/* See COPYRIGHT for copyright information. */ #include #include #include #include #include #include #include #include #include #include #include struct Env *envs = NULL; // All environments struct Env *curenv = NULL; // The current env static struct Env_list env_free_list; // Free list #define ENVGENSHIFT 12 // >= LOGNENV // // Converts an envid to an env pointer. // // RETURNS // 0 on success, -E_BAD_ENV on error. // On success, sets *penv to the environment. // On error, sets *penv to NULL. // int envid2env(envid_t envid, struct Env **env_store, bool checkperm) { struct Env *e; // If envid is zero, return the current environment. if (envid == 0) { *env_store = curenv; return 0; } // Look up the Env structure via the index part of the envid, // then check the env_id field in that struct Env // to ensure that the envid is not stale // (i.e., does not refer to a _previous_ environment // that used the same slot in the envs[] array). e = &envs[ENVX(envid)]; if (e->env_status == ENV_FREE || e->env_id != envid) { *env_store = 0; cprintf("environment is free or has bad value in env_id field \n"); return -E_BAD_ENV; } // Check that the calling environment has legitimate permission // to manipulate the specified environment. // If checkperm is set, the specified environment // must be either the current environment // or an immediate child of the current environment. if (checkperm && e != curenv && e->env_parent_id != curenv->env_id) { *env_store = 0; cprintf("env does not have proper permissions: parent_id %d current id %d e=dest_id %d \n", e->env_parent_id, curenv->env_id, e->env_id); return -E_BAD_ENV; } *env_store = e; return 0; } // // Mark all environments in 'envs' as free, set their env_ids to 0, // and insert them into the env_free_list. // Insert in reverse order, so that the first call to env_alloc() // returns envs[0]. // void env_init(void) { //cprintf("entering env init\n"); int i; LIST_INIT(&env_free_list); for (i = NENV-1; i >= 0; i--) { envs[i].env_id = 0; LIST_INSERT_HEAD(&env_free_list, &envs[i], env_link); } } // // Initialize the kernel virtual memory layout for environment e. // Allocate a page directory, set e->env_pgdir and e->env_cr3 accordingly, // and initialize the kernel portion of the new environment's address space. // Do NOT (yet) map anything into the user portion // of the environment's virtual address space. // // Returns 0 on success, < 0 on error. Errors include: // -E_NO_MEM if page directory or table could not be allocated. // static int env_setup_vm(struct Env *e) { int i, r; struct Page *p = NULL; //cprintf("entering env_setup_vm\n"); // Allocate a page for the page directory if ((r = page_alloc(&p)) < 0) return r; // Now, set e->env_pgdir and e->env_cr3, // and initialize the page directory. // // Hint: // - The VA space of all envs is identical above UTOP // (except at VPT and UVPT, which we've set below). // See inc/memlayout.h for permissions and layout. // Can you use boot_pgdir as a template? Hint: Yes. // (Make sure you got the permissions right in Lab 2.) // - The initial VA below UTOP is empty. // - You do not need to make any more calls to page_alloc. // - Note: pp_ref is not maintained for most physical pages // mapped above UTOP -- but you do need to increment // env_pgdir's pp_ref! // LAB 3: Your code here. p->pp_ref++; //make the page filled with zero but every entry writable e->env_pgdir = (pde_t *)KADDR(page2pa(p)); e->env_cr3 = (physaddr_t)page2pa(p); //should the VA below UTOP be made not present? think no //either make everything zero with PTE_W or use the segment_alloc for (i = PDX(UTOP); i <= PDX(0xffffffff); i++) { e->env_pgdir[i] = boot_pgdir[i] | PTE_W | PTE_U; } for (i = 0; i < PDX(UTOP); i++) { e->env_pgdir[i] = 0 | PTE_U ; //| PTE_W; } //cprintf("in env_setup_vm pgdir of 800000: %x\n", e->env_pgdir[PDX(0x00800000)]); // VPT and UVPT map the env's own page table, with // different permissions. e->env_pgdir[PDX(VPT)] = e->env_cr3 | PTE_P | PTE_W; e->env_pgdir[PDX(UVPT)] = e->env_cr3 | PTE_P | PTE_U; return 0; } // // Allocates and initializes a new environment. // On success, the new environment is stored in *newenv_store. // // Returns 0 on success, < 0 on failure. Errors include: // -E_NO_FREE_ENV if all NENVS environments are allocated // -E_NO_MEM on memory exhaustion // int env_alloc(struct Env **newenv_store, envid_t parent_id) { int32_t generation; int r; struct Env *e; //cprintf("entering environment alloc \n"); if (!(e = LIST_FIRST(&env_free_list))) { cprintf("env_alloc: fails when trying to find an empty environment, all occuppied \n"); return -E_NO_FREE_ENV; } // Allocate and set up the page directory for this environment. if ((r = env_setup_vm(e)) < 0) { cprintf("env_alloc: env_setup_vm fails \n"); return r; } //cprintf("after env_setup_vm in env_alloc pgdir of 800000: %x\n", e->env_pgdir[PDX(0x00800000)]); // Generate an env_id for this environment. generation = (e->env_id + (1 << ENVGENSHIFT)) & ~(NENV - 1); if (generation <= 0) // Don't create a negative env_id. generation = 1 << ENVGENSHIFT; e->env_id = generation | (e - envs); // Set the basic status variables. e->env_parent_id = parent_id; e->env_status = ENV_RUNNABLE; e->env_runs = 0; // Clear out all the saved register state, // to prevent the register values // of a prior environment inhabiting this Env structure // from "leaking" into our new environment. memset(&e->env_tf, 0, sizeof(e->env_tf)); // Set up appropriate initial values for the segment registers. // GD_UD is the user data segment selector in the GDT, and // GD_UT is the user text segment selector (see inc/memlayout.h). // The low 2 bits of each segment register contains the // Requestor Privilege Level (RPL); 3 means user mode. e->env_tf.tf_ds = GD_UD | 3; e->env_tf.tf_es = GD_UD | 3; e->env_tf.tf_ss = GD_UD | 3; e->env_tf.tf_esp = USTACKTOP; e->env_tf.tf_cs = GD_UT | 3; // You will set e->env_tf.tf_eip later. // Enable interrupts while in user mode. // LAB 4: Your code here. e->env_tf.tf_eflags |=FL_IF; // Clear the page fault handler until user installs one. e->env_pgfault_upcall = 0; // Also clear the IPC receiving flag. e->env_ipc_recving = 0; // If this is the file server (e == &envs[1]) give it I/O privileges. // LAB 5: Your code here. if (e == &envs[1]) { e->env_tf.tf_eflags = e->env_tf.tf_eflags | FL_IOPL_3; } else { e->env_tf.tf_eflags = e->env_tf.tf_eflags & (~FL_IOPL_3); } // commit the allocation LIST_REMOVE(e, env_link); *newenv_store = e; cprintf("[%08x] new env %08x\n", curenv ? curenv->env_id : 0, e->env_id); return 0; } // // Allocate len bytes of physical memory for environment env, // and map it at virtual address va in the environment's address space. // Does not zero or otherwise initialize the mapped pages in any way. // Pages should be writable by user and kernel. // Panic if any allocation attempt fails. // static void segment_alloc(struct Env *e, void *va, size_t len) { int i; //cprintf("entering segment alloc \n"); // LAB 3: Your code here. // (But only if you need it for load_icode.) // // Hint: It is easier to use segment_alloc if the caller can pass // 'va' and 'len' values that are not page-aligned. // You should round va down, and round len up. va = (void *)ROUNDDOWN((uintptr_t)va, PGSIZE); len = ROUNDUP(len, PGSIZE); for (i = 0; i < len/PGSIZE ; i++) { //cprintf("in segment alloc loop i = %d va+i*PGSIZE = %x \n", i, va+i*PGSIZE); //allocate a page struct Page *p = NULL; // Allocate a page for the page directory if (page_alloc(&p) < 0) panic("allocation has failed"); //map it at the virtual address if (page_insert(e->env_pgdir, p, va+i*PGSIZE, PTE_U|PTE_W|PTE_P) != 0) { panic("could not insert in segment_alloc\n"); } } //cprintf("done with segment alloc \n"); } // // Set up the initial program binary, stack, and processor flags // for a user process. // This function is ONLY called during kernel initialization, // before running the first user-mode environment. // // This function loads all loadable segments from the ELF binary image // into the environment's user memory, starting at the appropriate // virtual addresses indicated in the ELF program header. // At the same time it clears to zero any portions of these segments // that are marked in the program header as being mapped // but not actually present in the ELF file - i.e., the program's bss section. // // All this is very similar to what our boot loader does, except the boot // loader also needs to read the code from disk. Take a look at // boot/main.c to get ideas. // // Finally, this function maps one page for the program's initial stack. // // load_icode panics if it encounters problems. // - How might load_icode fail? What might be wrong with the given input? // static void load_icode(struct Env *e, uint8_t *binary, size_t size) { // Hints: // Load each program segment into virtual memory // at the address specified in the ELF section header. // You should only load segments with ph->p_type == ELF_PROG_LOAD. // Each segment's virtual address can be found in ph->p_va // and its size in memory can be found in ph->p_memsz. // The ph->p_filesz bytes from the ELF binary, starting at // 'binary + ph->p_offset', should be copied to virtual address // ph->p_va. Any remaining memory bytes should be cleared to zero. // (The ELF header should have ph->p_filesz <= ph->p_memsz.) // Use functions from the previous lab to allocate and map pages. // // All page protection bits should be user read/write for now. // ELF segments are not necessarily page-aligned, but you can // assume for this function that no two segments will touch // the same virtual page. // // You may find a function like segment_alloc useful. // // Loading the segments is much simpler if you can move data // directly into the virtual addresses stored in the ELF binary. // So which page directory should be in force during // this function? // // Hint: // You must also do something with the program's entry point, // to make sure that the environment starts executing there. // What? (See env_run() and env_pop_tf() below.) int min_size; //cprintf("entering load_icode \n"); // LAB 3: Your code here. struct Proghdr *ph, *eph; ph = (struct Proghdr *) ((uint8_t *) binary + ((struct Elf *)binary)->e_phoff); eph = ph + ((struct Elf *)binary)->e_phnum; lcr3(e->env_cr3); for (; ph < eph; ph++) { //allocate some space segment_alloc(e, (void *)ph->p_va, ROUNDUP(ph->p_memsz, PGSIZE)); //cprintf("before memset \n"); memset((void *)ROUNDDOWN(ph->p_va, PGSIZE), 0, ROUNDUP(ph->p_memsz, PGSIZE)); if (ph->p_type == ELF_PROG_LOAD) { memmove((void *)ph->p_va, (void *)binary+ph->p_offset, ph->p_filesz); } } e->env_tf.tf_eip = ((struct Elf *)binary)->e_entry & 0xFFFFFF; lcr3(boot_cr3); // Now map one page for the program's initial stack // at virtual address USTACKTOP - PGSIZE. struct Page *ppstore; if (page_alloc(&ppstore) != 0) { panic("panicked while doing page_alloc in iload\n"); } if (page_insert(e->env_pgdir, ppstore, (void *)USTACKTOP-PGSIZE, PTE_U | PTE_W | PTE_P) != 0) { panic("problem with page insert in iload\n"); } } // // Allocates a new env and loads the named elf binary into it. // This function is ONLY called during kernel initialization, // before running the first user-mode environment. // The new env's parent ID is set to 0. // // Where does the result go? // By convention, envs[0] is the first environment allocated, so // whoever calls env_create simply looks for the newly created // environment there. void env_create(uint8_t *binary, size_t size) { //cprintf("entering env_create\n"); struct Env * e; if (env_alloc(&e, 0) != 0 ) { panic("problem with env_alloc in env_create\n"); } //cprintf("in env_Create before load_icode pgdir of 800000: %x\n", e->env_pgdir[PDX(0x00800000)]); load_icode(e, binary, size); } // // Frees env e and all memory it uses. // void env_free(struct Env *e) { pte_t *pt; uint32_t pdeno, pteno; physaddr_t pa; // If freeing the current environment, switch to boot_pgdir // before freeing the page directory, just in case the page // gets reused. if (e == curenv) lcr3(boot_cr3); // Note the environment's demise. cprintf("[%08x] free env %08x\n", curenv ? curenv->env_id : 0, e->env_id); // Flush all mapped pages in the user portion of the address space static_assert(UTOP % PTSIZE == 0); for (pdeno = 0; pdeno < PDX(UTOP); pdeno++) { // only look at mapped page tables if (!(e->env_pgdir[pdeno] & PTE_P)) continue; // find the pa and va of the page table pa = PTE_ADDR(e->env_pgdir[pdeno]); pt = (pte_t*) KADDR(pa); // unmap all PTEs in this page table for (pteno = 0; pteno <= PTX(~0); pteno++) { if (pt[pteno] & PTE_P) page_remove(e->env_pgdir, PGADDR(pdeno, pteno, 0)); } // free the page table itself e->env_pgdir[pdeno] = 0; page_decref(pa2page(pa)); } // free the page directory pa = e->env_cr3; e->env_pgdir = 0; e->env_cr3 = 0; page_decref(pa2page(pa)); // return the environment to the free list e->env_status = ENV_FREE; LIST_INSERT_HEAD(&env_free_list, e, env_link); } // // Frees environment e. // If e was the current env, then runs a new environment (and does not return // to the caller). // void env_destroy(struct Env *e) { env_free(e); if (curenv == e) { curenv = NULL; sched_yield(); } } // // Restores the register values in the Trapframe with the 'iret' instruction. // This exits the kernel and starts executing some environment's code. // This function does not return. // void env_pop_tf(struct Trapframe *tf) { __asm __volatile("movl %0,%%esp\n" "\tpopal\n" "\tpopl %%es\n" "\tpopl %%ds\n" "\taddl $0x8,%%esp\n" /* skip tf_trapno and tf_errcode */ "\tiret" : : "g" (tf) : "memory"); panic("iret failed"); /* mostly to placate the compiler */ } // // Context switch from curenv to env e. // Note: if this is the first call to env_run, curenv is NULL. // (This function does not return.) // void env_run(struct Env *e) { // Step 1: If this is a context switch (a new environment is running), // then set 'curenv' to the new environment, // update its 'env_runs' counter, and // and use lcr3() to switch to its address space. // Step 2: Use env_pop_tf() to restore the environment's // registers and drop into user mode in the // environment. // Hint: This function loads the new environment's state from // e->env_tf. Go back through the code you wrote above // and make sure you have set the relevant parts of // e->env_tf to sensible values. // LAB 3: Your code here. // cprintf("entering env_run\n"); curenv = e; //cprintf("check envrun 1\n"); e->env_runs++; //cprintf("check envrun 2\n"); lcr3(e->env_cr3); env_pop_tf(&e->env_tf); }