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Add framework for tunables

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The tunables framework allows us to uniformly manage and expose global
variables inside glibc as switches to users.  tunables/README has
instructions for glibc developers to add new tunables.

Tunables support can be enabled by passing the --enable-tunables
configure flag to the configure script.  This patch only adds a
framework and does not pose any limitations on how tunable values are
read from the user.  It also adds environment variables used in malloc
behaviour tweaking to the tunables framework as a PoC of the
compatibility interface.

	* manual/install.texi: Add --enable-tunables option.
	* INSTALL: Regenerate.
	* README.tunables: New file.
	* Makeconfig (CPPFLAGS): Define TOP_NAMESPACE.
	(before-compile): Generate dl-tunable-list.h early.
	* config.h.in: Add HAVE_TUNABLES.
	* config.make.in: Add have-tunables.
	* configure.ac: Add --enable-tunables option.
	* configure: Regenerate.
	* csu/init-first.c (__libc_init_first): Move
	__libc_init_secure earlier...
	* csu/init-first.c (LIBC_START_MAIN):... to here.
	Include dl-tunables.h, libc-internal.h.
	(LIBC_START_MAIN) [!SHARED]: Initialize tunables for static
	binaries.
	* elf/Makefile (dl-routines): Add dl-tunables.
	* elf/Versions (ld): Add __tunable_set_val to GLIBC_PRIVATE
	namespace.
	* elf/dl-support (_dl_nondynamic_init): Unset MALLOC_CHECK_
	only when !HAVE_TUNABLES.
	* elf/rtld.c (process_envvars): Likewise.
	* elf/dl-sysdep.c [HAVE_TUNABLES]: Include dl-tunables.h
	(_dl_sysdep_start): Call __tunables_init.
	* elf/dl-tunable-types.h: New file.
	* elf/dl-tunables.c: New file.
	* elf/dl-tunables.h: New file.
	* elf/dl-tunables.list: New file.
	* malloc/tst-malloc-usable-static.c: New test case.
	* malloc/Makefile (tests-static): Add it.
	* malloc/arena.c [HAVE_TUNABLES]: Include dl-tunables.h.
	Define TUNABLE_NAMESPACE.
	(DL_TUNABLE_CALLBACK (set_mallopt_check)): New function.
	(DL_TUNABLE_CALLBACK_FNDECL): New macro.  Use it to define
	callback functions.
	(ptmalloc_init): Set tunable values.
	* scripts/gen-tunables.awk: New file.
	* sysdeps/mach/hurd/dl-sysdep.c: Include dl-tunables.h.
	(_dl_sysdep_start): Call __tunables_init.
This commit is contained in:
Siddhesh Poyarekar 2016-12-31 23:32:17 +05:30
parent bbe989ee87
commit 67e58f3941
25 changed files with 947 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

41
ChangeLog
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@ -1,3 +1,44 @@
2016-12-31 Siddhesh Poyarekar <siddhesh@sourceware.org>
* manual/install.texi: Add --enable-tunables option.
* INSTALL: Regenerate.
* README.tunables: New file.
* Makeconfig (CPPFLAGS): Define TOP_NAMESPACE.
(before-compile): Generate dl-tunable-list.h early.
* config.h.in: Add HAVE_TUNABLES.
* config.make.in: Add have-tunables.
* configure.ac: Add --enable-tunables option.
* configure: Regenerate.
* csu/init-first.c (__libc_init_first): Move
__libc_init_secure earlier...
* csu/init-first.c (LIBC_START_MAIN):... to here.
Include dl-tunables.h, libc-internal.h.
(LIBC_START_MAIN) [!SHARED]: Initialize tunables for static
binaries.
* elf/Makefile (dl-routines): Add dl-tunables.
* elf/Versions (ld): Add __tunable_set_val to GLIBC_PRIVATE
namespace.
* elf/dl-support (_dl_nondynamic_init): Unset MALLOC_CHECK_
only when !HAVE_TUNABLES.
* elf/rtld.c (process_envvars): Likewise.
* elf/dl-sysdep.c [HAVE_TUNABLES]: Include dl-tunables.h
(_dl_sysdep_start): Call __tunables_init.
* elf/dl-tunable-types.h: New file.
* elf/dl-tunables.c: New file.
* elf/dl-tunables.h: New file.
* elf/dl-tunables.list: New file.
* malloc/tst-malloc-usable-static.c: New test case.
* malloc/Makefile (tests-static): Add it.
* malloc/arena.c [HAVE_TUNABLES]: Include dl-tunables.h.
Define TUNABLE_NAMESPACE.
(DL_TUNABLE_CALLBACK (set_mallopt_check)): New function.
(DL_TUNABLE_CALLBACK_FNDECL): New macro. Use it to define
callback functions.
(ptmalloc_init): Set tunable values.
* scripts/gen-tunables.awk: New file.
* sysdeps/mach/hurd/dl-sysdep.c: Include dl-tunables.h.
(_dl_sysdep_start): Call __tunables_init.
2016-12-31 Florian Weimer <fweimer@redhat.com>
* resolv/resolv.h (RES_BLAST): Deprecate.

5
INSTALL
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@ -169,6 +169,11 @@ will be used, and CFLAGS sets optimization options for the compiler.
By default for x86_64, the GNU C Library is built with the vector
math library. Use this option to disable the vector math library.
'--enable-tunables'
Tunables support allows additional library parameters to be
customized at runtime. This is an experimental feature and affects
startup time and is thus disabled by default.
'--build=BUILD-SYSTEM'
'--host=HOST-SYSTEM'
These options are for cross-compiling. If you specify both options

16
Makeconfig
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@ -934,6 +934,11 @@ CPPFLAGS = $(config-extra-cppflags) $(CPPUNDEFS) $(CPPFLAGS-config) \
$(foreach lib,$(libof-$(basename $(@F))) \
$(libof-$(<F)) $(libof-$(@F)),$(CPPFLAGS-$(lib))) \
$(CPPFLAGS-$(<F)) $(CPPFLAGS-$(@F)) $(CPPFLAGS-$(basename $(@F)))
ifeq (yes,$(have-tunables))
CPPFLAGS += -DTOP_NAMESPACE=glibc
endif
override CFLAGS = -std=gnu11 -fgnu89-inline $(config-extra-cflags) \
$(filter-out %frame-pointer,$(+cflags)) $(+gccwarn-c) \
$(sysdep-CFLAGS) $(CFLAGS-$(suffix $@)) $(CFLAGS-$(<F)) \
@ -1108,6 +1113,17 @@ $(common-objpfx)libc-modules.stmp: $(..)scripts/gen-libc-modules.awk \
endif
# Build the tunables list header early since it could be used by any module in
# glibc.
ifeq (yes,$(have-tunables))
before-compile += $(common-objpfx)dl-tunable-list.h
$(common-objpfx)dl-tunable-list.h: $(..)scripts/gen-tunables.awk \
$(..)elf/dl-tunables.list
$(AWK) -f $^ > $@.tmp
mv $@.tmp $@
endif
common-generated += libc-modules.h libc-modules.stmp
# The name under which the run-time dynamic linker is installed.

85
README.tunables Normal file
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@ -0,0 +1,85 @@
TUNABLE FRAMEWORK
=================
Tunables is a feature in the GNU C Library that allows application authors and
distribution maintainers to alter the runtime library behaviour to match their
workload.
The tunable framework allows modules within glibc to register variables that
may be tweaked through an environment variable. It aims to enforce a strict
namespace rule to bring consistency to naming of these tunable environment
variables across the project. This document is a guide for glibc developers to
add tunables to the framework.
ADDING A NEW TUNABLE
--------------------
The TOP_NAMESPACE macro is defined by default as 'glibc'. If distributions
intend to add their own tunables, they should do so in a different top
namespace by overriding the TOP_NAMESPACE macro for that tunable. Downstream
implementations are discouraged from using the 'glibc' top namespace for
tunables they don't already have consensus to push upstream.
There are two steps to adding a tunable:
1. Add a tunable ID:
Modules that wish to use the tunables interface must define the
TUNABLE_NAMESPACE macro. Following this, for each tunable you want to
add, make an entry in elf/dl-tunables.list. The format of the file is as
follows:
TOP_NAMESPACE {
NAMESPACE1 {
TUNABLE1 {
# tunable attributes, one per line
}
# A tunable with default attributes, i.e. string variable.
TUNABLE2
TUNABLE3 {
# its attributes
}
}
NAMESPACE2 {
...
}
}
The list of allowed attributes are:
- type: Data type. Defaults to STRING. Allowed types are:
INT_32, SIZE_T and STRING.
- minval: Optional minimum acceptable value. For a string type
this is the minimum length of the value.
- maxval: Optional maximum acceptable value. For a string type
this is the maximum length of the value.
- env_alias: An alias environment variable
- is_secure: Specify whether the tunable should be read for setuid
binaries. True allows the tunable to be read for
setuid binaries while false disables it. Note that
even if this is set as true and the value is read, it
may not be used if it does not validate against the
acceptable values or is not considered safe by the
module.
2. Call either the TUNABLE_SET_VALUE and pass into it the tunable name and a
pointer to the variable that should be set with the tunable value.
If additional work needs to be done after setting the value, use the
TUNABLE_SET_VALUE_WITH_CALLBACK instead and additionally pass a pointer to
the function that should be called if the tunable value has been set.
FUTURE WORK
-----------
The framework currently only allows a one-time initialization of variables
through environment variables and in some cases, modification of variables via
an API call. A future goals for this project include:
- Setting system-wide and user-wide defaults for tunables through some
mechanism like a configuration file.
- Allow tweaking of some tunables at runtime

3
config.h.in
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@ -256,4 +256,7 @@
/* PowerPC32 uses fctidz for floating point to long long conversions. */
#define HAVE_PPC_FCTIDZ 0
/* Build glibc with tunables support. */
#define HAVE_TUNABLES 0
#endif

1
config.make.in
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@ -96,6 +96,7 @@ use-nscd = @use_nscd@
build-hardcoded-path-in-tests= @hardcoded_path_in_tests@
build-pt-chown = @build_pt_chown@
enable-lock-elision = @enable_lock_elision@
have-tunables = @have_tunables@
# Build tools.
CC = @CC@

16
configure vendored
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@ -666,6 +666,7 @@ libc_cv_ssp
base_machine
add_on_subdirs
add_ons
have_tunables
build_pt_chown
build_nscd
link_obsolete_rpc
@ -782,6 +783,7 @@ enable_systemtap
enable_build_nscd
enable_nscd
enable_pt_chown
enable_tunables
enable_mathvec
with_cpu
'
@ -1452,6 +1454,7 @@ Optional Features:
--disable-build-nscd disable building and installing the nscd daemon
--disable-nscd library functions will not contact the nscd daemon
--enable-pt_chown Enable building and installing pt_chown
--enable-tunables Enable tunables support
--enable-mathvec Enable building and installing mathvec [default
depends on architecture]
@ -3698,6 +3701,19 @@ if test "$build_pt_chown" = yes; then
fi
# Check whether --enable-tunables was given.
if test "${enable_tunables+set}" = set; then :
enableval=$enable_tunables; have_tunables=$enableval
else
have_tunables=no
fi
if test "$have_tunables" = yes; then
$as_echo "#define HAVE_TUNABLES 1" >>confdefs.h
fi
# The abi-tags file uses a fairly simplistic model for name recognition that
# can't distinguish i486-pc-linux-gnu fully from i486-pc-gnu. So we mutate a
# $host_os of `gnu*' here to be `gnu-gnu*' just so that it can tell.

10
configure.ac
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@ -421,6 +421,16 @@ if test "$build_pt_chown" = yes; then
AC_DEFINE(HAVE_PT_CHOWN)
fi
AC_ARG_ENABLE([tunables],
[AS_HELP_STRING([--enable-tunables],
[Enable tunables support])],
[have_tunables=$enableval],
[have_tunables=no])
AC_SUBST(have_tunables)
if test "$have_tunables" = yes; then
AC_DEFINE(HAVE_TUNABLES)
fi
# The abi-tags file uses a fairly simplistic model for name recognition that
# can't distinguish i486-pc-linux-gnu fully from i486-pc-gnu. So we mutate a
# $host_os of `gnu*' here to be `gnu-gnu*' just so that it can tell.

2
csu/init-first.c
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@ -72,8 +72,6 @@ _init (int argc, char **argv, char **envp)
__environ = envp;
#ifndef SHARED
__libc_init_secure ();
/* First the initialization which normally would be done by the
dynamic linker. */
_dl_non_dynamic_init ();

8
csu/libc-start.c
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@ -21,6 +21,9 @@
#include <unistd.h>
#include <ldsodefs.h>
#include <exit-thread.h>
#include <libc-internal.h>
#include <elf/dl-tunables.h>
extern void __libc_init_first (int argc, char **argv, char **envp);
@ -174,6 +177,11 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
}
}
/* Initialize very early so that tunables can use it. */
__libc_init_secure ();
__tunables_init (__environ);
/* Perform IREL{,A} relocations. */
apply_irel ();

5
elf/Makefile
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@ -35,6 +35,11 @@ dl-routines = $(addprefix dl-,load lookup object reloc deps hwcaps \
ifeq (yes,$(use-ldconfig))
dl-routines += dl-cache
endif
ifeq (yes,$(have-tunables))
dl-routines += dl-tunables
endif
all-dl-routines = $(dl-routines) $(sysdep-dl-routines)
# But they are absent from the shared libc, because that code is in ld.so.
elide-routines.os = $(all-dl-routines) dl-support enbl-secure dl-origin \

3
elf/Versions
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@ -70,5 +70,8 @@ ld {
# Internal error handling support. Interposed by libc.so.
_dl_signal_error; _dl_catch_error;
# Set value of a tunable.
__tunable_set_val;
}
}

2
elf/dl-support.c
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@ -354,8 +354,10 @@ _dl_non_dynamic_init (void)
cp = (const char *) __rawmemchr (cp, '\0') + 1;
}
#if !HAVE_TUNABLES
if (__access ("/etc/suid-debug", F_OK) != 0)
__unsetenv ("MALLOC_CHECK_");
#endif
}
#ifdef DL_PLATFORM_INIT

4
elf/dl-sysdep.c
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@ -44,6 +44,8 @@
#include <hp-timing.h>
#include <tls.h>
#include <dl-tunables.h>
extern char **_environ attribute_hidden;
extern char _end[] attribute_hidden;
@ -219,6 +221,8 @@ _dl_sysdep_start (void **start_argptr,
}
#endif
__tunables_init (_environ);
#ifdef DL_SYSDEP_INIT
DL_SYSDEP_INIT;
#endif

46
elf/dl-tunable-types.h Normal file
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@ -0,0 +1,46 @@
/* Tunable type information.
Copyright (C) 2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#ifndef _TUNABLE_TYPES_H_
# define _TUNABLE_TYPES_H_
#include <stddef.h>
typedef void (*tunable_callback_t) (void *);
typedef enum
{
TUNABLE_TYPE_INT_32,
TUNABLE_TYPE_SIZE_T,
TUNABLE_TYPE_STRING
} tunable_type_code_t;
typedef struct
{
tunable_type_code_t type_code;
int64_t min;
int64_t max;
} tunable_type_t;
typedef union
{
int64_t numval;
const char *strval;
} tunable_val_t;
#endif

320
elf/dl-tunables.c Normal file
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@ -0,0 +1,320 @@
/* The tunable framework. See the README.tunables to know how to use the
tunable in a glibc module.
Copyright (C) 2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <stdint.h>
#include <stdbool.h>
#include <unistd.h>
#include <stdlib.h>
#include <libc-internal.h>
#include <sysdep.h>
#include <fcntl.h>
#include <ldsodefs.h>
#define TUNABLES_INTERNAL 1
#include "dl-tunables.h"
/* Compare environment names, bounded by the name hardcoded in glibc. */
static bool
is_name (const char *orig, const char *envname)
{
for (;*orig != '\0' && *envname != '\0'; envname++, orig++)
if (*orig != *envname)
break;
/* The ENVNAME is immediately followed by a value. */
if (*orig == '\0' && *envname == '=')
return true;
else
return false;
}
static char **
get_next_env (char **envp, char **name, size_t *namelen, char **val)
{
while (envp != NULL && *envp != NULL)
{
char *envline = *envp;
int len = 0;
while (envline[len] != '\0' && envline[len] != '=')
len++;
/* Just the name and no value, go to the next one. */
if (envline[len] == '\0')
continue;
*name = envline;
*namelen = len;
*val = &envline[len + 1];
return ++envp;
}
return NULL;
}
static int
tunables_unsetenv (char **ep, const char *name)
{
while (*ep != NULL)
{
size_t cnt = 0;
while ((*ep)[cnt] == name[cnt] && name[cnt] != '\0')
++cnt;
if (name[cnt] == '\0' && (*ep)[cnt] == '=')
{
/* Found it. Remove this pointer by moving later ones to
the front. */
char **dp = ep;
do
dp[0] = dp[1];
while (*dp++);
/* Continue the loop in case NAME appears again. */
}
else
++ep;
}
return 0;
}
/* A stripped down strtoul-like implementation for very early use. It does not
set errno if the result is outside bounds because it gets called before
errno may have been set up. */
static unsigned long int
tunables_strtoul (const char *nptr)
{
unsigned long int result = 0;
long int sign = 1;
unsigned max_digit;
while (*nptr == ' ' || *nptr == '\t')
++nptr;
if (*nptr == '-')
{
sign = -1;
++nptr;
}
else if (*nptr == '+')
++nptr;
if (*nptr < '0' || *nptr > '9')
return 0UL;
int base = 10;
max_digit = 9;
if (*nptr == '0')
{
if (nptr[1] == 'x' || nptr[1] == 'X')
{
base = 16;
nptr += 2;
}
else
{
base = 8;
max_digit = 7;
}
}
while (1)
{
unsigned long int digval;
if (*nptr >= '0' && *nptr <= '0' + max_digit)
digval = *nptr - '0';
else if (base == 16)
{
if (*nptr >= 'a' && *nptr <= 'f')
digval = *nptr - 'a' + 10;
else if (*nptr >= 'A' && *nptr <= 'F')
digval = *nptr - 'A' + 10;
else
break;
}
else
break;
if (result > ULONG_MAX / base
|| (result == ULONG_MAX / base && digval > ULONG_MAX % base))
return ULONG_MAX;
result *= base;
result += digval;
++nptr;
}
return result * sign;
}
/* Initialize the internal type if the value validates either using the
explicit constraints of the tunable or with the implicit constraints of its
type. */
static void
tunable_set_val_if_valid_range (tunable_t *cur, const char *strval,
int64_t default_min, int64_t default_max)
{
int64_t val = tunables_strtoul (strval);
int64_t min = cur->type.min;
int64_t max = cur->type.max;
if (min == max)
{
min = default_min;
max = default_max;
}
if (val >= min && val <= max)
{
cur->val.numval = val;
cur->strval = strval;
}
}
/* Validate range of the input value and initialize the tunable CUR if it looks
good. */
static void
tunable_initialize (tunable_t *cur, const char *strval)
{
switch (cur->type.type_code)
{
case TUNABLE_TYPE_INT_32:
{
tunable_set_val_if_valid_range (cur, strval, INT32_MIN, INT32_MAX);
break;
}
case TUNABLE_TYPE_SIZE_T:
{
tunable_set_val_if_valid_range (cur, strval, 0, SIZE_MAX);
break;
}
case TUNABLE_TYPE_STRING:
{
cur->val.strval = cur->strval = strval;
break;
}
default:
__builtin_unreachable ();
}
}
/* Disable a tunable if it is set. */
static void
disable_tunable (tunable_id_t id, char **envp)
{
const char *env_alias = tunable_list[id].env_alias;
if (env_alias != NULL)
tunables_unsetenv (envp, tunable_list[id].env_alias);
}
/* Disable the glibc.malloc.check tunable in SETUID/SETGID programs unless
the system administrator overrides it by creating the /etc/suid-debug
file. This is a special case where we want to conditionally enable/disable
a tunable even for setuid binaries. We use the special version of access()
to avoid setting ERRNO, which is a TLS variable since TLS has not yet been
set up. */
static inline void
__always_inline
maybe_disable_malloc_check (void)
{
if (__libc_enable_secure && __access_noerrno ("/etc/suid-debug", F_OK) != 0)
disable_tunable (TUNABLE_ENUM_NAME(glibc, malloc, check), __environ);
}
/* Initialize the tunables list from the environment. For now we only use the
ENV_ALIAS to find values. Later we will also use the tunable names to find
values. */
void
__tunables_init (char **envp)
{
char *envname = NULL;
char *envval = NULL;
size_t len = 0;
maybe_disable_malloc_check ();
while ((envp = get_next_env (envp, &envname, &len, &envval)) != NULL)
{
for (int i = 0; i < sizeof (tunable_list) / sizeof (tunable_t); i++)
{
tunable_t *cur = &tunable_list[i];
/* Skip over tunables that have either been set already or should be
skipped. */
if (cur->strval != NULL || cur->env_alias == NULL
|| (__libc_enable_secure && !cur->is_secure))
continue;
const char *name = cur->env_alias;
/* We have a match. Initialize and move on to the next line. */
if (is_name (name, envname))
{
tunable_initialize (cur, envval);
break;
}
}
}
}
/* Set the tunable value. This is called by the module that the tunable exists
in. */
void
__tunable_set_val (tunable_id_t id, void *valp, tunable_callback_t callback)
{
tunable_t *cur = &tunable_list[id];
/* Don't do anything if our tunable was not set during initialization or if
it failed validation. */
if (cur->strval == NULL)
return;
if (valp == NULL)
goto cb;
switch (cur->type.type_code)
{
case TUNABLE_TYPE_INT_32:
{
*((int32_t *) valp) = (int32_t) cur->val.numval;
break;
}
case TUNABLE_TYPE_SIZE_T:
{
*((size_t *) valp) = (size_t) cur->val.numval;
break;
}
case TUNABLE_TYPE_STRING:
{
*((const char **)valp) = cur->val.strval;
break;
}
default:
__builtin_unreachable ();
}
cb:
if (callback)
callback (&cur->val);
}

88
elf/dl-tunables.h Normal file
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@ -0,0 +1,88 @@
/* The tunable framework. See the README to know how to use the tunable in
a glibc module.
Copyright (C) 2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#ifndef _TUNABLES_H_
#define _TUNABLES_H_
#if !HAVE_TUNABLES
static inline void
__always_inline
__tunables_init (char **unused __attribute_unused)
{
/* This is optimized out if tunables are not enabled. */
}
#else
# include <stddef.h>
# include "dl-tunable-types.h"
/* A tunable. */
struct _tunable
{
const char *name; /* Internal name of the tunable. */
tunable_type_t type; /* Data type of the tunable. */
tunable_val_t val; /* The value. */
const char *strval; /* The string containing the value,
points into envp. */
bool is_secure; /* Whether the tunable must be read
even for setuid binaries. Note that
even if the tunable is read, it may
not get used by the target module if
the value is considered unsafe. */
/* Compatibility elements. */
const char *env_alias; /* The compatibility environment
variable name. */
};
typedef struct _tunable tunable_t;
/* Full name for a tunable is top_ns.tunable_ns.id. */
# define TUNABLE_NAME_S(top,ns,id) #top "." #ns "." #id
# define TUNABLE_ENUM_NAME(top,ns,id) TUNABLE_ENUM_NAME1 (top,ns,id)
# define TUNABLE_ENUM_NAME1(top,ns,id) top ## _ ## ns ## _ ## id
# include "dl-tunable-list.h"
extern void __tunables_init (char **);
extern void __tunable_set_val (tunable_id_t, void *, tunable_callback_t);
/* Check if the tunable has been set to a non-default value and if it is, copy
it over into __VAL. */
# define TUNABLE_SET_VAL(__id,__val) \
({ \
__tunable_set_val \
(TUNABLE_ENUM_NAME (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id), (__val), \
NULL); \
})
/* Same as TUNABLE_SET_VAL, but also call the callback function __CB. */
# define TUNABLE_SET_VAL_WITH_CALLBACK(__id,__val,__cb) \
({ \
__tunable_set_val \
(TUNABLE_ENUM_NAME (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id), (__val), \
DL_TUNABLE_CALLBACK (__cb)); \
})
/* Namespace sanity for callback functions. Use this macro to keep the
namespace of the modules clean. */
# define DL_TUNABLE_CALLBACK(__name) _dl_tunable_ ## __name
#endif
#endif

69
elf/dl-tunables.list Normal file
View File

@ -0,0 +1,69 @@
# Copyright (C) 2016 Free Software Foundation, Inc.
# This file is part of the GNU C Library.
# The GNU C Library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
# The GNU C Library 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
# Lesser General Public License for more details.
# You should have received a copy of the GNU Lesser General Public
# License along with the GNU C Library; if not, see
# <http://www.gnu.org/licenses/>.
# Allowed attributes for tunables:
#
# type: Defaults to STRING
# minval: Optional minimum acceptable value
# maxval: Optional maximum acceptable value
# env_alias: An alias environment variable
# is_secure: Specify whether the environment variable should be read for
# setuid binaries.
glibc {
malloc {
check {
type: INT_32
minval: 0
maxval: 3
env_alias: MALLOC_CHECK_
is_secure: true
}
top_pad {
type: SIZE_T
env_alias: MALLOC_TOP_PAD_
}
perturb {
type: INT_32
minval: 0
maxval: 0xff
env_alias: MALLOC_PERTURB_
}
mmap_threshold {
type: SIZE_T
env_alias: MALLOC_MMAP_THRESHOLD_
}
trim_threshold {
type: SIZE_T
env_alias: MALLOC_TRIM_THRESHOLD_
}
mmap_max {
type: INT_32
env_alias: MALLOC_MMAP_MAX_
}
arena_max {
type: SIZE_T
env_alias: MALLOC_ARENA_MAX
minval: 1
}
arena_test {
type: SIZE_T
env_alias: MALLOC_ARENA_TEST
minval: 1
}
}
}

2
elf/rtld.c
View File

@ -2510,7 +2510,9 @@ process_envvars (enum mode *modep)
if (__access ("/etc/suid-debug", F_OK) != 0)
{
#if !HAVE_TUNABLES
unsetenv ("MALLOC_CHECK_");
#endif
GLRO(dl_debug_mask) = 0;
}

2
malloc/Makefile
View File

@ -37,6 +37,7 @@ tests := mallocbug tst-malloc tst-valloc tst-calloc tst-obstack \
tests-static := \
tst-interpose-static-nothread \
tst-interpose-static-thread \
tst-malloc-usable-static
tests += $(tests-static)
test-srcs = tst-mtrace
@ -158,6 +159,7 @@ endif
tst-mcheck-ENV = MALLOC_CHECK_=3
tst-malloc-usable-ENV = MALLOC_CHECK_=3
tst-malloc-usable-static-ENV = $(tst-malloc-usable-ENV)
# Uncomment this for test releases. For public releases it is too expensive.
#CPPFLAGS-malloc.o += -DMALLOC_DEBUG=1

54
malloc/arena.c
View File

@ -19,6 +19,11 @@
#include <stdbool.h>
#if HAVE_TUNABLES
# define TUNABLE_NAMESPACE malloc
#endif
#include <elf/dl-tunables.h>
/* Compile-time constants. */
#define HEAP_MIN_SIZE (32 * 1024)
@ -204,6 +209,34 @@ __malloc_fork_unlock_child (void)
__libc_lock_init (list_lock);
}
#if HAVE_TUNABLES
static inline int do_set_mallopt_check (int32_t value);
void
DL_TUNABLE_CALLBACK (set_mallopt_check) (void *valp)
{
int32_t value = *(int32_t *) valp;
do_set_mallopt_check (value);
if (check_action != 0)
__malloc_check_init ();
}
# define DL_TUNABLE_CALLBACK_FNDECL(__name, __type) \
static inline int do_ ## __name (__type value); \
void \
DL_TUNABLE_CALLBACK (__name) (void *valp) \
{ \
__type value = *(__type *) valp; \
do_ ## __name (value); \
}
DL_TUNABLE_CALLBACK_FNDECL (set_mmap_threshold, size_t)
DL_TUNABLE_CALLBACK_FNDECL (set_mmaps_max, int32_t)
DL_TUNABLE_CALLBACK_FNDECL (set_top_pad, size_t)
DL_TUNABLE_CALLBACK_FNDECL (set_perturb_byte, int32_t)
DL_TUNABLE_CALLBACK_FNDECL (set_trim_threshold, size_t)
DL_TUNABLE_CALLBACK_FNDECL (set_arena_max, size_t)
DL_TUNABLE_CALLBACK_FNDECL (set_arena_test, size_t)
#else
/* Initialization routine. */
#include <string.h>
extern char **_environ;
@ -238,6 +271,7 @@ next_env_entry (char ***position)
return result;
}
#endif
#ifdef SHARED
@ -272,6 +306,24 @@ ptmalloc_init (void)
#endif
thread_arena = &main_arena;
#if HAVE_TUNABLES
/* Ensure initialization/consolidation and do it under a lock so that a
thread attempting to use the arena in parallel waits on us till we
finish. */
__libc_lock_lock (main_arena.mutex);
malloc_consolidate (&main_arena);
TUNABLE_SET_VAL_WITH_CALLBACK (check, NULL, set_mallopt_check);
TUNABLE_SET_VAL_WITH_CALLBACK (top_pad, NULL, set_top_pad);
TUNABLE_SET_VAL_WITH_CALLBACK (perturb, NULL, set_perturb_byte);
TUNABLE_SET_VAL_WITH_CALLBACK (mmap_threshold, NULL, set_mmap_threshold);
TUNABLE_SET_VAL_WITH_CALLBACK (trim_threshold, NULL, set_trim_threshold);
TUNABLE_SET_VAL_WITH_CALLBACK (mmap_max, NULL, set_mmaps_max);
TUNABLE_SET_VAL_WITH_CALLBACK (arena_max, NULL, set_arena_max);
TUNABLE_SET_VAL_WITH_CALLBACK (arena_test, NULL, set_arena_test);
__libc_lock_unlock (main_arena.mutex);
#else
const char *s = NULL;
if (__glibc_likely (_environ != NULL))
{
@ -340,6 +392,8 @@ ptmalloc_init (void)
if (check_action != 0)
__malloc_check_init ();
}
#endif
#if HAVE_MALLOC_INIT_HOOK
void (*hook) (void) = atomic_forced_read (__malloc_initialize_hook);
if (hook != NULL)

1
malloc/tst-malloc-usable-static.c Normal file
View File

@ -0,0 +1 @@
#include <malloc/tst-malloc-usable.c>

5
manual/install.texi
View File

@ -200,6 +200,11 @@ configure with @option{--disable-werror}.
By default for x86_64, @theglibc{} is built with the vector math library.
Use this option to disable the vector math library.
@item --enable-tunables
Tunables support allows additional library parameters to be customized at
runtime. This is an experimental feature and affects startup time and is thus
disabled by default.
@item --build=@var{build-system}
@itemx --host=@var{host-system}
These options are for cross-compiling. If you specify both options and

157
scripts/gen-tunables.awk Normal file
View File

@ -0,0 +1,157 @@
# Generate dl-tunable-list.h from dl-tunables.list
BEGIN {
tunable=""
ns=""
top_ns=""
}
# Skip over blank lines and comments.
/^#/ {
next
}
/^[ \t]*$/ {
next
}
# Beginning of either a top namespace, tunable namespace or a tunable, decided
# on the current value of TUNABLE, NS or TOP_NS.
$2 == "{" {
if (top_ns == "") {
top_ns = $1
}
else if (ns == "") {
ns = $1
}
else if (tunable == "") {
tunable = $1
}
else {
printf ("Unexpected occurrence of '{': %s:%d\n", FILENAME, FNR)
exit 1
}
next
}
# End of either a top namespace, tunable namespace or a tunable.
$1 == "}" {
if (tunable != "") {
# Tunables definition ended, now fill in default attributes.
if (!types[top_ns][ns][tunable]) {
types[top_ns][ns][tunable] = "STRING"
}
if (!minvals[top_ns][ns][tunable]) {
minvals[top_ns][ns][tunable] = "0"
}
if (!maxvals[top_ns][ns][tunable]) {
maxvals[top_ns][ns][tunable] = "0"
}
if (!env_alias[top_ns][ns][tunable]) {
env_alias[top_ns][ns][tunable] = "NULL"
}
if (!is_secure[top_ns][ns][tunable]) {
is_secure[top_ns][ns][tunable] = "false"
}
tunable = ""
}
else if (ns != "") {
ns = ""
}
else if (top_ns != "") {
top_ns = ""
}
else {
printf ("syntax error: extra }: %s:%d\n", FILENAME, FNR)
exit 1
}
next
}
# Everything else, which could either be a tunable without any attributes or a
# tunable attribute.
{
if (ns == "") {
printf("Line %d: Invalid tunable outside a namespace: %s\n", NR, $0)
exit 1
}
if (tunable == "") {
# We encountered a tunable without any attributes, so note it with a
# default.
types[top_ns][ns][$1] = "STRING"
next
}
# Otherwise, we have encountered a tunable attribute.
split($0, arr, ":")
attr = gensub(/^[ \t]+|[ \t]+$/, "", "g", arr[1])
val = gensub(/^[ \t]+|[ \t]+$/, "", "g", arr[2])
if (attr == "type") {
types[top_ns][ns][tunable] = val
}
else if (attr == "minval") {
minvals[top_ns][ns][tunable] = val
}
else if (attr == "maxval") {
maxvals[top_ns][ns][tunable] = val
}
else if (attr == "env_alias") {
env_alias[top_ns][ns][tunable] = sprintf("\"%s\"", val)
}
else if (attr == "is_secure") {
if (val == "true" || val == "false") {
is_secure[top_ns][ns][tunable] = val
}
else {
printf("Line %d: Invalid value (%s) for is_secure: %s, ", NR, val,
$0)
print("Allowed values are 'true' or 'false'")
exit 1
}
}
}
END {
if (ns != "") {
print "Unterminated namespace. Is a closing brace missing?"
exit 1
}
print "/* AUTOGENERATED by gen-tunables.awk. */"
print "#ifndef _TUNABLES_H_"
print "# error \"Do not include this file directly.\""
print "# error \"Include tunables.h instead.\""
print "#endif"
# Now, the enum names
print "\ntypedef enum"
print "{"
for (t in types) {
for (n in types[t]) {
for (m in types[t][n]) {
printf (" TUNABLE_ENUM_NAME(%s, %s, %s),\n", t, n, m);
}
}
}
print "} tunable_id_t;\n"
# Finally, the tunable list.
print "\n#ifdef TUNABLES_INTERNAL"
print "static tunable_t tunable_list[] = {"
for (t in types) {
for (n in types[t]) {
for (m in types[t][n]) {
printf (" {TUNABLE_NAME_S(%s, %s, %s)", t, n, m)
printf (", {TUNABLE_TYPE_%s, %s, %s}, {.numval = 0}, NULL, %s, %s},\n",
types[t][n][m], minvals[t][n][m], maxvals[t][n][m],
is_secure[t][n][m], env_alias[t][n][m]);
}
}
}
print "};"
print "#endif"
}

4
sysdeps/mach/hurd/dl-sysdep.c
View File

@ -44,6 +44,8 @@
#include <dl-machine.h>
#include <dl-procinfo.h>
#include <dl-tunables.h>
extern void __mach_init (void);
extern int _dl_argc;
@ -143,6 +145,8 @@ _dl_sysdep_start (void **start_argptr,
__libc_enable_secure = _dl_hurd_data->flags & EXEC_SECURE;
__tunables_init (_environ);
if (_dl_hurd_data->flags & EXEC_STACK_ARGS &&
_dl_hurd_data->user_entry == 0)
_dl_hurd_data->user_entry = (vm_address_t) ENTRY_POINT;