[segment] Add "Requested memory not available" error message

prep_segment() can sometimes fail because an image requests memory
that is already in use by gPXE.  This will happen if
e.g. undionly.kpxe is used to boot memtest86; the memtest86 image is
an old-format kernel that needs to be loaded at 9000:0000, but this
area of memory may well already be in use by the underlying PXE stack.

Add a human-friendly error message, so that the cause is more
immediately visible.

1 files changed, 11 insertions, 0 deletions

diff --git a/src/image/segment.c b/src/image/segment.c
index 9bd60f9c..3d2b8a4b 100644
--- a/src/image/segment.c
+++ b/src/image/segment.c
@@ -26,6 +26,7 @@
 #include <errno.h>
 #include <gpxe/uaccess.h>
 #include <gpxe/memmap.h>
+#include <gpxe/errortab.h>
 #include <gpxe/segment.h>
 
 /**
@@ -72,3 +73,13 @@ int prep_segment ( userptr_t segment, size_t filesz, size_t memsz ) {
 	      start, mid, end );
 	return -ERANGE;
 }
+
+/**
+ * Segment-specific error messages
+ *
+ * This error happens sufficiently often to merit a user-friendly
+ * description.
+ */
+struct errortab segment_errors[] __errortab = {
+	{ ERANGE, "Requested memory not available" },
+};