unknown section type: %progbits

[VeXocide]

The stack markings introduced in #60 lead to a compilation failure on OS X 10.8 using GCC 4.7 from MacPorts, with the following error:

  CCAS     crypto_stream/salsa20/amd64_xmm6/stream_salsa20_amd64_xmm6.lo
crypto_stream/salsa20/amd64_xmm6/stream_salsa20_amd64_xmm6.s:949:unknown section type: %progbits

This is rather odd given it's wrapped in an #if as follows:

#if defined(__linux__) && defined(__ELF__)
.section .note.GNU-stack,"",%progbits
#endif

Neither of the two defined hold true.

[jedisct1]

Duh? This is indeed super weird.
So, preprocessor directives are blindly ignored in asm code when using this compiler? Wow. Crap.

We can work around it using autoconf magic, but this is pretty annoying.

[VeXocide]

http://www.gentoo.org/proj/en/hardened/gnu-stack.xml#doc_chap6 lists a second alternative, compiling with --noexecstack.

[jedisct1]

That sounds like a better option. Still.. #if statements not working is worrying.

Can anybody running Gentoo check that the --nonexecstack option actually works as expected?

[VeXocide]

The relevant command from make -n is:

echo "  CCAS    " crypto_stream/salsa20/amd64_xmm6/stream_salsa20_amd64_xmm6.lo;/bin/sh ../../libtool --silent   --mode=compile /opt/local/bin/gcc-mp-4.7 -std=gnu99  -g -O2 -c -o crypto_stream/salsa20/amd64_xmm6/stream_salsa20_amd64_xmm6.lo crypto_stream/salsa20/amd64_xmm6/stream_salsa20_amd64_xmm6.s

Now it turns out there's the following subtlety, from http://stackoverflow.com/a/7190511:

• If the file name ends with ".s" (lowercase 's'), then gcc calls the assembler.
• If the file name ends with ".S" (uppercase 'S'), then gcc applies the C preprocessor on the source file (i.e. it recognizes directives such as #if and replaces macros), and then calls the assembler on the result.

Thus we want to call gcc as follows to solve the problem:

gcc -S file.c -o file.s
gcc -c file.s

Still, the --nonexecstack might be the better option in this particular case.

[jedisct1]

Good catch. Hope it will work on case-insensitive filesystems as well. Let's give it a shot.

[jedisct1]

Can you try with the current git master?

[VeXocide]

It compiles as expected, fixed!

[jedisct1]

Neat! And good to know!

Thanks a lot for your report!