From 066f1f06c1fd694d0c4b92311d4c6e7bf2a645a1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophile=20Bastian?= <contact@tobast.fr>
Date: Wed, 9 May 2018 15:26:27 +0200
Subject: [PATCH] Add compare_sizes: compare eh_elf vs eh_frame size

---
 compare_sizes.py | 174 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 174 insertions(+)
 create mode 100755 compare_sizes.py

diff --git a/compare_sizes.py b/compare_sizes.py
new file mode 100755
index 0000000..0b4f76c
--- /dev/null
+++ b/compare_sizes.py
@@ -0,0 +1,174 @@
+#!/usr/bin/env python3
+
+""" Compare the sizes of the .eh_frame section in the original binary and of
+the .text in the generated .eh_elf.so. """
+
+
+import argparse
+import os
+import subprocess
+from collections import namedtuple
+
+from generate_eh_elf import elf_so_deps
+
+
+''' An ELF object, including the path to the ELF itself, and the path to its
+matching eh_elf '''
+ElfObject = namedtuple('ElfObject', 'elf eh_elf')
+
+
+def format_size(size):
+    ''' Format a size to a human-readable string '''
+
+    units = ['B', 'KiB', 'MiB', 'GiB']  # We'll never go over that
+    cur_unit = 0
+    while cur_unit < len(units) and size >= 1024:
+        size /= 1024
+        cur_unit += 1
+
+    return '{:.1f} {}'.format(size, units[cur_unit])
+
+
+def section_size(elf_loc, section_name):
+    ''' Find the size of a given section in some elf file '''
+
+    if not os.path.isfile(elf_loc):
+        raise FileNotFoundError
+
+    try:
+        objdump_out = subprocess.check_output(['objdump', '-h', elf_loc]) \
+            .decode('utf-8')
+    except subprocess.CalledProcessError as exn:
+        raise Exception(("Cannot obtain section {} size for {}: objdump "
+                         "terminated with exit code {}.").format(
+                             section_name, elf_loc))
+
+    for line in objdump_out.split('\n'):
+        line = line.strip()
+        if not line or not ('0' <= line[0] <= '9'):  # not a section line
+            continue
+
+        spl = line.split()
+        if spl[1] != section_name:
+            continue
+
+        return int(spl[2], 0x10)
+    raise Exception("No such section {} in {}".format(section_name, elf_loc))
+
+
+def matching_eh_elf(eh_locs, elf_name):
+    ''' Get the .eh_elf.so file matching elf_name in the list of directories
+    eh_locs.
+
+    Raises FileNotFoundError if there is no such file '''
+
+    basename = os.path.basename(elf_name) + '.eh_elf.so'
+    for prefix in eh_locs:
+        eh_elf_path = os.path.join(prefix, basename)
+        if os.path.isfile(eh_elf_path):
+            return eh_elf_path
+    raise FileNotFoundError("No such file {}".format(basename))
+
+
+def objects_list(args):
+    ''' Get the list of elf objects to process '''
+
+    out = []
+
+    if args.deps:
+        objects = set(args.object)
+        for obj in args.object:
+            objects = objects.union(elf_so_deps(obj))
+        objects = list(objects)
+        objects.sort()
+    else:
+        objects = args.object
+
+    for obj in objects:
+        out.append(ElfObject(obj, matching_eh_elf(args.eh_elfs, obj)))
+
+    return out
+
+
+def process_args():
+    ''' Process `sys.argv` arguments '''
+
+    parser = argparse.ArgumentParser(
+        description=("Compare the sizes of the .eh_frame section in the "
+                     "original binary and of the .text in the generated "
+                     ".eh_elf.so."),
+    )
+
+    parser.add_argument('--deps', action='store_true',
+                        help=("Also compare the shared objects this object "
+                              "depends on"))
+    parser.add_argument('--eh-elfs', required=True, action='append',
+                        help=("Indicate the directory in which eh_elfs are "
+                              "located"))
+    parser.add_argument('object', nargs='+',
+                        help="The ELF object(s) to process")
+    return parser.parse_args()
+
+
+def main():
+    args = process_args()
+    objs = objects_list(args)
+
+    section_size(objs[0].elf, '.eh_frame')
+
+    col_names = [
+        'Shared object',
+        'Orig eh_frame',
+        'Gen eh_elf',
+        'Growth',
+    ]
+
+    col_len = []
+
+    displayed_name_filter = lambda x: os.path.basename(x.elf)
+    max_elf_name = max(map(lambda x: len(displayed_name_filter(x)), objs))
+    col_len.append(max(max_elf_name, len(col_names[0])))
+    for i in range(1, 4):
+        col_len.append(len(col_names[i]) + 1)
+    col_len = list(map(str, col_len))
+
+    header_format = ('{:<' + col_len[0] + '}   '
+                     '{:<' + col_len[1] + '}   '
+                     '{:<' + col_len[2] + '}   '
+                     '{:<' + col_len[3] + '}')
+    row_format = ('{:>' + col_len[0] + '}   '
+                  '{:>' + col_len[1] + '}   '
+                  '{:>' + col_len[2] + '}   '
+                  '{:>' + col_len[3] + '}')
+    print(header_format.format(
+        col_names[0],
+        col_names[1],
+        col_names[2],
+        col_names[3],
+    ))
+
+    total_eh_frame_size = 0
+    total_eh_elf_size = 0
+
+    for obj in objs:
+        eh_frame_size = section_size(obj.elf, '.eh_frame')
+        eh_elf_size = section_size(obj.eh_elf, '.text')
+
+        total_eh_frame_size += eh_frame_size
+        total_eh_elf_size += eh_elf_size
+
+        print(row_format.format(
+            displayed_name_filter(obj),
+            format_size(eh_frame_size),
+            format_size(eh_elf_size),
+            '{:.2f}'.format(eh_elf_size / eh_frame_size)))
+
+    print(row_format.format(
+        'Total',
+        format_size(total_eh_frame_size),
+        format_size(total_eh_elf_size),
+        '{:.2f}'.format(total_eh_elf_size / total_eh_frame_size)))
+
+
+if __name__ == '__main__':
+    main()