[PATCH 3.10 211/268] ACPI: Fix incompatibility with mcount-based function graph tracing

From: Willy Tarreau
Date: Mon Jun 19 2017 - 14:39:10 EST

From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>

commit 61b79e16c68d703dde58c25d3935d67210b7d71b upstream.

Paul Menzel reported a warning:

WARNING: CPU: 0 PID: 774 at /build/linux-ROBWaj/linux-4.9.13/kernel/trace/trace_functions_graph.c:233 ftrace_return_to_handler+0x1aa/0x1e0
Bad frame pointer: expected f6919d98, received f6919db0
from func acpi_pm_device_sleep_wake return to c43b6f9d

The warning means that function graph tracing is broken for the
acpi_pm_device_sleep_wake() function. That's because the ACPI Makefile
unconditionally sets the '-Os' gcc flag to optimize for size. That's an
issue because mcount-based function graph tracing is incompatible with
'-Os' on x86, thanks to the following gcc bug:


I have another patch pending which will ensure that mcount-based
function graph tracing is never used with CONFIG_CC_OPTIMIZE_FOR_SIZE on

But this patch is needed in addition to that one because the ACPI
Makefile overrides that config option for no apparent reason. It has
had this flag since the beginning of git history, and there's no related
comment, so I don't know why it's there. As far as I can tell, there's
no reason for it to be there. The appropriate behavior is for it to
honor CONFIG_CC_OPTIMIZE_FOR_{SIZE,PERFORMANCE} like the rest of the

Reported-by: Paul Menzel <pmenzel@xxxxxxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Acked-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
drivers/acpi/Makefile | 1 -
1 file changed, 1 deletion(-)

diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
index 97c949a..2af5b5a 100644
--- a/drivers/acpi/Makefile
+++ b/drivers/acpi/Makefile
@@ -2,7 +2,6 @@
# Makefile for the Linux ACPI interpreter

-ccflags-y := -Os