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Lee Lup Yuen 2022-08-22 16:28:44 +08:00
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@ -174,9 +174,86 @@ https://github.com/apache/incubator-nuttx/tree/master/arch/arm64/src/qemu
https://github.com/apache/incubator-nuttx/tree/master/arch/arm64/src/common
# Analyse PinePhone Image with Ghidra
# NuttX Image
TODO: Disassemble a PinePhone Image with Ghidra to look at the Startup Code
TODO: Analyse NuttX Image with Ghidra and NuttX Disassembly
Top Part of NuttX Image Header...
![Top Part of NuttX Image Header](https://lupyuen.github.io/images/Screenshot%202022-08-22%20at%204.09.55%20PM.png)
Bottom Part of NuttX Image Header...
![Bottom Part of NuttX Image Header](https://lupyuen.github.io/images/Screenshot%202022-08-22%20at%204.10.04%20PM.png)
When we refer to the NuttX Disassembly `nuttx.S`, we see this...
https://github.com/lupyuen/incubator-nuttx/blob/pinephone/arch/arm64/src/common/arm64_head.S#L79-L117
```text
/* Kernel startup entry point.
* ---------------------------
*
* The requirements are:
* MMU = off, D-cache = off, I-cache = on or off,
* x0 = physical address to the FDT blob.
* it will be used when NuttX support device tree in the future
*
* This must be the very first address in the loaded image.
* It should be loaded at any 4K-aligned address.
*/
.globl __start;
__start:
/* DO NOT MODIFY. Image header expected by Linux boot-loaders.
*
* This add instruction has no meaningful effect except that
* its opcode forms the magic "MZ" signature of a PE/COFF file
* that is required for UEFI applications.
*
* Some bootloader (such imx8 uboot) checking the magic "MZ" to see
* if the image is a valid Linux image. but modifying the bootLoader is
* unnecessary unless we need to do a customize secure boot.
* so just put the ''MZ" in the header to make bootloader happiness
*/
add x13, x18, #0x16 /* the magic "MZ" signature */
b real_start /* branch to kernel start */
.quad 0x480000 /* Image load offset from start of RAM */
.quad _e_initstack - __start /* Effective size of kernel image, little-endian */
.quad __HEAD_FLAGS /* Informative flags, little-endian */
.quad 0 /* reserved */
.quad 0 /* reserved */
.quad 0 /* reserved */
.ascii "ARM\x64" /* Magic number, "ARM\x64" */
.long 0 /* reserved */
real_start:
/* Disable all exceptions and interrupts */
```
NuttX Image actually follows the Linux Kernel Image Format, as defined here...
- ["Booting AArch64 Linux"](https://www.kernel.org/doc/html/latest/arm64/booting.html)
Linux Kernel Image contains a 64-byte header as follows:
```text
u32 code0; /* Executable code */
u32 code1; /* Executable code */
u64 text_offset; /* Image load offset, little endian */
u64 image_size; /* Effective Image size, little endian */
u64 flags; /* kernel flags, little endian */
u64 res2 = 0; /* reserved */
u64 res3 = 0; /* reserved */
u64 res4 = 0; /* reserved */
u32 magic = 0x644d5241; /* Magic number, little endian, "ARM\x64" */
u32 res5; /* reserved (used for PE COFF offset) */
```
# PinePhone Image
TODO: Disassemble a PinePhone Image with Ghidra to look at the Linux Kernel Header and Startup Code
https://github.com/dreemurrs-embedded/Jumpdrive
@ -211,9 +288,11 @@ https://linux-sunxi.org/A64/Memory_map
- Change Start Address to 40000000
Kernel Header Magic Value `ARMd` (`ARM\x64`) is at offset 0x38...
According to this doc...
https://github.com/raspberrypi/firmware/issues/1415#issuecomment-649637129
- ["Booting AArch64 Linux"](https://www.kernel.org/doc/html/latest/arm64/booting.html)
Linux Kernel Magic Number `ARM\x64` is at offset 0x38
# TODO