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resizerootfs: don’t touch user-modified table, disable on first boot (Thanks mrvnr)

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fixes #3
This commit is contained in:
Michael Stapelberg
2018-01-04 09:02:47 +01:00
parent 28566d7f29
commit 96fc719bef
2 changed files with 31 additions and 0 deletions
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30
rpi3-resizerootfs
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@@ -58,6 +58,33 @@ sub boot_code { 446; }
sub partition_table_entry { 16; }
sub partition_table_start_offset { 8; }
sub partition_table_length_offset { 12; }
sub partition_count { 4; }
sub partition_signature_len { 2; }
sub tablelength { partition_table_entry() * partition_count() + partition_signature_len(); }
# The contents of $original_partition_table must be updated whenever the
# partition layout on the SD card image changes.
# This layout matches
# https://people.debian.org/~stapelberg/raspberrypi3/2017-10-08/2017-10-08-raspberry-pi-3-buster-PREVIEW.img.bz2
my $original_partition_table = pack('H4' x (tablelength()/2),
"0020", "2100", "0c3e", "1826", "0008", "0000", "0058", "0900",
"003e", "1926", "837a", "3b7f", "0060", "0900", "00e0", "1500",
"0000", "0000", "0000", "0000", "0000", "0000", "0000", "0000",
"0000", "0000", "0000", "0000", "0000", "0000", "0000", "0000",
"55aa");
sub check_orig_partition_table {
my ($offset, $len, $bytes) = @_;
sysseek($root, $offset, SEEK_SET)
or die qq|sysseek($offset): $!|;
my $buf;
sysread($root, $buf, $len)
or die qq|sysread(): $!|;
if ($buf ne $bytes) {
print "Partition table already modified\n";
exit 0;
}
}
sub read_uint32_le {
my ($offset) = @_;
@@ -70,6 +97,9 @@ sub read_uint32_le {
return $val;
}
# Ensure partition table has not been modified by the user.
check_orig_partition_table(boot_code(), tablelength(), $original_partition_table);
my $entry_offset = boot_code() + (partition_table_entry() * ($pno - 1));
my $start = 512 * read_uint32_le($entry_offset + partition_table_start_offset());
my $oldlength = 512 * read_uint32_le($entry_offset + partition_table_length_offset());