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riscv: Enable multi-arg ifunc resolvers

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RISC-V is apparently the first architecture to pass more than one
argument to ifunc resolvers. The helper macros in libc-symbols.h,
__ifunc_resolver(), __ifunc(), and __ifunc_hidden(), are incompatible
with this. These macros have an "arg" (non-final) parameter that
represents the parameter signature of the ifunc resolver. The result is
an inability to pass the required comma through in a single preprocessor
argument.

Rearrange the __ifunc_resolver() macro to be variadic, and pass the
types as those variable parameters. Move the guts of __ifunc() and
__ifunc_hidden() into new macros, __ifunc_args(), and
__ifunc_args_hidden(), that pass the variable arguments down through to
__ifunc_resolver(). Then redefine __ifunc() and __ifunc_hidden(), which
are used in a bunch of places, to simply shuffle the arguments down into
__ifunc_args[_hidden]. Finally, define a riscv-ifunc.h header, which
provides convenience macros to those looking to write ifunc selectors
that use both arguments.

Signed-off-by: Evan Green <evan@rivosinc.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Evan Green 2024-02-27 14:56:41 -08:00 committed by Palmer Dabbelt
parent 78308ce77a
commit a29bb320a1
No known key found for this signature in database
GPG Key ID: 2E1319F35FBB1889
2 changed files with 44 additions and 11 deletions
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28
include/libc-symbols.h
View File

@ -667,9 +667,9 @@ for linking")
#endif
/* Helper / base macros for indirect function symbols. */
#define __ifunc_resolver(type_name, name, expr, arg, init, classifier) \
#define __ifunc_resolver(type_name, name, expr, init, classifier, ...) \
classifier inhibit_stack_protector \
__typeof (type_name) *name##_ifunc (arg) \
__typeof (type_name) *name##_ifunc (__VA_ARGS__) \
{ \
init (); \
__typeof (type_name) *res = expr; \
@ -677,13 +677,13 @@ for linking")
}
#ifdef HAVE_GCC_IFUNC
# define __ifunc(type_name, name, expr, arg, init) \
# define __ifunc_args(type_name, name, expr, init, ...) \
extern __typeof (type_name) name __attribute__ \
((ifunc (#name "_ifunc"))); \
__ifunc_resolver (type_name, name, expr, arg, init, static)
__ifunc_resolver (type_name, name, expr, init, static, __VA_ARGS__)
# define __ifunc_hidden(type_name, name, expr, arg, init) \
__ifunc (type_name, name, expr, arg, init)
# define __ifunc_args_hidden(type_name, name, expr, init, ...) \
__ifunc_args (type_name, name, expr, init, __VA_ARGS__)
#else
/* Gcc does not support __attribute__ ((ifunc (...))). Use the old behaviour
as fallback. But keep in mind that the debug information for the ifunc
@ -694,18 +694,24 @@ for linking")
different signatures. (Gcc support is disabled at least on a ppc64le
Ubuntu 14.04 system.) */
# define __ifunc(type_name, name, expr, arg, init) \
# define __ifunc_args(type_name, name, expr, init, ...) \
extern __typeof (type_name) name; \
__typeof (type_name) *name##_ifunc (arg) __asm__ (#name); \
__ifunc_resolver (type_name, name, expr, arg, init,) \
__typeof (type_name) *name##_ifunc (__VA_ARGS__) __asm__ (#name); \
__ifunc_resolver (type_name, name, expr, init, , __VA_ARGS__) \
__asm__ (".type " #name ", %gnu_indirect_function");
# define __ifunc_hidden(type_name, name, expr, arg, init) \
# define __ifunc_args_hidden(type_name, name, expr, init, ...) \
extern __typeof (type_name) __libc_##name; \
__ifunc (type_name, __libc_##name, expr, arg, init) \
__ifunc (type_name, __libc_##name, expr, __VA_ARGS__, init) \
strong_alias (__libc_##name, name);
#endif /* !HAVE_GCC_IFUNC */
#define __ifunc(type_name, name, expr, arg, init) \
__ifunc_args (type_name, name, expr, init, arg)
#define __ifunc_hidden(type_name, name, expr, arg, init) \
__ifunc_args_hidden (type_name, name, expr, init, arg)
/* The following macros are used for indirect function symbols in libc.so.
First of all, you need to have the function prototyped somewhere,
say in foo.h:

27
sysdeps/riscv/riscv-ifunc.h Normal file
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@ -0,0 +1,27 @@
/* Common definition for ifunc resolvers. Linux/RISC-V version.
This file is part of the GNU C Library.
Copyright (C) 2024 Free Software Foundation, Inc.
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/>. */
#include <sysdep.h>
#include <ifunc-init.h>
#include <sys/hwprobe.h>
#define INIT_ARCH()
#define riscv_libc_ifunc(name, expr) \
__ifunc_args (name, name, expr(hwcap, hwprobe), INIT_ARCH, \
uint64_t hwcap, __riscv_hwprobe_t hwprobe)