Re: [PATCH v3 2/9] x86/entry/vdso: refactor the vdso build

On Wed, Nov 12, 2025 at 3:23 PM H. Peter Anvin <[email protected]> wrote:
>
> - Separate out the vdso sources into common, vdso32, and vdso64
>   directories.
> - Move the vdso2c tool to arch/x86/tools.
> - Build the 32- and 64-bit vdsos in their respective subdirectories;
>   this greatly simplifies the build flags handling.
> - Unify the mangling of Makefile flags between the 32- and 64-bit
>   vdso code as much as possible; all common rules are put in
>   arch/x86/entry/vdso/common/Makefile.include. The remaining
>   is very simple for 32 bits; the 64-bit one is only slightly more
>   complicated because it contains the x32 generation rule.
> - Define __DISABLE_EXPORTS when building the vdso. This need seems to
>   have been masked by different ordering compile flags before.
> - Change CONFIG_X86_64 to BUILD_VDSO32_64 in vdso32/system_call.S,
>   to make it compatible with including fake_32bit_build.h.
> - The -fcf-protection= option was "leaking" from the kernel build,
>   for reasons that was not clear to me. Futhermore, several
>   distributions ship with it set to a default value other than
>   "-fcf-protection=none". Make it match the configuration options
>   for *user space*.
>
> Note that this patch may seem large, but the vast majority of it is
> simply code movement.

Some of these changes (like moving vdso2c) can be split out into
smaller patches.