binman: Support accessing binman tables at run time

Binman construct images consisting of multiple binary files. These files
sometimes need to know (at run timme) where their peers are located. For
example, SPL may want to know where U-Boot is located in the image, so
that it can jump to U-Boot correctly on boot.

In general the positions where the binaries end up after binman has
finished packing them cannot be known at compile time. One reason for
this is that binman does not know the size of the binaries until
everything is compiled, linked and converted to binaries with objcopy.

To make this work, we add a feature to binman which checks each binary
for symbol names starting with '_binman'. These are then decoded to figure
out which entry and property they refer to. Then binman writes the value
of this symbol into the appropriate binary. With this, the symbol will
have the correct value at run time.

Macros are used to make this easier to use. As an example, this declares
a symbol that will access the 'u-boot-spl' entry to find the 'pos' value
(i.e. the position of SPL in the image):

   binman_sym_declare(unsigned long, u_boot_spl, pos);

This converts to a symbol called '_binman_u_boot_spl_prop_pos' in any
binary that includes it. Binman then updates the value in that binary,
ensuring that it can be accessed at runtime with:

   ulong u_boot_pos = binman_sym(ulong, u_boot_spl, pos);

This assigns the variable u_boot_pos to the position of SPL in the image.

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

include/binman_sym.h

@@ -0,0 +1,80 @@
+/*
+ * Symbol access for symbols set up by binman as part of the build.
+ *
+ * This allows C code to access the position of a particular part of the image
+ * assembled by binman.
+ *
+ * Copyright (c) 2017 Google, Inc
+ *
+ * SPDX-License-Identifier:     GPL-2.0+
+ */
+
+#ifndef __BINMAN_SYM_H
+#define __BINMAN_SYM_H
+
+#define BINMAN_SYM_MISSING	(-1UL)
+
+#ifdef CONFIG_BINMAN
+
+/**
+ * binman_symname() - Internal fnuction to get a binman symbol name
+ *
+ * @entry_name: Name of the entry to look for (e.g. 'u_boot_spl')
+ * @_prop_name: Property value to get from that entry (e.g. 'pos')
+ * @returns name of the symbol for that entry and property
+ */
+#define binman_symname(_entry_name, _prop_name) \
+	_binman_ ## _entry_name ## _prop_ ## _prop_name
+
+/**
+ * binman_sym_declare() - Declare a symbol that will be used at run-time
+ *
+ * @_type: Type f the symbol (e.g. unsigned long)
+ * @entry_name: Name of the entry to look for (e.g. 'u_boot_spl')
+ * @_prop_name: Property value to get from that entry (e.g. 'pos')
+ */
+#define binman_sym_declare(_type, _entry_name, _prop_name) \
+	_type binman_symname(_entry_name, _prop_name) \
+		__attribute__((aligned(4), unused, section(".binman_sym")))
+
+/**
+ * binman_sym_declare_optional() - Declare an optional symbol
+ *
+ * If this symbol cannot be provided by binman, an error will not be generated.
+ * Instead the image will be assigned the value BINMAN_SYM_MISSING.
+ *
+ * @_type: Type f the symbol (e.g. unsigned long)
+ * @entry_name: Name of the entry to look for (e.g. 'u_boot_spl')
+ * @_prop_name: Property value to get from that entry (e.g. 'pos')
+ */
+#define binman_sym_declare_optional(_type, _entry_name, _prop_name) \
+	_type binman_symname(_entry_name, _prop_name) \
+		__attribute__((aligned(4), weak, unused, \
+		section(".binman_sym")))
+
+/**
+ * binman_sym() - Access a previously declared symbol
+ *
+ * This is used to get the value of a symbol. E.g.:
+ *
+ *    ulong address = binman_sym(ulong, u_boot_spl, pos);
+ *
+ * @_type: Type f the symbol (e.g. unsigned long)
+ * @entry_name: Name of the entry to look for (e.g. 'u_boot_spl')
+ * @_prop_name: Property value to get from that entry (e.g. 'pos')
+ * @returns value of that property (filled in by binman)
+ */
+#define binman_sym(_type, _entry_name, _prop_name) \
+	(*(_type *)&binman_symname(_entry_name, _prop_name))
+
+#else /* !BINMAN */
+
+#define binman_sym_declare(_type, _entry_name, _prop_name)
+
+#define binman_sym_declare_optional(_type, _entry_name, _prop_name)
+
+#define binman_sym(_type, _entry_name, _prop_name) BINMAN_SYM_MISSING
+
+#endif /* BINMAN */
+
+#endif

tools/binman/binman.py

@@ -37,6 +37,7 @@ def RunTests(debug):
     import entry_test
     import fdt_test
     import ftest
+    import image_test
     import test
     import doctest
 
@@ -53,7 +54,8 @@ def RunTests(debug):
     # 'entry' module.
     suite = unittest.TestLoader().loadTestsFromTestCase(entry_test.TestEntry)
     suite.run(result)
-    for module in (ftest.TestFunctional, fdt_test.TestFdt, elf_test.TestElf):
+    for module in (ftest.TestFunctional, fdt_test.TestFdt, elf_test.TestElf,
+                   image_test.TestImage):
         suite = unittest.TestLoader().loadTestsFromTestCase(module)
         suite.run(result)
 

tools/binman/control.py

@@ -90,8 +90,7 @@ def Binman(options, args):
 
     try:
         tout.Init(options.verbosity)
-        if options.debug:
-            elf.debug = True
+        elf.debug = options.debug
         try:
             tools.SetInputDirs(options.indir)
             tools.PrepareOutputDir(options.outdir, options.preserve)
@@ -112,6 +111,7 @@ def Binman(options, args):
                 image.CheckSize()
                 image.CheckEntries()
                 image.ProcessEntryContents()
+                image.WriteSymbols()
                 image.BuildImage()
         finally:
             tools.FinaliseOutputDir()

tools/binman/elf.py

@@ -19,9 +19,6 @@ debug = False
 
 Symbol = namedtuple('Symbol', ['section', 'address', 'size', 'weak'])
 
-# Used for tests which don't have an ELF file to read
-ignore_missing_files = False
-
 
 def GetSymbols(fname, patterns):
     """Get the symbols from an ELF file
@@ -78,3 +75,55 @@ def GetSymbolAddress(fname, sym_name):
     if not sym:
         return None
     return sym.address
+
+def LookupAndWriteSymbols(elf_fname, entry, image):
+    """Replace all symbols in an entry with their correct values
+
+    The entry contents is updated so that values for referenced symbols will be
+    visible at run time. This is done by finding out the symbols positions in
+    the entry (using the ELF file) and replacing them with values from binman's
+    data structures.
+
+    Args:
+        elf_fname: Filename of ELF image containing the symbol information for
+            entry
+        entry: Entry to process
+        image: Image which can be used to lookup symbol values
+    """
+    fname = tools.GetInputFilename(elf_fname)
+    syms = GetSymbols(fname, ['image', 'binman'])
+    if not syms:
+        return
+    base = syms.get('__image_copy_start')
+    if not base:
+        return
+    for name, sym in syms.iteritems():
+        if name.startswith('_binman'):
+            msg = ("Image '%s': Symbol '%s'\n   in entry '%s'" %
+                   (image.GetPath(), name, entry.GetPath()))
+            offset = sym.address - base.address
+            if offset < 0 or offset + sym.size > entry.contents_size:
+                raise ValueError('%s has offset %x (size %x) but the contents '
+                                 'size is %x' % (entry.GetPath(), offset,
+                                                 sym.size, entry.contents_size))
+            if sym.size == 4:
+                pack_string = '<I'
+            elif sym.size == 8:
+                pack_string = '<Q'
+            else:
+                raise ValueError('%s has size %d: only 4 and 8 are supported' %
+                                 (msg, sym.size))
+
+            # Look up the symbol in our entry tables.
+            value = image.LookupSymbol(name, sym.weak, msg)
+            if value is not None:
+                value += base.address
+            else:
+                value = -1
+                pack_string = pack_string.lower()
+            value_bytes = struct.pack(pack_string, value)
+            if debug:
+                print('%s:\n   insert %s, offset %x, value %x, length %d' %
+                      (msg, name, offset, value, len(value_bytes)))
+            entry.data = (entry.data[:offset] + value_bytes +
+                        entry.data[offset + sym.size:])

tools/binman/elf_test.py

@@ -6,21 +6,60 @@
 #
 # Test for the elf module
 
+from contextlib import contextmanager
 import os
 import sys
 import unittest
 
+try:
+  from StringIO import StringIO
+except ImportError:
+  from io import StringIO
+
 import elf
 
 binman_dir = os.path.dirname(os.path.realpath(sys.argv[0]))
-fname = os.path.join(binman_dir, 'test', 'u_boot_ucode_ptr')
+
+# Use this to suppress stdout/stderr output:
+# with capture_sys_output() as (stdout, stderr)
+#   ...do something...
+@contextmanager
+def capture_sys_output():
+  capture_out, capture_err = StringIO(), StringIO()
+  old_out, old_err = sys.stdout, sys.stderr
+  try:
+    sys.stdout, sys.stderr = capture_out, capture_err
+    yield capture_out, capture_err
+  finally:
+    sys.stdout, sys.stderr = old_out, old_err
+
+
+class FakeEntry:
+    def __init__(self, contents_size):
+        self.contents_size = contents_size
+        self.data = 'a' * contents_size
+
+    def GetPath(self):
+        return 'entry_path'
+
+class FakeImage:
+    def __init__(self, sym_value=1):
+        self.sym_value = sym_value
+
+    def GetPath(self):
+        return 'image_path'
+
+    def LookupSymbol(self, name, weak, msg):
+        return self.sym_value
 
 class TestElf(unittest.TestCase):
     def testAllSymbols(self):
+        fname = os.path.join(binman_dir, 'test', 'u_boot_ucode_ptr')
         syms = elf.GetSymbols(fname, [])
         self.assertIn('.ucode', syms)
 
     def testRegexSymbols(self):
+        fname = os.path.join(binman_dir, 'test', 'u_boot_ucode_ptr')
         syms = elf.GetSymbols(fname, ['ucode'])
         self.assertIn('.ucode', syms)
         syms = elf.GetSymbols(fname, ['missing'])
@@ -28,5 +67,56 @@ class TestElf(unittest.TestCase):
         syms = elf.GetSymbols(fname, ['missing', 'ucode'])
         self.assertIn('.ucode', syms)
 
+    def testMissingFile(self):
+        entry = FakeEntry(10)
+        image = FakeImage()
+        with self.assertRaises(ValueError) as e:
+            syms = elf.LookupAndWriteSymbols('missing-file', entry, image)
+        self.assertIn("Filename 'missing-file' not found in input path",
+                      str(e.exception))
+
+    def testOutsideFile(self):
+        entry = FakeEntry(10)
+        image = FakeImage()
+        elf_fname = os.path.join(binman_dir, 'test', 'u_boot_binman_syms')
+        with self.assertRaises(ValueError) as e:
+            syms = elf.LookupAndWriteSymbols(elf_fname, entry, image)
+        self.assertIn('entry_path has offset 4 (size 8) but the contents size '
+                      'is a', str(e.exception))
+
+    def testMissingImageStart(self):
+        entry = FakeEntry(10)
+        image = FakeImage()
+        elf_fname = os.path.join(binman_dir, 'test', 'u_boot_binman_syms_bad')
+        self.assertEqual(elf.LookupAndWriteSymbols(elf_fname, entry, image),
+                         None)
+
+    def testBadSymbolSize(self):
+        entry = FakeEntry(10)
+        image = FakeImage()
+        elf_fname = os.path.join(binman_dir, 'test', 'u_boot_binman_syms_size')
+        with self.assertRaises(ValueError) as e:
+            syms = elf.LookupAndWriteSymbols(elf_fname, entry, image)
+        self.assertIn('has size 1: only 4 and 8 are supported',
+                      str(e.exception))
+
+    def testNoValue(self):
+        entry = FakeEntry(20)
+        image = FakeImage(sym_value=None)
+        elf_fname = os.path.join(binman_dir, 'test', 'u_boot_binman_syms')
+        syms = elf.LookupAndWriteSymbols(elf_fname, entry, image)
+        self.assertEqual(chr(255) * 16 + 'a' * 4, entry.data)
+
+    def testDebug(self):
+        elf.debug = True
+        entry = FakeEntry(20)
+        image = FakeImage()
+        elf_fname = os.path.join(binman_dir, 'test', 'u_boot_binman_syms')
+        with capture_sys_output() as (stdout, stderr):
+            syms = elf.LookupAndWriteSymbols(elf_fname, entry, image)
+        elf.debug = False
+        self.assertTrue(len(stdout.getvalue()) > 0)
+
+
 if __name__ == '__main__':
     unittest.main()

tools/binman/etype/entry.py

@@ -198,3 +198,11 @@ class Entry(object):
 
     def ProcessContents(self):
         pass
+
+    def WriteSymbols(self, image):
+        """Write symbol values into binary files for access at run time
+
+        Args:
+          image: Image containing the entry
+        """
+        pass

tools/binman/etype/u_boot_spl.py

@@ -6,12 +6,18 @@
 # Entry-type module for spl/u-boot-spl.bin
 #
 
+import elf
+
 from entry import Entry
 from blob import Entry_blob
 
 class Entry_u_boot_spl(Entry_blob):
     def __init__(self, image, etype, node):
         Entry_blob.__init__(self, image, etype, node)
+        self.elf_fname = 'spl/u-boot-spl'
 
     def GetDefaultFilename(self):
         return 'spl/u-boot-spl.bin'
+
+    def WriteSymbols(self, image):
+        elf.LookupAndWriteSymbols(self.elf_fname, self, image)

tools/binman/ftest.py

@@ -20,6 +20,7 @@ import binman
 import cmdline
 import command
 import control
+import elf
 import fdt
 import fdt_util
 import tools
@@ -573,6 +574,8 @@ class TestFunctional(unittest.TestCase):
 
     def testImagePadByte(self):
         """Test that the image pad byte can be specified"""
+        with open(self.TestFile('bss_data')) as fd:
+            TestFunctional._MakeInputFile('spl/u-boot-spl', fd.read())
         data = self._DoReadFile('21_image_pad.dts')
         self.assertEqual(U_BOOT_SPL_DATA + (chr(0xff) * 1) + U_BOOT_DATA, data)
 
@@ -889,6 +892,22 @@ class TestFunctional(unittest.TestCase):
         data = self._DoReadFile('52_u_boot_spl_nodtb.dts')
         self.assertEqual(U_BOOT_SPL_NODTB_DATA, data[:len(U_BOOT_SPL_NODTB_DATA)])
 
+    def testSymbols(self):
+        """Test binman can assign symbols embedded in U-Boot"""
+        elf_fname = self.TestFile('u_boot_binman_syms')
+        syms = elf.GetSymbols(elf_fname, ['binman', 'image'])
+        addr = elf.GetSymbolAddress(elf_fname, '__image_copy_start')
+        self.assertEqual(syms['_binman_u_boot_spl_prop_pos'].address, addr)
+
+        with open(self.TestFile('u_boot_binman_syms')) as fd:
+            TestFunctional._MakeInputFile('spl/u-boot-spl', fd.read())
+        data = self._DoReadFile('53_symbols.dts')
+        sym_values = struct.pack('<LQL', 0x24 + 0, 0x24 + 24, 0x24 + 20)
+        expected = (sym_values + U_BOOT_SPL_DATA[16:] + chr(0xff) +
+                    U_BOOT_DATA +
+                    sym_values + U_BOOT_SPL_DATA[16:])
+        self.assertEqual(expected, data)
+
 
 if __name__ == "__main__":
     unittest.main()

tools/binman/image.py

@@ -6,8 +6,12 @@
 # Class for an image, the output of binman
 #
 
+from __future__ import print_function
+
 from collections import OrderedDict
 from operator import attrgetter
+import re
+import sys
 
 import fdt_util
 import tools
@@ -45,7 +49,7 @@ class Image:
              address.
         _entries: OrderedDict() of entries
     """
-    def __init__(self, name, node):
+    def __init__(self, name, node, test=False):
         global entry
         global Entry
         import entry
@@ -64,8 +68,9 @@ class Image:
         self._end_4gb = False
         self._entries = OrderedDict()
 
-        self._ReadNode()
-        self._ReadEntries()
+        if not test:
+            self._ReadNode()
+            self._ReadEntries()
 
     def _ReadNode(self):
         """Read properties from the image node"""
@@ -119,6 +124,14 @@ class Image:
         """
         raise ValueError("Image '%s': %s" % (self._node.path, msg))
 
+    def GetPath(self):
+        """Get the path of an image (in the FDT)
+
+        Returns:
+            Full path of the node for this image
+        """
+        return self._node.path
+
     def _ReadEntries(self):
         for node in self._node.subnodes:
             self._entries[node.name] = Entry.Create(self, node)
@@ -220,6 +233,11 @@ class Image:
         for entry in self._entries.values():
             entry.ProcessContents()
 
+    def WriteSymbols(self):
+        """Write symbol values into binary files for access at run time"""
+        for entry in self._entries.values():
+            entry.WriteSymbols(self)
+
     def BuildImage(self):
         """Write the image to a file"""
         fname = tools.GetOutputFilename(self._filename)
@@ -230,3 +248,58 @@ class Image:
                 data = entry.GetData()
                 fd.seek(self._pad_before + entry.pos - self._skip_at_start)
                 fd.write(data)
+
+    def LookupSymbol(self, sym_name, optional, msg):
+        """Look up a symbol in an ELF file
+
+        Looks up a symbol in an ELF file. Only entry types which come from an
+        ELF image can be used by this function.
+
+        At present the only entry property supported is pos.
+
+        Args:
+            sym_name: Symbol name in the ELF file to look up in the format
+                _binman_<entry>_prop_<property> where <entry> is the name of
+                the entry and <property> is the property to find (e.g.
+                _binman_u_boot_prop_pos). As a special case, you can append
+                _any to <entry> to have it search for any matching entry. E.g.
+                _binman_u_boot_any_prop_pos will match entries called u-boot,
+                u-boot-img and u-boot-nodtb)
+            optional: True if the symbol is optional. If False this function
+                will raise if the symbol is not found
+            msg: Message to display if an error occurs
+
+        Returns:
+            Value that should be assigned to that symbol, or None if it was
+                optional and not found
+
+        Raises:
+            ValueError if the symbol is invalid or not found, or references a
+                property which is not supported
+        """
+        m = re.match(r'^_binman_(\w+)_prop_(\w+)$', sym_name)
+        if not m:
+            raise ValueError("%s: Symbol '%s' has invalid format" %
+                             (msg, sym_name))
+        entry_name, prop_name = m.groups()
+        entry_name = entry_name.replace('_', '-')
+        entry = self._entries.get(entry_name)
+        if not entry:
+            if entry_name.endswith('-any'):
+                root = entry_name[:-4]
+                for name in self._entries:
+                    if name.startswith(root):
+                        rest = name[len(root):]
+                        if rest in ['', '-img', '-nodtb']:
+                            entry = self._entries[name]
+        if not entry:
+            err = ("%s: Entry '%s' not found in list (%s)" %
+                   (msg, entry_name, ','.join(self._entries.keys())))
+            if optional:
+                print('Warning: %s' % err, file=sys.stderr)
+                return None
+            raise ValueError(err)
+        if prop_name == 'pos':
+            return entry.pos
+        else:
+            raise ValueError("%s: No such property '%s'" % (msg, prop_name))

tools/binman/image_test.py

@@ -0,0 +1,46 @@
+#
+# Copyright (c) 2017 Google, Inc
+# Written by Simon Glass <sjg@chromium.org>
+#
+# SPDX-License-Identifier:      GPL-2.0+
+#
+# Test for the image module
+
+import unittest
+
+from image import Image
+from elf_test import capture_sys_output
+
+class TestImage(unittest.TestCase):
+    def testInvalidFormat(self):
+        image = Image('name', 'node', test=True)
+        with self.assertRaises(ValueError) as e:
+            image.LookupSymbol('_binman_something_prop_', False, 'msg')
+        self.assertIn(
+            "msg: Symbol '_binman_something_prop_' has invalid format",
+            str(e.exception))
+
+    def testMissingSymbol(self):
+        image = Image('name', 'node', test=True)
+        image._entries = {}
+        with self.assertRaises(ValueError) as e:
+            image.LookupSymbol('_binman_type_prop_pname', False, 'msg')
+        self.assertIn("msg: Entry 'type' not found in list ()",
+                      str(e.exception))
+
+    def testMissingSymbolOptional(self):
+        image = Image('name', 'node', test=True)
+        image._entries = {}
+        with capture_sys_output() as (stdout, stderr):
+            val = image.LookupSymbol('_binman_type_prop_pname', True, 'msg')
+        self.assertEqual(val, None)
+        self.assertEqual("Warning: msg: Entry 'type' not found in list ()\n",
+                         stderr.getvalue())
+        self.assertEqual('', stdout.getvalue())
+
+    def testBadProperty(self):
+        image = Image('name', 'node', test=True)
+        image._entries = {'u-boot': 1}
+        with self.assertRaises(ValueError) as e:
+            image.LookupSymbol('_binman_u_boot_prop_bad', False, 'msg')
+        self.assertIn("msg: No such property 'bad", str(e.exception))

tools/binman/test/53_symbols.dts

@@ -0,0 +1,20 @@
+/dts-v1/;
+
+/ {
+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	binman {
+		pad-byte = <0xff>;
+		u-boot-spl {
+		};
+
+		u-boot {
+			pos = <20>;
+		};
+
+		u-boot-spl2 {
+			type = "u-boot-spl";
+		};
+	};
+};