[glibc] linux: Introduce INTERNAL_VSYSCALL

[glibc] linux: Introduce INTERNAL_VSYSCALL

[Palmer Dabbelt]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=c6c33339b45281590f9db138ba6c9d79acb1da27

commit c6c33339b45281590f9db138ba6c9d79acb1da27
Author: Evan Green <evan@rivosinc.com>
Date:   Tue Feb 27 14:56:38 2024 -0800

    linux: Introduce INTERNAL_VSYSCALL
    
    Add an INTERNAL_VSYSCALL() macro that makes a vDSO call, falling back to
    a regular syscall, but without setting errno. Instead, the return value
    is plumbed straight out of the macro.
    
    Signed-off-by: Evan Green <evan@rivosinc.com>
    Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Diff:
---
 sysdeps/unix/sysv/linux/sysdep-vdso.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/sysdeps/unix/sysv/linux/sysdep-vdso.h b/sysdeps/unix/sysv/linux/sysdep-vdso.h
index 189319ad98..2f53ada6e5 100644
--- a/sysdeps/unix/sysv/linux/sysdep-vdso.h
+++ b/sysdeps/unix/sysv/linux/sysdep-vdso.h
@@ -53,4 +53,16 @@
     sc_ret;								      \
   })
 
+#define INTERNAL_VSYSCALL(name, nr, args...)				      \
+  ({									      \
+    long int sc_ret = -ENOSYS;						      \
+									      \
+    __typeof (GLRO(dl_vdso_##name)) vdsop = GLRO(dl_vdso_##name);	      \
+    if (vdsop != NULL)							      \
+	sc_ret = INTERNAL_VSYSCALL_CALL (vdsop, nr, ##args);		      \
+    if (sc_ret == -ENOSYS)						      \
+	sc_ret = INTERNAL_SYSCALL_CALL (name, ##args);			      \
+    sc_ret;								      \
+  })
+
 #endif /* SYSDEP_VDSO_LINUX_H  */