Re: [PATCH 3/7] [HACK] x86: crypto: fix link error with LTO

Nicolas Pitre
2018-02-02T19:49:14Z

On Fri, 2 Feb 2018, Arnd Bergmann wrote:

> crypto_it_tab and the other symbols like it are defined in
> crypto/aes_generic.c and exported for loadable modules. When
> building with LTO and CONFIG_TRIM_UNUSED_KSYMS, the exports
> are eliminated, since kbuild fails to take the users in
> the arch/x86/crypto/aes-i586-asm_32.S assembler file into
> account.
>
> This adds an ugly workaround by adding a reference to each symbol
> into aes_glue.c, which gets linked together with the assembler
> file.
>
> We obviously want to fix the CONFIG_TRIM_UNUSED_KSYMS logic
> to do the right thing here instead, but I couldn't come up
> with a good fix, so I use this instead to get a clean build
> for testing.

Could you give me the .config you used for this? So far I can't
reproduce, and guessing with LTO takes lots of time.

> This fix only works most of the time, but I still ran into
> some cases where combining an .S with a .c file did not
> produce the correct .ko file, as the lto linker apparently
> did not expect that kind of input. 'nm' on the file after
> 'ld -r' showed only the contents of the assembler file, and
> after the lto-ld stage, only the contents of the .c file
> are there.

'ld -r' does not support mixed (LTO and non-LTO) objects.

Nicolas