[PATCH] syscalls/x86: fix UML syscall table

[Dominik Brodowski]

To differentiate the different calling regime used on x86, the syscall
functions received __sys_x86_ as prefix (instead of sys_). This breaks
the build of UML on 64-bit x86, as it re-uses the same syscall table.

To fix this, replace the __sys_x86_ prefix with sys_ during the generation
of <asm/syscalls_64.h>.

Fixes: syscalls/x86: rename struct pt_regs-based sys_*() to __sys_x86_*()
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>

diff --git a/arch/x86/entry/syscalls/syscalltbl.sh b/arch/x86/entry/syscalls/syscalltbl.sh
index d71ef4bd3615..d6376b87ecb2 100644
--- a/arch/x86/entry/syscalls/syscalltbl.sh
+++ b/arch/x86/entry/syscalls/syscalltbl.sh
@@ -20,17 +20,47 @@ syscall_macro() {
     echo "__SYSCALL_${abi}($nr, $real_entry, $qualifier)"
 }
 
-emit() {
+emit64() {
     abi="$1"
     nr="$2"
     entry="$3"
     compat="$4"
 
-    if [ "$abi" = "64" -a -n "$compat" ]; then
+    if [ "$abi" = "I386" ]; then
+	echo "emit64() called for a 32-bit syscall" >&2
+	exit 1
+    fi
+
+    if [ -n "$compat" ]; then
 	echo "a compat entry for a 64-bit syscall makes no sense" >&2
 	exit 1
     fi
 
+    if [ -n "$entry" ]; then
+	# For CONFIG_UML, we need to strip the __sys_x86 prefix
+	if [ "${entry}" = "${entry#__compat_sys}" ]; then
+            umlentry="sys${entry#__sys_x86}"
+	fi
+
+	echo "#ifdef CONFIG_X86"
+	syscall_macro "$abi" "$nr" "$entry"
+	echo "#else /* CONFIG_UML */"
+	syscall_macro "$abi" "$nr" "$umlentry"
+	echo "#endif"
+    fi
+}
+
+emit32() {
+    abi="$1"
+    nr="$2"
+    entry="$3"
+    compat="$4"
+
+    if [ "$abi" = "64" ]; then
+	echo "emit32() called for a 64-bit syscall" >&2
+	exit 1
+    fi
+
     if [ -z "$compat" ]; then
 	if [ -n "$entry" ]; then
 	    syscall_macro "$abi" "$nr" "$entry"
@@ -53,14 +83,14 @@ grep '^[0-9]' "$in" | sort -n | (
 	    # COMMON is the same as 64, except that we don't expect X32
 	    # programs to use it.  Our expectation has nothing to do with
 	    # any generated code, so treat them the same.
-	    emit 64 "$nr" "$entry" "$compat"
+	    emit64 64 "$nr" "$entry" "$compat"
 	elif [ "$abi" = "X32" ]; then
 	    # X32 is equivalent to 64 on an X32-compatible kernel.
 	    echo "#ifdef CONFIG_X86_X32_ABI"
-	    emit 64 "$nr" "$entry" "$compat"
+	    emit64 64 "$nr" "$entry" "$compat"
 	    echo "#endif"
 	elif [ "$abi" = "I386" ]; then
-	    emit "$abi" "$nr" "$entry" "$compat"
+	    emit32 "$abi" "$nr" "$entry" "$compat"
 	else
 	    echo "Unknown abi $abi" >&2
 	    exit 1