[PATCH 17/17] add mtab prototype

[Justus Winter]

---
 trans/Makefile |    8 +-
 trans/mtab.c   |  541 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 546 insertions(+), 3 deletions(-)
 create mode 100644 trans/mtab.c

diff --git a/trans/Makefile b/trans/Makefile
index b3210b6..6eb51d0 100644
--- a/trans/Makefile
+++ b/trans/Makefile
@@ -20,14 +20,15 @@ dir := trans
 makemode := servers
 
 targets = symlink firmlink ifsock magic null fifo new-fifo fwd crash \
-         password hello hello-mt streamio fakeroot proxy-defpager remap
+         password hello hello-mt streamio fakeroot proxy-defpager remap \
+         mtab
 SRCS = ifsock.c symlink.c magic.c null.c fifo.c new-fifo.c fwd.c \
        crash.c firmlink.c password.c hello.c hello-mt.c streamio.c \
-       fakeroot.c proxy-defpager.c remap.c
+       fakeroot.c proxy-defpager.c remap.c mtab.c
 OBJS = $(SRCS:.c=.o) fsysServer.o ifsockServer.o passwordServer.o \
        crashServer.o crash_replyUser.o msgServer.o \
        default_pagerServer.o default_pagerUser.o \
-       device_replyServer.o elfcore.o
+       device_replyServer.o elfcore.o fsysUser.o
 HURDLIBS = ports netfs trivfs iohelp fshelp pipe ihash shouldbeinlibc
 LDLIBS += -lpthread
 password-LDLIBS = $(LIBCRYPT)
@@ -51,6 +52,7 @@ magic: ../libiohelp/libiohelp.a
 hello: ../libtrivfs/libtrivfs.a ../libfshelp/libfshelp.a 
../libports/libports.a ../libihash/libihash.a
 fakeroot: ../libnetfs/libnetfs.a ../libfshelp/libfshelp.a 
../libiohelp/libiohelp.a ../libports/libports.a ../libihash/libihash.a
 remap: ../libtrivfs/libtrivfs.a ../libfshelp/libfshelp.a 
../libports/libports.a ../libihash/libihash.a
+mtab: ../libtrivfs/libtrivfs.a ../libfshelp/libfshelp.a ../libports/libports.a 
../libihash/libihash.a fsysUser.o
 $(targets): ../libshouldbeinlibc/libshouldbeinlibc.a
 
 $(targets): %: %.o
diff --git a/trans/mtab.c b/trans/mtab.c
new file mode 100644
index 0000000..f47d03d
--- /dev/null
+++ b/trans/mtab.c
@@ -0,0 +1,541 @@
+/* This is an mtab translator.
+
+   Copyright (C) 2013 Free Software Foundation, Inc.
+
+   Written by Justus Winter <4winter@informatik.uni-hamburg.de>
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation; either version 2, or (at
+   your option) any later version.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+#include <argp.h>
+#include <argz.h>
+#include <error.h>
+#include <fcntl.h>
+#include <hurd.h>
+#include <hurd/trivfs.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <version.h>
+
+#include "fsys_U.h"
+
+static char *path = NULL;
+static int insecure = 0;
+
+/* XXX */
+struct mtab
+{
+  char *contents;
+  size_t contents_len;
+  off_t offs;
+};
+
+const char *argp_program_version = STANDARD_HURD_VERSION (mtab);
+
+static const struct argp_option options[] =
+{
+  {"insecure", 'I', 0, 0, "Follow translators not started by root"},
+  {}
+};
+
+/* Parse a command line option.  */
+error_t parse_opt (int key, char *arg, struct argp_state *state)
+{
+  switch (key)
+    {
+    case 'I':
+      insecure = 1;
+      break;
+
+    case ARGP_KEY_ARG:
+      path = arg;
+      break;
+
+    case ARGP_KEY_NO_ARGS:
+      argp_usage (state);
+      return EINVAL;
+
+    default:
+      return ARGP_ERR_UNKNOWN;
+    }
+  return 0;
+}
+
+static struct argp argp =
+  {
+    options,
+    parse_opt,
+    "TARGET",
+    "A translator providing mtab compatible information about active "
+    "and passive translators below TARGET.",
+  };
+
+/* This will be called from libtrivfs to help construct the answer
+   to an fsys_get_options RPC.  */
+error_t
+trivfs_append_args (struct trivfs_control *fsys,
+                   char **argz, size_t *argz_len)
+{
+  error_t err;
+
+  if (insecure)
+    {
+      err = argz_add (argz, argz_len, path);
+      if (err)
+        return err;
+    }
+
+  err = argz_add (argz, argz_len, path);
+  return err;
+}
+
+/* Setting this variable makes libtrivfs use our argp to
+   parse options passed in an fsys_set_options RPC.  */
+struct argp *trivfs_runtime_argp = &argp;
+
+error_t
+mtab_populate (struct mtab *mtab, const char *path, int insecure);
+
+error_t
+argz_add_device (char **options, size_t *options_len, const char *device);
+
+error_t
+map_device_to_path (const char *device, char **path);
+
+int
+main (int argc, char *argv[])
+{
+  error_t err;
+
+  err = argp_parse (&argp, argc, argv, ARGP_IN_ORDER, 0, 0);
+  if (err)
+    error (1, err, "argument parsing");
+
+  mach_port_t bootstrap;
+  task_get_bootstrap_port (mach_task_self (), &bootstrap);
+  if (bootstrap != MACH_PORT_NULL) {
+    /* Started as a translator. */
+
+    /* Reply to our parent. */
+    struct trivfs_control *fsys;
+    err = trivfs_startup (bootstrap, 0, 0, 0, 0, 0, &fsys);
+    mach_port_deallocate (mach_task_self (), bootstrap);
+    if (err)
+      error (3, err, "trivfs_startup");
+
+    /* Launch. */
+    ports_manage_port_operations_one_thread (fsys->pi.bucket,
+                                             trivfs_demuxer,
+                                             0);
+  }
+  else
+    {
+      /* One-shot mode. */
+      struct mtab mtab = { NULL, 0, 0 };
+      err = mtab_populate (&mtab, path, insecure);
+      if (err)
+        error (5, err, "%s", path);
+
+      printf ("%s", mtab.contents);
+    }
+
+  return 0;
+}
+
+error_t
+mtab_add_entry (struct mtab *mtab, const char *entry, size_t length)
+{
+  char *p = realloc (mtab->contents, mtab->contents_len + length + 1);
+  if (! p)
+    return ENOMEM;
+
+  memcpy (&p[mtab->contents_len], entry, length);
+
+  /* Zero-terminate contents so that we can also interpret it as
+     string. */
+  p[mtab->contents_len + length + 1] = '\0';
+
+  mtab->contents = p;
+  mtab->contents_len += length;
+  return 0;
+}
+
+/* XXX */
+/* XXX split up */
+error_t
+mtab_populate (struct mtab *mtab, const char *path, int insecure)
+{
+  error_t err = 0;
+
+  /* These resources are freed in the epilogue. */
+  file_t node = MACH_PORT_NULL;
+  char *argz = NULL;
+  size_t argz_len = 0;
+  char **argv = NULL;
+  char *type = NULL;
+  char *options = NULL;
+  size_t options_len = 0;
+  char *src = NULL;
+  char *entry = NULL;
+  size_t entry_len = 0;
+  char *children = NULL;
+  size_t children_len = 0;
+
+  if (! insecure)
+    {
+      /* XXX check who owns the translator */
+    }
+
+  node = file_name_lookup (path, 0, 0666);
+  if (node == MACH_PORT_NULL)
+    {
+      err = errno;
+      goto errout;
+    }
+
+  err = file_get_fs_options (node, &argz, &argz_len);
+  if (err)
+    goto errout;
+
+  size_t count = argz_count (argz, argz_len);
+  argv = malloc ((count + 1) * sizeof (char *));
+  if (! argv)
+    {
+      err = ENOMEM;
+      goto errout;
+    }
+
+  argz_extract (argz, argz_len, argv);
+
+  type = strdup (argv[0]);
+  if (! type)
+    {
+      err = ENOMEM;
+      goto errout;
+    }
+
+  for (int i = 1; i < count - 1; i++)
+    {
+      char *v = argv[i];
+
+      if (*v == '-')
+        v++;
+      if (*v == '-')
+        v++;
+
+      err = argz_add (&options, &options_len, v);
+      if (err)
+        goto errout;
+    }
+
+  err = argz_add_device (&options, &options_len, argv[count - 1]);
+  if (err)
+    goto errout;
+
+  argz_stringify (options, options_len, ',');
+
+  string_t source;
+  err = fsys_get_source (node, source);
+  if (err)
+    {
+      if (err == EOPNOTSUPP)
+        {
+          /* Guess based on the last argument. */
+          err = map_device_to_path (argv[count - 1], &src);
+          if (err)
+            goto errout;
+        }
+      else
+        goto errout;
+    }
+  else
+    src = source;
+
+  entry_len = asprintf (&entry, "%s %s %s %s 0 0\n", src, path, type, options);
+  if (! entry)
+    {
+      err = ENOMEM;
+      goto errout;
+    }
+
+  err = mtab_add_entry (mtab, entry, entry_len);
+  if (err)
+    goto errout;
+
+  err = fsys_get_children (node, &children, &children_len);
+  if (err == EOPNOTSUPP)
+    err = 0;
+
+  if (err)
+    goto errout;
+
+  if (children_len)
+    for (char *c = children; c; c = argz_next (children, children_len, c))
+      {
+        char *p = NULL;
+        asprintf (&p, "%s/%s", path, c);
+        if (! p)
+          {
+            err = ENOMEM;
+            goto errout;
+          }
+
+        err = mtab_populate (mtab, p, insecure);
+        free (p);
+        if (err)
+          goto errout;
+      }
+
+ errout:
+  if (node != MACH_PORT_NULL)
+    mach_port_deallocate (mach_task_self (), node);
+
+  if (argz)
+    vm_deallocate (mach_task_self (), (vm_address_t) argz, argz_len);
+
+  free (argv);
+  free (type);
+  free (options);
+
+  if (src != source)
+    free (src);
+
+  free (entry);
+
+  if (children)
+    vm_deallocate (mach_task_self (), (vm_address_t) children, children_len);
+
+  return err;
+}
+
+/* XXX */
+error_t
+argz_add_device (char **options, size_t *options_len, const char *device)
+{
+  error_t err;
+  char *end = NULL;
+  intmax_t size = strtoimax (device, &end, 0);
+  if (end == NULL || end == device)
+    return 0;
+
+  if (size < 0)
+    return 0;
+
+  switch (*end)
+    {
+      case 'g':
+      case 'G':
+      case 'm':
+      case 'M':
+      case 'k':
+      case 'K':
+        break;
+    default:
+      return 0;
+    }
+
+  /* device is a size */
+  char *arg = NULL;
+  asprintf (&arg, "size=%s", device);
+  if (! arg)
+    return ENOMEM;
+
+  err = argz_add (options, options_len, arg);
+
+  free (arg);
+  return err;
+}
+
+/* XXX */
+error_t
+map_device_to_path (const char *device, char **path)
+{
+  if (strcmp (device, "device:") == 0)
+    asprintf (path, "/dev/%s", &device[7]);
+  else
+    *path = strdup ("none");
+
+  if (! *path)
+    return ENOMEM;
+
+  return 0;
+}
+
+/* Trivfs hooks. */
+int trivfs_fstype = FSTYPE_MISC;
+int trivfs_fsid = 0;
+
+int trivfs_allow_open = O_READ;
+
+int trivfs_support_read = 1;
+int trivfs_support_write = 0;
+int trivfs_support_exec = 0;
+
+/* NOTE: This example is not robust: it is possible to trigger some
+   assertion failures because we don't implement the following:
+
+   $ cd /src/hurd/libtrivfs
+   $ grep -l 'assert.*!trivfs_support_read' *.c |
+     xargs grep '^trivfs_S_' | sed 's/^[^:]*:\([^      ]*\).*$/\1/'
+   trivfs_S_io_get_openmodes
+   trivfs_S_io_clear_some_openmodes
+   trivfs_S_io_set_some_openmodes
+   trivfs_S_io_set_all_openmodes
+   trivfs_S_io_readable
+   trivfs_S_io_select
+   $
+
+   For that reason, you should run this as an active translator
+   `settrans -ac testnode /path/to/thello' so that you can see the
+   error messages when they appear. */
+
+void
+trivfs_modify_stat (struct trivfs_protid *cred, struct stat *st)
+{
+  /* Mark the node as a read-only plain file. */
+  st->st_mode &= ~(S_IFMT | ALLPERMS);
+  st->st_mode |= (S_IFREG | S_IRUSR | S_IRGRP | S_IROTH);
+  st->st_size = ((struct mtab *) cred->po->hook)->contents_len;
+}
+
+error_t
+trivfs_goaway (struct trivfs_control *cntl, int flags)
+{
+  exit (EXIT_SUCCESS);
+}
+
+
+static error_t
+open_hook (struct trivfs_peropen *peropen)
+{
+  struct mtab *mtab = malloc (sizeof (struct mtab));
+  if (mtab == NULL)
+    return ENOMEM;
+
+  /* Hook! */
+  peropen->hook = mtab;
+
+  /* Initialize the fields. */
+  mtab->offs = 0;
+  mtab->contents = NULL;
+  mtab->contents_len = 0;
+
+  return mtab_populate (mtab, path, insecure);
+}
+
+
+static void
+close_hook (struct trivfs_peropen *peropen)
+{
+  free (((struct mtab *) peropen->hook)->contents);
+  free (peropen->hook);
+}
+
+
+/* Read data from an IO object.  If offset is -1, read from the object
+   maintained file pointer.  If the object is not seekable, offset is
+   ignored.  The amount desired to be read is in AMOUNT.  */
+error_t
+trivfs_S_io_read (struct trivfs_protid *cred,
+                 mach_port_t reply, mach_msg_type_name_t reply_type,
+                 char **data, mach_msg_type_number_t *data_len,
+                 loff_t offs, mach_msg_type_number_t amount)
+{
+  struct mtab *op;
+
+  /* Deny access if they have bad credentials. */
+  if (! cred)
+    return EOPNOTSUPP;
+  else if (! (cred->po->openmodes & O_READ))
+    return EBADF;
+
+  /* Get the offset. */
+  op = cred->po->hook;
+  if (offs == -1)
+    offs = op->offs;
+
+  /* Prune the amount they want to read. */
+  if (offs > op->contents_len)
+    offs = op->contents_len;
+  if (offs + amount > op->contents_len)
+    amount = op->contents_len - offs;
+
+  if (amount > 0)
+    {
+      /* Possibly allocate a new buffer. */
+      if (*data_len < amount)
+       {
+         *data = mmap (0, amount, PROT_READ|PROT_WRITE, MAP_ANON, 0, 0);
+         if (*data == MAP_FAILED)
+           return ENOMEM;
+       }
+
+      /* Copy the constant data into the buffer. */
+      memcpy ((char *) *data, op->contents + offs, amount);
+
+      /* Update the saved offset. */
+      op->offs += amount;
+    }
+
+  *data_len = amount;
+  return 0;
+}
+
+
+/* Change current read/write offset */
+error_t
+trivfs_S_io_seek (struct trivfs_protid *cred,
+                 mach_port_t reply, mach_msg_type_name_t reply_type,
+                 off_t offs, int whence, off_t *new_offs)
+{
+  struct mtab *op;
+  error_t err = 0;
+  if (! cred)
+    return EOPNOTSUPP;
+
+  op = cred->po->hook;
+  switch (whence)
+    {
+    case SEEK_CUR:
+      offs += op->offs;
+      goto check;
+    case SEEK_END:
+      offs += op->contents_len;
+    case SEEK_SET:
+    check:
+      if (offs >= 0)
+       {
+         *new_offs = op->offs = offs;
+         break;
+       }
+    default:
+      err = EINVAL;
+    }
+
+  return err;
+}
+
+/* If this variable is set, it is called every time a new peropen
+   structure is created and initialized. */
+error_t (*trivfs_peropen_create_hook)(struct trivfs_peropen *) = open_hook;
+
+/* If this variable is set, it is called every time a peropen structure
+   is about to be destroyed. */
+void (*trivfs_peropen_destroy_hook) (struct trivfs_peropen *) = close_hook;
+
+/* XXX more trivfs stuff */
-- 
1.7.10.4