diff options
| author | Wojtek Kosior <kwojtus@protonmail.com> | 2019-10-03 14:04:31 +0200 |
|---|---|---|
| committer | Wojtek Kosior <kwojtus@protonmail.com> | 2019-10-03 14:04:31 +0200 |
| commit | 24ab4678b96dec56129f7e36b9304b6767777e0a (patch) | |
| tree | 1ab41614fc0b6e20322ef44ec3f7a29bc3bc4877 | |
| parent | 47c327eac36e78793173496f18b56f0f2159d648 (diff) | |
| download | rpi-MMU-example-24ab4678b96dec56129f7e36b9304b6767777e0a.tar.gz rpi-MMU-example-24ab4678b96dec56129f7e36b9304b6767777e0a.zip | |
specify load address only in linker script; change it to 0x10000 (for now); avoid padding
| -rw-r--r-- | Makefile | 10 | ||||
| -rw-r--r-- | boot.S | 8 | ||||
| -rw-r--r-- | linker.ld | 7 |
3 files changed, 13 insertions, 12 deletions
@@ -1,7 +1,7 @@ all : kernel7.img kernel.o : kernel.c - arm-none-eabi-gcc -mcpu=cortex-a7 -ffreestanding -std=gnu99 -c -O2 -Wall -Wextra $^ -o $@ + arm-none-eabi-gcc -mcpu=cortex-a7 -ffreestanding -std=gnu99 -c -Wall -Wextra $^ -o $@ boot.o : boot.S arm-none-eabi-as -mcpu=cortex-a7 boot.S -o boot.o @@ -9,13 +9,9 @@ boot.o : boot.S kernel.elf : boot.o kernel.o arm-none-eabi-gcc -T linker.ld -o $@ -ffreestanding -O2 -nostdlib boot.o kernel.o -lgcc -# objcopy pads 0x0000 to 0x8000 with zeros, we get rid of them in the next recipe -kernel_padded.img : kernel.elf +kernel7.img : kernel.elf arm-none-eabi-objcopy $^ -O binary $@ -kernel7.img : kernel_padded.img - dd bs=4096 skip=8 if=$^ of=$@ - qemu-elf : kernel.elf qemu-system-arm -m 256 -M raspi2 -serial stdio -kernel $^ @@ -23,6 +19,6 @@ qemu-bin : kernel7.img qemu-system-arm -m 256 -M raspi2 -serial stdio -kernel $^ clean : - -rm kernel7.img kernel_padded.img kernel.elf boot.o kernel.o + -rm kernel7.img kernel.elf boot.o kernel.o .PHONY: all qemu-elf qemu-bin clean @@ -2,11 +2,12 @@ // To keep this in the first portion of the binary. .section ".text.boot" - + +//.org 0x8000 + // Make _start global. .globl _start -.org 0x8000 // Entry point for the kernel. // r15 -> should begin execution at 0x8000. // r0 -> 0x00000000 @@ -21,7 +22,8 @@ _start: bne halt // Setup the stack. - ldr r5, =_start + // It shall be directly below our kernel image + ldr r5, =__start mov sp, r5 // Clear out bss. @@ -3,8 +3,11 @@ ENTRY(_start) SECTIONS { /* Starts at LOADER_ADDR. */ - . = 0x8000; - /* For AArch64, use . = 0x80000; */ + /* Warning! Internet says RPis in 32-bit mode load kernel at 0x8000! */ + /* My experiments do, however, show, that qemu emulating RPi2 */ + /* Loads the kernel at 0x10000! (took some pain to find out) */ + . = 0x10000; + /* For AArch64, use . = 0x80000; Unless this too is wrong */ __start = .; __text_start = .; .text : |