genprotimg: add relocator for stage3b

Add support for the placement of the stage3b loader at other addresses
than 0xa000. For this add a position independent relocator that first
copies the original stage3b code to the memory location 0xa000 and
then starts it.

Reviewed-by: Philipp Rudo <prudo@linux.ibm.com>
Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

genprotimg/boot/Makefile

@@ -17,7 +17,7 @@ ALL_CFLAGS := $(NO_PIE_CFLAGS) -Os -g \
 	-mstack-size=4096 -mstack-guard=128 -msoft-float \
 	-Wall -Wformat-security -Wextra -Werror
 
-FILES := stage3a.bin stage3b.bin
+FILES := stage3a.bin stage3b.bin stage3b_reloc.bin
 
 ZIPL_SRCS_C := libc.c ebcdic.c ebcdic_conv.c sclp.c
 ZIPL_SRCS_ASM := entry.S
@@ -66,14 +66,17 @@ ifneq ($(MAKECMDGOALS),clean)
 -include $(dependencies_zipl_c)
 endif
 
+stage3b_reloc.o: stage3b.bin
 
 stage3a.elf: head.o stage3a_init.o stage3a.o stage3a.lds $(ZIPL_OBJS)
 stage3b.elf: head.o stage3b.o stage3b.lds $(ZIPL_OBJS)
+stage3b_reloc.elf:
 
 %.elf:	%.o
 	case $* in \
 		stage3a) SFLAGS="$(NO_PIE_LINKFLAGS) -nostdlib -Wl,-T,stage3a.lds";; \
 		stage3b) SFLAGS="$(NO_PIE_LINKFLAGS) -nostdlib -Wl,-T,stage3b.lds";; \
+		stage3b_reloc) SFLAGS="$(NO_PIE_LINKFLAGS) -nostdlib -Wl,-estage3b_reloc_start,-Ttext,0";; \
 	esac; \
 	$(LINK) $$SFLAGS -m64 $(filter %.o, $^) -o $@
 	@chmod a-x $@

genprotimg/boot/stage3b_reloc.S

@@ -0,0 +1,53 @@
+/*
+ * Relocator code for stage 3b boot loader
+ *
+ * Copyright IBM Corp. 2020
+ *
+ * s390-tools is free software; you can redistribute it and/or modify
+ * it under the terms of the MIT license. See LICENSE for details.
+ */
+
+#include "stage3b.h"
+#include "boot/sigp.h"
+
+.macro MEMCPY dst,src,len
+	lgr	%r0, \dst
+	lgr	%r1, \len
+	lgr	%r2, \src
+	lgr	%r3, \len
+
+20:	mvcle	%r0, %r2, 0
+	jo	20b
+.endm
+
+.org 0x0
+.section .text.start
+.globl stage3b_reloc_start
+stage3b_reloc_start:
+	/* Might be called after a diag308 so better set
+	 * architecture and addressing mode
+	 */
+	lhi	%r1, 1
+	sigp	%r1, %r0, SIGP_SET_ARCHITECTURE
+	sam64
+
+.copy_stage3b:
+	/* Location of stage3b in memory */
+	larl	%r8, stage3b_start
+
+	/* Destination for stage3b */
+	lgfi	%r9, STAGE3B_LOAD_ADDRESS
+
+	/* Size of stage3b */
+	lghi	%r11, stage3b_end - stage3b_start
+
+	/* Copy the stage3b loader to address STAGE3B_LOAD_ADDRESS */
+	MEMCPY	%r9, %r8, %r11
+
+	/* Branch to STAGE3B_ENTRY */
+	lgfi	%r9, STAGE3B_ENTRY
+	br	%r9
+stage3b_start:
+	.incbin	"stage3b.bin"
+stage3b_end:
+.previous