From 642bb66b63cf5d199e99df898a26238d7aed86da Mon Sep 17 00:00:00 2001
From: Konstantin Belousov <kib@FreeBSD.org>
Date: Thu, 14 Feb 2019 13:53:11 +0000
Subject: [PATCH] Provide userspace versions of do_cpuid() and cpuid_count() on
 i386.

Some older compilers, when generating PIC code, cannot handle inline
asm that clobbers %ebx (because %ebx is used as the GOT offset
register).  Userspace versions avoid clobbering %ebx by saving it to
stack before executing the CPUID instruction.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
---
 sys/i386/include/cpufunc.h | 34 ++++++++++++++++++++++++++++++----
 1 file changed, 30 insertions(+), 4 deletions(-)

diff --git a/sys/i386/include/cpufunc.h b/sys/i386/include/cpufunc.h
index da9a3e3a086..0e935e8c7d7 100644
--- a/sys/i386/include/cpufunc.h
+++ b/sys/i386/include/cpufunc.h
@@ -108,21 +108,47 @@ disable_intr(void)
 	__asm __volatile("cli" : : : "memory");
 }
 
+#ifdef _KERNEL
 static __inline void
 do_cpuid(u_int ax, u_int *p)
 {
 	__asm __volatile("cpuid"
-			 : "=a" (p[0]), "=b" (p[1]), "=c" (p[2]), "=d" (p[3])
-			 :  "0" (ax));
+	    : "=a" (p[0]), "=b" (p[1]), "=c" (p[2]), "=d" (p[3])
+	    :  "0" (ax));
 }
 
 static __inline void
 cpuid_count(u_int ax, u_int cx, u_int *p)
 {
 	__asm __volatile("cpuid"
-			 : "=a" (p[0]), "=b" (p[1]), "=c" (p[2]), "=d" (p[3])
-			 :  "0" (ax), "c" (cx));
+	    : "=a" (p[0]), "=b" (p[1]), "=c" (p[2]), "=d" (p[3])
+	    :  "0" (ax), "c" (cx));
 }
+#else
+static __inline void
+do_cpuid(u_int ax, u_int *p)
+{
+	__asm __volatile(
+	    "pushl\t%%ebx\n\t"
+	    "cpuid\n\t"
+	    "movl\t%%ebx,%1\n\t"
+	    "popl\t%%ebx"
+	    : "=a" (p[0]), "=DS" (p[1]), "=c" (p[2]), "=d" (p[3])
+	    :  "0" (ax));
+}
+
+static __inline void
+cpuid_count(u_int ax, u_int cx, u_int *p)
+{
+	__asm __volatile(
+	    "pushl\t%%ebx\n\t"
+	    "cpuid\n\t"
+	    "movl\t%%ebx,%1\n\t"
+	    "popl\t%%ebx"
+	    : "=a" (p[0]), "=DS" (p[1]), "=c" (p[2]), "=d" (p[3])
+	    :  "0" (ax), "c" (cx));
+}
+#endif
 
 static __inline void
 enable_intr(void)