[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v3 7/7] livepatch-build: Strip all metadata symbols from hotpatch modules
Strip all unneeded metadata symbols from generated hotpatch modules. The metadata symbols are the symbols from metadata-like sections (e.g. '.livepatch.funcs') or livepatch hooks symbols (defined by a set of prefixes. E.g. 'livepatch_load_data_'). By default the create-diff-object does not create symbols in metadata sections. However, such symbols may be implicitly added by speciying extra entries in the sections manually (in a given patch). The symbols are not needed for the hotpatch modules and should be stripped to avoid symbol names collisions and to save hotpatch files space. Signed-off-by: Pawel Wieczorkiewicz <wipawel@xxxxxxxxx> Reviewed-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx> --- livepatch-build | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 53 insertions(+), 2 deletions(-) diff --git a/livepatch-build b/livepatch-build index 9e5bad3..e1715ea 100755 --- a/livepatch-build +++ b/livepatch-build @@ -112,10 +112,39 @@ function build_special() unset LIVEPATCH_CAPTURE_DIR } -strip_extra_symbols () +elf_section_exists () +{ + local ELF="$1" + local SEC="$2" + + objdump -h -j "$SEC" "$ELF" &> /dev/null +} + +# Extract a set of unique symbols for a specified section. +elf_extract_section_symbols () +{ + local -r ELF="$1" + local -r SEC="$2" + + if elf_section_exists "$ELF" "$SEC" + then + # Example objdump command output to be parsed: + # + # SYMBOL TABLE: + # 0000000000000000 l d .livepatch.funcs 0000000000000000 .livepatch.funcs + objdump -w -j "$SEC" -t "$ELF" | awk '/^SYMBOL TABLE:/ {seen = 1; next} seen && $NF {print $NF}' | sort -u + fi +} + +# Strip all metadata symbols belonging to a metadata section +# or whose name starts with a livepatch hook prefix. +# The function constructs the 'strip' utility command line +# and then invokes strip with that command line. +strip_metadata_symbols () { local -r FILE="$1" local -a STRIP_CMD_OPTS=() + local -a SYM_SECTIONS=(".livepatch.funcs") local -a SYM_PREFIX=("livepatch_load_data_" "livepatch_unload_data_" "livepatch_preapply_data_" @@ -124,13 +153,35 @@ strip_extra_symbols () "livepatch_prerevert_data_" "livepatch_revert_data_" "livepatch_postrevert_data_") + local -a SYMS=() + # Enable wildcard STRIP_CMD_OPTS+=("-w") + + # Strip all livepatch hooks metadata symbols for sym in "${SYM_PREFIX[@]}"; do STRIP_CMD_OPTS+=("-N") STRIP_CMD_OPTS+=("\"${sym}*\"") done + # Find all symbols from metadata sections + # Note: There may be name conflicts between global + # and local symbols belonging to the same section. + # For the '.livepatch.funcs' section it is not a + # problem. Think about it before adding more sections. + for sec in "${SYM_SECTIONS[@]}"; do + SYMS+=($(elf_extract_section_symbols "$FILE" "$sec")) + done + + # Strip metadata sections' symbols + if [ ${#SYMS[@]} -gt 0 ] + then + for sym in "${SYMS[@]}"; do + STRIP_CMD_OPTS+=("-N") + STRIP_CMD_OPTS+=("${sym}") + done + fi + strip "${STRIP_CMD_OPTS[@]}" "$FILE" } @@ -200,7 +251,7 @@ function create_patch() "${TOOLSDIR}"/prelink $debugopt output.o "${PATCHNAME}.livepatch" "$XENSYMS" &>> "${OUTPUT}/prelink.log" || die fi - strip_extra_symbols "${PATCHNAME}.livepatch" + strip_metadata_symbols "${PATCHNAME}.livepatch" objcopy --add-section .livepatch.depends=depends.bin "${PATCHNAME}.livepatch" objcopy --set-section-flags .livepatch.depends=alloc,readonly "${PATCHNAME}.livepatch" -- 2.16.5 Amazon Development Center Germany GmbH Krausenstr. 38 10117 Berlin Geschaeftsfuehrung: Christian Schlaeger, Ralf Herbrich Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B Sitz: Berlin Ust-ID: DE 289 237 879 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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