diff options
| -rw-r--r-- | src/userprog/load.c | 65 |
1 files changed, 40 insertions, 25 deletions
diff --git a/src/userprog/load.c b/src/userprog/load.c index eabc056..32bc42e 100644 --- a/src/userprog/load.c +++ b/src/userprog/load.c @@ -77,7 +77,7 @@ 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, +static bool load_segment (struct file *file, off_t ofs, uint8_t *upage, uint32_t uoffset, uint32_t read_bytes, uint32_t zero_bytes, bool writable); @@ -157,7 +157,7 @@ load (const char *file_name, void (**eip) (void), void **esp) if (validate_segment (&phdr, file)) { bool writable = (phdr.p_flags & PF_W) != 0; - uint32_t file_page = phdr.p_offset & ~PGMASK; + uint32_t file_offset = phdr.p_offset; uint32_t mem_page = phdr.p_vaddr & ~PGMASK; uint32_t page_offset = phdr.p_vaddr & PGMASK; uint32_t read_bytes, zero_bytes; @@ -165,18 +165,18 @@ load (const char *file_name, void (**eip) (void), void **esp) { /* Normal segment. Read initial part from disk and zero the rest. */ - read_bytes = page_offset + phdr.p_filesz; + read_bytes = phdr.p_filesz; zero_bytes = (ROUND_UP (page_offset + phdr.p_memsz, PGSIZE) - - read_bytes); + - read_bytes - page_offset); } - else + else { /* Entirely zero. Don't read anything from disk. */ read_bytes = 0; - zero_bytes = ROUND_UP (page_offset + phdr.p_memsz, PGSIZE); + zero_bytes = ROUND_UP (page_offset + phdr.p_memsz, PGSIZE) - page_offset; } - if (!load_segment (file, file_page, (void *) mem_page, + if (!load_segment (file, file_offset, (void *) mem_page, page_offset, read_bytes, zero_bytes, writable)) goto done; } @@ -261,45 +261,60 @@ validate_segment (const struct Elf32_Phdr *phdr, struct file *file) 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) +load_segment (struct file *file, off_t ofs, uint8_t *upage, uint32_t page_offset, + uint32_t read_bytes, uint32_t zero_bytes, bool writable) { - ASSERT ((read_bytes + zero_bytes) % PGSIZE == 0); + ASSERT ((page_offset + read_bytes + zero_bytes) % PGSIZE == 0); ASSERT (pg_ofs (upage) == 0); - ASSERT (ofs % PGSIZE == 0); + + struct thread *t = thread_current(); file_seek (file, ofs); - while (read_bytes > 0 || zero_bytes > 0) + while (read_bytes > 0 || zero_bytes > 0) { /* 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_read_bytes = page_offset + read_bytes; + if (page_read_bytes > PGSIZE) + page_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); + /* Get a page of memory. + * If it was present previously at the indicated address in userspace, then we use that. */ + bool new_kpage = false; + uint8_t *kpage = pagedir_get_page (t->pagedir, upage); + if (!kpage) + { + new_kpage = true; + kpage = palloc_get_page (PAL_USER); + } if (kpage == NULL) return false; /* Load this page. */ - if (file_read (file, kpage, page_read_bytes) != (int) page_read_bytes) + if (file_read (file, kpage + page_offset, page_read_bytes - page_offset) != (int) (page_read_bytes - page_offset)) { - palloc_free_page (kpage); - return false; + if (new_kpage) + palloc_free_page (kpage); + return false; } memset (kpage + page_read_bytes, 0, page_zero_bytes); - /* Add the page to the process's address space. */ - if (!install_page (upage, kpage, writable)) - { - palloc_free_page (kpage); - return false; - } + /* Add the page to the process's address space if not done already */ + if (new_kpage) + { + if (!install_page (upage, kpage, writable)) + { + palloc_free_page (kpage); + return false; + } + } /* Advance. */ - read_bytes -= page_read_bytes; + read_bytes -= page_read_bytes - page_offset; zero_bytes -= page_zero_bytes; + page_offset = 0; upage += PGSIZE; } return true; |