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riscv: Add __riscv_hwprobe pointer to ifunc calls

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The new __riscv_hwprobe() function is designed to be used by ifunc
selector functions. This presents a challenge for applications and
libraries, as ifunc selectors are invoked before all relocations have
been performed, so an external call to __riscv_hwprobe() from an ifunc
selector won't work. To address this, pass a pointer to the
__riscv_hwprobe() function into ifunc selectors as the second
argument (alongside dl_hwcap, which was already being passed).

Include a typedef as well for convenience, so that ifunc users don't
have to go through contortions to call this routine. Users will need to
remember to check the second argument for NULL, to account for older
glibcs that don't pass the function.

Signed-off-by: Evan Green <evan@rivosinc.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Evan Green 2024-02-27 14:56:40 -08:00 committed by Palmer Dabbelt
parent e7919e0db2
commit 78308ce77a
No known key found for this signature in database
GPG Key ID: 2E1319F35FBB1889
2 changed files with 15 additions and 4 deletions
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9
sysdeps/riscv/dl-irel.h
View File

@ -24,6 +24,7 @@
#include <unistd.h>
#include <ldsodefs.h>
#include <sysdep.h>
#include <sys/hwprobe.h>
#define ELF_MACHINE_IRELA 1
@ -31,10 +32,10 @@ static inline ElfW(Addr)
__attribute ((always_inline))
elf_ifunc_invoke (ElfW(Addr) addr)
{
/* The second argument is a void pointer to preserve the extension
fexibility. */
return ((ElfW(Addr) (*) (uint64_t, void *)) (addr))
(GLRO(dl_hwcap), NULL);
/* The third argument is a void pointer to preserve the extension
flexibility. */
return ((ElfW(Addr) (*) (uint64_t, void *, void *)) (addr))
(GLRO(dl_hwcap), __riscv_hwprobe, NULL);
}
static inline void

10
sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h
View File

@ -69,6 +69,16 @@ extern int __riscv_hwprobe (struct riscv_hwprobe *__pairs, size_t __pair_count,
__fortified_attr_access (__read_write__, 1, 2)
__fortified_attr_access (__read_only__, 4, 3);
/* A pointer to the __riscv_hwprobe vDSO function is passed as the second
argument to ifunc selector routines. Include a function pointer type for
convenience in calling the function in those settings. */
typedef int (*__riscv_hwprobe_t) (struct riscv_hwprobe *__pairs, size_t __pair_count,
size_t __cpu_count, unsigned long int *__cpus,
unsigned int __flags)
__nonnull ((1)) __wur
__fortified_attr_access (__read_write__, 1, 2)
__fortified_attr_access (__read_only__, 4, 3);
__END_DECLS
#endif /* sys/hwprobe.h */