From a4f7386b8a6875fdaa477e6280503f08bb8370ef Mon Sep 17 00:00:00 2001
From: NIIBE Yutaka <gniibe@fsij.org>
Date: Thu, 7 Mar 2013 11:25:59 +0900
Subject: [PATCH] relocatable reGNUal

---
 ChangeLog          | 16 ++++++++++++++++
 regnual/Makefile   |  1 +
 regnual/regnual.ld |  7 +++++++
 regnual/sys.c      | 42 ++++++++++++++++++++++++++++++++++++------
 4 files changed, 60 insertions(+), 6 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 8d0cc51..c58a9bb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,19 @@
+2013-03-08  Niibe Yutaka  <gniibe@fsij.org>
+
+	Relocatable reGNUal.
+
+	* regnual/regnual.ld (MEMORY): 0x1400 was the value of Gnuk 1.0.1.
+	Keep this value.
+	(.text): Include .text.entry next to the .vectors.
+	(.got): New.
+
+	* regnual/sys.c (entry): Now, it's at .text.entry section.
+	Do relocations.
+	Don't use absolute values which causes relocations, but
+	access at GOT.
+
+	* regnual/Makefile (CFLAGS): Add -fpie.
+
 2013-03-07  Niibe Yutaka  <gniibe@fsij.org>
 
 	* src/usb_stm32f103.c (handle_setup0): Fix selecting handler.
diff --git a/regnual/Makefile b/regnual/Makefile
index 154877b..09ce344 100644
--- a/regnual/Makefile
+++ b/regnual/Makefile
@@ -22,6 +22,7 @@ MCFLAGS= -mcpu=$(MCU) -mfix-cortex-m3-ldrd
 DEFS = -DFREE_STANDING
 
 CFLAGS = -O2 -g
+CFLAGS += -Wa,-alms=$(notdir $(<:.c=.lst)) -fpie
 CFLAGS += $(CWARN) -I . -I ../src -fno-common $(MCFLAGS) $(TOPT) $(DEFS)
 
 LDFLAGS = -T$(LDSCRIPT) -nostartfiles $(MCFLAGS) $(TOPT)
diff --git a/regnual/regnual.ld b/regnual/regnual.ld
index c470c1d..3efabef 100644
--- a/regnual/regnual.ld
+++ b/regnual/regnual.ld
@@ -39,6 +39,7 @@ SECTIONS
     {
         _text = .;
         KEEP(*(.vectors))
+        *(.text.entry)
         *(.text)
         *(.text.*)
         *(.rodata)
@@ -48,6 +49,12 @@ SECTIONS
         *(.gcc*)
     } > ram1
 
+    .got :
+    {
+	*(.got)
+	*(.got.*)
+    } > ram1
+
     .ctors :
     {
         PROVIDE(_ctors_start_ = .);
diff --git a/regnual/sys.c b/regnual/sys.c
index 702e4c8..7222c42 100644
--- a/regnual/sys.c
+++ b/regnual/sys.c
@@ -9,17 +9,41 @@ static void none (void)
 {
 }
 
-/* Note: it is not reset */
-static __attribute__ ((naked))
+/*
+ * Note: the address of this routine 'entry' will be in the vectors as
+ * RESET, but this will be called from application.  It's not RESET
+ * state, then.
+ */
+static __attribute__ ((naked,section(".text.entry")))
 void entry (void)
 {
-  asm volatile ("ldr	r0, =__ram_end__\n\t"
-		"ldr	r1, =__main_stack_size__\n\t"
+  asm volatile ("mov	r0, pc\n\t"
+		"bic	r0, r0, #255\n\t" /* R0 := vector_table address */
+		"mov	r1, #0x90\n"	  /* R1 := numbers of entries * 4 */
+	"0:\n\t"
+		"ldr	r2, [r0, r1]\n\t"
+		"add	r2, r2, #-0x20000000\n\t"
+		"sub	r2, r2, #0x1400\n\t"
+		"add	r2, r2, r0\n\t" /* Relocate: -0x20001400 + R0 */
+		"str	r2, [r0, r1]\n\t"
+		"subs	r1, r1, #4\n\t"
+		"bne	0b\n\t"
+		/* Relocation done.  We don't care the first entry.  */
+		"ldr	r3, .L00\n"
+	".LPIC00:\n\t"
+		"add	r3, pc\n\t" /* R3 := @_GLOBAL_OFFSET_TABLE_ */
+		"ldr	r4, .L00+4\n\t"
+		"ldr	r0, [r3, r4]\n\t"
+		"ldr	r4, .L00+8\n\t"
+		"ldr	r1, [r3, r4]\n\t"
 		"sub	r0, r0, r1\n\t"
 		"mov	sp, r0\n\t"
+		/* Clear BSS.  */
 		"mov	r0, #0\n\t"
-		"ldr	r1, =_bss_start\n\t"
-		"ldr	r2, =_bss_end\n"
+		"ldr	r4, .L00+12\n\t"
+		"ldr	r1, [r3, r4]\n\t"
+		"ldr	r4, .L00+16\n\t"
+		"ldr	r2, [r3, r4]\n"
 	"0:\n\t"
 		"str	r0, [r1], #4\n\t"
 		"cmp	r2, r1\n\t"
@@ -30,6 +54,12 @@ void entry (void)
 		"bl	main\n"
 	"1:\n\t"
 		"b	1b\n"
+	".L00:\n\t"
+		".word	_GLOBAL_OFFSET_TABLE_-(.LPIC00+4)\n\t"
+		".word	__ram_end__(GOT)\n\t"
+		".word	__main_stack_size__(GOT)\n\t"
+		".word	_bss_start(GOT)\n\t"
+		".word	_bss_end(GOT)"
 		: /* no output */ : /* no input */ : "memory");
 }