--- /dev/null
+#! /bin/bash
+# (c) 2015, Quentin Casasnovas <quentin.casasnovas@oracle.com>
+
+obj=$1
+
+file ${obj} | grep -q ELF || (echo "${obj} is not and ELF file." 1>&2 ; exit 0)
+
+# Bail out early if there isn't an __ex_table section in this object file.
+objdump -hj __ex_table ${obj} 2> /dev/null > /dev/null
+[ $? -ne 0 ] && exit 0
+
+white_list=.text,.fixup
+
+suspicious_relocs=$(objdump -rj __ex_table ${obj} | tail -n +6 |
+ grep -v $(eval echo -e{${white_list}}) | awk '{print $3}')
+
+# No suspicious relocs in __ex_table, jobs a good'un
+[ -z "${suspicious_relocs}" ] && exit 0
+
+
+# After this point, something is seriously wrong since we just found out we
+# have some relocations in __ex_table which point to sections which aren't
+# white listed. If you're adding a new section in the Linux kernel, and
+# you're expecting this section to contain code which can fault (i.e. the
+# __ex_table relocation to your new section is expected), simply add your
+# new section to the white_list variable above. If not, you're probably
+# doing something wrong and the rest of this code is just trying to print
+# you more information about it.
+
+function find_section_offset_from_symbol()
+{
+ eval $(objdump -t ${obj} | grep ${1} | sed 's/\([0-9a-f]\+\) .\{7\} \([^ \t]\+\).*/section="\2"; section_offset="0x\1" /')
+
+ # addr2line takes addresses in hexadecimal...
+ section_offset=$(printf "0x%016x" $(( ${section_offset} + $2 )) )
+}
+
+function find_symbol_and_offset_from_reloc()
+{
+ # Extract symbol and offset from the objdump output
+ eval $(echo $reloc | sed 's/\([^+]\+\)+\?\(0x[0-9a-f]\+\)\?/symbol="\1"; symbol_offset="\2"/')
+
+ # When the relocation points to the begining of a symbol or section, it
+ # won't print the offset since it is zero.
+ if [ -z "${symbol_offset}" ]; then
+ symbol_offset=0x0
+ fi
+}
+
+function find_alt_replacement_target()
+{
+ # The target of the .altinstr_replacement is the relocation just before
+ # the .altinstr_replacement one.
+ eval $(objdump -rj .altinstructions ${obj} | grep -B1 "${section}+${section_offset}" | head -n1 | awk '{print $3}' |
+ sed 's/\([^+]\+\)+\(0x[0-9a-f]\+\)/alt_target_section="\1"; alt_target_offset="\2"/')
+}
+
+function handle_alt_replacement_reloc()
+{
+ # This will define alt_target_section and alt_target_section_offset
+ find_alt_replacement_target ${section} ${section_offset}
+
+ echo "Error: found a reference to .altinstr_replacement in __ex_table:"
+ addr2line -fip -j ${alt_target_section} -e ${obj} ${alt_target_offset} | awk '{print "\t" $0}'
+
+ error=true
+}
+
+function is_executable_section()
+{
+ objdump -hwj ${section} ${obj} | grep -q CODE
+ return $?
+}
+
+function handle_suspicious_generic_reloc()
+{
+ if is_executable_section ${section}; then
+ # We've got a relocation to a non white listed _executable_
+ # section, print a warning so the developper adds the section to
+ # the white list or fix his code. We try to pretty-print the file
+ # and line number where that relocation was added.
+ echo "Warning: found a reference to section \"${section}\" in __ex_table:"
+ addr2line -fip -j ${section} -e ${obj} ${section_offset} | awk '{print "\t" $0}'
+ else
+ # Something is definitively wrong here since we've got a relocation
+ # to a non-executable section, there's no way this would ever be
+ # running in the kernel.
+ echo "Error: found a reference to non-executable section \"${section}\" in __ex_table at offset ${section_offset}"
+ error=true
+ fi
+}
+
+function handle_suspicious_reloc()
+{
+ case "${section}" in
+ ".altinstr_replacement")
+ handle_alt_replacement_reloc ${section} ${section_offset}
+ ;;
+ *)
+ handle_suspicious_generic_reloc ${section} ${section_offset}
+ ;;
+ esac
+}
+
+function diagnose()
+{
+
+ for reloc in ${suspicious_relocs}; do
+ # Let's find out where the target of the relocation in __ex_table
+ # is, this will define ${symbol} and ${symbol_offset}
+ find_symbol_and_offset_from_reloc ${reloc}
+
+ # When there's a global symbol at the place of the relocation,
+ # objdump will use it instead of giving us a section+offset, so
+ # let's find out which section is this symbol in and the total
+ # offset withing that section.
+ find_section_offset_from_symbol ${symbol} ${symbol_offset}
+
+ # In this case objdump was presenting us with a reloc to a symbol
+ # rather than a section. Now that we've got the actual section,
+ # we can skip it if it's in the white_list.
+ if [ -z "$( echo $section | grep -v $(eval echo -e{${white_list}}))" ]; then
+ continue;
+ fi
+
+ # Will either print a warning if the relocation happens to be in a
+ # section we do not know but has executable bit set, or error out.
+ handle_suspicious_reloc
+ done
+}
+
+function check_debug_info() {
+ objdump -hj .debug_info ${obj} 2> /dev/null > /dev/null ||
+ echo -e "${obj} does not contain debug information, the addr2line output will be limited.\n" \
+ "Recompile ${obj} with CONFIG_DEBUG_INFO to get a more useful output."
+}
+
+check_debug_info
+
+diagnose
+
+if [ "${error}" ]; then
+ exit 1
+fi
+
+exit 0
Code Review / kvmfornfv.git / blobdiff