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tunables: Simplify TUNABLE_SET interface 

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.
This commit is contained in:
Siddhesh Poyarekar 2021-02-05 13:18:58 +05:30
parent e604a5e4bb
commit 61117bfa1b
6 changed files with 76 additions and 128 deletions
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4
elf/dl-tunable-types.h
View File

@ -38,8 +38,8 @@ typedef enum
typedef struct
{
tunable_type_code_t type_code;
int64_t min;
int64_t max;
tunable_num_t min;
tunable_num_t max;
} tunable_type_t;
/* Security level for tunables. This decides what to do with individual

130
elf/dl-tunables.c
View File

@ -93,87 +93,45 @@ get_next_env (char **envp, char **name, size_t *namelen, char **val,
return NULL;
}
#define TUNABLE_SET_VAL_IF_VALID_RANGE(__cur, __val, __type) \
({ \
__type min = (__cur)->type.min; \
__type max = (__cur)->type.max; \
\
if ((__type) (__val) >= min && (__type) (__val) <= max) \
{ \
(__cur)->val.numval = (__val); \
(__cur)->initialized = true; \
} \
})
#define TUNABLE_SET_BOUNDS_IF_VALID(__cur, __minp, __maxp, __type) \
({ \
if (__minp != NULL) \
{ \
/* MIN is specified. */ \
__type min = *((__type *) __minp); \
if (__maxp != NULL) \
{ \
/* Both MIN and MAX are specified. */ \
__type max = *((__type *) __maxp); \
if (max >= min \
&& max <= (__cur)->type.max \
&& min >= (__cur)->type.min) \
{ \
(__cur)->type.min = min; \
(__cur)->type.max = max; \
} \
} \
else if (min > (__cur)->type.min && min <= (__cur)->type.max) \
{ \
/* Only MIN is specified. */ \
(__cur)->type.min = min; \
} \
} \
else if (__maxp != NULL) \
{ \
/* Only MAX is specified. */ \
__type max = *((__type *) __maxp); \
if (max < (__cur)->type.max && max >= (__cur)->type.min) \
(__cur)->type.max = max; \
} \
})
static void
do_tunable_update_val (tunable_t *cur, const void *valp,
const void *minp, const void *maxp)
do_tunable_update_val (tunable_t *cur, const tunable_val_t *valp,
const tunable_num_t *minp,
const tunable_num_t *maxp)
{
uint64_t val;
tunable_num_t val, min, max;
if (cur->type.type_code != TUNABLE_TYPE_STRING)
val = *((int64_t *) valp);
switch (cur->type.type_code)
if (cur->type.type_code == TUNABLE_TYPE_STRING)
{
case TUNABLE_TYPE_INT_32:
{
TUNABLE_SET_BOUNDS_IF_VALID (cur, minp, maxp, int64_t);
TUNABLE_SET_VAL_IF_VALID_RANGE (cur, val, int64_t);
break;
}
case TUNABLE_TYPE_UINT_64:
{
TUNABLE_SET_BOUNDS_IF_VALID (cur, minp, maxp, uint64_t);
TUNABLE_SET_VAL_IF_VALID_RANGE (cur, val, uint64_t);
break;
}
case TUNABLE_TYPE_SIZE_T:
{
TUNABLE_SET_BOUNDS_IF_VALID (cur, minp, maxp, uint64_t);
TUNABLE_SET_VAL_IF_VALID_RANGE (cur, val, uint64_t);
break;
}
case TUNABLE_TYPE_STRING:
{
cur->val.strval = valp;
break;
}
default:
__builtin_unreachable ();
cur->val.strval = valp->strval;
cur->initialized = true;
return;
}
val = valp->numval;
min = minp != NULL ? *minp : cur->type.min;
max = maxp != NULL ? *maxp : cur->type.max;
/* We allow only increasingly restrictive bounds. */
if (min < cur->type.min)
min = cur->type.min;
if (max > cur->type.max)
max = cur->type.max;
/* Skip both bounds if they're inconsistent. */
if (min > max)
{
min = cur->type.min;
max = cur->type.max;
}
/* Write everything out if the value and the bounds are valid. */
if (min <= val && val <= max)
{
cur->val.numval = val;
cur->type.min = min;
cur->type.max = max;
cur->initialized = true;
}
}
@ -182,24 +140,18 @@ do_tunable_update_val (tunable_t *cur, const void *valp,
static void
tunable_initialize (tunable_t *cur, const char *strval)
{
uint64_t val;
const void *valp;
tunable_val_t val;
if (cur->type.type_code != TUNABLE_TYPE_STRING)
{
val = _dl_strtoul (strval, NULL);
valp = &val;
}
val.numval = (tunable_num_t) _dl_strtoul (strval, NULL);
else
{
cur->initialized = true;
valp = strval;
}
do_tunable_update_val (cur, valp, NULL, NULL);
val.strval = strval;
do_tunable_update_val (cur, &val, NULL, NULL);
}
void
__tunable_set_val (tunable_id_t id, void *valp, void *minp, void *maxp)
__tunable_set_val (tunable_id_t id, tunable_val_t *valp, tunable_num_t *minp,
tunable_num_t *maxp)
{
tunable_t *cur = &tunable_list[id];

37
elf/dl-tunables.h
View File

@ -33,9 +33,11 @@ __tunables_init (char **unused __attribute__ ((unused)))
# include <stddef.h>
# include <stdint.h>
typedef intmax_t tunable_num_t;
typedef union
{
int64_t numval;
tunable_num_t numval;
const char *strval;
} tunable_val_t;
@ -52,7 +54,8 @@ typedef void (*tunable_callback_t) (tunable_val_t *);
extern void __tunables_init (char **);
extern void __tunables_print (void);
extern void __tunable_get_val (tunable_id_t, void *, tunable_callback_t);
extern void __tunable_set_val (tunable_id_t, void *, void *, void *);
extern void __tunable_set_val (tunable_id_t, tunable_val_t *, tunable_num_t *,
tunable_num_t *);
rtld_hidden_proto (__tunables_init)
rtld_hidden_proto (__tunables_print)
rtld_hidden_proto (__tunable_get_val)
@ -64,20 +67,18 @@ rtld_hidden_proto (__tunable_set_val)
#if defined TOP_NAMESPACE && defined TUNABLE_NAMESPACE
# define TUNABLE_GET(__id, __type, __cb) \
TUNABLE_GET_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, __type, __cb)
# define TUNABLE_SET(__id, __type, __val) \
TUNABLE_SET_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, __type, __val)
# define TUNABLE_SET_WITH_BOUNDS(__id, __type, __val, __min, __max) \
# define TUNABLE_SET(__id, __val) \
TUNABLE_SET_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, __val)
# define TUNABLE_SET_WITH_BOUNDS(__id, __val, __min, __max) \
TUNABLE_SET_WITH_BOUNDS_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, \
__type, __val, __min, __max)
__val, __min, __max)
#else
# define TUNABLE_GET(__top, __ns, __id, __type, __cb) \
TUNABLE_GET_FULL (__top, __ns, __id, __type, __cb)
# define TUNABLE_SET(__top, __ns, __id, __type, __val) \
TUNABLE_SET_FULL (__top, __ns, __id, __type, __val)
# define TUNABLE_SET_WITH_BOUNDS(__top, __ns, __id, __type, __val, \
__min, __max) \
TUNABLE_SET_WITH_BOUNDS_FULL (__top, __ns, __id, __type, __val, \
__min, __max)
# define TUNABLE_SET(__top, __ns, __id, __val) \
TUNABLE_SET_FULL (__top, __ns, __id, __val)
# define TUNABLE_SET_WITH_BOUNDS(__top, __ns, __id, __val, __min, __max) \
TUNABLE_SET_WITH_BOUNDS_FULL (__top, __ns, __id, __val, __min, __max)
#endif
/* Get and return a tunable value. If the tunable was set externally and __CB
@ -91,19 +92,19 @@ rtld_hidden_proto (__tunable_set_val)
})
/* Set a tunable value. */
# define TUNABLE_SET_FULL(__top, __ns, __id, __type, __val) \
# define TUNABLE_SET_FULL(__top, __ns, __id, __val) \
({ \
__tunable_set_val (TUNABLE_ENUM_NAME (__top, __ns, __id), \
& (__type) {__val}, NULL, NULL); \
& (tunable_val_t) {.numval = __val}, NULL, NULL); \
})
/* Set a tunable value together with min/max values. */
# define TUNABLE_SET_WITH_BOUNDS_FULL(__top, __ns, __id, __type, __val, \
__min, __max) \
# define TUNABLE_SET_WITH_BOUNDS_FULL(__top, __ns, __id,__val, __min, __max) \
({ \
__tunable_set_val (TUNABLE_ENUM_NAME (__top, __ns, __id), \
& (__type) {__val}, & (__type) {__min}, \
& (__type) {__max}); \
& (tunable_val_t) {.numval = __val}, \
& (tunable_num_t) {__min}, \
& (tunable_num_t) {__max}); \
})
/* Namespace sanity for callback functions. Use this macro to keep the

16
manual/README.tunables
View File

@ -98,17 +98,16 @@ where it can expect the tunable value to be passed in VALP.
Tunables in the module can be updated using:
TUNABLE_SET (check, int32_t, val)
TUNABLE_SET (check, val)
where 'check' is the tunable name, 'int32_t' is the C type of the tunable and
'val' is a value of same type.
where 'check' is the tunable name and 'val' is a value of same type.
To get and set tunables in a different namespace from that module, use the full
form of the macros as follows:
val = TUNABLE_GET_FULL (glibc, cpu, hwcap_mask, uint64_t, NULL)
TUNABLE_SET_FULL (glibc, cpu, hwcap_mask, uint64_t, val)
TUNABLE_SET_FULL (glibc, cpu, hwcap_mask, val)
where 'glibc' is the top namespace, 'cpu' is the tunable namespace and the
remaining arguments are the same as the short form macros.
@ -116,18 +115,17 @@ remaining arguments are the same as the short form macros.
The minimum and maximum values can updated together with the tunable value
using:
TUNABLE_SET_WITH_BOUNDS (check, int32_t, val, min, max)
TUNABLE_SET_WITH_BOUNDS (check, val, min, max)
where 'check' is the tunable name, 'int32_t' is the C type of the tunable,
'val' is a value of same type, 'min' and 'max' are the minimum and maximum
values of the tunable.
where 'check' is the tunable name, 'val' is a value of same type, 'min' and
'max' are the minimum and maximum values of the tunable.
To set the minimum and maximum values of tunables in a different namespace
from that module, use the full form of the macros as follows:
val = TUNABLE_GET_FULL (glibc, cpu, hwcap_mask, uint64_t, NULL)
TUNABLE_SET_WITH_BOUNDS_FULL (glibc, cpu, hwcap_mask, uint64_t, val, min, max)
TUNABLE_SET_WITH_BOUNDS_FULL (glibc, cpu, hwcap_mask, val, min, max)
where 'glibc' is the top namespace, 'cpu' is the tunable namespace and the
remaining arguments are the same as the short form macros.

2
sysdeps/unix/sysv/linux/aarch64/cpu-features.c
View File

@ -104,7 +104,7 @@ init_cpu_features (struct cpu_features *cpu_features)
cpu_features->mte_state = (GLRO (dl_hwcap2) & HWCAP2_MTE) ? mte_state : 0;
/* If we lack the MTE feature, disable the tunable, since it will
otherwise cause instructions that won't run on this CPU to be used. */
TUNABLE_SET (glibc, mem, tagging, unsigned, cpu_features->mte_state);
TUNABLE_SET (glibc, mem, tagging, cpu_features->mte_state);
# endif
if (cpu_features->mte_state & 2)

15
sysdeps/x86/dl-cacheinfo.h
View File

@ -929,17 +929,14 @@ dl_init_cacheinfo (struct cpu_features *cpu_features)
rep_stosb_threshold = TUNABLE_GET (x86_rep_stosb_threshold,
long int, NULL);
TUNABLE_SET_WITH_BOUNDS (x86_data_cache_size, long int, data,
TUNABLE_SET_WITH_BOUNDS (x86_data_cache_size, data, 0, (long int) -1);
TUNABLE_SET_WITH_BOUNDS (x86_shared_cache_size, shared, 0, (long int) -1);
TUNABLE_SET_WITH_BOUNDS (x86_non_temporal_threshold, non_temporal_threshold,
0, (long int) -1);
TUNABLE_SET_WITH_BOUNDS (x86_shared_cache_size, long int, shared,
0, (long int) -1);
TUNABLE_SET_WITH_BOUNDS (x86_non_temporal_threshold, long int,
non_temporal_threshold, 0, (long int) -1);
TUNABLE_SET_WITH_BOUNDS (x86_rep_movsb_threshold, long int,
rep_movsb_threshold,
TUNABLE_SET_WITH_BOUNDS (x86_rep_movsb_threshold, rep_movsb_threshold,
minimum_rep_movsb_threshold, (long int) -1);
TUNABLE_SET_WITH_BOUNDS (x86_rep_stosb_threshold, long int,
rep_stosb_threshold, 1, (long int) -1);
TUNABLE_SET_WITH_BOUNDS (x86_rep_stosb_threshold, rep_stosb_threshold, 1,
(long int) -1);
#endif
cpu_features->data_cache_size = data;