[PATCH v4 2/4] libatomic: Add support for __ifunc_arg_t arg in ifunc resolver

[Victor Do Nascimento]

With support for new atomic features in Armv9.4-a being indicated by
HWCAP2 bits, Libatomic's ifunc resolver must now query its second
argument, of type __ifunc_arg_t*.

We therefore make this argument known to libatomic, allowing us to
query hwcap2 bits in the following manner:

  bool
  resolver (unsigned long hwcap, const __ifunc_arg_t *features);
  {
    return (features->hwcap2 & HWCAP2_<FEAT_NAME>);
  }

libatomic/ChangeLog:

        * config/linux/aarch64/host-config.h (__ifunc_arg_t):
        Conditionally-defined if `sys/ifunc.h' not found.
        (_IFUNC_ARG_HWCAP): Likewise.
        (IFUNC_COND_1): Pass __ifunc_arg_t argument to ifunc.
        (ifunc1): Modify function signature to accept __ifunc_arg_t
        argument.
        * configure.tgt: Add second `const __ifunc_arg_t *features'
        argument to IFUNC_RESOLVER_ARGS.
---
 libatomic/config/linux/aarch64/host-config.h | 15 +++++++++++++--
 libatomic/configure.tgt                      |  2 +-
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/libatomic/config/linux/aarch64/host-config.h 
b/libatomic/config/linux/aarch64/host-config.h
index 4200293c4e3..8fd4fe3321a 100644
--- a/libatomic/config/linux/aarch64/host-config.h
+++ b/libatomic/config/linux/aarch64/host-config.h
@@ -24,9 +24,20 @@
 #if HAVE_IFUNC
 #include <sys/auxv.h>
 
+#if __has_include(<sys/ifunc.h>)
+# include <sys/ifunc.h>
+#else
+typedef struct __ifunc_arg_t {
+  unsigned long _size;
+  unsigned long _hwcap;
+  unsigned long _hwcap2;
+} __ifunc_arg_t;
+# define _IFUNC_ARG_HWCAP (1ULL << 62)
+#endif
+
 #ifdef HWCAP_USCAT
 # if N == 16
-#  define IFUNC_COND_1 ifunc1 (hwcap)
+#  define IFUNC_COND_1 ifunc1 (hwcap, features)
 # else
 #  define IFUNC_COND_1 (hwcap & HWCAP_ATOMICS)
 # endif
@@ -48,7 +59,7 @@
 #define MIDR_PARTNUM(midr)     (((midr) >> 4) & 0xfff)
 
 static inline bool
-ifunc1 (unsigned long hwcap)
+ifunc1 (unsigned long hwcap, const __ifunc_arg_t *features)
 {
   if (hwcap & HWCAP_USCAT)
     return true;
diff --git a/libatomic/configure.tgt b/libatomic/configure.tgt
index b7609132c58..67a5f2dff80 100644
--- a/libatomic/configure.tgt
+++ b/libatomic/configure.tgt
@@ -194,7 +194,7 @@ esac
 # The type may be different on different architectures.
 case "${target}" in
   aarch64*-*-*)
-       IFUNC_RESOLVER_ARGS="uint64_t hwcap"
+       IFUNC_RESOLVER_ARGS="uint64_t hwcap, const __ifunc_arg_t *features"
        ;;
   *)
        IFUNC_RESOLVER_ARGS="void"
-- 
2.42.0