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elf: Add a way to check if tunable is set (BZ 27069)

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The patch adds two new macros, TUNABLE_GET_DEFAULT and TUNABLE_IS_INITIALIZED,
here the former get the default value with a signature similar to
TUNABLE_GET, while the later returns whether the tunable was set by
the environment variable.

Checked on x86_64-linux-gnu.
Reviewed-by: DJ Delorie <dj@redhat.com>
Tested-by: Zhangfei Gao <zhangfei.gao@linaro.org>
This commit is contained in:
Adhemerval Zanella 2023-11-23 14:29:14 -03:00
parent 9469261cf1
commit a4c3f5f46e
6 changed files with 73 additions and 2 deletions
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1
elf/Versions
View File

@ -77,6 +77,7 @@ ld {
_dl_signal_error;
# Set value of a tunable.
__tunable_is_initialized;
__tunable_get_val;
}
}

1
elf/dl-tunable-types.h
View File

@ -61,6 +61,7 @@ struct _tunable
{
const char name[TUNABLE_NAME_MAX]; /* Internal name of the tunable. */
tunable_type_t type; /* Data type of the tunable. */
const tunable_val_t def; /* The value. */
tunable_val_t val; /* The value. */
bool initialized; /* Flag to indicate that the tunable is
initialized. */

40
elf/dl-tunables.c
View File

@ -145,6 +145,13 @@ tunable_initialize (tunable_t *cur, const char *strval)
do_tunable_update_val (cur, &val, NULL, NULL);
}
bool
__tunable_is_initialized (tunable_id_t id)
{
return tunable_list[id].initialized;
}
rtld_hidden_def (__tunable_is_initialized)
void
__tunable_set_val (tunable_id_t id, tunable_val_t *valp, tunable_num_t *minp,
tunable_num_t *maxp)
@ -333,6 +340,39 @@ __tunables_print (void)
}
}
void
__tunable_get_default (tunable_id_t id, void *valp)
{
tunable_t *cur = &tunable_list[id];
switch (cur->type.type_code)
{
case TUNABLE_TYPE_UINT_64:
{
*((uint64_t *) valp) = (uint64_t) cur->def.numval;
break;
}
case TUNABLE_TYPE_INT_32:
{
*((int32_t *) valp) = (int32_t) cur->def.numval;
break;
}
case TUNABLE_TYPE_SIZE_T:
{
*((size_t *) valp) = (size_t) cur->def.numval;
break;
}
case TUNABLE_TYPE_STRING:
{
*((const char **)valp) = cur->def.strval;
break;
}
default:
__builtin_unreachable ();
}
}
rtld_hidden_def (__tunable_get_default)
/* Set the tunable value. This is called by the module that the tunable exists
in. */
void

28
elf/dl-tunables.h
View File

@ -45,18 +45,26 @@ typedef void (*tunable_callback_t) (tunable_val_t *);
extern void __tunables_init (char **);
extern void __tunables_print (void);
extern bool __tunable_is_initialized (tunable_id_t);
extern void __tunable_get_val (tunable_id_t, void *, tunable_callback_t);
extern void __tunable_set_val (tunable_id_t, tunable_val_t *, tunable_num_t *,
tunable_num_t *);
extern void __tunable_get_default (tunable_id_t id, void *valp);
rtld_hidden_proto (__tunables_init)
rtld_hidden_proto (__tunables_print)
rtld_hidden_proto (__tunable_is_initialized)
rtld_hidden_proto (__tunable_get_val)
rtld_hidden_proto (__tunable_set_val)
rtld_hidden_proto (__tunable_get_default)
/* Define TUNABLE_GET and TUNABLE_SET in short form if TOP_NAMESPACE and
TUNABLE_NAMESPACE are defined. This is useful shorthand to get and set
tunables within a module. */
#if defined TOP_NAMESPACE && defined TUNABLE_NAMESPACE
# define TUNABLE_IS_INITIALIZED(__id) \
TUNABLE_IS_INITIALIZED_FULL(TOP_NAMESPACE, TUNABLE_NAMESPACE, __id)
# define TUNABLE_GET_DEFAULT(__id, __type) \
TUNABLE_GET_DEFAULT_FULL(TOP_NAMESPACE, TUNABLE_NAMESPACE,__id, __type)
# define TUNABLE_GET(__id, __type, __cb) \
TUNABLE_GET_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, __type, __cb)
# define TUNABLE_SET(__id, __val) \
@ -65,6 +73,10 @@ rtld_hidden_proto (__tunable_set_val)
TUNABLE_SET_WITH_BOUNDS_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, \
__val, __min, __max)
#else
# define TUNABLE_IS_INITIALIZED(__top, __ns, __id) \
TUNABLE_IS_INITIALIZED_FULL(__top, __ns, __id)
# define TUNABLE_GET_DEFAULT(__top, __ns, __type) \
TUNABLE_GET_DEFAULT_FULL(__top, __ns, __id, __type)
# define TUNABLE_GET(__top, __ns, __id, __type, __cb) \
TUNABLE_GET_FULL (__top, __ns, __id, __type, __cb)
# define TUNABLE_SET(__top, __ns, __id, __val) \
@ -73,6 +85,22 @@ rtld_hidden_proto (__tunable_set_val)
TUNABLE_SET_WITH_BOUNDS_FULL (__top, __ns, __id, __val, __min, __max)
#endif
/* Return whether the tunable was initialized by the environment variable. */
#define TUNABLE_IS_INITIALIZED_FULL(__top, __ns, __id) \
({ \
tunable_id_t id = TUNABLE_ENUM_NAME (__top, __ns, __id); \
__tunable_is_initialized (id); \
})
/* Return the default value of the tunable. */
#define TUNABLE_GET_DEFAULT_FULL(__top, __ns, __id, __type) \
({ \
tunable_id_t id = TUNABLE_ENUM_NAME (__top, __ns, __id); \
__type __ret; \
__tunable_get_default (id, &__ret); \
__ret; \
})
/* Get and return a tunable value. If the tunable was set externally and __CB
is defined then call __CB before returning the value. */
#define TUNABLE_GET_FULL(__top, __ns, __id, __type, __cb) \

1
elf/dl-tunables.list
View File

@ -20,6 +20,7 @@
# type: Defaults to STRING
# minval: Optional minimum acceptable value
# maxval: Optional maximum acceptable value
# default: Optional default value (if not specified it will be 0 or "")
# env_alias: An alias environment variable
glibc {

4
scripts/gen-tunables.awk
View File

@ -163,8 +163,8 @@ END {
n = indices[2];
m = indices[3];
printf (" {TUNABLE_NAME_S(%s, %s, %s)", t, n, m)
printf (", {TUNABLE_TYPE_%s, %s, %s}, {%s}, false, %s},\n",
types[t,n,m], minvals[t,n,m], maxvals[t,n,m],
printf (", {TUNABLE_TYPE_%s, %s, %s}, {%s}, {%s}, false, %s},\n",
types[t,n,m], minvals[t,n,m], maxvals[t,n,m], default_val[t,n,m],
default_val[t,n,m], env_alias[t,n,m]);
}
print "};"