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07c496c53c7835c0db882ef6761309db4952ebf6
libguestfs/generator/erlang.ml
Richard W.M. Jones 07c496c53c Use less stack. 
GCC has two warnings related to large stack frames.  We were already
using the -Wframe-larger-than warning, but this reduces the threshold
from 10000 to 5000 bytes.

However that warning only covers the static part of frames (not
alloca).  So this change also enables -Wstack-usage=10000 which covers
both the static and dynamic usage (alloca and variable length arrays).

Multiple changes are made throughout the code to reduce frames to fit
within these new limits.

Note that stack allocation of large strings can be a security issue.
For example, we had code like:

 size_t len = strlen (fs->windows_systemroot) + 64;
 char software[len];
 snprintf (software, len, "%s/system32/config/software",
           fs->windows_systemroot);

where fs->windows_systemroot is guest controlled.  It's not clear what
the effects might be of allowing the guest to allocate potentially
very large stack frames, but at best it allows the guest to cause
libguestfs to segfault.  It turns out we are very lucky that
fs->windows_systemroot cannot be set arbitrarily large (see checks in
is_systemroot).

This commit changes those to large heap allocations instead.
2016-03-07 17:36:24 +00:00

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(* libguestfs
* Copyright (C) 2011 Red Hat Inc.
*
* 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 of the License, 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*)
(* Please read generator/README first. *)
open Printf
open Types
open Utils
open Pr
open Docstrings
open Optgroups
open Actions
open Structs
open C
open Events
let generate_header = generate_header ~inputs:["generator/erlang.ml"]
let rec generate_erlang_erl () =
generate_header ErlangStyle LGPLv2plus;
pr "-module(guestfs).\n";
pr "\n";
pr "-export([create/0, create/1, close/1, init/1]).\n";
pr "\n";
(* Export the public actions. *)
List.iter (
fun { name = name; style = _, args, optargs; non_c_aliases = aliases } ->
let nr_args = List.length args in
let export name =
if optargs = [] then
pr "-export([%s/%d]).\n" name (nr_args+1)
else
pr "-export([%s/%d, %s/%d]).\n" name (nr_args+1) name (nr_args+2)
in
export name;
List.iter export aliases
) external_functions_sorted;
pr "\n";
pr "\
create() ->
create(\"erl-guestfs\").
create(ExtProg) ->
G = spawn(?MODULE, init, [ExtProg]),
{ok, G}.
close(G) ->
G ! close,
ok.
call_port(G, Args) ->
G ! {call, self(), Args},
receive
{guestfs, Result} ->
Result
end.
init(ExtProg) ->
process_flag(trap_exit, true),
Port = open_port({spawn, ExtProg}, [{packet, 4}, binary]),
loop(Port).
loop(Port) ->
receive
{call, Caller, Args} ->
Port ! { self(), {command, term_to_binary(Args)}},
receive
{Port, {data, Result}} ->
Caller ! { guestfs, binary_to_term(Result)}
end,
loop(Port);
close ->
port_close(Port),
exit(normal);
{ 'EXIT', Port, _ } ->
exit(port_terminated)
end.
";
(* These bindings just marshal the parameters and call the back-end
* process which dispatches them to the port.
*)
List.iter (
fun { name = name; style = _, args, optargs; non_c_aliases = aliases } ->
pr "%s(G" name;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
if optargs <> [] then
pr ", Optargs";
pr ") ->\n";
pr " call_port(G, {%s" name;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
if optargs <> [] then
pr ", Optargs";
pr "}).\n";
(* For functions with optional arguments, make a variant that
* has no optarg array, which just calls the function above with
* an empty list as the final arg.
*)
if optargs <> [] then (
pr "%s(G" name;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
pr ") ->\n";
pr " %s(G" name;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
pr ", []";
pr ").\n"
);
(* Aliases. *)
List.iter (
fun alias ->
pr "%s(G" alias;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
if optargs <> [] then
pr ", Optargs";
pr ") ->\n";
pr " %s(G" name;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
if optargs <> [] then
pr ", Optargs";
pr ").\n";
if optargs <> [] then (
pr "%s(G" alias;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
pr ") ->\n";
pr " %s(G" name;
List.iter (
fun arg ->
pr ", %s" (String.capitalize (name_of_argt arg))
) args;
pr ").\n"
)
) aliases;
pr "\n"
) external_functions_sorted
and generate_erlang_c () =
generate_header CStyle GPLv2plus;
pr "\
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <erl_interface.h>
/* We should switch over to using
#include <ei.h>
instead of erl_interface.
*/
#include \"guestfs.h\"
#include \"guestfs-internal-frontend.h\"
extern guestfs_h *g;
extern ETERM *dispatch (ETERM *message);
extern int atom_equals (ETERM *atom, const char *name);
extern ETERM *make_error (const char *funname);
extern ETERM *unknown_optarg (const char *funname, ETERM *optargname);
extern ETERM *unknown_function (ETERM *fun);
extern ETERM *make_string_list (char **r);
extern ETERM *make_table (char **r);
extern ETERM *make_bool (int r);
extern char **get_string_list (ETERM *term);
extern int get_bool (ETERM *term);
extern int get_int (ETERM *term);
extern int64_t get_int64 (ETERM *term);
#define ARG(i) (ERL_TUPLE_ELEMENT(message,(i)+1))
";
(* Struct copy functions. *)
let emit_copy_list_function typ =
pr "static ETERM *\n";
pr "make_%s_list (const struct guestfs_%s_list *%ss)\n" typ typ typ;
pr "{\n";
pr " size_t len = %ss->len;\n" typ;
pr " size_t i;\n";
pr " CLEANUP_FREE ETERM **t;\n";
pr "\n";
pr " t = malloc (sizeof (ETERM *) * len);\n";
pr " if (t == NULL)\n";
pr " return make_error (\"make_%s_list\");\n" typ;
pr "\n";
pr " for (i = 0; i < len; ++i)\n";
pr " t[i] = make_%s (&%ss->val[i]);\n" typ typ;
pr "\n";
pr " return erl_mk_list (t, len);\n";
pr "}\n";
pr "\n";
in
List.iter (
fun { s_name = typ; s_cols = cols } ->
pr "static ETERM *\n";
pr "make_%s (const struct guestfs_%s *%s)\n" typ typ typ;
pr "{\n";
pr " ETERM *t[%d];\n" (List.length cols);
pr "\n";
iteri (
fun i col ->
(match col with
| name, FString ->
pr " t[%d] = erl_mk_string (%s->%s);\n" i typ name
| name, FBuffer ->
pr " t[%d] = erl_mk_estring (%s->%s, %s->%s_len);\n"
i typ name typ name
| name, FUUID ->
pr " t[%d] = erl_mk_estring (%s->%s, 32);\n" i typ name
| name, (FBytes|FInt64|FUInt64) ->
pr " t[%d] = erl_mk_longlong (%s->%s);\n" i typ name
| name, (FInt32|FUInt32) ->
pr " t[%d] = erl_mk_int (%s->%s);\n" i typ name
| name, FOptPercent ->
pr " if (%s->%s >= 0)\n" typ name;
pr " t[%d] = erl_mk_float (%s->%s);\n" i typ name;
pr " else\n";
pr " t[%d] = erl_mk_atom (\"undefined\");\n" i;
| name, FChar ->
pr " t[%d] = erl_mk_int (%s->%s);\n" i typ name
);
) cols;
pr "\n";
pr " return erl_mk_list (t, %d);\n" (List.length cols);
pr "}\n";
pr "\n";
) external_structs;
(* Emit a copy_TYPE_list function definition only if that function is used. *)
List.iter (
function
| typ, (RStructListOnly | RStructAndList) ->
(* generate the function for typ *)
emit_copy_list_function typ
| typ, _ -> () (* empty *)
) (rstructs_used_by external_functions);
(* The wrapper functions. *)
List.iter (
fun { name = name; style = (ret, args, optargs as style);
c_function = c_function; c_optarg_prefix = c_optarg_prefix } ->
pr "static ETERM *\n";
pr "run_%s (ETERM *message)\n" name;
pr "{\n";
iteri (
fun i ->
function
| Pathname n
| Device n | Mountable n | Dev_or_Path n | Mountable_or_Path n
| String n
| FileIn n
| FileOut n
| Key n
| GUID n ->
pr " CLEANUP_FREE char *%s = erl_iolist_to_string (ARG (%d));\n" n i
| OptString n ->
pr " CLEANUP_FREE char *%s;\n" n;
pr " if (atom_equals (ARG (%d), \"undefined\"))\n" i;
pr " %s = NULL;\n" n;
pr " else\n";
pr " %s = erl_iolist_to_string (ARG (%d));\n" n i
| BufferIn n ->
pr " ETERM *%s_bin = erl_iolist_to_binary (ARG (%d));\n" n i;
pr " const void *%s = ERL_BIN_PTR (%s_bin);\n" n n;
pr " size_t %s_size = ERL_BIN_SIZE (%s_bin);\n" n n
| StringList n | DeviceList n | FilenameList n ->
pr " CLEANUP_FREE_STRING_LIST char **%s = get_string_list (ARG (%d));\n" n i
| Bool n ->
pr " int %s = get_bool (ARG (%d));\n" n i
| Int n ->
pr " int %s = get_int (ARG (%d));\n" n i
| Int64 n ->
pr " int64_t %s = get_int64 (ARG (%d));\n" n i
| Pointer (t, n) ->
pr " void * /* %s */ %s = POINTER_NOT_IMPLEMENTED (\"%s\");\n" t n t
) args;
(* Optional arguments. *)
if optargs <> [] then (
pr "\n";
pr " struct %s optargs_s = { .bitmask = 0 };\n" c_function;
pr " struct %s *optargs = &optargs_s;\n" c_function;
pr " ETERM *optargst = ARG (%d);\n" (List.length args);
pr " while (!ERL_IS_EMPTY_LIST (optargst)) {\n";
pr " ETERM *hd = ERL_CONS_HEAD (optargst);\n";
pr " ETERM *hd_name = ERL_TUPLE_ELEMENT (hd, 0);\n";
pr " ETERM *hd_value = ERL_TUPLE_ELEMENT (hd, 1);\n";
pr "\n";
List.iter (
fun argt ->
let n = name_of_optargt argt in
let uc_n = String.uppercase n in
pr " if (atom_equals (hd_name, \"%s\")) {\n" n;
pr " optargs_s.bitmask |= %s_%s_BITMASK;\n"
c_optarg_prefix uc_n;
pr " optargs_s.%s = " n;
(match argt with
| OBool _ -> pr "get_bool (hd_value)"
| OInt _ -> pr "get_int (hd_value)"
| OInt64 _ -> pr "get_int64 (hd_value)"
| OString _ -> pr "erl_iolist_to_string (hd_value)"
| OStringList n -> pr "get_string_list (hd_value)"
);
pr ";\n";
pr " }\n";
pr " else\n";
) optargs;
pr " return unknown_optarg (\"%s\", hd_name);\n" name;
pr " optargst = ERL_CONS_TAIL (optargst);\n";
pr " }\n";
pr "\n";
);
(match ret with
| RErr -> pr " int r;\n"
| RInt _ -> pr " int r;\n"
| RInt64 _ -> pr " int64_t r;\n"
| RBool _ -> pr " int r;\n"
| RConstString _ | RConstOptString _ ->
pr " const char *r;\n"
| RString _ -> pr " char *r;\n"
| RStringList _ ->
pr " char **r;\n"
| RStruct (_, typ) ->
pr " struct guestfs_%s *r;\n" typ
| RStructList (_, typ) ->
pr " struct guestfs_%s_list *r;\n" typ
| RHashtable _ ->
pr " char **r;\n"
| RBufferOut _ ->
pr " char *r;\n";
pr " size_t size;\n"
);
pr "\n";
pr " r = %s " c_function;
generate_c_call_args ~handle:"g" style;
pr ";\n";
(* Free strings if we copied them above. *)
List.iter (
function
| OBool _ | OInt _ | OInt64 _ -> ()
| OString n ->
let uc_n = String.uppercase n in
pr " if ((optargs_s.bitmask & %s_%s_BITMASK))\n"
c_optarg_prefix uc_n;
pr " free ((char *) optargs_s.%s);\n" n
| OStringList n ->
let uc_n = String.uppercase n in
pr " if ((optargs_s.bitmask & %s_%s_BITMASK))\n"
c_optarg_prefix uc_n;
pr " guestfs_int_free_string_list ((char **) optargs_s.%s);\n" n
) optargs;
(match errcode_of_ret ret with
| `CannotReturnError -> ()
| `ErrorIsMinusOne ->
pr " if (r == -1)\n";
pr " return make_error (\"%s\");\n" name;
| `ErrorIsNULL ->
pr " if (r == NULL)\n";
pr " return make_error (\"%s\");\n" name;
);
pr "\n";
(match ret with
| RErr -> pr " return erl_mk_atom (\"ok\");\n"
| RInt _ -> pr " return erl_mk_int (r);\n"
| RInt64 _ -> pr " return erl_mk_longlong (r);\n"
| RBool _ -> pr " return make_bool (r);\n"
| RConstString _ -> pr " return erl_mk_string (r);\n"
| RConstOptString _ ->
pr " ETERM *rt;\n";
pr " if (r)\n";
pr " rt = erl_mk_string (r);\n";
pr " else\n";
pr " rt = erl_mk_atom (\"undefined\");\n";
pr " return rt;\n"
| RString _ ->
pr " ETERM *rt = erl_mk_string (r);\n";
pr " free (r);\n";
pr " return rt;\n"
| RStringList _ ->
pr " ETERM *rt = make_string_list (r);\n";
pr " guestfs_int_free_string_list (r);\n\n";
pr " return rt;\n"
| RStruct (_, typ) ->
pr " ETERM *rt = make_%s (r);\n" typ;
pr " guestfs_free_%s (r);\n" typ;
pr " return rt;\n"
| RStructList (_, typ) ->
pr " ETERM *rt = make_%s_list (r);\n" typ;
pr " guestfs_free_%s_list (r);\n" typ;
pr " return rt;\n"
| RHashtable _ ->
pr " ETERM *rt = make_table (r);\n";
pr " guestfs_int_free_string_list (r);\n";
pr " return rt;\n"
| RBufferOut _ ->
pr " ETERM *rt = erl_mk_estring (r, size);\n";
pr " free (r);\n";
pr " return rt;\n"
);
pr "}\n";
pr "\n";
) external_functions_sorted;
pr "\
ETERM *
dispatch (ETERM *message)
{
ETERM *fun;
fun = ERL_TUPLE_ELEMENT (message, 0);
/* XXX We should use gperf here. */
";
List.iter (
fun { name = name; style = ret, args, optargs } ->
pr "if (atom_equals (fun, \"%s\"))\n" name;
pr " return run_%s (message);\n" name;
pr " else ";
) external_functions_sorted;
pr "return unknown_function (fun);
}
";
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