• Rasmus Villemoes's avatar
    scripts: add stackusage script · 56d4a381
    Rasmus Villemoes authored
    The current checkstack.pl script has a few problems, stemming from the
    overly simplistic attempt at parsing objdump output with regular
    expressions: For example, on x86_64 it doesn't take the push
    instruction into account, making it consistently underestimate the
    real stack use, and it also doesn't capture stack pointer adjustments
    of exactly 128 bytes [1].
    
    Since newer gcc (>= 4.6) knows about -fstack-usage, we might as well
    take the information straight from the horse's mouth. This patch
    introduces scripts/stackusage, which is a simple wrapper for running
    make with KCFLAGS set to -fstack-usage. Example use is
    
    scripts/stackusage -o out.su -j8 lib/
    
    The script understands "-o foo" for writing to 'foo' and -h for a
    trivial help text; anything else is passed to make.
    
    Afterwards, we find all newly created .su files, massage them a
    little, sort by stack use and write the result to a single output
    file.
    
    Note that the function names printed by (at least) gcc 4.7 are
    sometimes useless. For example, the first three lines of out.su
    generated above are
    
    ./lib/decompress_bunzip2.c:155  get_next_block  448     static
    ./lib/decompress_unlzma.c:537   unlzma  336     static
    ./lib/vsprintf.c:616    8       304     static
    
    That function '8' is really the static symbol_string(), but it has
    been subject to 'interprocedural scalar replacement of aggregates', so
    its name in the object file is 'symbol_string.isra.8'. gcc 5.0 doesn't
    have this problem; it uses the full name as seen in the object file.
    
    [1] Since gcc encodes that by
    
    48 83 c4 80             add    $0xffffffffffffff80,%rsp
    
    and not
    
    48 81 ec 80 00 00 00    sub    $0x80,%rsp
    
    since -128 fits in an imm8.
    Signed-off-by: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
    Signed-off-by: default avatarMichal Marek <mmarek@suse.com>
    56d4a381