1. 28 Aug, 2015 1 commit
    • 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