[glibc] riscv: Add __riscv_hwprobe pointer to ifunc calls

[glibc] riscv: Add __riscv_hwprobe pointer to ifunc calls

[Palmer Dabbelt]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=78308ce77ad55191d2e578bbcd19bb55c68926cb

commit 78308ce77ad55191d2e578bbcd19bb55c68926cb
Author: Evan Green <evan@rivosinc.com>
Date:   Tue Feb 27 14:56:40 2024 -0800

    riscv: Add __riscv_hwprobe pointer to ifunc calls
    
    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>

Diff:
---
 sysdeps/riscv/dl-irel.h                     |  9 +++++----
 sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h | 10 ++++++++++
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/sysdeps/riscv/dl-irel.h b/sysdeps/riscv/dl-irel.h
index e6ab51ccd4..61b3511c96 100644
--- a/sysdeps/riscv/dl-irel.h
+++ b/sysdeps/riscv/dl-irel.h
@@ -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
diff --git a/sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h b/sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h
index 5592b9e100..34a2e3dbc2 100644
--- a/sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h
+++ b/sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h
@@ -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 */