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faddr2line: Fix overlapping text section failures, the sequel

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If a function lives in a section other than .text, but .text also exists
in the object, faddr2line may wrongly assume .text.  This can result in
comically wrong output.  For example:

  $ scripts/faddr2line vmlinux.o enter_from_user_mode+0x1c
  enter_from_user_mode+0x1c/0x30:
  find_next_bit at /home/jpoimboe/git/linux/./include/linux/find.h:40
  (inlined by) perf_clear_dirty_counters at /home/jpoimboe/git/linux/arch/x86/events/core.c:2504

Fix it by passing the section name to addr2line, unless the object file
is vmlinux, in which case the symbol table uses absolute addresses.

Fixes: 1d1a0e7c51 ("scripts/faddr2line: Fix overlapping text section failures")
Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/7d25bc1408bd3a750ac26e60d2f2815a5f4a8363.1654130536.git.jpoimboe@kernel.org
This commit is contained in:
Josh Poimboeuf 2022-06-01 17:42:22 -07:00
parent c2f75a43f5
commit dcea997bee
1 changed files with 34 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

45
scripts/faddr2line
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@ -95,17 +95,25 @@ __faddr2line() {
local print_warnings=$4
local sym_name=${func_addr%+*}
local offset=${func_addr#*+}
offset=${offset%/*}
local func_offset=${func_addr#*+}
func_offset=${func_offset%/*}
local user_size=
local file_type
local is_vmlinux=0
[[ $func_addr =~ "/" ]] && user_size=${func_addr#*/}
if [[ -z $sym_name ]] || [[ -z $offset ]] || [[ $sym_name = $func_addr ]]; then
if [[ -z $sym_name ]] || [[ -z $func_offset ]] || [[ $sym_name = $func_addr ]]; then
warn "bad func+offset $func_addr"
DONE=1
return
fi
# vmlinux uses absolute addresses in the section table rather than
# section offsets.
local file_type=$(${READELF} --file-header $objfile |
${AWK} '$1 == "Type:" { print $2; exit }')
[[ $file_type = "EXEC" ]] && is_vmlinux=1
# Go through each of the object's symbols which match the func name.
# In rare cases there might be duplicates, in which case we print all
# matches.
@ -114,9 +122,11 @@ __faddr2line() {
local sym_addr=0x${fields[1]}
local sym_elf_size=${fields[2]}
local sym_sec=${fields[6]}
local sec_size
local sec_name
# Get the section size:
local sec_size=$(${READELF} --section-headers --wide $objfile |
sec_size=$(${READELF} --section-headers --wide $objfile |
sed 's/\[ /\[/' |
${AWK} -v sec=$sym_sec '$1 == "[" sec "]" { print "0x" $6; exit }')
@ -126,6 +136,17 @@ __faddr2line() {
return
fi
# Get the section name:
sec_name=$(${READELF} --section-headers --wide $objfile |
sed 's/\[ /\[/' |
${AWK} -v sec=$sym_sec '$1 == "[" sec "]" { print $2; exit }')
if [[ -z $sec_name ]]; then
warn "bad section name: section: $sym_sec"
DONE=1
return
fi
# Calculate the symbol size.
#
# Unfortunately we can't use the ELF size, because kallsyms
@ -174,10 +195,10 @@ __faddr2line() {
sym_size=0x$(printf %x $sym_size)
# Calculate the section address from user-supplied offset:
local addr=$(($sym_addr + $offset))
# Calculate the address from user-supplied offset:
local addr=$(($sym_addr + $func_offset))
if [[ -z $addr ]] || [[ $addr = 0 ]]; then
warn "bad address: $sym_addr + $offset"
warn "bad address: $sym_addr + $func_offset"
DONE=1
return
fi
@ -191,9 +212,9 @@ __faddr2line() {
fi
# Make sure the provided offset is within the symbol's range:
if [[ $offset -gt $sym_size ]]; then
if [[ $func_offset -gt $sym_size ]]; then
[[ $print_warnings = 1 ]] &&
echo "skipping $sym_name address at $addr due to size mismatch ($offset > $sym_size)"
echo "skipping $sym_name address at $addr due to size mismatch ($func_offset > $sym_size)"
continue
fi
@ -202,11 +223,13 @@ __faddr2line() {
[[ $FIRST = 0 ]] && echo
FIRST=0
echo "$sym_name+$offset/$sym_size:"
echo "$sym_name+$func_offset/$sym_size:"
# Pass section address to addr2line and strip absolute paths
# from the output:
local output=$(${ADDR2LINE} -fpie $objfile $addr | sed "s; $dir_prefix\(\./\)*; ;")
local args="--functions --pretty-print --inlines --exe=$objfile"
[[ $is_vmlinux = 0 ]] && args="$args --section=$sec_name"
local output=$(${ADDR2LINE} $args $addr | sed "s; $dir_prefix\(\./\)*; ;")
[[ -z $output ]] && continue
# Default output (non --list):