[PATCH v2] bloat-o-meter: avoid double counting

[Denys Vlasenko]

Applied, thanks

On Mon, Mar 8, 2021 at 8:31 PM Ron Yorston <rmy at pobox.com> wrote:
>
> Disable 'echo' in the default config, run 'make baseline', then
> re-enable 'echo' and run 'make bloatcheck':
>
> function                                             old     new   delta
> .rodata                                           182521  182622    +101
> packed_usage                                       33714   33792     +78
> applet_main                                         3168    3176      +8
> applet_names                                        2730    2735      +5
> applet_suid                                           99     100      +1
> applet_install_loc                                   198     199      +1
> ------------------------------------------------------------------------------
> (add/remove: 0/0 grow/shrink: 6/0 up/down: 194/0)             Total: 194 bytes
>    text    data     bss     dec     hex filename
>  955052    4195    1808  961055   eaa1f busybox_old
>  955153    4195    1808  961156   eaa84 busybox_unstripped
>
> The Total bytes value doesn't equal the change in the size of the
> binary.  The packed_usage and applet_* items are in .rodata and
> are counted twice.  With this modified bloat-o-meter the size of
> named items is deducted from .rodata:
>
> function                                             old     new   delta
> packed_usage                                       33714   33792     +78
> applet_main                                         3168    3176      +8
> .rodata                                           105105  105113      +8
> applet_names                                        2730    2735      +5
> applet_suid                                           99     100      +1
> applet_install_loc                                   198     199      +1
> ------------------------------------------------------------------------------
> (add/remove: 0/0 grow/shrink: 6/0 up/down: 101/0)             Total: 101 bytes
>    text    data     bss     dec     hex filename
>  955052    4195    1808  961055   eaa1f busybox_old
>  955153    4195    1808  961156   eaa84 busybox_unstripped
>
> v2: Sections numbered less than 10 were always being omitted from
>     consideration because splitting "[ 1] .interp" leaves "1]" in
>     x[1] where the section name is expected.  This wasn't a problem
>     for .rodata (numbered 15 in my testing) but let's fix it anyway.
>
> Signed-off-by: Ron Yorston <rmy at pobox.com>
> ---
>  scripts/bloat-o-meter | 21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/scripts/bloat-o-meter b/scripts/bloat-o-meter
> index cb861b8e9..b4a1d2811 100755
> --- a/scripts/bloat-o-meter
> +++ b/scripts/bloat-o-meter
> @@ -43,7 +43,15 @@ if f1 is None or f2 is None:
>
>  sym_args = " ".join(sys.argv[3 + flag_timing + dashes:])
>  def getsizes(file):
> -    sym, alias, lut = {}, {}, {}
> +    sym, alias, lut, section = {}, {}, {}, {}
> +    for l in os.popen("readelf -W -S " + file).readlines():
> +        x = l.replace("[ ", "[", 1).split()
> +        if len(x)<6: continue
> +        # Should take these into account too!
> +        #if x[1] not in [".text", ".rodata", ".symtab", ".strtab"]: continue
> +        if x[1] not in [".rodata"]: continue
> +        sym[x[1]] = {"addr" : int(x[3], 16), "size" : int(x[5], 16)}
> +        section[x[0][1:-1]] = {"name" : x[1]}
>      for l in os.popen("readelf -W -s %s %s" % (sym_args, file)).readlines():
>          l = l.strip()
>          if not (len(l) and l[0].isdigit() and len(l.split()) == 8):
> @@ -59,6 +67,10 @@ def getsizes(file):
>          else:
>              sym[name] = {"addr" : value, "size":  size}
>              lut[(value, size)] = 0
> +            # If this item is in a known section deduct its size from
> +            # the size of the section
> +            if ndx in section:
> +                sym[section[ndx]["name"]]["size"] -= size
>      for addr, sz in iter(alias.keys()):
>          # If the non-GLOBAL sym has an implementation elsewhere then
>          # it's an alias, disregard it.
> @@ -66,13 +78,6 @@ def getsizes(file):
>              # If this non-GLOBAL sym does not have an implementation at
>              # another address, then treat it as a normal symbol.
>              sym[alias[(addr, sz)]["name"]] = {"addr" : addr, "size": sz}
> -    for l in os.popen("readelf -W -S " + file).readlines():
> -        x = l.split()
> -        if len(x)<6: continue
> -        # Should take these into account too!
> -        #if x[1] not in [".text", ".rodata", ".symtab", ".strtab"]: continue
> -        if x[1] not in [".rodata"]: continue
> -        sym[x[1]] = {"addr" : int(x[3], 16), "size" : int(x[5], 16)}
>      return sym
>
>  if flag_timing:
> --
> 2.29.2
>
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