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Lee Lup Yuen 2022-08-22 18:25:50 +08:00
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README.md
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@ -270,7 +270,7 @@ u32 magic = 0x644d5241; /* Magic number, little endian, "ARM\x64" */
u32 res5; /* reserved (used for PE COFF offset) */
```
Start of RAM is 0x4000 0000. I wonder if this Image Load Offset in our NuttX Image Header might be incorrect...
Start of RAM is 0x4000 0000. The Image Load Offset in our NuttX Image Header is 0x48 0000...
https://github.com/lupyuen/incubator-nuttx/blob/pinephone/arch/arm64/src/common/arm64_head.S#L107
@ -278,9 +278,13 @@ https://github.com/lupyuen/incubator-nuttx/blob/pinephone/arch/arm64/src/common/
.quad 0x480000 /* Image load offset from start of RAM */
```
This means that our NuttX Image will be loaded at 0x4048 0000.
I wonder if this Image Load Offset should have been 0x28 0000? (Instead of 0x48 0000)
Remember that Ghidra (and the Arm Disassembly) says that our NuttX Image is actually loaded at 0x4028 0000. (Instead of 0x4048 0000)
RAM Size and RAM Start are defined here...
RAM Size and RAM Start are defined in the NuttX Configuration...
https://github.com/lupyuen/incubator-nuttx/blob/pinephone/boards/arm64/qemu/qemu-a53/configs/nsh_smp/defconfig#L47-L48
@ -289,7 +293,7 @@ CONFIG_RAM_SIZE=134217728
CONFIG_RAM_START=0x40000000
```
That's 128 MB RAM. Which should work OK with PinePhone's 2 GB RAM.
That's 128 MB RAM. Which should fit inside PinePhone's 2 GB RAM.
The NuttX Image was built with this Linker Command, based on `make --trace`...
@ -317,7 +321,7 @@ aarch64-none-elf-ld \
--end-group
```
NuttX Image begins at `__start`, which is defined as 0x4028 0000 here...
NuttX Image begins at `__start`, which is defined as 0x4028 0000 in the NuttX Linker Script...
https://github.com/lupyuen/incubator-nuttx/blob/pinephone/boards/arm64/qemu/qemu-a53/scripts/dramboot.ld#L30-L33
@ -391,6 +395,8 @@ Note that the first instruction at 0x4000 0000 jumps to 0x4081 0000 (to skip the
40000000 00 40 20 14 b FUN_40810000
```
(Note: The magic "MZ" signature is not needed)
The Linux Kernel Code actually begins at 0x4081 0000...
![Linux Kernel Code actually begins at 0x4081 0000](https://lupyuen.github.io/images/Screenshot%202022-08-22%20at%205.53.58%20PM.png)