Super simple boot ROM for npcm7xx

This is able to parse the boot block header, copy it into SRAM and jump
to it.

Secure booting or anything vaguely advanced is not supported.

Signed-off-by: Havard Skinnemoen <hskinnemoen@google.com>
Change-Id: I88b567e8dba25cd75a3f37824698bcbefc89a98f

1 files changed, 56 insertions, 0 deletions

diff --git a/bootrom.ld b/bootrom.ld
new file mode 100644
index 0000000..34d59ad
--- /dev/null
+++ b/bootrom.ld
@@ -0,0 +1,56 @@
+/*
+ * Linker script for the Boot ROM.
+ *
+ * Copyright 2020 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+MEMORY
+{
+	rom (rx) : ORIGIN = 0xFFFF0000, LENGTH = 64K
+	ram (a!rx) : ORIGIN = 0xFFFD0000, LENGTH = 128K
+}
+
+SECTIONS
+{
+	/* Vectors are loaded into ROM, and copied into SRAM. */
+	.text.vectors : {
+		*(.text.vectors)
+		. = 0x100;
+	} >ram AT>rom
+	/* The rest of the code follows the vectors, but is not copied. */
+	.text : {
+		*(.text .text.*)
+		*(.rodata .rodata.*)
+		. = ALIGN(32);
+		_etext = .;
+	} >rom
+	/*
+	 * Data follows the code in ROM, and is copied after the vectors in RAM.
+	 * 32-byte aligned so we can use simple and fast copy loops.
+	 */
+	.data : {
+		_data = .;
+		*(.data.rom_status)
+		*(.data .data.*)
+		. = ALIGN(32);
+		_edata = .;
+	} >ram AT>rom
+	/* BSS lives in RAM, after the data section. */
+	.bss : {
+		*(.bss .bss.*)
+		. = ALIGN(32);
+		_end = .;
+	} >ram
+}