X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fuserprog%2Faddrspace.c;h=10d561658146c5f0f329b4ba74ae56ef85586ff3;hb=7f2927ecf1a95b88002b344c5427644e75467beb;hp=3fa6777e269ad71d845c49c2b997cd67ee11f827;hpb=08d4e82cb3ef48071c8130af662b649711092381;p=pintos-anon diff --git a/src/userprog/addrspace.c b/src/userprog/addrspace.c index 3fa6777..10d5616 100644 --- a/src/userprog/addrspace.c +++ b/src/userprog/addrspace.c @@ -1,29 +1,101 @@ -#include "addrspace.h" +#include "userprog/addrspace.h" +#include #include -#include "debug.h" -#include "file.h" -#include "filesys.h" -#include "init.h" -#include "lib.h" -#include "mmu.h" -#include "paging.h" -#include "palloc.h" -#include "thread.h" -#include "tss.h" +#include +#include +#include +#include "userprog/gdt.h" +#include "userprog/pagedir.h" +#include "userprog/tss.h" +#include "filesys/directory.h" +#include "filesys/file.h" +#include "filesys/filesys.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" + +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 + addrspace_execute() returns.*/ +tid_t +addrspace_execute (const char *filename) +{ + char *fn_copy; + tid_t tid; + + /* Make a copy of FILENAME. + Otherwise there's a race between the caller and load(). */ + fn_copy = palloc_get (0); + if (fn_copy == NULL) + return TID_ERROR; + strlcpy (fn_copy, filename, PGSIZE); + + /* Create a new thread to execute FILENAME. */ + tid = thread_create (filename, PRI_DEFAULT, execute_thread, fn_copy); + if (tid == TID_ERROR) + palloc_free (fn_copy); + return tid; +} +/* A thread function that loads a user process and starts it + running. */ +static void +execute_thread (void *filename_) +{ + char *filename = filename_; + 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_.cs = SEL_UCSEG; + if_.eflags = FLAG_IF | FLAG_MBS; + if_.ss = SEL_UDSEG; + success = load (filename, &if_.eip, &if_.esp); + + /* If load failed, quit. */ + palloc_free (filename); + if (!success) + thread_exit (); + + /* Switch page tables. */ + addrspace_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 + 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_)); + NOT_REACHED (); +} + /* We load ELF binaries. The following definitions are taken - from the ELF specification, [ELF], more-or-less verbatim. */ + 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; -#define PE32Wx PRIx32 -#define PE32Ax PRIx32 -#define PE32Ox PRIx32 -#define PE32Hx PRIx16 +/* For use with ELF types in printf(). */ +#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. +/* Executable header. See [ELF1] 1-4 to 1-8. This appears at the very beginning of an ELF binary. */ struct Elf32_Ehdr { @@ -43,8 +115,9 @@ 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; @@ -57,7 +130,7 @@ struct Elf32_Phdr Elf32_Word p_align; }; -/* Values for p_type. */ +/* 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. */ @@ -67,32 +140,33 @@ struct Elf32_Phdr #define PT_PHDR 6 /* Program header table. */ #define PT_STACK 0x6474e551 /* Stack segment. */ -/* Flags for p_flags. */ +/* 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 install_page (struct thread *, void *upage, void *kpage); -static bool load_segment (struct thread *, struct file *, - const struct Elf32_Phdr *); -static bool setup_stack (struct thread *); +static bool load_segment (struct file *, const struct Elf32_Phdr *); +static bool setup_stack (void **esp); /* Aborts loading an executable, with an error message. */ #define LOAD_ERROR(MSG) \ do { \ - printk ("addrspace_load: %s: ", filename); \ - printk MSG; \ - printk ("\n"); \ - goto error; \ + printf ("load: %s: ", filename); \ + printf MSG; \ + printf ("\n"); \ + goto done; \ } while (0) +/* Loads an ELF executable from FILENAME 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 -addrspace_load (struct thread *t, const char *filename, - void (**start) (void)) +load (const char *filename, void (**eip) (void), void **esp) { + struct thread *t = thread_current (); struct Elf32_Ehdr ehdr; - struct file file; - bool file_open = false; + struct file *file = NULL; off_t file_ofs; bool success = false; int i; @@ -103,12 +177,12 @@ addrspace_load (struct thread *t, const char *filename, LOAD_ERROR (("page directory allocation failed")); /* Open executable file. */ - file_open = filesys_open (filename, &file); - if (!file_open) + file = filesys_open (filename); + if (file == NULL) 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, "\177ELF\1\1\1", 7) != 0) LOAD_ERROR (("file is not ELF")); @@ -130,8 +204,8 @@ addrspace_load (struct thread *t, const char *filename, { struct Elf32_Phdr phdr; - file_seek (&file, file_ofs); - if (file_read (&file, &phdr, sizeof phdr) != sizeof 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) @@ -149,35 +223,37 @@ addrspace_load (struct thread *t, const char *filename, LOAD_ERROR (("unsupported ELF segment type %d\n", phdr.p_type)); break; default: - printk ("unknown ELF segment type %08x\n", phdr.p_type); + printf ("unknown ELF segment type %08x\n", phdr.p_type); break; case PT_LOAD: - if (!load_segment (t, &file, &phdr)) - goto error; + if (!load_segment (file, &phdr)) + goto done; break; } } /* Set up stack. */ - if (!setup_stack (t)) - goto error; + if (!setup_stack (esp)) + goto done; /* Start address. */ - *start = (void (*) (void)) ehdr.e_entry; + *eip = (void (*) (void)) ehdr.e_entry; success = true; - error: - if (file_open) - file_close (&file); - if (!success) - addrspace_destroy (t); + done: + /* We arrive here whether the load is successful or not. */ + file_close (file); return success; } +/* Destroys the user address space in T and frees all of its + resources. */ void addrspace_destroy (struct thread *t) { + ASSERT (t != thread_current ()); + if (t->pagedir != NULL) { pagedir_destroy (t->pagedir); @@ -185,103 +261,141 @@ addrspace_destroy (struct thread *t) } } +/* Sets up the CPU for running user code in the current + thread. */ void -addrspace_activate (struct thread *t) +addrspace_activate (void) { - ASSERT (t != NULL); - + struct thread *t = thread_current (); + + /* 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); } /* addrspace_load() helpers. */ -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. */ - if (pagedir_get_page (t->pagedir, upage) == NULL - && pagedir_set_page (t->pagedir, upage, kpage, true)) - return true; - else - { - palloc_free (kpage); - return false; - } -} +static bool install_page (void *upage, void *kpage); +/* Loads the segment described by PHDR from FILE into user + address space. Return true if successful, false otherwise. */ static bool -load_segment (struct thread *t, struct file *file, - const struct Elf32_Phdr *phdr) +load_segment (struct file *file, const struct Elf32_Phdr *phdr) { - void *start, *end; - uint8_t *upage; - off_t filesz_left; + 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 (t != NULL); ASSERT (file != NULL); ASSERT (phdr != NULL); ASSERT (phdr->p_type == PT_LOAD); - /* p_offset and p_vaddr must be congruent modulo PGSIZE. */ + /* [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", + printf ("%#08"PE32Ox" and %#08"PE32Ax" not congruent modulo %#x\n", phdr->p_offset, phdr->p_vaddr, (unsigned) PGSIZE); return false; } - /* p_memsz must be at least as big as p_filesz. */ + /* [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", + printf ("p_memsz (%08"PE32Wx") < p_filesz (%08"PE32Wx")\n", phdr->p_memsz, phdr->p_filesz); return false; } - /* Validate virtual memory region to be mapped. */ + /* 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", + printf ("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); + uint8_t *kpage = palloc_get (PAL_USER); if (kpage == NULL) return false; - if (file_read (file, kpage, read_bytes) != (int) read_bytes) - return false; + /* 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; - if (!install_page (t, upage, kpage)) - return false; + /* Add the page to the process's address space. */ + if (!install_page (upage, kpage)) + { + palloc_free (kpage); + return false; + } } return true; } +/* Create a minimal stack by mapping a zeroed page at the top of + user virtual memory. */ static bool -setup_stack (struct thread *t) +setup_stack (void **esp) { - uint8_t *kpage = palloc_get (PAL_ZERO); - if (kpage == NULL) + uint8_t *kpage; + bool success = false; + + kpage = palloc_get (PAL_USER | PAL_ZERO); + if (kpage != NULL) { - printk ("failed to allocate process stack\n"); - return false; + success = install_page (((uint8_t *) PHYS_BASE) - PGSIZE, kpage); + if (success) + *esp = PHYS_BASE; + else + palloc_free (kpage); } + else + printf ("failed to allocate process stack\n"); - return install_page (t, ((uint8_t *) PHYS_BASE) - PGSIZE, kpage); + 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. */ +static bool +install_page (void *upage, void *kpage) +{ + 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)); +}