Decode Linux Header

2025-01-12 20:58:31 +08:00 · 2023-10-28 16:53:13 +08:00 · 2023-10-28 16:53:13 +08:00 · 4ee77983ba
commit 4ee77983ba
parent c1ebdd0e3c
1 changed files with 138 additions and 2 deletions
--- a/README.md
+++ b/README.md
@ -1,2 +1,138 @@
-# nuttx-ox64
-Apache NuttX RTOS for Pine64 Ox64 64-bit RISC-V SBC (BouffaloLab BL808)
+# Apache NuttX RTOS for Pine64 Ox64 64-bit RISC-V SBC (BouffaloLab BL808)
+
+TODO
+
+Download [bl808-linux-pine64_ox64_full_defconfig.tar.gz](https://github.com/openbouffalo/buildroot_bouffalo/releases/download/v1.0.1/bl808-linux-pine64_ox64_full_defconfig.tar.gz) from [openbouffalo/buildroot_bouffalo/releases/tag/v1.0.1](https://github.com/openbouffalo/buildroot_bouffalo/releases/tag/v1.0.1)
+
+Unzip and mount the SD Card Image.
+
+```bash
+→ ls -l /Users/Luppy/ox64/sdcard-pine64_ox64_full_defconfig     
+total 25744
+-rwxrwxrwx@ 1 Luppy  staff  13154816 Mar  6  2023 Image
+-rwxrwxrwx@ 1 Luppy  staff      4012 Mar  6  2023 bl808-pine64-ox64.dtb
+-rwxrwxrwx@ 1 Luppy  staff      4106 Mar  6  2023 bl808-sipeed-m1s.dtb
+-rwxrwxrwx@ 1 Luppy  staff       350 Mar  6  2023 boot-m1s.scr
+-rwxrwxrwx@ 1 Luppy  staff       352 Mar  6  2023 boot-pine64.scr
+-rwxrwxrwx@ 1 Luppy  staff       352 Mar  6  2023 boot.scr
+drwxrwxrwx@ 3 Luppy  staff        96 Mar  6  2023 extlinux
+```
+
+Dump `Image` as hex...
+
+```bash
+→ hexdump /Users/Luppy/ox64/sdcard-pine64_ox64_full_defconfig/Image | mor
+e
+0000000 4d 5a 6f 10 20 08 01 00 00 00 20 00 00 00 00 00
+0000010 00 80 cd 00 00 00 00 00 00 00 00 00 00 00 00 00
+0000020 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
+0000030 52 49 53 43 56 00 00 00 52 53 43 05 40 00 00 00
+0000040 50 45 00 00 64 50 02 00 00 00 00 00 00 00 00 00
+0000050 00 00 00 00 a0 00 06 02 0b 02 02 14 00 f0 5f 00
+0000060 00 80 6d 00 00 00 00 00 3e 2a 42 00 00 10 00 00
+0000070 00 00 00 00 00 00 00 00 00 10 00 00 00 02 00 00
+0000080 00 00 00 00 01 00 01 00 00 00 00 00 00 00 00 00
+0000090 00 80 cd 00 00 10 00 00 00 00 00 00 0a 00 00 00
+00000a0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
+```
+
+Which will begin with this __RISC-V Linux Image Header__...
+
+-   [__"Boot Image Header in RISC-V Linux"__](https://www.kernel.org/doc/html/latest/riscv/boot-image-header.html)
+
+Here are the decoded bytes...
+
+1.  __code0__: Executable code
+
+    (4 bytes, offset `0x00`)
+
+    ```text
+    4d 5a 6f 10 
+    ```
+
+1.  __code1__: Executable code 
+
+    (4 bytes, offset `0x04`)
+
+    ```text
+    20 08 01 00 
+    ```
+
+1.  __text_offset__: Image load offset, little endian
+
+    (8 bytes, offset `0x08`)
+
+    ```text
+    00 00 20 00 00 00 00 00
+    ```
+
+1.  __image_size__: Effective Image size, little endian 
+
+    (8 bytes, offset `0x10`)
+
+    ```text
+    00 80 cd 00 00 00 00 00
+    aaaa 00  C0  56  01  00  00  00  00
+    ```
+
+1.  __flags__: Kernel flags, little endian 
+
+    (8 bytes, offset `0x18`)
+
+    ```text
+    00 00 00 00 00 00 00 00
+    ```
+
+1.  __version__: Version of this header (_MinL_ _MinM_ `.` _MajL_ _MajM_)
+
+    (4 bytes, offset `0x20`)
+
+    ```text
+    02 00 00 00
+    ```
+
+1.  __res1__: Reserved
+
+    (4 bytes, offset `0x24`)
+
+    ```text
+    00 00 00 00
+    ```
+
+1.  __res2__: Reserved
+
+    (8 bytes, offset `0x28`)
+
+    ```text
+    00 00 00 00 00 00 00 00
+    ```
+
+1.  __magic__: Magic number, little endian, "RISCV\x00\x00\x00" 
+    
+    (8 bytes, offset `0x30`)
+
+    ```text
+    52 49 53 43 56 00 00 00
+    ```
+
+1.  __magic2__: Magic number 2, little endian, "RSC\x05" 
+
+    (4 bytes, offset `0x38`)
+
+    ```text
+    52 53 43 05
+    ```
+
+1.  __res3__: Reserved for PE COFF offset
+
+    (4 bytes, offset `0x3C`)
+    
+    ```text
+    40 00 00 00
+    ```
+
+Our NuttX Kernel shall __recreate this RISC-V Linux Image Header__. (Total `0x40` bytes)
+
+(Or U-Boot Bootloader might refuse to boot NuttX)
+
+Header Values are exactly the same as Star64. (Except the Executable Code, since the Jump Address is different)