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61117bfa1b
The TUNABLE_SET interface took a primitive C type argument, which resulted in inconsistent type conversions internally due to incorrect dereferencing of types, especialy on 32-bit architectures. This change simplifies the TUNABLE setting logic along with the interfaces. Now all numeric tunable values are stored as signed numbers in tunable_num_t, which is intmax_t. All calls to set tunables cast the input value to its primitive type and then to tunable_num_t for storage. This relies on gcc-specific (although I suspect other compilers woul also do the same) unsigned to signed integer conversion semantics, i.e. the bit pattern is conserved. The reverse conversion is guaranteed by the standard.
135 lines
4.7 KiB
C++
135 lines
4.7 KiB
C++
/* The tunable framework. See the README to know how to use the tunable in
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a glibc module.
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Copyright (C) 2016-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef _TUNABLES_H_
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#define _TUNABLES_H_
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#if !HAVE_TUNABLES
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static inline void
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__always_inline
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__tunables_init (char **unused __attribute__ ((unused)))
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{
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/* This is optimized out if tunables are not enabled. */
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}
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#else
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# include <stdbool.h>
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# include <stddef.h>
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# include <stdint.h>
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typedef intmax_t tunable_num_t;
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typedef union
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{
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tunable_num_t numval;
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const char *strval;
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} tunable_val_t;
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typedef void (*tunable_callback_t) (tunable_val_t *);
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/* Full name for a tunable is top_ns.tunable_ns.id. */
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# define TUNABLE_NAME_S(top,ns,id) #top "." #ns "." #id
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# define TUNABLE_ENUM_NAME(__top,__ns,__id) TUNABLE_ENUM_NAME1 (__top,__ns,__id)
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# define TUNABLE_ENUM_NAME1(__top,__ns,__id) __top ## _ ## __ns ## _ ## __id
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# include "dl-tunable-list.h"
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extern void __tunables_init (char **);
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extern void __tunables_print (void);
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extern void __tunable_get_val (tunable_id_t, void *, tunable_callback_t);
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extern void __tunable_set_val (tunable_id_t, tunable_val_t *, tunable_num_t *,
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tunable_num_t *);
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rtld_hidden_proto (__tunables_init)
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rtld_hidden_proto (__tunables_print)
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rtld_hidden_proto (__tunable_get_val)
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rtld_hidden_proto (__tunable_set_val)
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/* Define TUNABLE_GET and TUNABLE_SET in short form if TOP_NAMESPACE and
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TUNABLE_NAMESPACE are defined. This is useful shorthand to get and set
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tunables within a module. */
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#if defined TOP_NAMESPACE && defined TUNABLE_NAMESPACE
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# define TUNABLE_GET(__id, __type, __cb) \
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TUNABLE_GET_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, __type, __cb)
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# define TUNABLE_SET(__id, __val) \
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TUNABLE_SET_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, __val)
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# define TUNABLE_SET_WITH_BOUNDS(__id, __val, __min, __max) \
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TUNABLE_SET_WITH_BOUNDS_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, \
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__val, __min, __max)
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#else
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# define TUNABLE_GET(__top, __ns, __id, __type, __cb) \
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TUNABLE_GET_FULL (__top, __ns, __id, __type, __cb)
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# define TUNABLE_SET(__top, __ns, __id, __val) \
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TUNABLE_SET_FULL (__top, __ns, __id, __val)
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# define TUNABLE_SET_WITH_BOUNDS(__top, __ns, __id, __val, __min, __max) \
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TUNABLE_SET_WITH_BOUNDS_FULL (__top, __ns, __id, __val, __min, __max)
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#endif
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/* Get and return a tunable value. If the tunable was set externally and __CB
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is defined then call __CB before returning the value. */
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# define TUNABLE_GET_FULL(__top, __ns, __id, __type, __cb) \
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({ \
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tunable_id_t id = TUNABLE_ENUM_NAME (__top, __ns, __id); \
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__type ret; \
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__tunable_get_val (id, &ret, __cb); \
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ret; \
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})
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/* Set a tunable value. */
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# define TUNABLE_SET_FULL(__top, __ns, __id, __val) \
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({ \
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__tunable_set_val (TUNABLE_ENUM_NAME (__top, __ns, __id), \
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& (tunable_val_t) {.numval = __val}, NULL, NULL); \
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})
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/* Set a tunable value together with min/max values. */
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# define TUNABLE_SET_WITH_BOUNDS_FULL(__top, __ns, __id,__val, __min, __max) \
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({ \
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__tunable_set_val (TUNABLE_ENUM_NAME (__top, __ns, __id), \
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& (tunable_val_t) {.numval = __val}, \
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& (tunable_num_t) {__min}, \
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& (tunable_num_t) {__max}); \
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})
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/* Namespace sanity for callback functions. Use this macro to keep the
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namespace of the modules clean. */
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# define TUNABLE_CALLBACK(__name) _dl_tunable_ ## __name
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# define TUNABLES_FRONTEND_valstring 1
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/* The default value for TUNABLES_FRONTEND. */
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# define TUNABLES_FRONTEND_yes TUNABLES_FRONTEND_valstring
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/* Compare two name strings, bounded by the name hardcoded in glibc. */
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static __always_inline bool
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tunable_is_name (const char *orig, const char *envname)
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{
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for (;*orig != '\0' && *envname != '\0'; envname++, orig++)
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if (*orig != *envname)
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break;
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/* The ENVNAME is immediately followed by a value. */
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if (*orig == '\0' && *envname == '=')
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return true;
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else
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return false;
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}
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#endif
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#endif
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