Thread (212 messages) 212 messages, 19 authors, 2020-09-10

Re: [PATCH 04/22] kbuild: lto: fix recordmcount

From: Peter Zijlstra <peterz@infradead.org>
Date: 2020-06-24 21:28:00
Also in: linux-arch, linux-kbuild, linux-pci, lkml

On Wed, Jun 24, 2020 at 01:31:42PM -0700, Sami Tolvanen wrote:
With LTO, LLVM bitcode won't be compiled into native code until
modpost_link. This change postpones calls to recordmcount until after
this step.

In order to exclude specific functions from inspection, we add a new
code section .text..nomcount, which we tell recordmcount to ignore, and
a __nomcount attribute for moving functions to this section.
I'm confused, you only add this to functions in ftrace itself, which is
compiled with:

 KBUILD_CFLAGS = $(subst $(CC_FLAGS_FTRACE),,$(ORIG_CFLAGS))

and so should not have mcount/fentry sites anyway. So what's the point
of ignoring them further?

This Changelog does not explain.

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