linux-kernel - Re: [PATCH 2/8] ACPI: Don't build ACPICA with '-Os'

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Message-ID: <CAJZ5v0hMLRPqMOBjbJ9AFbBQ00TJ7VyntnXwBJqtuSw6FsHaxg@mail.gmail.com>
Date:   Tue, 10 Jan 2023 14:45:55 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, Len Brown <lenb@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Robert Moore <robert.moore@...el.com>, catalin.marinas@....com,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        mhiramat@...nel.org, ndesaulniers@...gle.com, ojeda@...nel.org,
        peterz@...radead.org, revest@...omium.org, rostedt@...dmis.org,
        will@...nel.org
Subject: Re: [PATCH 2/8] ACPI: Don't build ACPICA with '-Os'

On Mon, Jan 9, 2023 at 2:58 PM Mark Rutland <mark.rutland@....com> wrote:
>
> The ACPICA code has been built with '-Os' since the beginning of git
> history, though there's no explanatory comment as to why.
>
> This is unfortunate as building with '-Os' overrides -falign-functions,
> which prevents CONFIG_FUNCITON_ALIGNMENT and
> CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_64B from having their expected effect
> on the ACPICA code. This is doubly unfortunate as in subsequent patches
> arm64 will depend upon CONFIG_FUNCTION_ALIGNMENT for its ftrace
> implementation.
>
> Drop the '-Os' flag when building the ACPICA code. With this removed,
> the code builds cleanly and works correctly in testing so far.

Fair enough.

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

and please feel free to route this through the arch tree along with
the rest of the series.

Thanks!

> I've tested this by selecting CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_64B=y,
> building and booting a kernel using ACPI, and looking for misaligned
> text symbols:
>
> * arm64:
>
>   Before:
>     #  grep ' [Tt] ' /proc/kallsyms | grep -iv '[048c]0 [Tt] ' | wc -l
>     908
>     #  grep ' [Tt] ' /proc/kallsyms | grep -iv '[048c]0 [Tt] ' | grep acpi | wc -l
>     576
>
>   After:
>     # grep ' [Tt] ' /proc/kallsyms | grep -iv '[048c]0 [Tt] ' | wc -l
>     322
>     # grep ' [Tt] ' /proc/kallsyms | grep -iv '[048c]0 [Tt] ' | grep acpi | wc -l
>     0
>
> * x86_64:
>
>   Before:
>     # grep ' [Tt] ' /proc/kallsyms | grep -iv '[048c]0 [Tt] ' | wc -l
>     2057
>     # grep ' [Tt] ' /proc/kallsyms | grep -iv '[048c]0 [Tt] ' | grep acpi | wc -l
>     706
>
>   After:
>     # grep ' [Tt] ' /proc/kallsyms | grep -iv '[048c]0 [Tt] ' | wc -l
>     1351
>     # grep ' [Tt] ' /proc/kallsyms | grep -iv '[048c]0 [Tt] ' | grep acpi | wc -l
>     0
>
> With the patch applied, the remaining unaligned text labels are a
> combination of static call trampolines and labels in assembly, which
> will be dealt with in subsequent patches.
>
> Signed-off-by: Mark Rutland <mark.rutland@....com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Florent Revest <revest@...omium.org>
> Cc: Len Brown <lenb@...nel.org>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Cc: Robert Moore <robert.moore@...el.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Will Deacon <will@...nel.org>
> Cc: linux-acpi@...r.kernel.org
> ---
>  drivers/acpi/acpica/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/acpica/Makefile b/drivers/acpi/acpica/Makefile
> index 9e0d95d76fff7..30f3fc13c29d1 100644
> --- a/drivers/acpi/acpica/Makefile
> +++ b/drivers/acpi/acpica/Makefile
> @@ -3,7 +3,7 @@
>  # Makefile for ACPICA Core interpreter
>  #
>
> -ccflags-y                      := -Os -D_LINUX -DBUILDING_ACPICA
> +ccflags-y                      := -D_LINUX -DBUILDING_ACPICA
>  ccflags-$(CONFIG_ACPI_DEBUG)   += -DACPI_DEBUG_OUTPUT
>
>  # use acpi.o to put all files here into acpi.o modparam namespace
> --
> 2.30.2
>