From 7211bd49452e67e0b53ea06ca474f4e54af991ae Mon Sep 17 00:00:00 2001
From: xengineering <me@xengineering.eu>
Date: Sat, 25 Sep 2021 15:47:25 +0200
Subject: Implement Linker Script and Startup File
---
.gitignore | 3 +++
Makefile | 12 ++++++++++++
ld/stm32.ld | 32 ++++++++++++++++++++++++++++++++
src/startup.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
src/test_program.c | 8 ++++++++
5 files changed, 105 insertions(+)
create mode 100644 .gitignore
create mode 100644 Makefile
create mode 100644 ld/stm32.ld
create mode 100644 src/startup.c
create mode 100644 src/test_program.c
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..8765efc
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+docs
+baremetal
+build
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..4ef61dd
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,12 @@
+
+.PHONY: all clean
+
+all:
+ mkdir build
+ arm-none-eabi-gcc -O0 -c -g -mcpu=cortex-m3 -mthumb -o build/test_program.o src/test_program.c
+ arm-none-eabi-gcc -O0 -c -g -mcpu=cortex-m3 -mthumb -o build/startup.o src/startup.c
+ arm-none-eabi-ld -Tld/stm32.ld -o build/test_program.elf build/startup.o build/test_program.o
+ arm-none-eabi-objcopy -O binary build/test_program.elf build/test_program.bin
+
+clean:
+ rm -rf build
diff --git a/ld/stm32.ld b/ld/stm32.ld
new file mode 100644
index 0000000..9f74206
--- /dev/null
+++ b/ld/stm32.ld
@@ -0,0 +1,32 @@
+SECTIONS
+{
+ . = 0x0; /* From 0x00000000 */
+
+ .text :
+ {
+ *(vectors) /* Vector table */
+ *(.text) /* Program code */
+ }
+ .rodata :
+ {
+ *(.rodata) /* Read only data */
+ }
+ _DATA_ROM_START = .;
+
+ . = 0x20000000; /* From 0x20000000 */
+
+ _DATA_RAM_START = .;
+ .data : AT(_DATA_ROM_START)
+ {
+ *(.data) /* Data memory */
+ }
+ _DATA_RAM_END = .;
+
+ _BSS_START = .; /* Indicates where BSS section starts in RAM */
+ .bss :
+ {
+ *(.bss) /* Zero-filled run time allocate data memory */
+ }
+ _BSS_END = .; /* Indicates where BSS section ends in RAM */
+}
+
diff --git a/src/startup.c b/src/startup.c
new file mode 100644
index 0000000..b71a805
--- /dev/null
+++ b/src/startup.c
@@ -0,0 +1,50 @@
+
+
+#define STACK_TOP 0x20005000
+
+
+extern unsigned int _BSS_START;
+extern unsigned int _BSS_END;
+extern unsigned int _DATA_ROM_START;
+extern unsigned int _DATA_RAM_START;
+extern unsigned int _DATA_RAM_END;
+
+void startup();
+void main();
+
+// Define the vector table
+unsigned int * myvectors[2]
+__attribute__ ((section("vectors")))= {
+ (unsigned int *) STACK_TOP, // stack pointer
+ (unsigned int *) startup // code entry point
+};
+
+void startup()
+{
+ /* Set memory in bss segment to zeros */
+ unsigned int * bss_start_p = &_BSS_START;
+ unsigned int * bss_end_p = &_BSS_END;
+
+ while(bss_start_p != bss_end_p)
+ {
+ *bss_start_p = 0;
+ bss_start_p++;
+ }
+
+ /* Copy memory in data segment from its position
+ * in the flash image to its position in the
+ * read/write memory */
+ unsigned int * data_rom_start_p = &_DATA_ROM_START;
+ unsigned int * data_ram_start_p = &_DATA_RAM_START;
+ unsigned int * data_ram_end_p = &_DATA_RAM_END;
+
+ while(data_ram_start_p != data_ram_end_p)
+ {
+ *data_ram_start_p = *data_rom_start_p;
+ data_ram_start_p++;
+ data_rom_start_p++;
+ }
+
+ /* Now we are ready to start the main function */
+ main();
+}
diff --git a/src/test_program.c b/src/test_program.c
new file mode 100644
index 0000000..80f569b
--- /dev/null
+++ b/src/test_program.c
@@ -0,0 +1,8 @@
+static const int a = 7;
+static int b = 8;
+static int sum;
+
+void main()
+{
+ sum = a + b;
+}
--
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