#include "addrspace.h"
+#include <inttypes.h>
+#include "tss.h"
+#include "filesys/file.h"
+#include "filesys/filesys.h"
+#include "lib/debug.h"
+#include "lib/lib.h"
+#include "threads/init.h"
+#include "threads/mmu.h"
+#include "threads/paging.h"
+#include "threads/palloc.h"
+#include "threads/thread.h"
/* We load ELF binaries. The following definitions are taken
- from the ELF specification more-or-less literally. */
+ from the ELF specification, [ELF1], more-or-less verbatim. */
-/* ELF types. */
+/* ELF types. See [ELF1] 1-2. */
typedef uint32_t Elf32_Word, Elf32_Addr, Elf32_Off;
typedef uint16_t Elf32_Half;
-/* Executable header.
+/* For use with ELF types in printk(). */
+#define PE32Wx PRIx32 /* Print Elf32_Word in hexadecimal. */
+#define PE32Ax PRIx32 /* Print Elf32_Addr in hexadecimal. */
+#define PE32Ox PRIx32 /* Print Elf32_Off in hexadecimal. */
+#define PE32Hx PRIx16 /* Print Elf32_Half in hexadecimal. */
+
+/* Executable header. See [ELF1] 1-4 to 1-8.
This appears at the very beginning of an ELF binary. */
struct Elf32_Ehdr
{
Elf32_Half e_shstrndx;
};
-/* Program header.
- There are e_phnum of these, starting at file offset e_phoff. */
+/* Program header. See [ELF1] 2-2 to 2-4.
+ There are e_phnum of these, starting at file offset e_phoff
+ (see [ELF1] 1-6). */
struct Elf32_Phdr
{
Elf32_Word p_type;
Elf32_Word p_align;
};
-/* Values for p_type in struct Elf32_Phdr. */
-#define PT_NULL 0 /* Ignore this program header. */
-#define PT_LOAD 1 /* Loadable segment. */
-#define PT_DYNAMIC 2 /* Dynamic linking info. */
-#define PT_INTERP 3 /* Name of dynamic loader. */
-#define PT_NOTE 4 /* Auxiliary info. */
-#define PT_SHLIB 5 /* Reserved. */
-#define PT_PHDR 6 /* Program header table. */
+/* Values for p_type. See [ELF1] 2-3. */
+#define PT_NULL 0 /* Ignore. */
+#define PT_LOAD 1 /* Loadable segment. */
+#define PT_DYNAMIC 2 /* Dynamic linking info. */
+#define PT_INTERP 3 /* Name of dynamic loader. */
+#define PT_NOTE 4 /* Auxiliary info. */
+#define PT_SHLIB 5 /* Reserved. */
+#define PT_PHDR 6 /* Program header table. */
+#define PT_STACK 0x6474e551 /* Stack segment. */
+
+/* Flags for p_flags. See [ELF3] 2-3 and 2-4. */
+#define PF_X 1 /* Executable. */
+#define PF_W 2 /* Writable. */
+#define PF_R 4 /* Readable. */
+
+static bool load_segment (struct thread *, struct file *,
+ const struct Elf32_Phdr *);
+static bool setup_stack (struct thread *);
+/* Aborts loading an executable, with an error message. */
#define LOAD_ERROR(MSG) \
do { \
printk ("addrspace_load: %s: ", filename); \
printk MSG; \
printk ("\n"); \
- goto error; \
+ goto done; \
} while (0)
+/* Loads an ELF executable from FILENAME into T,
+ and stores the executable's entry point into *START.
+ Returns true if successful, false otherwise. */
bool
-addrspace_load (struct addrspace *as, const char *filename)
+addrspace_load (struct thread *t, const char *filename, void (**start) (void))
{
- Elf32_Ehdr ehdr;
- struct file *file;
+ struct Elf32_Ehdr ehdr;
+ struct file file;
+ bool file_open = false;
+ off_t file_ofs;
+ bool success = false;
+ int i;
- file = filesys_open (filename);
- if (file == NULL)
+ /* Allocate page directory. */
+ t->pagedir = pagedir_create ();
+ if (t->pagedir == NULL)
+ LOAD_ERROR (("page directory allocation failed"));
+
+ /* Open executable file. */
+ file_open = filesys_open (filename, &file);
+ if (!file_open)
LOAD_ERROR (("open failed"));
/* Read and verify executable header. */
- if (file_read (file, &ehdr, sizeof ehdr) != sizeof ehdr)
+ if (file_read (&file, &ehdr, sizeof ehdr) != sizeof ehdr)
LOAD_ERROR (("error reading executable header"));
- if (memcmp (ehdr.e_ident, "\x7fELF\1\1\1", 7) != 0)
- LOAD_ERROR (("not an ELF file"));
+ if (memcmp (ehdr.e_ident, "\177ELF\1\1\1", 7) != 0)
+ LOAD_ERROR (("file is not ELF"));
if (ehdr.e_type != 2)
- LOAD_ERROR (("not an executable"));
+ LOAD_ERROR (("ELF file is not an executable"));
if (ehdr.e_machine != 3)
- LOAD_ERROR (("not an x86 binary"));
+ LOAD_ERROR (("ELF executable is not x86"));
if (ehdr.e_version != 1)
- LOAD_ERROR (("unknown ELF version %d", (int) ehdr.e_version));
+ LOAD_ERROR (("ELF executable hasunknown version %d",
+ (int) ehdr.e_version));
if (ehdr.e_phentsize != sizeof (struct Elf32_Phdr))
- LOAD_ERROR (("bad program header size", (int) ehdr.e_phentsize));
+ LOAD_ERROR (("bad ELF program header size"));
if (ehdr.e_phnum > 1024)
- LOAD_ERROR (("too many program headers"));
+ LOAD_ERROR (("too many ELF program headers"));
/* Read program headers. */
+ file_ofs = ehdr.e_phoff;
+ for (i = 0; i < ehdr.e_phnum; i++)
+ {
+ struct Elf32_Phdr phdr;
+
+ file_seek (&file, file_ofs);
+ if (file_read (&file, &phdr, sizeof phdr) != sizeof phdr)
+ LOAD_ERROR (("error reading program header"));
+ file_ofs += sizeof phdr;
+ switch (phdr.p_type)
+ {
+ case PT_NULL:
+ case PT_NOTE:
+ case PT_PHDR:
+ case PT_STACK:
+ /* Ignore this segment. */
+ break;
+ case PT_DYNAMIC:
+ case PT_INTERP:
+ case PT_SHLIB:
+ /* Reject the executable. */
+ LOAD_ERROR (("unsupported ELF segment type %d\n", phdr.p_type));
+ break;
+ default:
+ printk ("unknown ELF segment type %08x\n", phdr.p_type);
+ break;
+ case PT_LOAD:
+ if (!load_segment (t, &file, &phdr))
+ goto done;
+ break;
+ }
+ }
+
+ /* Set up stack. */
+ if (!setup_stack (t))
+ goto done;
+
+ /* Start address. */
+ *start = (void (*) (void)) ehdr.e_entry;
+
+ success = true;
+
+ done:
+ /* We arrive here whether the load is successful or not.
+ We can distinguish based on `success'. */
+ if (file_open)
+ file_close (&file);
+ if (!success)
+ addrspace_destroy (t);
+ return success;
+}
+
+/* Destroys the user address space in T and frees all of its
+ resources. */
+void
+addrspace_destroy (struct thread *t)
+{
+ if (t->pagedir != NULL)
+ {
+ pagedir_destroy (t->pagedir);
+ t->pagedir = NULL;
+ }
+}
+
+/* Sets up the CPU for running user code in thread T, if any. */
+void
+addrspace_activate (struct thread *t)
+{
+ ASSERT (t != NULL);
+
+ /* Activate T's page tables. */
+ pagedir_activate (t->pagedir);
+
+ /* Set T's kernel stack for use in processing interrupts. */
+ tss_set_esp0 ((uint8_t *) t + PGSIZE);
+}
+\f
+/* addrspace_load() helpers. */
+
+static bool install_page (struct thread *, void *upage, void *kpage);
+
+/* Loads the segment described by PHDR from FILE into thread T's
+ user address space. Return true if successful, false
+ otherwise. */
+static bool
+load_segment (struct thread *t, struct file *file,
+ const struct Elf32_Phdr *phdr)
+{
+ void *start, *end; /* Page-rounded segment start and end. */
+ uint8_t *upage; /* Iterator from start to end. */
+ off_t filesz_left; /* Bytes left of file data (as opposed to
+ zero-initialized bytes). */
+
+ ASSERT (t != NULL);
+ ASSERT (file != NULL);
+ ASSERT (phdr != NULL);
+ ASSERT (phdr->p_type == PT_LOAD);
+
+ /* [ELF1] 2-2 says that p_offset and p_vaddr must be congruent
+ modulo PGSIZE. */
+ if (phdr->p_offset % PGSIZE != phdr->p_vaddr % PGSIZE)
+ {
+ printk ("%#08"PE32Ox" and %#08"PE32Ax" not congruent modulo %#x\n",
+ phdr->p_offset, phdr->p_vaddr, (unsigned) PGSIZE);
+ return false;
+ }
+
+ /* [ELF1] 2-3 says that p_memsz must be at least as big as
+ p_filesz. */
+ if (phdr->p_memsz < phdr->p_filesz)
+ {
+ printk ("p_memsz (%08"PE32Wx") < p_filesz (%08"PE32Wx")\n",
+ phdr->p_memsz, phdr->p_filesz);
+ return false;
+ }
+
+ /* Validate virtual memory region to be mapped.
+ The region must both start and end within the user address
+ space range starting at 0 and ending at PHYS_BASE (typically
+ 3 GB == 0xc0000000). */
+ start = pg_round_down ((void *) phdr->p_vaddr);
+ end = pg_round_up ((void *) (phdr->p_vaddr + phdr->p_memsz));
+ if (start >= PHYS_BASE || end >= PHYS_BASE || end < start)
+ {
+ printk ("bad virtual region %08lx...%08lx\n",
+ (unsigned long) start, (unsigned long) end);
+ return false;
+ }
+
+ /* Load the segment page-by-page into memory. */
+ filesz_left = phdr->p_filesz + (phdr->p_vaddr & PGMASK);
+ file_seek (file, ROUND_DOWN (phdr->p_offset, PGSIZE));
+ for (upage = start; upage < (uint8_t *) end; upage += PGSIZE)
+ {
+ /* We want to read min(PGSIZE, filesz_left) bytes from the
+ file into the page and zero the rest. */
+ size_t read_bytes = filesz_left >= PGSIZE ? PGSIZE : filesz_left;
+ size_t zero_bytes = PGSIZE - read_bytes;
+ uint8_t *kpage = palloc_get (0);
+ if (kpage == NULL)
+ return false;
- as->page_dir = create_page_dir ();
- list_init (&as->vmas);
+ /* Do the reading and zeroing. */
+ if (file_read (file, kpage, read_bytes) != (int) read_bytes)
+ {
+ palloc_free (kpage);
+ return false;
+ }
+ memset (kpage + read_bytes, 0, zero_bytes);
+ filesz_left -= read_bytes;
-
-
+ /* Add the page to the process's address space. */
+ if (!install_page (t, upage, kpage))
+ {
+ palloc_free (kpage);
+ return false;
+ }
+ }
+ return true;
+}
+
+/* Create a minimal stack for T by mapping a zeroed page at the
+ top of user virtual memory. */
+static bool
+setup_stack (struct thread *t)
+{
+ uint8_t *kpage;
+ bool success = false;
+
+ kpage = palloc_get (PAL_ZERO);
+ if (kpage != NULL)
+ {
+ success = install_page (t, ((uint8_t *) PHYS_BASE) - PGSIZE, kpage);
+ if (!success)
+ palloc_free (kpage);
+ }
+ else
+ printk ("failed to allocate process stack\n");
+
+ return success;
+}
+
+/* Adds a mapping from user virtual address UPAGE to kernel
+ virtual address KPAGE to T's page tables. Fails if UPAGE is
+ already mapped or if memory allocation fails. */
+static bool
+install_page (struct thread *t, void *upage, void *kpage)
+{
+ /* Verify that there's not already a page at that virtual
+ address, then map our page there. */
+ return (pagedir_get_page (t->pagedir, upage) == NULL
+ && pagedir_set_page (t->pagedir, upage, kpage, true));
}
projects / pintos-anon / blobdiff