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![Randy Dunlap](/assets/img/avatar_default.png)
Fix typo ("and" should be "an") in an error message. Link: https://lkml.kernel.org/r/20210727002943.29774-1-rdunlap@infradead.org Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
147 lines
4.9 KiB
Bash
Executable file
147 lines
4.9 KiB
Bash
Executable file
#! /bin/bash
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# SPDX-License-Identifier: GPL-2.0
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# (c) 2015, Quentin Casasnovas <quentin.casasnovas@oracle.com>
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obj=$1
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file ${obj} | grep -q ELF || (echo "${obj} is not an ELF file." 1>&2 ; exit 0)
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# Bail out early if there isn't an __ex_table section in this object file.
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objdump -hj __ex_table ${obj} 2> /dev/null > /dev/null
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[ $? -ne 0 ] && exit 0
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white_list=.text,.fixup
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suspicious_relocs=$(objdump -rj __ex_table ${obj} | tail -n +6 |
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grep -v $(eval echo -e{${white_list}}) | awk '{print $3}')
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# No suspicious relocs in __ex_table, jobs a good'un
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[ -z "${suspicious_relocs}" ] && exit 0
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# After this point, something is seriously wrong since we just found out we
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# have some relocations in __ex_table which point to sections which aren't
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# white listed. If you're adding a new section in the Linux kernel, and
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# you're expecting this section to contain code which can fault (i.e. the
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# __ex_table relocation to your new section is expected), simply add your
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# new section to the white_list variable above. If not, you're probably
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# doing something wrong and the rest of this code is just trying to print
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# you more information about it.
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function find_section_offset_from_symbol()
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{
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eval $(objdump -t ${obj} | grep ${1} | sed 's/\([0-9a-f]\+\) .\{7\} \([^ \t]\+\).*/section="\2"; section_offset="0x\1" /')
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# addr2line takes addresses in hexadecimal...
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section_offset=$(printf "0x%016x" $(( ${section_offset} + $2 )) )
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}
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function find_symbol_and_offset_from_reloc()
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{
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# Extract symbol and offset from the objdump output
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eval $(echo $reloc | sed 's/\([^+]\+\)+\?\(0x[0-9a-f]\+\)\?/symbol="\1"; symbol_offset="\2"/')
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# When the relocation points to the begining of a symbol or section, it
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# won't print the offset since it is zero.
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if [ -z "${symbol_offset}" ]; then
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symbol_offset=0x0
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fi
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}
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function find_alt_replacement_target()
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{
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# The target of the .altinstr_replacement is the relocation just before
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# the .altinstr_replacement one.
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eval $(objdump -rj .altinstructions ${obj} | grep -B1 "${section}+${section_offset}" | head -n1 | awk '{print $3}' |
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sed 's/\([^+]\+\)+\(0x[0-9a-f]\+\)/alt_target_section="\1"; alt_target_offset="\2"/')
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}
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function handle_alt_replacement_reloc()
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{
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# This will define alt_target_section and alt_target_section_offset
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find_alt_replacement_target ${section} ${section_offset}
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echo "Error: found a reference to .altinstr_replacement in __ex_table:"
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addr2line -fip -j ${alt_target_section} -e ${obj} ${alt_target_offset} | awk '{print "\t" $0}'
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error=true
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}
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function is_executable_section()
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{
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objdump -hwj ${section} ${obj} | grep -q CODE
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return $?
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}
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function handle_suspicious_generic_reloc()
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{
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if is_executable_section ${section}; then
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# We've got a relocation to a non white listed _executable_
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# section, print a warning so the developper adds the section to
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# the white list or fix his code. We try to pretty-print the file
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# and line number where that relocation was added.
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echo "Warning: found a reference to section \"${section}\" in __ex_table:"
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addr2line -fip -j ${section} -e ${obj} ${section_offset} | awk '{print "\t" $0}'
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else
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# Something is definitively wrong here since we've got a relocation
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# to a non-executable section, there's no way this would ever be
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# running in the kernel.
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echo "Error: found a reference to non-executable section \"${section}\" in __ex_table at offset ${section_offset}"
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error=true
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fi
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}
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function handle_suspicious_reloc()
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{
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case "${section}" in
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".altinstr_replacement")
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handle_alt_replacement_reloc ${section} ${section_offset}
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;;
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*)
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handle_suspicious_generic_reloc ${section} ${section_offset}
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;;
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esac
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}
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function diagnose()
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{
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for reloc in ${suspicious_relocs}; do
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# Let's find out where the target of the relocation in __ex_table
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# is, this will define ${symbol} and ${symbol_offset}
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find_symbol_and_offset_from_reloc ${reloc}
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# When there's a global symbol at the place of the relocation,
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# objdump will use it instead of giving us a section+offset, so
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# let's find out which section is this symbol in and the total
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# offset withing that section.
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find_section_offset_from_symbol ${symbol} ${symbol_offset}
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# In this case objdump was presenting us with a reloc to a symbol
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# rather than a section. Now that we've got the actual section,
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# we can skip it if it's in the white_list.
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if [ -z "$( echo $section | grep -v $(eval echo -e{${white_list}}))" ]; then
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continue;
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fi
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# Will either print a warning if the relocation happens to be in a
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# section we do not know but has executable bit set, or error out.
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handle_suspicious_reloc
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done
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}
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function check_debug_info() {
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objdump -hj .debug_info ${obj} 2> /dev/null > /dev/null ||
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echo -e "${obj} does not contain debug information, the addr2line output will be limited.\n" \
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"Recompile ${obj} with CONFIG_DEBUG_INFO to get a more useful output."
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}
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check_debug_info
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diagnose
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if [ "${error}" ]; then
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exit 1
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fi
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exit 0
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