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Improve performance for carving memory

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Rien Maertens 2020-10-31 18:53:49 +01:00
parent cdd88ac6a3
commit 0dc05496a9
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GPG Key ID: AE66CE42F1AF9DEF
1 changed files with 21 additions and 10 deletions
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31
reStream.sh
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@ -96,18 +96,29 @@ rm2_getpointer() {
"2.3."*)
echo "4121024"
;;
"2.4.*")
# TODO
echo "???"
;;
*) # use last known version if we cannot find a match
echo "WARNING: unknown reMarkable 2 release version" >&2
echo "consider updating if reStream doesn't work" >&2
echo "???"
echo "4121024"
;;
esac
}
# Print the instruction for reading a memory location.
# Using dd with bs=1 is too slow, so we first carve out the pages our desired
# bytes are located in, and then we trim the resulting data with what we need.
memread_instr() {
page_size=4096
ifile="$1" # input (device) file
offset="$2" # offset in bytes to start reading
count="$3" # byte count to read
window_start_blocks="$((offset / page_size))"
window_skip_bytes="$((offset % page_size))"
window_length_blocks="$((count / page_size + 1))"
"dd if=$ifile bs=$page_size skip=$window_start_blocks count=$window_length_blocks 2>/dev/null | dd if=/dev/stdin skip=$window_skip_bytes bs=$count count=1 2>/dev/null"
}
case "$rm_version" in
"reMarkable 1.0")
width=1408
@ -120,18 +131,18 @@ case "$rm_version" in
head_fb0="dd if=/dev/fb0 count=1 bs=$window_bytes 2>/dev/null"
;;
"reMarkable 2.0")
width=1404
height=1872
width=1872
height=1404
bytes_per_pixel=1
pixel_format="gray8"
pid="$(ssh_cmd pidof xochitl)"
pointer="$(rm2_getpointer)"
read_address="addr=\$(dd if=/proc/$pid/mem bs=1 count=4 skip=$pointer 2>/dev/null | hexdump | awk '{print \$3\$2}') && printf '%d' \$((16#\$addr))"
skipbytes="$(ssh_cmd "$read_address")"
read_address="addr=\$($(memread_instr "/proc/$pid/mem" "$pointer" 4) | hexdump | awk '{print \$3\$2}') && printf '%d' \$((16#\$addr))"
skip_bytes="$(ssh_cmd "$read_address")"
# calculate how much bytes the window is
window_bytes="$((width * height * bytes_per_pixel))"
# carve the framebuffer out of the process memory
head_fb0="dd if=/proc/$pid/mem bs=1 count=$window_bytes skip=$skipbytes 2>/dev/null"
head_fb0="$(memread_instr "/proc/$pid/mem" "$skip_bytes" "$window_bytes")"
;;
*)
echo "Unsupported reMarkable version: $rm_version."