Check all mmap() calls and print helpful Linux error message

Corresponding to flashrom svn r386 and coreboot v2 svn r3890.

Signed-off-by: Peter Stuge <peter@stuge.se>
Acked-by: Peter Stuge <peter@stuge.se>
diff --git a/flashrom.c b/flashrom.c
index 7e52fbc..26585fb 100644
--- a/flashrom.c
+++ b/flashrom.c
@@ -84,6 +84,17 @@
 	return NULL;
 }
 
+void mmap_errmsg()
+{
+	if (EINVAL == errno) {
+		fprintf(stderr, "In Linux this error can be caused by the CONFIG_NONPROMISC_DEVMEM (<2.6.27),\n");
+		fprintf(stderr, "CONFIG_STRICT_DEVMEM (>=2.6.27) and CONFIG_X86_PAT kernel options.\n");
+		fprintf(stderr, "Please check if either is enabled in your kernel before reporting a failure.\n");
+		fprintf(stderr, "You can override CONFIG_X86_PAT at boot with the nopat kernel parameter but\n");
+		fprintf(stderr, "disabling the other option unfortunately requires a kernel recompile. Sorry!\n");
+	}
+}
+
 int map_flash_registers(struct flashchip *flash)
 {
 	volatile uint8_t *registers;
@@ -94,6 +105,7 @@
 
 	if (registers == MAP_FAILED) {
 		perror("Can't mmap registers using " MEM_DEV);
+		mmap_errmsg();
 		exit(1);
 	}
 	flash->virtual_registers = registers;
@@ -139,13 +151,7 @@
 			    fd_mem, (off_t) base);
 		if (bios == MAP_FAILED) {
 			perror("Can't mmap memory using " MEM_DEV);
-			if (EINVAL == errno) {
-				fprintf(stderr, "In Linux this error can be caused by the CONFIG_NONPROMISC_DEVMEM (<2.6.27),\n");
-				fprintf(stderr, "CONFIG_STRICT_DEVMEM (>=2.6.27) and CONFIG_X86_PAT kernel options.\n");
-				fprintf(stderr, "Please check if either is enabled in your kernel before reporting a failure.\n");
-				fprintf(stderr, "You can override CONFIG_X86_PAT at boot with the nopat kernel parameter but\n");
-				fprintf(stderr, "disabling the other option unfortunately requires a kernel recompile. Sorry!\n");
-			}
+			mmap_errmsg();
 			exit(1);
 		}
 		flash->virtual_memory = bios;