[PATCH 1/1] symtab reader: fix up alternative addresses

[Giuliano Procida <gprocida@google.com>]

CFI symbols need special interpretation and this work is performed by
the add_alternative_address_lookups method.

Some symbol addresses need to be "tweaked" to be correctly interpreted
and this must also happen in add_alternative_address_lookups.

In particular, this commit fixes ARM32 CFI symbol interpretation.

	* src/abg-symtab-reader.cc
	(symtab::add_alternative_address_lookups): Tweak function
	addresses in the same manner as done in symtab::load_.

Signed-off-by: Giuliano Procida <gprocida@google.com>
---
 src/abg-symtab-reader.cc | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/abg-symtab-reader.cc b/src/abg-symtab-reader.cc
index 0f4d0b65..04e8b23c 100644
--- a/src/abg-symtab-reader.cc
+++ b/src/abg-symtab-reader.cc
@@ -351,6 +351,7 @@ symtab::load_(Elf*	       elf_handle,
 	      elf_helpers::maybe_adjust_et_rel_sym_addr_to_abs_addr(elf_handle,
 								    sym);
 
+	  // See also symtab::add_alternative_address_lookups.
 	  if (symbol_sptr->is_function())
 	    {
 	      if (is_arm32)
@@ -581,6 +582,9 @@ symtab::update_function_entry_address_symbol_map(
 void
 symtab::add_alternative_address_lookups(Elf* elf_handle)
 {
+  const bool is_arm32 = elf_helpers::architecture_is_arm32(elf_handle);
+  const bool is_ppc64 = elf_helpers::architecture_is_ppc64(elf_handle);
+
   Elf_Scn* symtab_section = elf_helpers::find_symtab_section(elf_handle);
   if (!symtab_section)
     return;
@@ -634,6 +638,19 @@ symtab::add_alternative_address_lookups(Elf* elf_handle)
 		  elf_helpers::maybe_adjust_et_rel_sym_addr_to_abs_addr(
 		      elf_handle, sym);
 
+	      // See also symtab::load_.
+	      if (symbol_sptr->is_function())
+		{
+		  if (is_arm32)
+		    // Clear bit zero of ARM32 addresses as per "ELF for the Arm
+		    // Architecture" section 5.5.3.
+		    // https://static.docs.arm.com/ihi0044/g/aaelf32.pdf
+		    symbol_value &= ~1;
+		  else if (is_ppc64)
+		    update_function_entry_address_symbol_map(elf_handle, sym,
+							     symbol_sptr);
+		}
+
 	      const auto result =
 		  addr_symbol_map_.emplace(symbol_value, symbol_sptr);
 	      ABG_ASSERT(result.second);
-- 
2.34.1.575.g55b058a8bb-goog