Re: [PATCH v5 00/29] Add support for Clang LTO

Steven Rostedt
2020-10-09T23:39:07Z

On Fri, 9 Oct 2020 14:05:48 -0700
Sami Tolvanen <samitolvanen@google.com> wrote:

> Ah yes, X86_DECODER_SELFTEST seems to be broken in tip/master. If you
> prefer, I have these patches on top of mainline here:
>
> https://github.com/samitolvanen/linux/tree/clang-lto
>
> Testing your config with LTO on this tree, it does build and boot for
> me, although I saw a couple of new objtool warnings, and with LLVM=1,
> one warning from llvm-objdump.

Thanks, I disabled X86_DECODER_SELFTEST and it now builds.

I forced the objdump mcount logic with the below patch, which produces:

CONFIG_FTRACE_MCOUNT_RECORD=y
CONFIG_FTRACE_MCOUNT_USE_OBJTOOL=y

But I don't see the __mcount_loc sections being created.

I applied patches 1 - 6.

-- Steve

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 89263210ab26..3042619e21b7 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -606,7 +606,7 @@ config FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY

config FTRACE_MCOUNT_USE_CC
def_bool y
- depends on $(cc-option,-mrecord-mcount)
+ depends on $(cc-option,-mrecord-mcount1)
depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
depends on FTRACE_MCOUNT_RECORD