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SubjectRe: doublefault debugging (was Re: Linux v2.5.62 --- spontaneous reboots)
Date
Linus Torvalds <torvalds@transmeta.com> wrote:
> A sorted list of bad stack users (more than 256 bytes) in my default build
> follows. Anybody can create their own with something like
>
> objdump -d linux/vmlinux |
> grep 'sub.*$0x...,.*esp' |
> awk '{ print $9,$1 }' |
> sort > bigstack
>
> and a script to look up the addresses.
>
> Yeah, and this assumes we don't have alloca() users or other dynamic
> stack allocators (non-constant-size automatic arrays). I hope we don't
> have that kind of crap anywhere..

We do.

kernel.stack identifies big offenders, dynamic stacks and tells you
which procedure is at fault. This must be at least the fifth time I
have published this script.

#!/bin/bash
#
# Run a compiled ix86 kernel and print large local stack usage.
#
# />:/{s/[<>:]*//g; h; } On lines that contain '>:' (headings like
# c0100000 <_stext>:), remove <, > and : and hold the line. Identifies
# the procedure and its start address.
#
# /subl\?.*\$0x[^,][^,][^,].*,%esp/{ Select lines containing
# subl\?...0x...,%esp but only if there are at least 3 digits between 0x and
# ,%esp. These are local stacks of at least 0x100 bytes.
#
# s/.*$0x\([^,]*\).*/\1/; Extract just the stack adjustment
# /^[89a-f].......$/d; Ignore lines with 8 digit offsets that are
# negative. Some compilers adjust the stack on exit, seems to be related
# to goto statements
# G; Append the held line (procedure and start address).
# s/\(.*\)\n.* \(.*\)/\1 \2/; Remove the newline and procedure start
# address. Leaves just stack size and procedure name.
# p; }; Print stack size and procedure name.
#
# /subl\?.*%.*,%esp/{ Selects adjustment of %esp by register, dynamic
# arrays on stack.
# G; Append the held line (procedure and start address).
# s/\(.*\)\n\(.*\)/Dynamic \2 \1/; Reformat to "Dynamic", procedure
# start address, procedure name and the instruction that adjusts the
# stack, including its offset within the proc.
# p; }; Print the dynamic line.
#
#
# Leading spaces in the sed string are required.
#
objdump --disassemble "$@" | \
sed -ne '/>:/{s/[<>:]*//g; h; }
/subl\?.*\$0x[^,][^,][^,].*,%esp/{
s/.*\$0x\([^,]*\).*/\1/; /^[89a-f].......$/d; G; s/\(.*\)\n.* \(.*\)/\1 \2/; p; };
/subl\?.*%.*,%esp/{ G; s/\(.*\)\n\(.*\)/Dynamic \2 \1/; p; }; ' | \
sort
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