On 2022-08-28, Rasmus Villemoes wrote:
On 26/08/2022 22.59, Tom Rini wrote:
On Thu, Aug 18, 2022 at 10:31:34AM -0700, Vagrant Cascadian wrote:
From: Vagrant Cascadian vagrant@reproducible-builds.org
The KBUILD_CFLAGS and KBUILD_AFLAGS variables are adjusted to use -ffile-prefix-map and --debug-prefix-map, respectively, to use relative paths for occurrences of __FILE__ and debug paths.
This enables reproducible builds regardless of the absolute path to the build directory:
https://reproducible-builds.org/docs/build-path/
Signed-off-by: Vagrant Cascadian vagrant@reproducible-builds.org Acked-by: Rasmus Villemoes rasmus.villemoes@prevas.dk
This needs some sort of clang check and then perhaps different flag used? How does the linux kernel handle this?
Well, interestingly it seems that the kernel doesn't do anything like this for debug info, they only apply the -fmacro-prefix-map. Which one should probably raise with them at some point.
It seems we're not actually calling gas directly, but always invokes $(CC) whatever that may be to compile assembler files. So I think the right fix is to simply pass the same -ffile-prefix-map in both KBUILD_CFLAGS as in KBUILD_AFLAGS - and if there's some variable that ends up being included in both automatically, then just adding it there should do the trick.
I tried just adding -ffile-prefix-map and that helped, but was not sufficient to solve the reproducibility issues. It also needs the --debug-prefix-map to make it the assembly code build reproducibly.
Though I guess I didn't try adding -ffile-prefix-map to KBUILD_AFLAGS, now that I think about it... will test that too, thanks!
live well, vagrant