#include <inttypes.h>
#include <round.h>
#include <stdio.h>
+#include <stdlib.h>
#include <string.h>
#include "userprog/gdt.h"
#include "userprog/pagedir.h"
#include "threads/flags.h"
#include "threads/init.h"
#include "threads/interrupt.h"
-#include "threads/mmu.h"
#include "threads/palloc.h"
#include "threads/thread.h"
+#include "threads/vaddr.h"
static thread_func execute_thread NO_RETURN;
static bool load (const char *cmdline, void (**eip) (void), void **esp);
/* Starts a new thread running a user program loaded from
- FILENAME. The new thread may be scheduled before
- process_execute() returns.*/
+ FILENAME. The new thread may be scheduled (and may even exit)
+ before process_execute() returns. Returns the new process's
+ thread id, or TID_ERROR if the thread cannot be created. */
tid_t
-process_execute (const char *filename)
+process_execute (const char *file_name)
{
char *fn_copy;
tid_t tid;
- /* Make a copy of FILENAME.
+ /* Make a copy of FILE_NAME.
Otherwise there's a race between the caller and load(). */
fn_copy = palloc_get_page (0);
if (fn_copy == NULL)
return TID_ERROR;
- strlcpy (fn_copy, filename, PGSIZE);
+ strlcpy (fn_copy, file_name, PGSIZE);
- /* Create a new thread to execute FILENAME. */
- tid = thread_create (filename, PRI_DEFAULT, execute_thread, fn_copy);
+ /* Create a new thread to execute FILE_NAME. */
+ tid = thread_create (file_name, PRI_DEFAULT, execute_thread, fn_copy);
if (tid == TID_ERROR)
palloc_free_page (fn_copy);
return tid;
/* A thread function that loads a user process and starts it
running. */
static void
-execute_thread (void *filename_)
+execute_thread (void *file_name_)
{
- char *filename = filename_;
+ char *file_name = file_name_;
struct intr_frame if_;
bool success;
/* Initialize interrupt frame and load executable. */
memset (&if_, 0, sizeof if_);
- if_.es = SEL_UDSEG;
- if_.ds = SEL_UDSEG;
+ if_.gs = if_.fs = if_.es = if_.ds = if_.ss = SEL_UDSEG;
if_.cs = SEL_UCSEG;
if_.eflags = FLAG_IF | FLAG_MBS;
- if_.ss = SEL_UDSEG;
- success = load (filename, &if_.eip, &if_.esp);
+ success = load (file_name, &if_.eip, &if_.esp);
/* If load failed, quit. */
- palloc_free_page (filename);
+ palloc_free_page (file_name);
if (!success)
thread_exit ();
- /* Switch page tables. */
- process_activate ();
-
/* Start the user process by simulating a return from an
interrupt, implemented by intr_exit (in
- threads/intr-stubs.pl). Because intr_exit takes all of its
+ threads/intr-stubs.S). Because intr_exit takes all of its
arguments on the stack in the form of a `struct intr_frame',
we just point the stack pointer (%esp) to our stack frame
and jump to it. */
- asm ("mov %0, %%esp\n"
- "jmp intr_exit\n"
- : /* no outputs */
- : "g" (&if_));
+ asm volatile ("movl %0, %%esp; jmp intr_exit" : : "g" (&if_) : "memory");
NOT_REACHED ();
}
+/* Waits for thread TID to die and returns its exit status. If
+ it was terminated by the kernel (i.e. killed due to an
+ exception), returns -1. If TID is invalid or if it was not a
+ child of the calling process, or if process_wait() has already
+ been successfully called for the given TID, returns -1
+ immediately, without waiting.
+
+ This function will be implemented in problem 2-2. For now, it
+ does nothing. */
+int
+process_wait (tid_t child_tid UNUSED)
+{
+ return -1;
+}
+
/* Free the current process's resources. */
void
process_exit (void)
uint32_t *pd;
/* Destroy the current process's page directory and switch back
- to the kernel-only page directory. We have to set
- cur->pagedir to NULL before switching page directories, or a
- timer interrupt might switch back to the process page
- directory. */
+ to the kernel-only page directory. */
pd = cur->pagedir;
if (pd != NULL)
{
+ /* Correct ordering here is crucial. We must set
+ cur->pagedir to NULL before switching page directories,
+ so that a timer interrupt can't switch back to the
+ process page directory. We must activate the base page
+ directory before destroying the process's page
+ directory, or our active page directory will be one
+ that's been freed (and cleared). */
cur->pagedir = NULL;
pagedir_activate (NULL);
pagedir_destroy (pd);
#define PF_W 2 /* Writable. */
#define PF_R 4 /* Readable. */
-static bool load_segment (struct file *, const struct Elf32_Phdr *);
static bool setup_stack (void **esp);
+static bool validate_segment (const struct Elf32_Phdr *, struct file *);
+static bool load_segment (struct file *file, off_t ofs, uint8_t *upage,
+ uint32_t read_bytes, uint32_t zero_bytes,
+ bool writable);
-/* Aborts loading an executable, with an error message. */
-#define LOAD_ERROR(MSG) \
- do { \
- printf ("load: %s: ", filename); \
- printf MSG; \
- printf ("\n"); \
- goto done; \
- } while (0)
-
-/* Loads an ELF executable from FILENAME into the current thread.
+/* Loads an ELF executable from FILE_NAME into the current thread.
Stores the executable's entry point into *EIP
and its initial stack pointer into *ESP.
Returns true if successful, false otherwise. */
bool
-load (const char *filename, void (**eip) (void), void **esp)
+load (const char *file_name, void (**eip) (void), void **esp)
{
struct thread *t = thread_current ();
struct Elf32_Ehdr ehdr;
bool success = false;
int i;
- /* Allocate page directory. */
+ /* Allocate and activate page directory. */
t->pagedir = pagedir_create ();
- if (t->pagedir == NULL)
- LOAD_ERROR (("page directory allocation failed"));
+ if (t->pagedir == NULL)
+ goto done;
+ process_activate ();
/* Open executable file. */
- file = filesys_open (filename);
- if (file == NULL)
- LOAD_ERROR (("open failed"));
+ file = filesys_open (file_name);
+ if (file == NULL)
+ {
+ printf ("load: %s: open failed\n", file_name);
+ goto done;
+ }
/* Read and verify executable header. */
- if (file_read (file, &ehdr, sizeof ehdr) != sizeof ehdr)
- LOAD_ERROR (("error reading executable header"));
- if (memcmp (ehdr.e_ident, "\177ELF\1\1\1", 7) != 0)
- LOAD_ERROR (("file is not ELF"));
- if (ehdr.e_type != 2)
- LOAD_ERROR (("ELF file is not an executable"));
- if (ehdr.e_machine != 3)
- LOAD_ERROR (("ELF executable is not x86"));
- if (ehdr.e_version != 1)
- LOAD_ERROR (("ELF executable has unknown version %d",
- (int) ehdr.e_version));
- if (ehdr.e_phentsize != sizeof (struct Elf32_Phdr))
- LOAD_ERROR (("bad ELF program header size"));
- if (ehdr.e_phnum > 1024)
- LOAD_ERROR (("too many ELF program headers"));
+ if (file_read (file, &ehdr, sizeof ehdr) != sizeof ehdr
+ || memcmp (ehdr.e_ident, "\177ELF\1\1\1", 7)
+ || ehdr.e_type != 2
+ || ehdr.e_machine != 3
+ || ehdr.e_version != 1
+ || ehdr.e_phentsize != sizeof (struct Elf32_Phdr)
+ || ehdr.e_phnum > 1024)
+ {
+ printf ("load: %s: error loading executable\n", file_name);
+ goto done;
+ }
/* Read program headers. */
file_ofs = ehdr.e_phoff;
{
struct Elf32_Phdr phdr;
+ if (file_ofs < 0 || file_ofs > file_length (file))
+ goto done;
file_seek (file, file_ofs);
+
if (file_read (file, &phdr, sizeof phdr) != sizeof phdr)
- LOAD_ERROR (("error reading program header"));
+ goto done;
file_ofs += sizeof phdr;
switch (phdr.p_type)
{
case PT_NOTE:
case PT_PHDR:
case PT_STACK:
+ default:
/* 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:
- printf ("unknown ELF segment type %08x\n", phdr.p_type);
- break;
+ goto done;
case PT_LOAD:
- if (!load_segment (file, &phdr))
+ if (validate_segment (&phdr, file))
+ {
+ bool writable = (phdr.p_flags & PF_W) != 0;
+ uint32_t file_page = phdr.p_offset & ~PGMASK;
+ uint32_t mem_page = phdr.p_vaddr & ~PGMASK;
+ uint32_t page_offset = phdr.p_vaddr & PGMASK;
+ uint32_t read_bytes, zero_bytes;
+ if (phdr.p_filesz > 0)
+ {
+ /* Normal segment.
+ Read initial part from disk and zero the rest. */
+ read_bytes = page_offset + phdr.p_filesz;
+ zero_bytes = (ROUND_UP (page_offset + phdr.p_memsz, PGSIZE)
+ - read_bytes);
+ }
+ else
+ {
+ /* Entirely zero.
+ Don't read anything from disk. */
+ read_bytes = 0;
+ zero_bytes = ROUND_UP (page_offset + phdr.p_memsz, PGSIZE);
+ }
+ if (!load_segment (file, file_page, (void *) mem_page,
+ read_bytes, zero_bytes, writable))
+ goto done;
+ }
+ else
goto done;
break;
}
\f
/* load() helpers. */
-static bool install_page (void *upage, void *kpage);
+static bool install_page (void *upage, void *kpage, bool writable);
-/* Loads the segment described by PHDR from FILE into user
- address space. Return true if successful, false otherwise. */
+/* Checks whether PHDR describes a valid, loadable segment in
+ FILE and returns true if so, false otherwise. */
static bool
-load_segment (struct file *file, const struct Elf32_Phdr *phdr)
+validate_segment (const struct Elf32_Phdr *phdr, struct file *file)
{
- 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). */
-
- /* Is this a read-only segment? Not currently used, so it's
- commented out. You'll want to use it when implementing VM
- to decide whether to page the segment from its executable or
- from swap. */
- //bool read_only = (phdr->p_flags & PF_W) == 0;
-
- 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)
- {
- printf ("%#08"PE32Ox" and %#08"PE32Ax" not congruent modulo %#x\n",
- phdr->p_offset, phdr->p_vaddr, (unsigned) PGSIZE);
- return false;
- }
+ /* p_offset and p_vaddr must have the same page offset. */
+ if ((phdr->p_offset & PGMASK) != (phdr->p_vaddr & PGMASK))
+ return false;
+
+ /* p_offset must point within FILE. */
+ if (phdr->p_offset > (Elf32_Off) file_length (file))
+ return false;
- /* [ELF1] 2-3 says that p_memsz must be at least as big as
- p_filesz. */
+ /* p_memsz must be at least as big as p_filesz. */
if (phdr->p_memsz < phdr->p_filesz)
- {
- printf ("p_memsz (%08"PE32Wx") < p_filesz (%08"PE32Wx")\n",
- phdr->p_memsz, phdr->p_filesz);
- return false;
- }
+ return false;
+
+ /* The segment must not be empty. */
+ if (phdr->p_memsz == 0)
+ return false;
+
+ /* The virtual memory region must both start and end within the
+ user address space range. */
+ if (!is_user_vaddr ((void *) phdr->p_vaddr))
+ return false;
+ if (!is_user_vaddr ((void *) (phdr->p_vaddr + phdr->p_memsz)))
+ return false;
+
+ /* The region cannot "wrap around" across the kernel virtual
+ address space. */
+ if (phdr->p_vaddr + phdr->p_memsz < phdr->p_vaddr)
+ return false;
+
+ /* Disallow mapping page 0.
+ Not only is it a bad idea to map page 0, but if we allowed
+ it then user code that passed a null pointer to system calls
+ could quite likely panic the kernel by way of null pointer
+ assertions in memcpy(), etc. */
+ if (phdr->p_vaddr < PGSIZE)
+ return false;
+
+ /* It's okay. */
+ return true;
+}
- /* 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)
- {
- printf ("bad virtual region %08lx...%08lx\n",
- (unsigned long) start, (unsigned long) end);
- return false;
- }
+/* Loads a segment starting at offset OFS in FILE at address
+ UPAGE. In total, READ_BYTES + ZERO_BYTES bytes of virtual
+ memory are initialized, as follows:
+
+ - READ_BYTES bytes at UPAGE must be read from FILE
+ starting at offset OFS.
- /* 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)
+ - ZERO_BYTES bytes at UPAGE + READ_BYTES must be zeroed.
+
+ The pages initialized by this function must be writable by the
+ user process if WRITABLE is true, read-only otherwise.
+
+ Return true if successful, false if a memory allocation error
+ or disk read error occurs. */
+static bool
+load_segment (struct file *file, off_t ofs, uint8_t *upage,
+ uint32_t read_bytes, uint32_t zero_bytes, bool writable)
+{
+ ASSERT ((read_bytes + zero_bytes) % PGSIZE == 0);
+ ASSERT (pg_ofs (upage) == 0);
+ ASSERT (ofs % PGSIZE == 0);
+
+ file_seek (file, ofs);
+ while (read_bytes > 0 || zero_bytes > 0)
{
- /* 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;
+ /* Calculate how to fill this page.
+ We will read PAGE_READ_BYTES bytes from FILE
+ and zero the final PAGE_ZERO_BYTES bytes. */
+ size_t page_read_bytes = read_bytes < PGSIZE ? read_bytes : PGSIZE;
+ size_t page_zero_bytes = PGSIZE - page_read_bytes;
+
+ /* Get a page of memory. */
uint8_t *kpage = palloc_get_page (PAL_USER);
if (kpage == NULL)
return false;
- /* Do the reading and zeroing. */
- if (file_read (file, kpage, read_bytes) != (int) read_bytes)
+ /* Load this page. */
+ if (file_read (file, kpage, page_read_bytes) != (int) page_read_bytes)
{
palloc_free_page (kpage);
return false;
}
- memset (kpage + read_bytes, 0, zero_bytes);
- filesz_left -= read_bytes;
+ memset (kpage + page_read_bytes, 0, page_zero_bytes);
/* Add the page to the process's address space. */
- if (!install_page (upage, kpage))
+ if (!install_page (upage, kpage, writable))
{
palloc_free_page (kpage);
return false;
}
- }
+ /* Advance. */
+ read_bytes -= page_read_bytes;
+ zero_bytes -= page_zero_bytes;
+ upage += PGSIZE;
+ }
return true;
}
kpage = palloc_get_page (PAL_USER | PAL_ZERO);
if (kpage != NULL)
{
- success = install_page (((uint8_t *) PHYS_BASE) - PGSIZE, kpage);
+ success = install_page (((uint8_t *) PHYS_BASE) - PGSIZE, kpage, true);
if (success)
*esp = PHYS_BASE;
else
palloc_free_page (kpage);
}
- else
- printf ("failed to allocate process stack\n");
-
return success;
}
/* Adds a mapping from user virtual address UPAGE to kernel
- virtual address KPAGE to the page table. Fails if UPAGE is
- already mapped or if memory allocation fails. */
+ virtual address KPAGE to the page table.
+ If WRITABLE is true, the user process may modify the page;
+ otherwise, it is read-only.
+ UPAGE must not already be mapped.
+ KPAGE should probably be a page obtained from the user pool
+ with palloc_get_page().
+ Returns true on success, false if UPAGE is already mapped or
+ if memory allocation fails. */
static bool
-install_page (void *upage, void *kpage)
+install_page (void *upage, void *kpage, bool writable)
{
struct thread *t = thread_current ();
/* 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));
+ && pagedir_set_page (t->pagedir, upage, kpage, writable));
}
projects / pintos-anon / blobdiff