Add x1 experiments

x1/Makefile

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+CROSS_COMPILE:=arm-linux-gnueabi-
+AS:=$(CROSS_COMPILE)as
+
+.PHONY:
+all: return.bin mrc.bin
+
+%.bin: %.S
+	@$(AS) $<
+	@./extract.py a.out $@
+	@rm -f a.out

x1/README.md

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+#### Code
+ - `mrc.S`  Read SCTLR (MMU etc.) and return
+ - `return.S`  Return immediately
+ - `extract.py`  Extract .text
+
+
+#### Build
+```sh
+pip3 install pyelftools
+make all
+```
+
+#### Run
+ - Create a directory `/path/to/sd/APP/foo`
+ - Create index.din `touch /path/to/sd/APP/foo/index.din`
+ - Copy and rename the raw executable `cp foo.bin /path/to/sd/APP/foo/AppMain.bin`

x1/extract.py

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+#!/usr/bin/env python3
+
+import sys
+from elftools.elf.elffile import ELFFile  # pip install pyelftools
+
+
+def main():
+    if len(sys.argv) < 3:
+        print(f'Usage: {sys.argv[0]} in.elf out.bin')
+        sys.exit(1)
+
+    with open(sys.argv[1], 'rb') as f:
+        extract(ELFFile(f))
+
+
+def extract(elf):
+    text = elf.get_section_by_name('.text')
+    if text is None:
+        print('Input ELF has no .text section', file=sys.stderr)
+
+    with open(sys.argv[2], 'wb') as f:
+        f.write(text.data())
+
+    print(f'Successfully extracted the .text section to "{sys.argv[2]}"')
+
+
+main()

x1/mrc.S

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+.text
+    .align 2
+    .global _start
+
+_start:
+    mrc p15, 0, r10, c1, c0, 0
+    mov pc, lr

x1/return.S

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+.text
+    .align 2
+    .global _start
+
+_start:
+    mov pc, lr