binman: Support positioning an entry by and ELF symbol

In some cases it is useful to position an entry over the top of a symbol
in an ELF file. For example, if the symbol holds a version string then it
allows the string to be accessed from the fdtmap.

Add support for this.

Suggested-by: Pali Rohár <pali@kernel.org>
Suggested-by: Keith Short <keithshort@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>

1 files changed, 23 insertions, 0 deletions

diff --git a/tools/binman/elf.py b/tools/binman/elf.py
index 9ac00ed9cc..3cc8a38449 100644
--- a/tools/binman/elf.py
+++ b/tools/binman/elf.py
@@ -210,6 +210,29 @@ def GetPackString(sym, msg):
         raise ValueError('%s has size %d: only 4 and 8 are supported' %
                          (msg, sym.size))
 
+def GetSymbolOffset(elf_fname, sym_name, base_sym=None):
+    """Read the offset of a symbol compared to base symbol
+
+    This is useful for obtaining the value of a single symbol relative to the
+    base of a binary blob.
+
+    Args:
+        elf_fname: Filename of the ELF file to read
+        sym_name (str): Name of symbol to read
+        base_sym (str): Base symbol to sue to calculate the offset (or None to
+            use '__image_copy_start'
+
+    Returns:
+        int: Offset of the symbol relative to the base symbol
+    """
+    if not base_sym:
+        base_sym = '__image_copy_start'
+    fname = tools.get_input_filename(elf_fname)
+    syms = GetSymbols(fname, [base_sym, sym_name])
+    base = syms[base_sym].address
+    val = syms[sym_name].address
+    return val - base
+
 def LookupAndWriteSymbols(elf_fname, entry, section, is_elf=False,
                           base_sym=None):
     """Replace all symbols in an entry with their correct values