mirror of
https://sourceware.org/git/glibc.git
synced 2025-08-08 17:42:12 +03:00
fcd6a8b5c5
Add a new helper function __ifunc_hwcap() as a portable way to
access HWCAP elements via the parameter(s) passed to an ifunc
resolver checking the _IFUNC_ARG_HWCAP bit in the first parameter
and size of the buffer in the second parameter.
Note that 0 is returned when the requested element is not available
or does not correspond to a valid AT_HWCAP{,2,...} value.
Also add relevant tests.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
96 lines
3.4 KiB
C
96 lines
3.4 KiB
C
/* Definitions used by AArch64 indirect function resolvers.
|
|
Copyright (C) 2019-2025 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with the GNU C Library; if not, see
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#ifndef _SYS_IFUNC_H
|
|
#define _SYS_IFUNC_H
|
|
|
|
#include <sys/cdefs.h>
|
|
|
|
/* A second argument is passed to the ifunc resolver. */
|
|
#define _IFUNC_ARG_HWCAP (1ULL << 62)
|
|
|
|
/* Maximum number of HWCAP elements that are currently supported. */
|
|
#define _IFUNC_HWCAP_MAX 4
|
|
|
|
/* The prototype of a GNU indirect function resolver on AArch64 is
|
|
|
|
ElfW(Addr) ifunc_resolver (uint64_t, const uint64_t *);
|
|
|
|
The following prototype is also compatible:
|
|
|
|
ElfW(Addr) ifunc_resolver (uint64_t, const __ifunc_arg_t *);
|
|
|
|
The first argument might have the _IFUNC_ARG_HWCAP bit set and
|
|
the remaining bits should match the AT_HWCAP settings.
|
|
|
|
If the _IFUNC_ARG_HWCAP bit is set in the first argument, then
|
|
the second argument is passed to the resolver function. In
|
|
this case, the second argument is a const pointer to a buffer
|
|
that allows to access all available HWCAP elements.
|
|
|
|
This buffer has its size in bytes at offset 0. The HWCAP elements
|
|
are available at offsets 8, 16, 24, 32... respectively for AT_HWCAP,
|
|
AT_HWCAP2, AT_HWCAP3, AT_HWCAP4... (these offsets are multiples of
|
|
sizeof (unsigned long)).
|
|
|
|
Indirect function resolvers must check availability of HWCAP
|
|
elements at runtime before accessing them using the size of the
|
|
buffer. */
|
|
|
|
struct __ifunc_arg_t
|
|
{
|
|
unsigned long _size; /* Size of the struct, so it can grow. */
|
|
unsigned long _hwcap;
|
|
unsigned long _hwcap2; /* End of 1st published struct. */
|
|
unsigned long _hwcap3;
|
|
unsigned long _hwcap4; /* End of 2nd published struct. */
|
|
};
|
|
|
|
typedef struct __ifunc_arg_t __ifunc_arg_t;
|
|
|
|
/* Constants for IDs of HWCAP elements to be used with the
|
|
__ifunc_hwcap function below. */
|
|
enum
|
|
{
|
|
_IFUNC_ARG_AT_HWCAP = 1,
|
|
_IFUNC_ARG_AT_HWCAP2 = 2,
|
|
_IFUNC_ARG_AT_HWCAP3 = 3,
|
|
_IFUNC_ARG_AT_HWCAP4 = 4,
|
|
};
|
|
|
|
/* A helper function to obtain HWCAP element by its ID from the
|
|
parameters ARG0 and ARG1 passed to the ifunc resolver. Note that
|
|
ID 1 corresponds to AT_HWCAP, ID 2 corresponds to AT_HWCAP2, etc.
|
|
If there is no element available for the requested ID then 0 is
|
|
returned. If ID doesn't much any supported AT_HWCAP{,2,...} value,
|
|
then 0 is also returned. */
|
|
static __inline unsigned long __attribute__ ((unused, always_inline))
|
|
__ifunc_hwcap (unsigned long __id,
|
|
unsigned long __arg0, const unsigned long *__arg1)
|
|
{
|
|
if (__glibc_likely (__arg0 & _IFUNC_ARG_HWCAP))
|
|
{
|
|
const unsigned long size = __arg1[0];
|
|
const unsigned long offset = __id * sizeof (unsigned long);
|
|
return offset < size && __id > 0 ? __arg1[__id] : 0;
|
|
}
|
|
return __id == 1 ? __arg0 : 0;
|
|
}
|
|
|
|
#endif
|