C++ do_brk函数代码示例

static void set_brk(unsigned long start, unsigned long end)
{
	start = ELF_PAGEALIGN(start);
	end = ELF_PAGEALIGN(end);
	if (end <= start)
		return;
	do_brk(start, end - start);
}

static void set_brk(unsigned long start, unsigned long end)
{
	start = PAGE_ALIGN(start);
	end = PAGE_ALIGN(end);
	if (end <= start)
		return;
	down_write(&current->mm->mmap_sem);
	do_brk(start, end - start);
	up_write(&current->mm->mmap_sem);
}

asmlinkage unsigned long
ia64_brk (unsigned long brk, long arg1, long arg2, long arg3,
	  long arg4, long arg5, long arg6, long arg7, long stack)
{
	extern int vm_enough_memory (long pages);
	struct pt_regs *regs = (struct pt_regs *) &stack;
	unsigned long rlim, retval, newbrk, oldbrk;
	struct mm_struct *mm = current->mm;

	/*
	 * Most of this replicates the code in sys_brk() except for an additional safety
	 * check and the clearing of r8.  However, we can't call sys_brk() because we need
	 * to acquire the mmap_sem before we can do the test...
	 */
	down_write(&mm->mmap_sem);

	if (brk < mm->end_code)
		goto out;
	newbrk = PAGE_ALIGN(brk);
	oldbrk = PAGE_ALIGN(mm->brk);
	if (oldbrk == newbrk)
		goto set_brk;

	/* Always allow shrinking brk. */
	if (brk <= mm->brk) {
		if (!do_munmap(mm, newbrk, oldbrk-newbrk,1))
			goto set_brk;
		goto out;
	}

	/* Check against unimplemented/unmapped addresses: */
	if ((newbrk - oldbrk) > RGN_MAP_LIMIT || rgn_offset(newbrk) > RGN_MAP_LIMIT)
		goto out;

	/* Check against rlimit.. */
	rlim = current->rlim[RLIMIT_DATA].rlim_cur;
	if (rlim < RLIM_INFINITY && brk - mm->start_data > rlim)
		goto out;

	/* Check against existing mmap mappings. */
	if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
		goto out;

	/* Ok, looks good - let it rip. */
	if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
		goto out;
set_brk:
	mm->brk = brk;
out:
	retval = mm->brk;
	up_write(&mm->mmap_sem);
	regs->r8 = 0;		/* ensure large retval isn't mistaken as error code */
	return retval;
}

static void *sys_brk(void *addr) {
	void *ret;
	int err;

	if (0 == (err = do_brk(addr, &ret))) {
		return ret;
	} else {
		curthr->kt_errno = -err;
		return (void *) -1;
	}
}

asmlinkage int sunos_brk(u32 baddr)
{
	int freepages, retval = -ENOMEM;
	unsigned long rlim;
	unsigned long newbrk, oldbrk, brk = (unsigned long) baddr;

	down_write(&current->mm->mmap_sem);
	if (brk < current->mm->end_code)
		goto out;
	newbrk = PAGE_ALIGN(brk);
	oldbrk = PAGE_ALIGN(current->mm->brk);
	retval = 0;
	if (oldbrk == newbrk) {
		current->mm->brk = brk;
		goto out;
	}
	/* Always allow shrinking brk. */
	if (brk <= current->mm->brk) {
		current->mm->brk = brk;
		do_munmap(current->mm, newbrk, oldbrk-newbrk);
		goto out;
	}
	/* Check against rlimit and stack.. */
	retval = -ENOMEM;
	rlim = current->rlim[RLIMIT_DATA].rlim_cur;
	if (rlim >= RLIM_INFINITY)
		rlim = ~0;
	if (brk - current->mm->end_code > rlim)
		goto out;
	/* Check against existing mmap mappings. */
	if (find_vma_intersection(current->mm, oldbrk, newbrk+PAGE_SIZE))
		goto out;
	/* stupid algorithm to decide if we have enough memory: while
	 * simple, it hopefully works in most obvious cases.. Easy to
	 * fool it, but this should catch most mistakes.
	 */
	freepages = get_page_cache_size();
	freepages >>= 1;
	freepages += nr_free_pages();
	freepages += nr_swap_pages;
	freepages -= num_physpages >> 4;
	freepages -= (newbrk-oldbrk) >> PAGE_SHIFT;
	if (freepages < 0)
		goto out;
	/* Ok, we have probably got enough memory - let it rip. */
	current->mm->brk = brk;
	do_brk(oldbrk, newbrk-oldbrk);
	retval = 0;
out:
	up_write(&current->mm->mmap_sem);
	return retval;
}

asmlinkage unsigned long
ia64_brk (unsigned long brk)
{
	unsigned long rlim, retval, newbrk, oldbrk;
	struct mm_struct *mm = current->mm;

	/*
	 * Most of this replicates the code in sys_brk() except for an additional safety
	 * check and the clearing of r8.  However, we can't call sys_brk() because we need
	 * to acquire the mmap_sem before we can do the test...
	 */
	down_write(&mm->mmap_sem);

	if (brk < mm->end_code)
		goto out;
	newbrk = PAGE_ALIGN(brk);
	oldbrk = PAGE_ALIGN(mm->brk);
	if (oldbrk == newbrk)
		goto set_brk;

	/* Always allow shrinking brk. */
	if (brk <= mm->brk) {
		if (!do_munmap(mm, newbrk, oldbrk-newbrk))
			goto set_brk;
		goto out;
	}

	/* Check against unimplemented/unmapped addresses: */
	if ((newbrk - oldbrk) > RGN_MAP_LIMIT || REGION_OFFSET(newbrk) > RGN_MAP_LIMIT)
		goto out;

	/* Check against rlimit.. */
	rlim = current->signal->rlim[RLIMIT_DATA].rlim_cur;
	if (rlim < RLIM_INFINITY && brk - mm->start_data > rlim)
		goto out;

	/* Check against existing mmap mappings. */
	if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
		goto out;

	/* Ok, looks good - let it rip. */
	if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
		goto out;
set_brk:
	mm->brk = brk;
out:
	retval = mm->brk;
	up_write(&mm->mmap_sem);
	force_successful_syscall_return();
	return retval;
}

SYSCALL_DEFINE1(brk, unsigned long, brk)
{
	unsigned long rlim, retval;
	unsigned long newbrk, oldbrk;
	struct mm_struct *mm = current->mm;
	unsigned long min_brk;

	down_write(&mm->mmap_sem);

#ifdef CONFIG_COMPAT_BRK
	if (current->brk_randomized)
		min_brk = mm->start_brk;
	else
		min_brk = mm->end_data;
#else
	min_brk = mm->start_brk;
#endif
	if (brk < min_brk)
		goto out;

	rlim = rlimit(RLIMIT_DATA);
	if (rlim < RLIM_INFINITY && (brk - mm->start_brk) +
			(mm->end_data - mm->start_data) > rlim)
		goto out;

	newbrk = PAGE_ALIGN(brk);
	oldbrk = PAGE_ALIGN(mm->brk);
	if (oldbrk == newbrk)
		goto set_brk;

	
	if (brk <= mm->brk) {
		if (!do_munmap(mm, newbrk, oldbrk-newbrk))
			goto set_brk;
		goto out;
	}

	
	if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
		goto out;

	
	if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
		goto out;
set_brk:
	mm->brk = brk;
out:
	retval = mm->brk;
	up_write(&mm->mmap_sem);
	return retval;
}

static int set_brk(unsigned long start, unsigned long end)
{
	start = PAGE_ALIGN(start);
	end = PAGE_ALIGN(end);
	if (end > start) {
		unsigned long addr;
		down_write(&current->mm->mmap_sem);
		addr = do_brk(start, end - start);
		up_write(&current->mm->mmap_sem);
		if (BAD_ADDR(addr))
			return addr;
	}
	return 0;
}

/*
 * IRIX maps a page at 0x200000 that holds information about the
 * process and the system, here we map the page and fill the
 * structure
 */
void irix_map_prda_page (void)
{
	unsigned long v;
	struct prda *pp;

	v =  do_brk (PRDA_ADDRESS, PAGE_SIZE);

	if (v < 0)
		return;

	pp = (struct prda *) v;
	pp->prda_sys.t_pid  = current->pid;
	pp->prda_sys.t_prid = read_c0_prid();
	pp->prda_sys.t_rpid = current->pid;

	/* We leave the rest set to zero */
}

/*
 * IRIX maps a page at 0x200000 that holds information about the
 * process and the system, here we map the page and fill the
 * structure
 */
static void irix_map_prda_page(void)
{
	unsigned long v;
	struct prda *pp;

	down_write(&current->mm->mmap_sem);
	v =  do_brk(PRDA_ADDRESS, PAGE_SIZE);
	up_write(&current->mm->mmap_sem);

	if (v < 0)
		return;

	pp = (struct prda *) v;
	pp->prda_sys.t_pid  = task_pid_vnr(current);
	pp->prda_sys.t_prid = read_c0_prid();
	pp->prda_sys.t_rpid = task_pid_vnr(current);

	/* We leave the rest set to zero */
}

/*
 *  sys_brk() for the most part doesn't need the global kernel
 *  lock, except when an application is doing something nasty
 *  like trying to un-brk an area that has already been mapped
 *  to a regular file.  in this case, the unmapping will need
 *  to invoke file system routines that need the global lock.
 */
asmlinkage unsigned long sys_brk(unsigned long brk)
{
	unsigned long rlim, retval;
	unsigned long newbrk, oldbrk;
	struct mm_struct *mm = current->mm;

	down_write(&mm->mmap_sem);

	if (brk < mm->end_code)
		goto out;
	newbrk = PAGE_ALIGN(brk);
	oldbrk = PAGE_ALIGN(mm->brk);
	if (oldbrk == newbrk)
		goto set_brk;

	/* Always allow shrinking brk. */
	if (brk <= mm->brk) {
		if (!do_munmap(mm, newbrk, oldbrk-newbrk))
			goto set_brk;
		goto out;
	}

	/* Check against rlimit.. */
	rlim = current->rlim[RLIMIT_DATA].rlim_cur;
	if (rlim < RLIM_INFINITY && brk - mm->start_data > rlim)
		goto out;

	/* Check against existing mmap mappings. */
	if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
		goto out;

	/* Ok, looks good - let it rip. */
	if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
		goto out;
set_brk:
	mm->brk = brk;
out:
	retval = mm->brk;
	up_write(&mm->mmap_sem);
	return retval;
}

static unsigned long load_elf_interp(struct elfhdr * interp_elf_ex,
				     struct file * interpreter,
				     unsigned long *interp_load_addr)
{
	struct elf_phdr *elf_phdata;
	struct elf_phdr *eppnt;
	unsigned long load_addr = 0;
	int load_addr_set = 0;
	unsigned long last_bss = 0, elf_bss = 0;
	unsigned long error = ~0UL;
	int retval, i, size;

	/* First of all, some simple consistency checks */
	if (interp_elf_ex->e_type != ET_EXEC &&
	    interp_elf_ex->e_type != ET_DYN)
		goto out;
	if (!elf_check_arch(interp_elf_ex))
		goto out;
	if (!interpreter->f_op || !interpreter->f_op->mmap)
		goto out;

	/*
	 * If the size of this structure has changed, then punt, since
	 * we will be doing the wrong thing.
	 */
	if (interp_elf_ex->e_phentsize != sizeof(struct elf_phdr))
		goto out;
	if (interp_elf_ex->e_phnum > 65536U / sizeof(struct elf_phdr))
		goto out;

	/* Now read in all of the header information */

	size = sizeof(struct elf_phdr) * interp_elf_ex->e_phnum;
	if (size > ELF_MIN_ALIGN)
		goto out;
	elf_phdata = (struct elf_phdr *) kmalloc(size, GFP_KERNEL);
	if (!elf_phdata)
		goto out;

	retval = kernel_read(interpreter,interp_elf_ex->e_phoff,(char *)elf_phdata,size);
	error = retval;
	if (retval < 0)
		goto out_close;

	eppnt = elf_phdata;
	for (i=0; i<interp_elf_ex->e_phnum; i++, eppnt++) {
	  if (eppnt->p_type == PT_LOAD) {
	    int elf_type = MAP_PRIVATE | MAP_DENYWRITE;
	    int elf_prot = 0;
	    unsigned long vaddr = 0;
	    unsigned long k, map_addr;

	    if (eppnt->p_flags & PF_R) elf_prot =  PROT_READ;
	    if (eppnt->p_flags & PF_W) elf_prot |= PROT_WRITE;
	    if (eppnt->p_flags & PF_X) elf_prot |= PROT_EXEC;
	    vaddr = eppnt->p_vaddr;
	    if (interp_elf_ex->e_type == ET_EXEC || load_addr_set)
	    	elf_type |= MAP_FIXED;

	    map_addr = elf_map(interpreter, load_addr + vaddr, eppnt, elf_prot, elf_type);
	    if (BAD_ADDR(map_addr))
	    	goto out_close;

	    if (!load_addr_set && interp_elf_ex->e_type == ET_DYN) {
		load_addr = map_addr - ELF_PAGESTART(vaddr);
		load_addr_set = 1;
	    }

	    /*
	     * Find the end of the file mapping for this phdr, and keep
	     * track of the largest address we see for this.
	     */
	    k = load_addr + eppnt->p_vaddr + eppnt->p_filesz;
	    if (k > elf_bss)
		elf_bss = k;

	    /*
	     * Do the same thing for the memory mapping - between
	     * elf_bss and last_bss is the bss section.
	     */
	    k = load_addr + eppnt->p_memsz + eppnt->p_vaddr;
	    if (k > last_bss)
		last_bss = k;
	  }
	}

	/* Now use mmap to map the library into memory. */

	/*
	 * Now fill out the bss section.  First pad the last page up
	 * to the page boundary, and then perform a mmap to make sure
	 * that there are zero-mapped pages up to and including the 
	 * last bss page.
	 */
	padzero(elf_bss);
	elf_bss = ELF_PAGESTART(elf_bss + ELF_MIN_ALIGN - 1);	/* What we have mapped so far */

	/* Map the last of the bss segment */
	if (last_bss > elf_bss)
		do_brk(elf_bss, last_bss - elf_bss);
//.........这里部分代码省略.........

/* This is really simpleminded and specialized - we are loading an
 * a.out library that is given an ELF header.
 */
static int load_irix_library(struct file *file)
{
	struct elfhdr elf_ex;
	struct elf_phdr *elf_phdata  =  NULL;
	unsigned int len = 0;
	int elf_bss = 0;
	int retval;
	unsigned int bss;
	int error;
	int i, j, k;

	error = kernel_read(file, 0, (char *) &elf_ex, sizeof(elf_ex));
	if (error != sizeof(elf_ex))
		return -ENOEXEC;

	if (memcmp(elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
		return -ENOEXEC;

	/* First of all, some simple consistency checks. */
	if (elf_ex.e_type != ET_EXEC || elf_ex.e_phnum > 2 ||
	   !file->f_op->mmap)
		return -ENOEXEC;

	/* Now read in all of the header information. */
	if (sizeof(struct elf_phdr) * elf_ex.e_phnum > PAGE_SIZE)
		return -ENOEXEC;

	elf_phdata = kmalloc(sizeof(struct elf_phdr) * elf_ex.e_phnum, GFP_KERNEL);
	if (elf_phdata == NULL)
		return -ENOMEM;

	retval = kernel_read(file, elf_ex.e_phoff, (char *) elf_phdata,
			   sizeof(struct elf_phdr) * elf_ex.e_phnum);

	j = 0;
	for (i=0; i<elf_ex.e_phnum; i++)
		if ((elf_phdata + i)->p_type == PT_LOAD) j++;

	if (j != 1)  {
		kfree(elf_phdata);
		return -ENOEXEC;
	}

	while (elf_phdata->p_type != PT_LOAD) elf_phdata++;

	/* Now use mmap to map the library into memory. */
	down_write(&current->mm->mmap_sem);
	error = do_mmap(file,
			elf_phdata->p_vaddr & 0xfffff000,
			elf_phdata->p_filesz + (elf_phdata->p_vaddr & 0xfff),
			PROT_READ | PROT_WRITE | PROT_EXEC,
			MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
			elf_phdata->p_offset & 0xfffff000);
	up_write(&current->mm->mmap_sem);

	k = elf_phdata->p_vaddr + elf_phdata->p_filesz;
	if (k > elf_bss) elf_bss = k;

	if (error != (elf_phdata->p_vaddr & 0xfffff000)) {
		kfree(elf_phdata);
		return error;
	}

	padzero(elf_bss);

	len = (elf_phdata->p_filesz + elf_phdata->p_vaddr+ 0xfff) & 0xfffff000;
	bss = elf_phdata->p_memsz + elf_phdata->p_vaddr;
	if (bss > len) {
	  down_write(&current->mm->mmap_sem);
	  do_brk(len, bss-len);
	  up_write(&current->mm->mmap_sem);
	}
	kfree(elf_phdata);
	return 0;
}

void do_m68k_simcall(CPUM68KState *env, int nr)
{
    uint32_t *args;

    args = (uint32_t *)(env->aregs[7] + 4);
    switch (nr) {
    case SYS_EXIT:
        exit(ARG(0));
    case SYS_READ:
        check_err(env, read(ARG(0), (void *)ARG(1), ARG(2)));
        break;
    case SYS_WRITE:
        check_err(env, write(ARG(0), (void *)ARG(1), ARG(2)));
        break;
    case SYS_OPEN:
        check_err(env, open((char *)ARG(0), translate_openflags(ARG(1)),
                            ARG(2)));
        break;
    case SYS_CLOSE:
        {
            /* Ignore attempts to close stdin/out/err.  */
            int fd = ARG(0);
            if (fd > 2)
              check_err(env, close(fd));
            else
              check_err(env, 0);
            break;
        }
    case SYS_BRK:
        {
            int32_t ret;

            ret = do_brk((void *)ARG(0));
            if (ret == -ENOMEM)
                ret = -1;
            check_err(env, ret);
        }
        break;
    case SYS_FSTAT:
        {
            struct stat s;
            int rc;
            struct m86k_sim_stat *p;
            rc = check_err(env, fstat(ARG(0), &s));
            if (rc == 0) {
                p = (struct m86k_sim_stat *)ARG(1);
                p->sim_st_dev = tswap16(s.st_dev);
                p->sim_st_ino = tswap16(s.st_ino);
                p->sim_st_mode = tswap32(s.st_mode);
                p->sim_st_nlink = tswap16(s.st_nlink);
                p->sim_st_uid = tswap16(s.st_uid);
                p->sim_st_gid = tswap16(s.st_gid);
                p->sim_st_rdev = tswap16(s.st_rdev);
                p->sim_st_size = tswap32(s.st_size);
                p->sim_st_atime = tswap32(s.st_atime);
                p->sim_st_mtime = tswap32(s.st_mtime);
                p->sim_st_ctime = tswap32(s.st_ctime);
                p->sim_st_blksize = tswap32(s.st_blksize);
                p->sim_st_blocks = tswap32(s.st_blocks);
            }
        }
        break;
    case SYS_ISATTY:
        check_err(env, isatty(ARG(0)));
        break;
    case SYS_LSEEK:
        check_err(env, lseek(ARG(0), (int32_t)ARG(1), ARG(2)));
        break;
    default:
        cpu_abort(env, "Unsupported m68k sim syscall %d\n", nr);
    }
}

/**
 * <Ring 1> The main loop of TASK MM.
 * 
 *****************************************************************************/
PUBLIC void task_mm()
{
	init_mm();

	while (1) {
		send_recv(RECEIVE, ANY, &mm_msg);
		int src = mm_msg.source;
		int reply = 1;

		int msgtype = mm_msg.type;

		switch (msgtype) {
		case FORK:
			mm_msg.RETVAL = do_fork();
			break;
		case EXIT:
			do_exit(mm_msg.STATUS);
			reply = 0;
			break;
		case EXEC:
			mm_msg.RETVAL = do_exec();
			break;
		case WAIT:
			do_wait();
			reply = 0;
			break;
		case KILL:
			mm_msg.RETVAL = do_kill();
			break; 
		case RAISE:
			mm_msg.RETVAL = do_raise();
			break;
		case BRK:
			mm_msg.RETVAL = do_brk();
			break;
		case ACCT:
			mm_msg.RETVAL = do_acct();
			break;
		case GETUID:
			mm_msg.RETVAL = do_getuid();
			break;
		case SETUID:
            mm_msg.RETVAL = do_setuid();
			break;
		case GETGID:
			mm_msg.RETVAL = do_getgid();
			break;
		case SETGID:
			mm_msg.RETVAL = do_setgid();
			break;
		case GETEUID:
			mm_msg.RETVAL = do_geteuid();
			break;
		case GETEGID:
			mm_msg.RETVAL = do_getegid();
			break;
		case SIGACTION:
			mm_msg.RETVAL = do_sigaction();
			break;
		case ALARM:
			mm_msg.RETVAL = do_alarm();
			break;
		default:
			dump_msg("MM::unknown msg", &mm_msg);
			assert(0);
			break;
		}

		if (reply) {
			mm_msg.type = SYSCALL_RET;
			send_recv(SEND, src, &mm_msg);
		}
	}
}