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Use a better way to find the framebuffer address

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Rien Maertens 2020-11-01 19:21:28 +01:00
parent 0dc05496a9
commit 221aa0e7b3
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GPG Key ID: AE66CE42F1AF9DEF
1 changed files with 23 additions and 38 deletions
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reStream.sh
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@ -76,6 +76,7 @@ while [ $# -gt 0 ]; do
done
ssh_cmd() {
echo "[SSH]" "$@" >&2
ssh -o ConnectTimeout=1 "$ssh_host" "$@"
}
@ -87,38 +88,6 @@ fi
rm_version="$(ssh_cmd cat /sys/devices/soc0/machine)"
# We cannot read the framebuffer directory in the reMarkable 2, but we know the
# address of the pointer to the framebuffer for some reMarkable 2 versions.
# This will need to be changed each time xochitl updates.
rm2_getpointer() {
xochitl_version="$(ssh_cmd "sed -n 's/^REMARKABLE_RELEASE_VERSION=//p' /usr/share/remarkable/update.conf")"
case "$xochitl_version" in
"2.3."*)
echo "4121024"
;;
*) # 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 "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 "$rm_version" in
"reMarkable 1.0")
width=1408
@ -131,18 +100,34 @@ case "$rm_version" in
head_fb0="dd if=/dev/fb0 count=1 bs=$window_bytes 2>/dev/null"
;;
"reMarkable 2.0")
pixel_format="gray8"
width=1872
height=1404
bytes_per_pixel=1
pixel_format="gray8"
pid="$(ssh_cmd pidof xochitl)"
pointer="$(rm2_getpointer)"
read_address="addr=\$($(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="$((width * height * bytes_per_pixel))"
# find xochitl's process
pid="$(ssh_cmd pidof xochitl)"
echo "xochitl's PID: $pid"
# find framebuffer location in memory
# it is actually the map allocated _after_ the fb0 mmap
read_address="grep -C1 '/dev/fb0' /proc/$pid/maps | tail -n1 | sed 's/-.*$//'"
skip_bytes_hex="$(ssh_cmd "$read_address")"
skip_bytes="$((0x$skip_bytes_hex))"
echo "framebuffer is at 0x$skip_bytes_hex"
# carve the framebuffer out of the process memory
head_fb0="$(memread_instr "/proc/$pid/mem" "$skip_bytes" "$window_bytes")"
page_size=4096
window_start_blocks="$((skip_bytes / page_size))"
window_offset="$((skip_bytes % page_size))"
window_length_blocks="$((window_bytes / page_size + 1))"
# Using dd with bs=1 is too slow, so we first carve out the pages our desired
# bytes are located in, and then we trim the resulting data with what we need.
head_fb0="dd if=/proc/$pid/mem bs=$page_size skip=$window_start_blocks count=$window_length_blocks 2>/dev/null | dd if=/dev/stdin skip=$window_offset bs=1 count=$window_bytes 2>/dev/null"
;;
*)
echo "Unsupported reMarkable version: $rm_version."