decompile

README.md

@@ -1059,4 +1059,49 @@ printf 0 > /sys/class/graphics/fb0/blank
 ```
 Starting and stopping XFCE also seems to work.
 
-Note that the GPU is not attached to the EINK, so some copying will be necessary to use the GPU. Maybe the RGA can be used for that?
+Note that the GPU is not attached to the EINK, so some copying will be necessary to use the GPU. Maybe the RGA can be used for that?
+
+## Ghidra
+
+https://github.com/Ralim/ebc-dev-reverse-engineering/issues/2
+
+>Here's a suggestion for anyone wanting to look at the pre-compiled files in Ghidra. This is most useful if you haven't already made a bunch of annotations; I don't know how to copy those over. So it's not really aimed at this repo, per se, but here's where the action seems to be.
+>
+>1. Run `make ARCH=arm64 rockchip_linux_defconfig` to start with a kernel config that builds the EBC driver.
+>2. Run `make ARCH=arm64 nconfig` and enable `CONFIG_DEBUG_INFO_DWARF4` (at "Kernel hacking" -> "Compile-time checks and compiler options" -> "Generate dwarf4 debuginfo"). DWARF4 is the newest debug info format that Ghidra understands, but recent GCC will generate DWARF5 by default.
+>3. Run `make ARCH=arm64` to compile the kernel. If it fails, that is fine, as long as `drivers/gpu/drm/rockchip/ebc-dev/built-in.a` gets created.
+>4. Finally, take the archive containing the EBC driver, and convert it to an object file: `aarch64-linux-gnu-ld -r -o drivers/gpu/drm/rockchip/ebc-dev/built-in.o --whole-archive drivers/gpu/drm/rockchip/ebc-dev/built-in.a`.
+> 
+>This will create a single file, built-in.o, that includes all of the C and pre-compiled source for the driver, so everything gets loaded together in one code browser, and you don't have to worry about function imports and thunks and whatnot.
+
+```sh
+export CROSS_COMPILE="$PWD/../gcc-arm-10.3-2021.07-x86_64-aarch64-none-linux-gnu/bin/aarch64-none-linux-gnu-"
+export ARCH=arm64
+make rockchip_linux_defconfig
+```
+Enable Dwarf4 and EBC. Add to `.config`:
+```conf
+CONFIG_ROCKCHIP_EBC_DEV=y
+CONFIG_EPD_TPS65185_SENSOR=y
+CONFIG_DEBUG_INFO_DWARF4=y
+```
+Or use the GUI:
+```sh
+make nconfig
+# "Kernel hacking" -> "Compile-time checks and compiler options" -> "Generate dwarf4 debuginfo"
+# "Device Drivers" -> "Graphics support" -> "DRM Support for Rockchip" -> "Rockchip eBook Device Driver"
+```
+Compile:
+```sh
+make -j$(nproc)
+${CROSS_COMPILE}ld -r -o drivers/gpu/drm/rockchip/ebc-dev/built-in.o --whole-archive drivers/gpu/drm/rockchip/ebc-dev/built-in.a
+```
+Now you can import the `built-in.o` file into ghidra.
+I got an error of the form
+```
+Low-level Error: Size too small for fields of structure dentry_operations.conflict
+```
+in the decompiler window.
+To fix this, go into the offending struct (here `dentry_operations.conflict`) and change the type of mismatched size (pick any type of the correct size).
+Ghidra points out which field has the wrong type in the "mnemonic" column.
+After changing the type of `ebc_buf_s.buf_mode` to `panel_refresh_mode`, I [exported](rev/ebc_dev_2.26.c) the code.