Sync the vendored helper with dell-bios-fan-control

Picks up the red zone fix, the x86-64 guard and the reordered status line
from the upstream repo the helper is copied from.

Author: mews-se

helper/Makefile

@@ -1,6 +1,8 @@
 #!/usr/bin/make -f
 
-CFLAGS ?= -O2 -Wall -Wextra
+# -mno-red-zone: the inline SMM asm pushes to the stack, which would
+# otherwise land in the 128-byte red zone the ABI lets gcc use
+CFLAGS ?= -O2 -Wall -Wextra -mno-red-zone
 
 all: dell-bios-fan-control
 

helper/dell-bios-fan-control.c

@@ -1,6 +1,6 @@
 /*
  * dell-bios-fan-control
- * user space utility to set control of fans by bios on Dell 9560 Laptops.
+ * user space utility to enable or disable BIOS fan control on Dell machines.
  *
  * SMM Management code from i8k. See file drivers/char/i8k.c at Linux kernel.
  *
@@ -28,6 +28,10 @@
 #include <unistd.h>
 #include <sys/io.h>
 
+#if !defined(__x86_64__)
+#error "x86-64 only: the SMM call goes out through ports 0xb2 and 0x84"
+#endif
+
 /*
  *
  * Most of the code was taken from https://github.com/clopez/dellfan
@@ -131,18 +135,16 @@ int main(int argc, char **argv) {
 
     init_ioperm();
 
-    if (enable) {
+    if (enable)
         rc = send(ENABLE_BIOS_METHOD2, 0);
-        printf ("BIOS CONTROL ENABLED\n");
-    }
-    else {
+    else
         rc = send(DISABLE_BIOS_METHOD2, 0);
-        printf ("BIOS CONTROL DISABLED\n");
-    }
 
     /* The error heuristic can misfire on some BIOSes, so warn only */
     if (rc != 0)
         fprintf(stderr, "warning: SMM call may have failed\n");
 
+    printf ("BIOS CONTROL %s\n", enable ? "ENABLED" : "DISABLED");
+
     return 0;
 }