From fbc4ba4b4ed13cc86cb8fdea0bac6c3be0164ed5 Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Wed, 4 Mar 2015 18:48:19 +0000 Subject: [build] Fix the REQUIRE_SYMBOL mechanism At some point in the past few years, binutils became more aggressive at removing unused symbols. To function as a symbol requirement, a relocation record must now be in a section marked with @progbits and must not be in a section which gets discarded during the link (either via --gc-sections or via /DISCARD/). Update REQUIRE_SYMBOL() to generate relocation records meeting these criteria. To minimise the impact upon the final binary size, we use existing symbols (specified via the REQUIRING_SYMBOL() macro) as the relocation targets where possible. We use R_386_NONE or R_X86_64_NONE relocation types to prevent any actual unwanted relocation taking place. Where no suitable symbol exists for REQUIRING_SYMBOL() (such as in config.c), the macro PROVIDE_REQUIRING_SYMBOL() can be used to generate a one-byte-long symbol to act as the relocation target. If there are versions of binutils for which this approach fails, then the fallback will probably involve killing off REQUEST_SYMBOL(), redefining REQUIRE_SYMBOL() to use the current definition of REQUEST_SYMBOL(), and postprocessing the linked ELF file with something along the lines of "nm -u | wc -l" to check that there are no undefined symbols remaining. Signed-off-by: Michael Brown --- src/util/elf2efi.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'src/util') diff --git a/src/util/elf2efi.c b/src/util/elf2efi.c index 1e7a99b79..e68fa5d14 100644 --- a/src/util/elf2efi.c +++ b/src/util/elf2efi.c @@ -478,6 +478,9 @@ static void process_reloc ( bfd *bfd __attribute__ (( unused )), /* Skip absolute symbols; the symbol value won't * change when the object is loaded. */ + } else if ( ( strcmp ( howto->name, "R_386_NONE" ) == 0 ) || + ( strcmp ( howto->name, "R_X86_64_NONE" ) == 0 ) ) { + /* Ignore dummy relocations used by REQUIRE_SYMBOL() */ } else if ( strcmp ( howto->name, "R_X86_64_64" ) == 0 ) { /* Generate an 8-byte PE relocation */ generate_pe_reloc ( pe_reltab, offset, 8 ); -- cgit v1.2.3-55-g7522