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0849d60f28
While prior this didn't work well, presumably due to stack size limitations, a shell script is included to raise the default stack size limit. This should be tried again.
167 lines
4.6 KiB
Bash
Executable File
167 lines
4.6 KiB
Bash
Executable File
# Raises `PT_GNU_STACK`'s memory to be at least 8 MB.
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#
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# This causes `musl` to use a 8 MB default for new threads, resolving the primary
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# compatibility issue faced when executing a program on a `musl` system.
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#
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# See https://wiki.musl-libc.org/functional-differences-from-glibc.html#Thread-stack-size
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# for reference. This differs that instead of setting at time of link, it
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# patches the binary as an already-linked ELF executable.
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#!/bin/bash
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set -eo pipefail
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ELF="$1"
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if [ ! -f "$ELF" ]; then
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echo "\`increase_default_stack_size.sh\` [ELF binary]"
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echo ""
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echo "Sets the \`PT_GNU_STACK\` program header to its existing value or 8 MB,"
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echo "whichever is greater."
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exit 1
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fi
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function hex {
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hexdump -e '1 1 "%.2x"' -v
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}
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function read_bytes {
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dd status=none bs=1 skip=$1 count=$2 if="$ELF" | hex
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}
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function write_bytes {
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POS=$1
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BYTES=$2
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while [ ! $BYTES = "" ]; do
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printf "\x$(printf $BYTES | head -c2)" | dd status=none conv=notrunc bs=1 seek=$POS of="$ELF"
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# Start with the third byte, as in, after the first two bytes
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BYTES=$(printf $BYTES | tail -c+3)
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POS=$(($POS + 1))
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done
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}
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# Magic
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MAGIC=$(read_bytes 0 4)
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if [ ! $MAGIC = $(printf "\x7fELF" | hex) ]; then
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echo "Not ELF"
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exit 2
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fi
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# 1 if 32-bit, 2 if 64-bit
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BITS=$(read_bytes 4 1)
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case $BITS in
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"01") BITS=32;;
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"02") BITS=64;;
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*)
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echo "Not 32- or 64- bit"
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exit 3
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;;
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esac
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# For `value_per_bits a b`, `a` if 32-bit and `b` if 64-bit
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function value_per_bits {
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RESULT=$(($1))
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if [ $BITS = 64 ]; then
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RESULT=$(($2))
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fi
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printf $RESULT
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}
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# Read an integer by its offset, differing depending on if 32- or 64-bit
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function read_integer_by_offset {
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OFFSET=$(value_per_bits $1 $2)
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printf $(( 0x$(swap_native_endian $(read_bytes $OFFSET $3)) ))
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}
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# 1 if little-endian, 2 if big-endian
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LITTLE_ENDIAN=$(read_bytes 5 1)
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case $LITTLE_ENDIAN in
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"01") LITTLE_ENDIAN=1;;
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"02") LITTLE_ENDIAN=0;;
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*)
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echo "Not little- or big- endian"
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exit 4
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;;
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esac
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# While this script is written in big-endian, we need to work with the file in
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# its declared endian. This function swaps from big to native, or vice versa,
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# as necessary.
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function swap_native_endian {
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BYTES="$1"
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if [ "$BYTES" = "" ]; then
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read BYTES
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fi
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if [ $LITTLE_ENDIAN -eq 0 ]; then
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printf $BYTES
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return
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fi
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while [ ! $BYTES = "" ]; do
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printf $(printf $BYTES | tail -c2)
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BYTES=$(printf $BYTES | head -c-2)
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done
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}
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ELF_VERSION=$(read_bytes 6 1)
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if [ ! $ELF_VERSION = "01" ]; then
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echo "Unknown ELF Version ($ELF_VERSION)"
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exit 5
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fi
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ELF_VERSION_2=$(read_bytes $((0x14)) 4)
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if [ ! $ELF_VERSION_2 = $(swap_native_endian 00000001) ]; then
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echo "Unknown secondary ELF Version ($ELF_VERSION_2)"
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exit 6
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fi
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# Find where the program headers are
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PROGRAM_HEADERS_OFFSET=$(read_integer_by_offset 0x1c 0x20 $(value_per_bits 4 8))
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PROGRAM_HEADER_SIZE=$(value_per_bits 0x20 0x38)
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DECLARED_PROGRAM_HEADER_SIZE=$(read_integer_by_offset 0x2a 0x36 2)
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if [ ! $PROGRAM_HEADER_SIZE -eq $DECLARED_PROGRAM_HEADER_SIZE ]; then
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echo "Unexpected size of a program header ($DECLARED_PROGRAM_HEADER_SIZE)"
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exit 7
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fi
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function program_header_start {
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printf $(($PROGRAM_HEADERS_OFFSET + ($1 * $PROGRAM_HEADER_SIZE)))
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}
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function read_program_header {
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read_bytes $(program_header_start $1) $PROGRAM_HEADER_SIZE
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}
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# Iterate over each program header
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PROGRAM_HEADERS=$(read_integer_by_offset 0x2c 0x38 2)
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NEXT_PROGRAM_HEADER=$(( $PROGRAM_HEADERS - 1 ))
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FOUND=0
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while [ $NEXT_PROGRAM_HEADER -ne -1 ]; do
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THIS_PROGRAM_HEADER=$NEXT_PROGRAM_HEADER
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NEXT_PROGRAM_HEADER=$(( $NEXT_PROGRAM_HEADER - 1 ))
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PROGRAM_HEADER=$(read_program_header $THIS_PROGRAM_HEADER)
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HEADER_TYPE=$(printf $PROGRAM_HEADER | head -c8)
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# `PT_GNU_STACK`
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# https://github.com/torvalds/linux/blob/c2f2b01b74be8b40a2173372bcd770723f87e7b2/include/uapi/linux/elf.h#L41
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if [ ! "$(swap_native_endian $HEADER_TYPE)" = "6474e551" ]; then
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continue
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fi
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FOUND=1
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MEMSZ_OFFSET=$(( $(program_header_start $THIS_PROGRAM_HEADER) + $(value_per_bits 0x14 0x28) ))
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MEMSZ_LEN=$(value_per_bits 4 8)
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# `MEMSZ_OFFSET MEMSZ_OFFSET` as we've already derived it depending on the amount of bits
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MEMSZ=$(read_integer_by_offset $MEMSZ_OFFSET $MEMSZ_OFFSET $MEMSZ_LEN)
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DESIRED_STACK_SIZE=$((8 * 1024 * 1024))
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# Only run if the inherent value is _smaller_
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if [ $MEMSZ -lt $DESIRED_STACK_SIZE ]; then
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# `2 *`, as this is its length in hexadecimal
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HEX_MEMSZ=$(printf %."$((2 * $MEMSZ_LEN))"x $DESIRED_STACK_SIZE)
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write_bytes $MEMSZ_OFFSET $(swap_native_endian $HEX_MEMSZ)
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fi
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done
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if [ $FOUND -eq 0 ]; then
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echo "\`PT_GNU_STACK\` program header not found"
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exit 8
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fi
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echo "All instances of \`PT_GNU_STACK\` patched to be at least 8 MB"
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exit 0
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