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2a969b53c0
The tunable parsing duplicates the tunable environment variable so it null-terminates each one since it simplifies the later parsing. It has the drawback of adding another point of failure (__minimal_malloc failing), and the memory copy requires tuning the compiler to avoid mem operations calls. The parsing now tracks the tunable start and its size. The dl-tunable-parse.h adds helper functions to help parsing, like a strcmp that also checks for size and an iterator for suboptions that are comma-separated (used on hwcap parsing by x86, powerpc, and s390x). Since the environment variable is allocated on the stack by the kernel, it is safe to keep the references to the suboptions for later parsing of string tunables (as done by set_hwcaps by multiple architectures). Checked on x86_64-linux-gnu, powerpc64le-linux-gnu, and aarch64-linux-gnu. Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
172 lines
6.0 KiB
C++
172 lines
6.0 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) 2016-2023 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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#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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struct tunable_str_t
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{
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const char *str;
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size_t len;
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} 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 bool __tunable_is_initialized (tunable_id_t);
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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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extern void __tunable_get_default (tunable_id_t id, void *valp);
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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_is_initialized)
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rtld_hidden_proto (__tunable_get_val)
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rtld_hidden_proto (__tunable_set_val)
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rtld_hidden_proto (__tunable_get_default)
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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_IS_INITIALIZED(__id) \
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TUNABLE_IS_INITIALIZED_FULL(TOP_NAMESPACE, TUNABLE_NAMESPACE, __id)
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# define TUNABLE_GET_DEFAULT(__id, __type) \
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TUNABLE_GET_DEFAULT_FULL(TOP_NAMESPACE, TUNABLE_NAMESPACE,__id, __type)
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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_IS_INITIALIZED(__top, __ns, __id) \
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TUNABLE_IS_INITIALIZED_FULL(__top, __ns, __id)
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# define TUNABLE_GET_DEFAULT(__top, __ns, __type) \
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TUNABLE_GET_DEFAULT_FULL(__top, __ns, __id, __type)
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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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/* Return whether the tunable was initialized by the environment variable. */
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#define TUNABLE_IS_INITIALIZED_FULL(__top, __ns, __id) \
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({ \
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tunable_id_t id = TUNABLE_ENUM_NAME (__top, __ns, __id); \
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__tunable_is_initialized (id); \
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})
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/* Return the default value of the tunable. */
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#define TUNABLE_GET_DEFAULT_FULL(__top, __ns, __id, __type) \
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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_default (id, &__ret); \
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__ret; \
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})
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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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static __always_inline bool
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tunable_val_lt (tunable_num_t lhs, tunable_num_t rhs, bool unsigned_cmp)
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{
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if (unsigned_cmp)
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return (uintmax_t) lhs < (uintmax_t) rhs;
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else
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return lhs < rhs;
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}
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static __always_inline bool
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tunable_val_gt (tunable_num_t lhs, tunable_num_t rhs, bool unsigned_cmp)
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{
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if (unsigned_cmp)
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return (uintmax_t) lhs > (uintmax_t) rhs;
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else
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return lhs > rhs;
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}
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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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