106 t->pagedir = pagedir_create ();
107 if (t->pagedir == NULL)
108 LOAD_ERROR (("page directory allocation failed"));
110 /* Open executable file. */
111 file_open = filesys_open (filename, &file);
113 LOAD_ERROR (("open failed"));
115 /* Read and verify executable header. */
116 if (file_read (&file, &ehdr, sizeof ehdr) != sizeof ehdr)
117 LOAD_ERROR (("error reading executable header"));
118 if (memcmp (ehdr.e_ident, "\177ELF\1\1\1", 7) != 0)
119 LOAD_ERROR (("file is not ELF"));
120 if (ehdr.e_type != 2)
121 LOAD_ERROR (("ELF file is not an executable"));
122 if (ehdr.e_machine != 3)
123 LOAD_ERROR (("ELF executable is not x86"));
124 if (ehdr.e_version != 1)
125 LOAD_ERROR (("ELF executable hasunknown version %d",
126 (int) ehdr.e_version));
127 if (ehdr.e_phentsize != sizeof (struct Elf32_Phdr))
128 LOAD_ERROR (("bad ELF program header size"));
129 if (ehdr.e_phnum > 1024)
130 LOAD_ERROR (("too many ELF program headers"));
132 /* Read program headers. */
133 file_ofs = ehdr.e_phoff;
134 for (i = 0; i < ehdr.e_phnum; i++)
136 struct Elf32_Phdr phdr;
138 file_seek (&file, file_ofs);
139 if (file_read (&file, &phdr, sizeof phdr) != sizeof phdr)
140 LOAD_ERROR (("error reading program header"));
141 file_ofs += sizeof phdr;
148 /* Ignore this segment. */
153 /* Reject the executable. */
154 LOAD_ERROR (("unsupported ELF segment type %d\n", phdr.p_type));
157 printf ("unknown ELF segment type %08x\n", phdr.p_type);
160 if (!load_segment (t, &file, &phdr))
167 if (!setup_stack (t))
171 *start = (void (*) (void)) ehdr.e_entry;
176 /* We arrive here whether the load is successful or not.
177 We can distinguish based on `success'. */
181 addrspace_destroy (t);
185 /* Destroys the user address space in T and frees all of its
188 addrspace_destroy (struct thread *t)
190 if (t->pagedir != NULL)
192 pagedir_destroy (t->pagedir);
197 /* Sets up the CPU for running user code in thread T, if any. */
199 addrspace_activate (struct thread *t)
203 /* Activate T's page tables. */
204 pagedir_activate (t->pagedir);
206 /* Set T's kernel stack for use in processing interrupts. */
207 tss_set_esp0 ((uint8_t *) t + PGSIZE);
210 /* addrspace_load() helpers. */
212 static bool install_page (struct thread *, void *upage, void *kpage);
214 /* Loads the segment described by PHDR from FILE into thread T's
215 user address space. Return true if successful, false
218 load_segment (struct thread *t, struct file *file,
219 const struct Elf32_Phdr *phdr)
221 void *start, *end; /* Page-rounded segment start and end. */
222 uint8_t *upage; /* Iterator from start to end. */
223 off_t filesz_left; /* Bytes left of file data (as opposed to
224 zero-initialized bytes). */
227 ASSERT (file != NULL);
228 ASSERT (phdr != NULL);
229 ASSERT (phdr->p_type == PT_LOAD);
231 /* [ELF1] 2-2 says that p_offset and p_vaddr must be congruent
233 if (phdr->p_offset % PGSIZE != phdr->p_vaddr % PGSIZE)
235 printf ("%#08"PE32Ox" and %#08"PE32Ax" not congruent modulo %#x\n",
236 phdr->p_offset, phdr->p_vaddr, (unsigned) PGSIZE);
240 /* [ELF1] 2-3 says that p_memsz must be at least as big as
242 if (phdr->p_memsz < phdr->p_filesz)
244 printf ("p_memsz (%08"PE32Wx") < p_filesz (%08"PE32Wx")\n",
245 phdr->p_memsz, phdr->p_filesz);
249 /* Validate virtual memory region to be mapped.
250 The region must both start and end within the user address
251 space range starting at 0 and ending at PHYS_BASE (typically
252 3 GB == 0xc0000000). */
253 start = pg_round_down ((void *) phdr->p_vaddr);
254 end = pg_round_up ((void *) (phdr->p_vaddr + phdr->p_memsz));
255 if (start >= PHYS_BASE || end >= PHYS_BASE || end < start)
257 printf ("bad virtual region %08lx...%08lx\n",
258 (unsigned long) start, (unsigned long) end);
262 /* Load the segment page-by-page into memory. */
263 filesz_left = phdr->p_filesz + (phdr->p_vaddr & PGMASK);
264 file_seek (file, ROUND_DOWN (phdr->p_offset, PGSIZE));
265 for (upage = start; upage < (uint8_t *) end; upage += PGSIZE)
267 /* We want to read min(PGSIZE, filesz_left) bytes from the
268 file into the page and zero the rest. */
269 size_t read_bytes = filesz_left >= PGSIZE ? PGSIZE : filesz_left;
270 size_t zero_bytes = PGSIZE - read_bytes;
271 uint8_t *kpage = palloc_get (0);
275 /* Do the reading and zeroing. */
276 if (file_read (file, kpage, read_bytes) != (int) read_bytes)
281 memset (kpage + read_bytes, 0, zero_bytes);
282 filesz_left -= read_bytes;
284 /* Add the page to the process's address space. */
285 if (!install_page (t, upage, kpage))
295 /* Create a minimal stack for T by mapping a zeroed page at the
296 top of user virtual memory. */
298 setup_stack (struct thread *t)
301 bool success = false;
303 kpage = palloc_get (PAL_ZERO);
306 success = install_page (t, ((uint8_t *) PHYS_BASE) - PGSIZE, kpage);
311 printf ("failed to allocate process stack\n");
316 /* Adds a mapping from user virtual address UPAGE to kernel
317 virtual address KPAGE to T's page tables. Fails if UPAGE is
318 already mapped or if memory allocation fails. */
320 install_page (struct thread *t, void *upage, void *kpage)
322 /* Verify that there's not already a page at that virtual
323 address, then map our page there. */
324 return (pagedir_get_page (t->pagedir, upage) == NULL
325 && pagedir_set_page (t->pagedir, upage, kpage, true));