linux-kernel - Re: [PATCH v4 00/45] x86: Kernel IBT

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Message-ID: <YjORbqKpn0QH/L7P@hirez.programming.kicks-ass.net>
Date:   Thu, 17 Mar 2022 20:52:14 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>,
        X86 ML <x86@...nel.org>, joao@...rdrivepizza.com,
        "H . J . Lu" <hjl.tools@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Mark Rutland <mark.rutland@....com>, alyssa.milburn@...el.com,
        Miroslav Benes <mbenes@...e.cz>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH v4 00/45] x86: Kernel IBT

On Fri, Mar 18, 2022 at 03:15:59AM +0900, Masahiro Yamada wrote:


This is somewhat similar to my first attempt, except I thought it had a
extra/superflous link pass in it..

> @@ -288,24 +289,24 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
>         $(call if_changed_rule,cc_o_c)
>         $(call cmd,force_checksrc)
> 
> -ifdef CONFIG_LTO_CLANG
> +ifneq ($(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT),)
>  # Module .o files may contain LLVM bitcode, compile them into native code
>  # before ELF processing
> -quiet_cmd_cc_lto_link_modules = LTO [M] $@
> -cmd_cc_lto_link_modules =                                              \
> +quiet_cmd_cc_prelink_modules = LD [M]  $@
> +      cmd_cc_prelink_modules =                                         \
>         $(LD) $(ld_flags) -r -o $@                                      \
> -               $(shell [ -s $(@:.lto.o=.o.symversions) ] &&            \
> -                       echo -T $(@:.lto.o=.o.symversions))             \
> +               $(shell [ -s $(@:.prelink.o=.o.symversions) ] &&
>          \
> +                       echo -T $(@:.prelink.o=.o.symversions))         \
>                 --whole-archive $(filter-out FORCE,$^)                  \
>                 $(cmd_objtool)
> 


> @@ -469,7 +470,7 @@ $(obj)/lib.a: $(lib-y) FORCE
>  # Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
>  # module is turned into a multi object module, $^ will contain header file
>  # dependencies recorded in the .*.cmd file.
> -ifdef CONFIG_LTO_CLANG
> +ifneq ($(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT),)
>  quiet_cmd_link_multi-m = AR [M]  $@
>  cmd_link_multi-m =                                             \
>         $(cmd_update_lto_symversions);                          \

Except I overlooked this part, where ar is used instead of ld to combine
the individual files.

Let me go make the change, Thanks!