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binfmt_aout32.c

/*
 *  linux/fs/binfmt_aout.c
 *
 *  Copyright (C) 1991, 1992, 1996  Linus Torvalds
 *
 *  Hacked a bit by DaveM to make it work with 32-bit SunOS
 *  binaries on the sparc64 port.
 */

#include <linux/module.h>

#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/a.out.h>
#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/string.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/ptrace.h>
#include <linux/user.h>
#include <linux/slab.h>
#include <linux/binfmts.h>
#include <linux/personality.h>
#include <linux/init.h>

#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/pgalloc.h>
#include <asm/mmu_context.h>

static int load_aout32_binary(struct linux_binprm *, struct pt_regs * regs);
static int load_aout32_library(struct file*);
static int aout32_core_dump(long signr, struct pt_regs *regs, struct file *file, unsigned long limit);

static struct linux_binfmt aout32_format = {
      .module           = THIS_MODULE,
      .load_binary      = load_aout32_binary,
      .load_shlib = load_aout32_library,
      .core_dump  = aout32_core_dump,
      .min_coredump     = PAGE_SIZE,
};

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);
}

/*
 * These are the only things you should do on a core-file: use only these
 * macros to write out all the necessary info.
 */

static int dump_write(struct file *file, const void *addr, int nr)
{
      return file->f_op->write(file, addr, nr, &file->f_pos) == nr;
}

#define DUMP_WRITE(addr, nr)  \
      if (!dump_write(file, (void *)(addr), (nr))) \
            goto end_coredump;

#define DUMP_SEEK(offset) \
if (file->f_op->llseek) { \
      if (file->f_op->llseek(file,(offset),0) != (offset)) \
            goto end_coredump; \
} else file->f_pos = (offset)

/*
 * Routine writes a core dump image in the current directory.
 * Currently only a stub-function.
 *
 * Note that setuid/setgid files won't make a core-dump if the uid/gid
 * changed due to the set[u|g]id. It's enforced by the "current->mm->dumpable"
 * field, which also makes sure the core-dumps won't be recursive if the
 * dumping of the process results in another error..
 */

static int aout32_core_dump(long signr, struct pt_regs *regs, struct file *file, unsigned long limit)
{
      mm_segment_t fs;
      int has_dumped = 0;
      unsigned long dump_start, dump_size;
      struct user dump;
#       define START_DATA(u)    (u.u_tsize)
#       define START_STACK(u)   ((regs->u_regs[UREG_FP]) & ~(PAGE_SIZE - 1))

      fs = get_fs();
      set_fs(KERNEL_DS);
      has_dumped = 1;
      current->flags |= PF_DUMPCORE;
            strncpy(dump.u_comm, current->comm, sizeof(dump.u_comm));
      dump.signal = signr;
      dump_thread(regs, &dump);

/* If the size of the dump file exceeds the rlimit, then see what would happen
   if we wrote the stack, but not the data area.  */
      if (dump.u_dsize + dump.u_ssize > limit)
            dump.u_dsize = 0;

/* Make sure we have enough room to write the stack and data areas. */
      if (dump.u_ssize > limit)
            dump.u_ssize = 0;

/* make sure we actually have a data and stack area to dump */
      set_fs(USER_DS);
      if (!access_ok(VERIFY_READ, (void __user *) START_DATA(dump), dump.u_dsize))
            dump.u_dsize = 0;
      if (!access_ok(VERIFY_READ, (void __user *) START_STACK(dump), dump.u_ssize))
            dump.u_ssize = 0;

      set_fs(KERNEL_DS);
/* struct user */
      DUMP_WRITE(&dump,sizeof(dump));
/* now we start writing out the user space info */
      set_fs(USER_DS);
/* Dump the data area */
      if (dump.u_dsize != 0) {
            dump_start = START_DATA(dump);
            dump_size = dump.u_dsize;
            DUMP_WRITE(dump_start,dump_size);
      }
/* Now prepare to dump the stack area */
      if (dump.u_ssize != 0) {
            dump_start = START_STACK(dump);
            dump_size = dump.u_ssize;
            DUMP_WRITE(dump_start,dump_size);
      }
/* Finally dump the task struct.  Not be used by gdb, but could be useful */
      set_fs(KERNEL_DS);
      DUMP_WRITE(current,sizeof(*current));
end_coredump:
      set_fs(fs);
      return has_dumped;
}

/*
 * create_aout32_tables() parses the env- and arg-strings in new user
 * memory and creates the pointer tables from them, and puts their
 * addresses on the "stack", returning the new stack pointer value.
 */

static u32 __user *create_aout32_tables(char __user *p, struct linux_binprm *bprm)
{
      u32 __user *argv;
      u32 __user *envp;
      u32 __user *sp;
      int argc = bprm->argc;
      int envc = bprm->envc;

      sp = (u32 __user *)((-(unsigned long)sizeof(char *))&(unsigned long)p);

      /* This imposes the proper stack alignment for a new process. */
      sp = (u32 __user *) (((unsigned long) sp) & ~7);
      if ((envc+argc+3)&1)
            --sp;

      sp -= envc+1;
      envp = sp;
      sp -= argc+1;
      argv = sp;
      put_user(argc,--sp);
      current->mm->arg_start = (unsigned long) p;
      while (argc-->0) {
            char c;
            put_user(((u32)(unsigned long)(p)),argv++);
            do {
                  get_user(c,p++);
            } while (c);
      }
      put_user(0,argv);
      current->mm->arg_end = current->mm->env_start = (unsigned long) p;
      while (envc-->0) {
            char c;
            put_user(((u32)(unsigned long)(p)),envp++);
            do {
                  get_user(c,p++);
            } while (c);
      }
      put_user(0,envp);
      current->mm->env_end = (unsigned long) p;
      return sp;
}

/*
 * These are the functions used to load a.out style executables and shared
 * libraries.  There is no binary dependent code anywhere else.
 */

static int load_aout32_binary(struct linux_binprm * bprm, struct pt_regs * regs)
{
      struct exec ex;
      unsigned long error;
      unsigned long fd_offset;
      unsigned long rlim;
      unsigned long orig_thr_flags;
      int retval;

      ex = *((struct exec *) bprm->buf);        /* exec-header */
      if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC &&
           N_MAGIC(ex) != QMAGIC && N_MAGIC(ex) != NMAGIC) ||
          N_TRSIZE(ex) || N_DRSIZE(ex) ||
          bprm->file->f_path.dentry->d_inode->i_size < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
            return -ENOEXEC;
      }

      fd_offset = N_TXTOFF(ex);

      /* Check initial limits. This avoids letting people circumvent
       * size limits imposed on them by creating programs with large
       * arrays in the data or bss.
       */
      rlim = current->signal->rlim[RLIMIT_DATA].rlim_cur;
      if (rlim >= RLIM_INFINITY)
            rlim = ~0;
      if (ex.a_data + ex.a_bss > rlim)
            return -ENOMEM;

      /* Flush all traces of the currently running executable */
      retval = flush_old_exec(bprm);
      if (retval)
            return retval;

      /* OK, This is the point of no return */
      set_personality(PER_SUNOS);

      current->mm->end_code = ex.a_text +
            (current->mm->start_code = N_TXTADDR(ex));
      current->mm->end_data = ex.a_data +
            (current->mm->start_data = N_DATADDR(ex));
      current->mm->brk = ex.a_bss +
            (current->mm->start_brk = N_BSSADDR(ex));
      current->mm->free_area_cache = current->mm->mmap_base;
      current->mm->cached_hole_size = 0;

      current->mm->mmap = NULL;
      compute_creds(bprm);
      current->flags &= ~PF_FORKNOEXEC;
      if (N_MAGIC(ex) == NMAGIC) {
            loff_t pos = fd_offset;
            /* Fuck me plenty... */
            down_write(&current->mm->mmap_sem); 
            error = do_brk(N_TXTADDR(ex), ex.a_text);
            up_write(&current->mm->mmap_sem);
            bprm->file->f_op->read(bprm->file, (char __user *)N_TXTADDR(ex),
                    ex.a_text, &pos);
            down_write(&current->mm->mmap_sem);
            error = do_brk(N_DATADDR(ex), ex.a_data);
            up_write(&current->mm->mmap_sem);
            bprm->file->f_op->read(bprm->file, (char __user *)N_DATADDR(ex),
                    ex.a_data, &pos);
            goto beyond_if;
      }

      if (N_MAGIC(ex) == OMAGIC) {
            loff_t pos = fd_offset;
            down_write(&current->mm->mmap_sem);
            do_brk(N_TXTADDR(ex) & PAGE_MASK,
                  ex.a_text+ex.a_data + PAGE_SIZE - 1);
            up_write(&current->mm->mmap_sem);
            bprm->file->f_op->read(bprm->file, (char __user *)N_TXTADDR(ex),
                    ex.a_text+ex.a_data, &pos);
      } else {
            static unsigned long error_time;
            if ((ex.a_text & 0xfff || ex.a_data & 0xfff) &&
                (N_MAGIC(ex) != NMAGIC) && (jiffies-error_time) > 5*HZ)
            {
                  printk(KERN_NOTICE "executable not page aligned\n");
                  error_time = jiffies;
            }

            if (!bprm->file->f_op->mmap) {
                  loff_t pos = fd_offset;
                  down_write(&current->mm->mmap_sem);
                  do_brk(0, ex.a_text+ex.a_data);
                  up_write(&current->mm->mmap_sem);
                  bprm->file->f_op->read(bprm->file,
                          (char __user *)N_TXTADDR(ex),
                          ex.a_text+ex.a_data, &pos);
                  goto beyond_if;
            }

              down_write(&current->mm->mmap_sem);
            error = do_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
                  PROT_READ | PROT_EXEC,
                  MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
                  fd_offset);
              up_write(&current->mm->mmap_sem);

            if (error != N_TXTADDR(ex)) {
                  send_sig(SIGKILL, current, 0);
                  return error;
            }

              down_write(&current->mm->mmap_sem);
            error = do_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
                        PROT_READ | PROT_WRITE | PROT_EXEC,
                        MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
                        fd_offset + ex.a_text);
              up_write(&current->mm->mmap_sem);
            if (error != N_DATADDR(ex)) {
                  send_sig(SIGKILL, current, 0);
                  return error;
            }
      }
beyond_if:
      set_binfmt(&aout32_format);

      set_brk(current->mm->start_brk, current->mm->brk);

      /* Make sure STACK_TOP returns the right thing.  */
      orig_thr_flags = current_thread_info()->flags;
      current_thread_info()->flags |= _TIF_32BIT;

      retval = setup_arg_pages(bprm, STACK_TOP, EXSTACK_DEFAULT);
      if (retval < 0) { 
            current_thread_info()->flags = orig_thr_flags;

            /* Someone check-me: is this error path enough? */ 
            send_sig(SIGKILL, current, 0); 
            return retval;
      }

      current->mm->start_stack =
            (unsigned long) create_aout32_tables((char __user *)bprm->p, bprm);
      tsb_context_switch(current->mm);

      start_thread32(regs, ex.a_entry, current->mm->start_stack);
      if (current->ptrace & PT_PTRACED)
            send_sig(SIGTRAP, current, 0);
      return 0;
}

/* N.B. Move to .h file and use code in fs/binfmt_aout.c? */
static int load_aout32_library(struct file *file)
{
      struct inode * inode;
      unsigned long bss, start_addr, len;
      unsigned long error;
      int retval;
      struct exec ex;

      inode = file->f_path.dentry->d_inode;

      retval = -ENOEXEC;
      error = kernel_read(file, 0, (char *) &ex, sizeof(ex));
      if (error != sizeof(ex))
            goto out;

      /* We come in here for the regular a.out style of shared libraries */
      if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
          N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
          inode->i_size < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
            goto out;
      }

      if (N_MAGIC(ex) == ZMAGIC && N_TXTOFF(ex) &&
          (N_TXTOFF(ex) < inode->i_sb->s_blocksize)) {
            printk("N_TXTOFF < BLOCK_SIZE. Please convert library\n");
            goto out;
      }

      if (N_FLAGS(ex))
            goto out;

      /* For  QMAGIC, the starting address is 0x20 into the page.  We mask
         this off to get the starting address for the page */

      start_addr =  ex.a_entry & 0xfffff000;

      /* Now use mmap to map the library into memory. */
      down_write(&current->mm->mmap_sem);
      error = do_mmap(file, start_addr, ex.a_text + ex.a_data,
                  PROT_READ | PROT_WRITE | PROT_EXEC,
                  MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
                  N_TXTOFF(ex));
      up_write(&current->mm->mmap_sem);
      retval = error;
      if (error != start_addr)
            goto out;

      len = PAGE_ALIGN(ex.a_text + ex.a_data);
      bss = ex.a_text + ex.a_data + ex.a_bss;
      if (bss > len) {
            down_write(&current->mm->mmap_sem);
            error = do_brk(start_addr + len, bss - len);
            up_write(&current->mm->mmap_sem);
            retval = error;
            if (error != start_addr + len)
                  goto out;
      }
      retval = 0;
out:
      return retval;
}

static int __init init_aout32_binfmt(void)
{
      return register_binfmt(&aout32_format);
}

static void __exit exit_aout32_binfmt(void)
{
      unregister_binfmt(&aout32_format);
}

module_init(init_aout32_binfmt);
module_exit(exit_aout32_binfmt);

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