Cleanup linker script and make .stack section

4 files changed, 57 insertions, 38 deletions

diff --git a/Makefile b/Makefile
index 348d974..becfccc 100644
--- a/Makefile
+++ b/Makefile
@@ -23,7 +23,7 @@ OBJ_START = $(BUILD_DIR)/start.o
 OBJ_MAIN = $(BUILD_DIR)/main.o
 SRC_LINK = $(SRC_DIR)/linker.ld
 
-CFLAGS := -Wall -ffreestanding -O2 -nostdlib -lgcc -mgeneral-regs-only -fstack-protector
+CFLAGS := -Wall -ffreestanding -nostartfiles -O2 -nostdlib -lgcc -mgeneral-regs-only -fno-stack-protector
 CFLAGS += -DRPI_VERSION=$(RPI_VERSION)
 AFLAGS :=
 LDFLAGS :=
diff --git a/src/common.h b/src/common.h
index 4c2c6b2..ad3aad8 100644
--- a/src/common.h
+++ b/src/common.h
@@ -22,8 +22,8 @@
 // Wait for N processor cycles before returning. Implemented in start.s.
 void delay(u64 ticks);
 
-// Clear N bytes at the given address. Implemented in start.s.
-void memzero(u64 src, u32 n);
+// Clear N bytes at the given address 8 bytes at a time. Implemented in start.s.
+void memzero64(void * src, u32 n);
 
 //
 // GPIO Registers.
diff --git a/src/linker.ld b/src/linker.ld
index cb8033f..994a50e 100644
--- a/src/linker.ld
+++ b/src/linker.ld
@@ -1,33 +1,52 @@
 ENTRY(_start)
 
+STACK_SIZE = 1024 * 1024 * 4;
+
 SECTIONS
 {
     . = 0x8000;
     __start = .;
-    .text :
-    {
+
+    .text : {
+        __text_start = .;
         KEEP(*(.text.boot))
         *(.text)
+        *(.text.*)
+        __text_end = .;
     }
-    . = ALIGN(4096);
-    .rodata :
-    {
+
+    .rodata : {
+        . = ALIGN(8);
+        __rodata_start = .;
         *(.rodata)
+        *(.rodata.*)
+        __rodata_end = .;
     }
-    . = ALIGN(4096);
-    .data :
-    {
+
+    .data : {
+        . = ALIGN(8);
+        __data_start = .;
         *(.data)
+        *(.data.*)
+        __data_end = .;
     }
-    . = ALIGN(4096);
-    __bss_start = .;
-    .bss :
-    {
-        bss = .;
+
+    .bss (NOLOAD) : {
+        . = ALIGN(8);
+        __bss_start = .;
         *(.bss)
+        *(.bss.*)
+        *(COMMON)
+        __bss_end = .;
+    }
+
+    .stack (NOLOAD) : {
+        . = ALIGN(8);
+        __stack_start = .;
+        . = . + STACK_SIZE;
+        __stack_end = .;
     }
-    . = ALIGN(4096);
-    __bss_end = .;
-    __bss_size = __bss_end - __bss_start;
+
+    . = ALIGN(8);
     __end = .;
 }
diff --git a/src/start.s b/src/start.s
index f6598ce..ecedeb4 100644
--- a/src/start.s
+++ b/src/start.s
@@ -1,44 +1,44 @@
 .section ".text.boot"
 
 .global _start
-
 _start:
     // Stop all cores except one.
     mrs     x0, mpidr_el1
     and     x0, x0, #0xFF
     cbz     x0, master
-    b halt
+    b       halt
 
 // Helper function to clear x1 bytes starting at the x0 memory address.
-.globl memzero
-memzero:
-    str xzr, [x0], #8
-    subs x1, x1, #8
-    b.gt memzero
-    ret
+.globl memzero64
+memzero64:
+        str     xzr, [x0], #8
+        subs    x1, x1, #8
+        b.gt    memzero64
+        ret
 
 // Helper function wait for N cycles before returning.
 .globl delay
 delay:
-    subs x0, x0, #1
-    bne delay
+    subs    x0, x0, #1
+    bne     delay
     ret
 
 master:
-    // Clear bss.
-    ldr x0, =__bss_start
-    ldr x1, =__bss_size
-    sub x1, x1, x0
-    bl memzero
-
-    // Set stack before our code.
-    ldr     x0, =_start
+    // Set the stack memory location. Since the stack grows towards zero we set
+    // the stack pointer to the end of the .stack memory section.
+    ldr     x0, =__stack_end
     mov     sp, x0
 
+    // Clear .bss memory.
+    ldr     x0, =__bss_start
+    ldr     x1, =__bss_end
+    sub     x1, x1, x0
+    bl      memzero64
+
     // Start C code, should not return.
     bl      main
     b       halt
 
 halt:
     wfe
-    b halt
+    b       halt