binman: Add a function to create a sample ELF file

It is useful to create an ELF file for testing purposes, with just the
right attributes used by the test. Add a function to handle this, along
with a test that it works correctly.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/binman/elf.py

@@ -5,11 +5,15 @@
 # Handle various things related to ELF images
 #
 
+from __future__ import print_function
+
 from collections import namedtuple, OrderedDict
 import command
 import os
 import re
+import shutil
 import struct
+import tempfile
 
 import tools
 
@@ -128,3 +132,96 @@ def LookupAndWriteSymbols(elf_fname, entry, section):
                       (msg, name, offset, value, len(value_bytes)))
             entry.data = (entry.data[:offset] + value_bytes +
                         entry.data[offset + sym.size:])
+
+def MakeElf(elf_fname, text, data):
+    """Make an elf file with the given data in a single section
+
+    The output file has a several section including '.text' and '.data',
+    containing the info provided in arguments.
+
+    Args:
+        elf_fname: Output filename
+        text: Text (code) to put in the file's .text section
+        data: Data to put in the file's .data section
+    """
+    outdir = tempfile.mkdtemp(prefix='binman.elf.')
+    s_file = os.path.join(outdir, 'elf.S')
+
+    # Spilt the text into two parts so that we can make the entry point two
+    # bytes after the start of the text section
+    text_bytes1 = ['\t.byte\t%#x' % tools.ToByte(byte) for byte in text[:2]]
+    text_bytes2 = ['\t.byte\t%#x' % tools.ToByte(byte) for byte in text[2:]]
+    data_bytes = ['\t.byte\t%#x' % tools.ToByte(byte) for byte in data]
+    with open(s_file, 'w') as fd:
+        print('''/* Auto-generated C program to produce an ELF file for testing */
+
+.section .text
+.code32
+.globl _start
+.type _start, @function
+%s
+_start:
+%s
+.ident "comment"
+
+.comm fred,8,4
+
+.section .empty
+.globl _empty
+_empty:
+.byte 1
+
+.globl ernie
+.data
+.type ernie, @object
+.size ernie, 4
+ernie:
+%s
+''' % ('\n'.join(text_bytes1), '\n'.join(text_bytes2), '\n'.join(data_bytes)),
+        file=fd)
+    lds_file = os.path.join(outdir, 'elf.lds')
+
+    # Use a linker script to set the alignment and text address.
+    with open(lds_file, 'w') as fd:
+        print('''/* Auto-generated linker script to produce an ELF file for testing */
+
+PHDRS
+{
+    text PT_LOAD ;
+    data PT_LOAD ;
+    empty PT_LOAD FLAGS ( 6 ) ;
+    note PT_NOTE ;
+}
+
+SECTIONS
+{
+    . = 0xfef20000;
+    ENTRY(_start)
+    .text . : SUBALIGN(0)
+    {
+        *(.text)
+    } :text
+    .data : {
+        *(.data)
+    } :data
+    _bss_start = .;
+    .empty : {
+        *(.empty)
+    } :empty
+    .note : {
+        *(.comment)
+    } :note
+    .bss _bss_start  (OVERLAY) : {
+        *(.bss)
+    }
+}
+''', file=fd)
+    # -static: Avoid requiring any shared libraries
+    # -nostdlib: Don't link with C library
+    # -Wl,--build-id=none: Don't generate a build ID, so that we just get the
+    #   text section at the start
+    # -m32: Build for 32-bit x86
+    # -T...: Specifies the link script, which sets the start address
+    stdout = command.Output('cc', '-static', '-nostdlib', '-Wl,--build-id=none',
+                            '-m32','-T', lds_file, '-o', elf_fname, s_file)
+    shutil.rmtree(outdir)

tools/binman/elf_test.py

@@ -5,9 +5,12 @@
 # Test for the elf module
 
 import os
+import shutil
 import sys
+import tempfile
 import unittest
 
+import command
 import elf
 import test_util
 import tools
@@ -136,6 +139,23 @@ class TestElf(unittest.TestCase):
         elf.debug = False
         self.assertTrue(len(stdout.getvalue()) > 0)
 
+    def testMakeElf(self):
+        """Test for the MakeElf function"""
+        outdir = tempfile.mkdtemp(prefix='elf.')
+        expected_text = b'1234'
+        expected_data = b'wxyz'
+        elf_fname = os.path.join(outdir, 'elf')
+        bin_fname = os.path.join(outdir, 'elf')
+
+        # Make an Elf file and then convert it to a fkat binary file. This
+        # should produce the original data.
+        elf.MakeElf(elf_fname, expected_text, expected_data)
+        stdout = command.Output('objcopy', '-O', 'binary', elf_fname, bin_fname)
+        with open(bin_fname, 'rb') as fd:
+            data = fd.read()
+        self.assertEqual(expected_text + expected_data, data)
+        shutil.rmtree(outdir)
+
 
 if __name__ == '__main__':
     unittest.main()