From 2323505be7e3fbc99b4d0c2838a870b244da06ad Mon Sep 17 00:00:00 2001
From: Suguru Saito <sg.sgch07@gmail.com>
Date: Tue, 14 Dec 2021 01:01:31 +0900
Subject: [PATCH] Add linkerscript (experimental)

---
 x1/linkerscript/Makefile | 31 ++++++++++++++++++++++++
 x1/linkerscript/crt0.s   | 41 ++++++++++++++++++++++++++++++++
 x1/linkerscript/main.c   |  4 ++++
 x1/linkerscript/x1.ld    | 51 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 127 insertions(+)
 create mode 100644 x1/linkerscript/Makefile
 create mode 100644 x1/linkerscript/crt0.s
 create mode 100644 x1/linkerscript/main.c
 create mode 100644 x1/linkerscript/x1.ld

diff --git a/x1/linkerscript/Makefile b/x1/linkerscript/Makefile
new file mode 100644
index 0000000..a107a2c
--- /dev/null
+++ b/x1/linkerscript/Makefile
@@ -0,0 +1,31 @@
+CROSS_COMPILE := arm-linux-gnueabihf-
+AS := $(CROSS_COMPILE)as
+CC := $(CROSS_COMPILE)gcc
+LD := $(CROSS_COMPILE)ld
+OBJCOPY := $(CROSS_COMPILE)objcopy
+
+TARGET := AppMain
+OBJS := crt0.o main.o
+
+ASFLAGS := -W
+CFLAGS := -Wall -ffreestanding -fomit-frame-pointer -Os
+LDFLAGS := -T x1.ld
+
+.PHONY:
+all: $(TARGET).bin
+
+.PHONY:
+clean:
+	-rm -f $(TARGET).bin $(TARGET).elf $(OBJS)
+
+%.o: %.s
+	$(AS) $(ASFLAGS) $< -o $@
+
+%.o: %.c
+	$(CC) -c $(CFLAGS) $<
+
+$(TARGET).elf: $(OBJS)
+	$(LD) $(LDFLAGS) $^ -o $@
+
+$(TARGET).bin: $(TARGET).elf
+	$(OBJCOPY) -O binary $< $@
diff --git a/x1/linkerscript/crt0.s b/x1/linkerscript/crt0.s
new file mode 100644
index 0000000..c31569b
--- /dev/null
+++ b/x1/linkerscript/crt0.s
@@ -0,0 +1,41 @@
+.text
+.arm
+.align 4
+
+.global _start
+_start:
+    stmdb   sp!, {r4, lr}
+    /* store context */
+    movs    r4, r0
+
+    /* Clear the .bss section */
+    bl      .L_clean_bss
+
+    /* restore context */
+    adr     r0, [.L_context]
+    str     r4, [r0]
+    ldr     r0, [r0]
+
+    /* call user's main */
+    bl      main
+
+    ldmia   sp!, {r4, pc}
+
+.L_context:
+.long 0
+
+/*
+    r0 = start address
+    r1 = end address
+    tmp: r2
+*/
+.L_clean_bss:
+    ldr     r0, =__bss_start
+    ldr     r1, =__bss_end
+    sub     r1, r1, #4
+    mov     r2, #0
+.L_clean_bss_loop:
+    cmp     r0, r1
+    strlt   r2, [r0], #4
+    blt     .L_clean_bss_loop
+    bx      lr
diff --git a/x1/linkerscript/main.c b/x1/linkerscript/main.c
new file mode 100644
index 0000000..9fbdf5d
--- /dev/null
+++ b/x1/linkerscript/main.c
@@ -0,0 +1,4 @@
+int main(void *arg)
+{
+    return 0;
+}
diff --git a/x1/linkerscript/x1.ld b/x1/linkerscript/x1.ld
new file mode 100644
index 0000000..b9a1a4f
--- /dev/null
+++ b/x1/linkerscript/x1.ld
@@ -0,0 +1,51 @@
+OUTPUT_FORMAT("elf32-littlearm", "elf32-bigarm", "elf32-littlearm")
+OUTPUT_ARCH(arm)
+ENTRY(_start)
+
+MEMORY {
+    RAM (xrw): ORIGIN = 0x90000000, LENGTH = 15M
+}
+
+SECTIONS {
+    .text : {
+        *(.text)
+        *(.text*)
+        *(.rodata)
+        *(.rodata*)
+        *(.glue_7)
+        *(.glue_7t)
+
+        KEEP (*(.init))
+        KEEP (*(.fini))
+
+        . = ALIGN(4);
+    } > RAM
+
+    .data : {
+        *(.data)
+        *(.data*)
+        . = ALIGN(4);
+    } > RAM
+
+    .bss : {
+        __bss_start = .;
+        *(.bss)
+        *(COMMON)
+        . = ALIGN(4);
+        __bss_end = .;
+    } > RAM
+
+    /DISCARD/ : {
+        *(.discard)
+        *(.discard.*)
+        *(.comment)
+    }
+
+    .stab 0 : { *(.stab) }
+	.stabstr 0 : { *(.stabstr) }
+	.stab.excl 0 : { *(.stab.excl) }
+	.stab.exclstr 0 : { *(.stab.exclstr) }
+	.stab.index 0 : { *(.stab.index) }
+	.stab.indexstr 0 : { *(.stab.indexstr) }
+    .ARM.attributes 0 : { *(.ARM.attributes) }
+}