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SubjectRe: how much stack space can I use
Date
On Sat, 23 Oct 1999 17:36:12 +0200, 
Manfred Spraul <manfreds@colorfullife.com> wrote:
>How much stack space can I use without causing a stack overflow? None of
>these functions are recursive, and they don't call any subfunctions
>which need more than a few bytes stack space.

Anybody looking at stack usage might find this script useful, it can
also be found in ftp://ftp.ocs.com.au/pub/kernel.stack.gz. It taks a
while to run, mainly because objdump --disassemble of everything takes
a while. Some interesting results from 2.2.23 :-

7c4 ncr53c8xx_detect
824 dvd_read_disckey
824 dvd_read_manufact
914 mmc_ioctl

mmc_ioctl is worrying. That code contains a switch statement with
allocations on individual case statements. gcc version egcs-2.91.66
19990314/Linux (egcs-1.1.2 release) has consolidated all the
allocations into a single large allocation at the start of the routine.

#!/bin/bash
#
# Run a compiled ix86 kernel and print large local stack usage.
#
# Before running this script, cd /usr/src/linux or wherever you keep
# your compiled kernel and modules.
#
# />:/{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 vmlinux modules/*.o | \
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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