diff options
| author | Michael Brown <mcb30@ipxe.org> | 2015-03-04 18:48:19 +0000 |
|---|---|---|
| committer | Michael Brown <mcb30@ipxe.org> | 2015-03-05 00:59:38 +0000 |
| commit | fbc4ba4b4ed13cc86cb8fdea0bac6c3be0164ed5 (patch) | |
| tree | a0c504e297806aa88e89a04e694333a7c5172757 /src/util | |
| parent | 86ae6e6c1836e43993a14db278398fc54e5419bd (diff) | |
| download | ipxe-fbc4ba4b4ed13cc86cb8fdea0bac6c3be0164ed5.tar.gz | |
[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 <mcb30@ipxe.org>
Diffstat (limited to 'src/util')
| -rw-r--r-- | src/util/elf2efi.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/src/util/elf2efi.c b/src/util/elf2efi.c index 1e7a99b7..e68fa5d1 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 ); |