Re: [PATCH 00/22] add support for Clang LTO

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Dear Sami,


Am 13.07.20 um 01:34 schrieb Sami Tolvanen:
On Sat, Jul 11, 2020 at 9:32 AM Paul Menzel <pmenzel@xxxxxxxxxxxxx> wrote:
Thank you very much for sending these changes.

Do you have a branch, where your current work can be pulled from? Your
branch on GitHub [1] seems 15 months old.

The clang-lto branch is rebased regularly on top of Linus' tree.
GitHub just looks at the commit date of the last commit in the tree,
which isn't all that informative.

Thank you for clearing this up, and sorry for not checking myself.

Out of curiosity, I applied the changes, allowed the selection for i386
(x86), and with Clang 1:11~++20200701093119+ffee8040534-1~exp1 from
Debian experimental, it failed with `Invalid absolute R_386_32
relocation: KERNEL_PAGES`:

I haven't looked at getting this to work on i386, which is why we only
select ARCH_SUPPORTS_LTO for x86_64. I would expect there to be a few
issues to address.

   arch/x86/tools/relocs vmlinux > arch/x86/boot/compressed/vmlinux.relocs;arch/x86/tools/relocs --abs-relocs vmlinux
Invalid absolute R_386_32 relocation: KERNEL_PAGES

KERNEL_PAGES looks like a constant, so it's probably safe to ignore
the absolute relocation in tools/relocs.c.

Thank you for pointing me to the right direction. I am happy to report, that with the diff below (no idea to what list to add the string), Linux 5.8-rc5 with the LLVM/Clang/LTO patches on top, builds and boots on the ASRock E350M1.

```
diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
index 8f3bf34840cef..e91af127ed3c0 100644
--- a/arch/x86/tools/relocs.c
+++ b/arch/x86/tools/relocs.c
@@ -79,6 +79,7 @@ static const char * const sym_regex_kernel[S_NSYMTYPES] = {
        "__end_rodata_hpage_align|"
 #endif
        "__vvar_page|"
+       "KERNEL_PAGES|"
        "_end)$"
 };
```


Kind regards,

Paul



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