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[PATCH 1/4] Add framework for tunables
- From: Siddhesh Poyarekar <siddhesh at sourceware dot org>
- To: libc-alpha at sourceware dot org
- Cc: carlos at redhat dot com, adhemerval dot zanella at linaro dot org
- Date: Wed, 16 Nov 2016 14:05:03 +0530
- Subject: [PATCH 1/4] Add framework for tunables
- Authentication-results: sourceware.org; auth=none
- References: <1479285306-11684-1-git-send-email-siddhesh@sourceware.org>
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/libc-start.c (LIBC_START_MAIN):... to here.
[HAVE_TUNABLES]: Include dl-tunables.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 [HAVE_TUNABLES]: Include
dl-tunables.h.
(_dl_sysdep_start): Call __tunables_init.
---
INSTALL | 5 +
Makeconfig | 16 ++
README.tunables | 84 +++++++++++
config.h.in | 3 +
config.make.in | 1 +
configure | 16 ++
configure.ac | 10 ++
csu/init-first.c | 2 -
csu/libc-start.c | 12 ++
elf/Makefile | 5 +
elf/Versions | 3 +
elf/dl-support.c | 2 +
elf/dl-sysdep.c | 8 +
elf/dl-tunable-types.h | 46 ++++++
elf/dl-tunables.c | 310 ++++++++++++++++++++++++++++++++++++++
elf/dl-tunables.h | 78 ++++++++++
elf/dl-tunables.list | 69 +++++++++
elf/rtld.c | 2 +
malloc/Makefile | 2 +
malloc/arena.c | 54 +++++++
malloc/tst-malloc-usable-static.c | 1 +
manual/install.texi | 5 +
scripts/gen-tunables.awk | 157 +++++++++++++++++++
sysdeps/mach/hurd/dl-sysdep.c | 8 +
24 files changed, 897 insertions(+), 2 deletions(-)
create mode 100644 README.tunables
create mode 100644 elf/dl-tunable-types.h
create mode 100644 elf/dl-tunables.c
create mode 100644 elf/dl-tunables.h
create mode 100644 elf/dl-tunables.list
create mode 100644 malloc/tst-malloc-usable-static.c
create mode 100644 scripts/gen-tunables.awk
diff --git a/INSTALL b/INSTALL
index b5acedc..ccacccc 100644
--- a/INSTALL
+++ b/INSTALL
@@ -158,6 +158,11 @@ 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
diff --git a/Makeconfig b/Makeconfig
index a785860..d0eb832 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -883,6 +883,11 @@ 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)) \
@@ -1057,6 +1062,17 @@ $(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.
diff --git a/README.tunables b/README.tunables
new file mode 100644
index 0000000..3d9c86a
--- /dev/null
+++ b/README.tunables
@@ -0,0 +1,84 @@
+ 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 or an API call. 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 is defined by default as 'glibc' and it may be overridden in
+distributions for specific tunables if they want to add their own tunables.
+Downstream implementations are discouraged from using the 'glibc' 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
diff --git a/config.h.in b/config.h.in
index 33757bd..fd93bb3 100644
--- a/config.h.in
+++ b/config.h.in
@@ -246,4 +246,7 @@
/* 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
diff --git a/config.make.in b/config.make.in
index 04a8b3e..6d0b607 100644
--- a/config.make.in
+++ b/config.make.in
@@ -93,6 +93,7 @@ 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@
diff --git a/configure b/configure
index d9f8c06..cbd5fb3 100755
--- a/configure
+++ b/configure
@@ -662,6 +662,7 @@ multi_arch
base_machine
add_on_subdirs
add_ons
+have_tunables
build_pt_chown
build_nscd
link_obsolete_rpc
@@ -776,6 +777,7 @@ enable_systemtap
enable_build_nscd
enable_nscd
enable_pt_chown
+enable_tunables
enable_mathvec
with_cpu
'
@@ -1443,6 +1445,7 @@ 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]
@@ -3649,6 +3652,19 @@ 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
# $host_os of `gnu*' here to be `gnu-gnu*' just so that it can tell.
diff --git a/configure.ac b/configure.ac
index de0a40f..3b7a0db 100644
--- a/configure.ac
+++ b/configure.ac
@@ -395,6 +395,16 @@ if test "$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.
diff --git a/csu/init-first.c b/csu/init-first.c
index 77c6e1c..465f25b 100644
--- a/csu/init-first.c
+++ b/csu/init-first.c
@@ -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 ();
diff --git a/csu/libc-start.c b/csu/libc-start.c
index 99c040a..4e5cafa 100644
--- a/csu/libc-start.c
+++ b/csu/libc-start.c
@@ -21,6 +21,11 @@
#include <unistd.h>
#include <ldsodefs.h>
#include <exit-thread.h>
+#include <libc-internal.h>
+
+#if HAVE_TUNABLES
+# include <elf/dl-tunables.h>
+#endif
extern void __libc_init_first (int argc, char **argv, char **envp);
@@ -184,6 +189,13 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
}
# endif
+ /* Initialize very early so that tunables can use it. */
+ __libc_init_secure ();
+
+#if HAVE_TUNABLES
+ __tunables_init (__environ);
+#endif
+
/* Perform IREL{,A} relocations. */
apply_irel ();
diff --git a/elf/Makefile b/elf/Makefile
index 82c7e05..477f8fc 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -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 \
diff --git a/elf/Versions b/elf/Versions
index 23deda9..1734697 100644
--- a/elf/Versions
+++ b/elf/Versions
@@ -64,5 +64,8 @@ ld {
# Pointer protection.
__pointer_chk_guard;
+
+ # Set value of a tunable.
+ __tunable_set_val;
}
}
diff --git a/elf/dl-support.c b/elf/dl-support.c
index c30194c..d350d6d 100644
--- a/elf/dl-support.c
+++ b/elf/dl-support.c
@@ -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
diff --git a/elf/dl-sysdep.c b/elf/dl-sysdep.c
index eaa7155..68f30f2 100644
--- a/elf/dl-sysdep.c
+++ b/elf/dl-sysdep.c
@@ -44,6 +44,10 @@
#include <hp-timing.h>
#include <tls.h>
+#if HAVE_TUNABLES
+# include <dl-tunables.h>
+#endif
+
extern char **_environ attribute_hidden;
extern char _end[] attribute_hidden;
@@ -219,6 +223,10 @@ _dl_sysdep_start (void **start_argptr,
}
#endif
+#if HAVE_TUNABLES
+ __tunables_init (_environ);
+#endif
+
#ifdef DL_SYSDEP_INIT
DL_SYSDEP_INIT;
#endif
diff --git a/elf/dl-tunable-types.h b/elf/dl-tunable-types.h
new file mode 100644
index 0000000..d1591b6
--- /dev/null
+++ b/elf/dl-tunable-types.h
@@ -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
diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
new file mode 100644
index 0000000..91340b6
--- /dev/null
+++ b/elf/dl-tunables.c
@@ -0,0 +1,310 @@
+/* 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/>. */
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <libc-internal.h>
+#include <sysdep.h>
+#include <fcntl.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;
+}
+
+/* If the value does not validate, don't bother initializing the internal type
+ and also take care to clear the recorded string value in STRVAL. */
+#define RETURN_IF_INVALID_RANGE(__cur, __val) \
+({ \
+ __typeof ((__cur)->type.min) min = (__cur)->type.min; \
+ __typeof ((__cur)->type.max) max = (__cur)->type.max; \
+ if (min != max && ((__val) < min || (__val) > max)) \
+ return; \
+})
+
+/* 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:
+ {
+ int32_t val = (int32_t) tunables_strtoul (strval);
+ RETURN_IF_INVALID_RANGE (cur, val);
+ cur->val.numval = (int64_t) val;
+ cur->strval = strval;
+ break;
+ }
+ case TUNABLE_TYPE_SIZE_T:
+ {
+ size_t val = (size_t) tunables_strtoul (strval);
+ RETURN_IF_INVALID_RANGE (cur, val);
+ cur->val.numval = (int64_t) val;
+ cur->strval = strval;
+ 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)
+ 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);
+}
diff --git a/elf/dl-tunables.h b/elf/dl-tunables.h
new file mode 100644
index 0000000..10a644b
--- /dev/null
+++ b/elf/dl-tunables.h
@@ -0,0 +1,78 @@
+/* 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_
+# 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 set the callback function to __CB and call
+ it. */
+# 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
diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list
new file mode 100644
index 0000000..11504c4
--- /dev/null
+++ b/elf/dl-tunables.list
@@ -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
+ }
+ }
+}
diff --git a/elf/rtld.c b/elf/rtld.c
index 647661c..eb211a2 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -2527,11 +2527,13 @@ process_envvars (enum mode *modep)
}
while (*nextp != '\0');
+#if !HAVE_TUNABLES
if (__access ("/etc/suid-debug", F_OK) != 0)
{
unsetenv ("MALLOC_CHECK_");
GLRO(dl_debug_mask) = 0;
}
+#endif
if (mode != normal)
_exit (5);
diff --git a/malloc/Makefile b/malloc/Makefile
index b8efcd6..4e4104e 100644
--- a/malloc/Makefile
+++ b/malloc/Makefile
@@ -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
diff --git a/malloc/arena.c b/malloc/arena.c
index eed4247..c2791b2 100644
--- a/malloc/arena.c
+++ b/malloc/arena.c
@@ -19,6 +19,11 @@
#include <stdbool.h>
+#if HAVE_TUNABLES
+# define TUNABLE_NAMESPACE malloc
+# include <elf/dl-tunables.h>
+#endif
+
/* 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)
diff --git a/malloc/tst-malloc-usable-static.c b/malloc/tst-malloc-usable-static.c
new file mode 100644
index 0000000..8907db0
--- /dev/null
+++ b/malloc/tst-malloc-usable-static.c
@@ -0,0 +1 @@
+#include <malloc/tst-malloc-usable.c>
diff --git a/manual/install.texi b/manual/install.texi
index de1c203..ffc166d 100644
--- a/manual/install.texi
+++ b/manual/install.texi
@@ -189,6 +189,11 @@ 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
diff --git a/scripts/gen-tunables.awk b/scripts/gen-tunables.awk
new file mode 100644
index 0000000..b65b5a4
--- /dev/null
+++ b/scripts/gen-tunables.awk
@@ -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"
+}
diff --git a/sysdeps/mach/hurd/dl-sysdep.c b/sysdeps/mach/hurd/dl-sysdep.c
index d730f82..40b5be5 100644
--- a/sysdeps/mach/hurd/dl-sysdep.c
+++ b/sysdeps/mach/hurd/dl-sysdep.c
@@ -44,6 +44,10 @@
#include <dl-machine.h>
#include <dl-procinfo.h>
+#if HAVE_TUNABLES
+# include <dl-tunables.h>
+#endif
+
extern void __mach_init (void);
extern int _dl_argc;
@@ -143,6 +147,10 @@ _dl_sysdep_start (void **start_argptr,
__libc_enable_secure = _dl_hurd_data->flags & EXEC_SECURE;
+#if HAVE_TUNABLES
+ __tunables_init (_environ);
+#endif
+
if (_dl_hurd_data->flags & EXEC_STACK_ARGS &&
_dl_hurd_data->user_entry == 0)
_dl_hurd_data->user_entry = (vm_address_t) ENTRY_POINT;
--
2.7.4