At the GNU Tools Cauldron 2016, the state of the current tunables
patchset was considered OK with the addition of a way to select the
frontend to be used for the tunables. That is, to avoid being locked
in to one type of frontend initially, it should be possible to build
tunables with a different frontend with something as simple as a
configure switch.
To that effect, this patch enhances the --enable-tunables option to
accept more values than just 'yes' or 'no'. The current frontend (and
default when enable-tunables is 'yes') is called 'valstring', to
select the frontend where a single environment variable is set to a
colon-separated value string. More such frontends can be added in
future.
* Makeconfig (have-tunables): Check for non-negative instead
of positive.
* configure.ac: Add 'valstring' as a valid value for
--enable-tunables.
* configure: Regenerate.
* elf/Makefile (have-tunables): Check for non-negative instead
of positive.
(CPPFLAGS-dl-tunables.c): Define TUNABLES_FRONTEND for
dl-tunables.c.
* elf/dl-tunables.c (GLIBC_TUNABLES): Define only when
TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring.
(tunables_strdup): Likewise.
(disable_tunables): Likewise.
(parse_tunables): Likewise.
(__tunables_init): Process GLIBC_TUNABLES envvar only when.
TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring.
* elf/dl-tunables.h (TUNABLES_FRONTEND_valstring): New macro.
(TUNABLES_FRONTEND_yes): New macro, define as
TUNABLES_FRONTEND_valstring by default.
* manual/install.texi: Document new acceptable values for
--enable-tunables.
* INSTALL: Regenerate.
---
INSTALL | 15 ++++++++++++++-
Makeconfig | 4 ++--
configure | 3 ++-
configure.ac | 2 +-
elf/Makefile | 4 +++-
elf/dl-tunables.c | 12 +++++++++++-
elf/dl-tunables.h | 4 ++++
manual/install.texi | 18 +++++++++++++++++-
8 files changed, 54 insertions(+), 8 deletions(-)
@@ -161,7 +161,20 @@ will be used, and CFLAGS sets optimization options for the compiler.
'--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.
+ startup time and is thus disabled by default. This option can take
+ the following values:
+
+ * NO This is the default if the option is not passed to
+ configure. This disables tunables.
+
+ * YES This is the default if the option is passed to configure.
+ This enables tunables and selects the default frontend
+ (currently VALSTRING).
+
+ * VALSTRING This enables tunables and selects the VALSTRING
+ frontend for tunables. This frontend allows users to specify
+ tunables as a colon-separated list in a single environment
+ variable GLIBC_TUNABLES.
'--build=BUILD-SYSTEM'
'--host=HOST-SYSTEM'
@@ -884,7 +884,7 @@ CPPFLAGS = $(config-extra-cppflags) $(CPPUNDEFS) $(CPPFLAGS-config) \
$(libof-$(<F)) $(libof-$(@F)),$(CPPFLAGS-$(lib))) \
$(CPPFLAGS-$(<F)) $(CPPFLAGS-$(@F)) $(CPPFLAGS-$(basename $(@F)))
-ifeq (yes,$(have-tunables))
+ifneq (no,$(have-tunables))
CPPFLAGS += -DTOP_NAMESPACE=glibc
endif
@@ -1064,7 +1064,7 @@ endif
# Build the tunables list header early since it could be used by any module in
# glibc.
-ifeq (yes,$(have-tunables))
+ifneq (no,$(have-tunables))
before-compile += $(common-objpfx)dl-tunable-list.h
$(common-objpfx)dl-tunable-list.h: $(..)scripts/gen-tunables.awk \
@@ -1445,7 +1445,8 @@ Optional Features:
--disable-build-nscd disable building and installing the nscd daemon
--disable-nscd library functions will not contact the nscd daemon
--enable-pt_chown Enable building and installing pt_chown
- --enable-tunables Enable tunables support
+ --enable-tunables Enable tunables support. Known values are 'yes',
+ 'no' and 'valstring'
--enable-mathvec Enable building and installing mathvec [default
depends on architecture]
@@ -397,7 +397,7 @@ fi
AC_ARG_ENABLE([tunables],
[AS_HELP_STRING([--enable-tunables],
- [Enable tunables support])],
+ [Enable tunables support. Known values are 'yes', 'no' and 'valstring'])],
[have_tunables=$enableval],
[have_tunables=no])
AC_SUBST(have_tunables)
@@ -36,8 +36,10 @@ ifeq (yes,$(use-ldconfig))
dl-routines += dl-cache
endif
-ifeq (yes,$(have-tunables))
+ifneq (no,$(have-tunables))
dl-routines += dl-tunables
+tunables-type = $(addprefix TUNABLES_FRONTEND_,$(have-tunables))
+CPPFLAGS-dl-tunables.c = -DTUNABLES_FRONTEND=$(tunables-type)
endif
all-dl-routines = $(dl-routines) $(sysdep-dl-routines)
@@ -30,7 +30,9 @@
#define TUNABLES_INTERNAL 1
#include "dl-tunables.h"
-#define GLIBC_TUNABLES "GLIBC_TUNABLES"
+#if TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring
+# define GLIBC_TUNABLES "GLIBC_TUNABLES"
+#endif
/* Compare environment names, bounded by the name hardcoded in glibc. */
static bool
@@ -47,6 +49,7 @@ is_name (const char *orig, const char *envname)
return false;
}
+#if TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring
static char *tunables_strdup (const char *in)
{
size_t i = 0;
@@ -67,6 +70,7 @@ static char *tunables_strdup (const char *in)
return out;
}
+#endif
static char **
get_next_env (char **envp, char **name, size_t *namelen, char **val)
@@ -232,6 +236,7 @@ tunable_initialize (tunable_t *cur, const char *strval)
}
}
+#if TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring
static void
parse_tunables (char *tunestr)
{
@@ -297,6 +302,7 @@ parse_tunables (char *tunestr)
return;
}
}
+#endif
/* Disable a tunable if it is set. */
static void
@@ -307,6 +313,7 @@ disable_tunable (tunable_id_t id, char **envp)
if (env_alias)
tunables_unsetenv (envp, tunable_list[id].env_alias);
+#if TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring
char *tunable = getenv (GLIBC_TUNABLES);
const char *cmp = tunable_list[id].name;
const size_t len = strlen (cmp);
@@ -323,6 +330,7 @@ disable_tunable (tunable_id_t id, char **envp)
}
tunable++;
}
+#endif
}
/* Disable the glibc.malloc.check tunable in SETUID/SETGID programs unless
@@ -353,6 +361,7 @@ __tunables_init (char **envp)
while ((envp = get_next_env (envp, &envname, &len, &envval)) != NULL)
{
+#if TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring
if (is_name (GLIBC_TUNABLES, envname))
{
char *val = tunables_strdup (envval);
@@ -360,6 +369,7 @@ __tunables_init (char **envp)
parse_tunables (val);
continue;
}
+#endif
for (int i = 0; i < sizeof (tunable_list) / sizeof (tunable_t); i++)
{
@@ -75,4 +75,8 @@ extern void __tunable_set_val (tunable_id_t, void *, tunable_callback_t);
/* Namespace sanity for callback functions. Use this macro to keep the
namespace of the modules clean. */
#define DL_TUNABLE_CALLBACK(__name) _dl_tunable_ ## __name
+
+# define TUNABLES_FRONTEND_valstring 1
+/* The default value for TUNABLES_FRONTEND. */
+# define TUNABLES_FRONTEND_yes TUNABLES_FRONTEND_valstring
#endif
@@ -192,7 +192,23 @@ 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.
+disabled by default. This option can take the following values:
+
+@itemize @bullet
+@item @var{no}
+This is the default if the option is not passed to configure. This disables
+tunables.
+
+@item @var{yes}
+This is the default if the option is passed to configure. This enables tunables
+and selects the default frontend (currently @var{valstring}).
+
+@item @var{valstring}
+This enables tunables and selects the @var{valstring} frontend for tunables.
+This frontend allows users to specify tunables as a colon-separated list in a
+single environment variable @var{GLIBC_TUNABLES}.
+
+@end itemize
@item --build=@var{build-system}
@itemx --host=@var{host-system}