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From b7033f0828ca07dbc4e3a8b4f4c91b23e09eb08c Mon Sep 17 00:00:00 2001
From: Nick Desaulniers <ndesaulniers@google.com>
Date: Wed, 16 Oct 2019 16:02:08 -0700
Subject: [PATCH 4309/4736] drm/amdgpu: fix stack alignment ABI mismatch for
GCC 7.1+
GCC earlier than 7.1 errors when compiling code that makes use of
`double`s and sets a stack alignment outside of the range of [2^4-2^12]:
$ cat foo.c
double foo(double x, double y) {
return x + y;
}
$ gcc-4.9 -mpreferred-stack-boundary=3 foo.c
error: -mpreferred-stack-boundary=3 is not between 4 and 12
This is likely why the AMDGPU driver was ever compiled with a different
stack alignment (and thus different ABI) than the rest of the x86
kernel. The kernel uses 8B stack alignment, while the driver was using
16B stack alignment in a few places.
Since GCC 7.1+ doesn't error, fix the ABI mismatch for users of newer
versions of GCC.
There was discussion about whether to mark the driver broken or not for
users of GCC earlier than 7.1, but since the driver currently is
working, don't explicitly break the driver for them here.
Relying on differing stack alignment is unspecified behavior, and
brittle, and may break in the future.
This patch is no functional change for GCC users earlier than 7.1. It's
been compile tested on GCC 4.9 and 8.3 to check the correct flags. It
should be boot tested when built with GCC 7.1+.
-mincoming-stack-boundary= or -mstackrealign may help keep this code
building for pre-GCC 7.1 users.
The version check for GCC is broken into two conditionals, both because
cc-ifversion is currently GCC specific, and it simplifies a subsequent
patch.
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
---
drivers/gpu/drm/amd/display/dc/calcs/Makefile | 9 +++++++++
drivers/gpu/drm/amd/display/dc/dcn20/Makefile | 9 +++++++++
drivers/gpu/drm/amd/display/dc/dcn21/Makefile | 9 +++++++++
drivers/gpu/drm/amd/display/dc/dml/Makefile | 9 +++++++++
drivers/gpu/drm/amd/display/dc/dsc/Makefile | 9 +++++++++
5 files changed, 45 insertions(+)
diff --git a/drivers/gpu/drm/amd/display/dc/calcs/Makefile b/drivers/gpu/drm/amd/display/dc/calcs/Makefile
index ab522ea992d2..393215ef9f98 100644
--- a/drivers/gpu/drm/amd/display/dc/calcs/Makefile
+++ b/drivers/gpu/drm/amd/display/dc/calcs/Makefile
@@ -27,6 +27,15 @@
calcs_ccflags := -mhard-float -msse
ifdef CONFIG_CC_IS_GCC
+ifeq ($(call cc-ifversion, -lt, 0701, y), y)
+IS_OLD_GCC = 1
+endif
+endif
+
+ifdef IS_OLD_GCC
+# Stack alignment mismatch, proceed with caution.
+# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
+# (8B stack alignment).
calcs_ccflags += -mpreferred-stack-boundary=4
endif
diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/Makefile b/drivers/gpu/drm/amd/display/dc/dcn20/Makefile
index a02e02980310..d684cb912d92 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn20/Makefile
+++ b/drivers/gpu/drm/amd/display/dc/dcn20/Makefile
@@ -13,6 +13,15 @@ endif
CFLAGS_dcn20_resource.o := -mhard-float -msse
ifdef CONFIG_CC_IS_GCC
+ifeq ($(call cc-ifversion, -lt, 0701, y), y)
+IS_OLD_GCC = 1
+endif
+endif
+
+ifdef IS_OLD_GCC
+# Stack alignment mismatch, proceed with caution.
+# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
+# (8B stack alignment).
CFLAGS_dcn20_resource.o += -mpreferred-stack-boundary=4
endif
diff --git a/drivers/gpu/drm/amd/display/dc/dcn21/Makefile b/drivers/gpu/drm/amd/display/dc/dcn21/Makefile
index 0fa857b69143..72609a40c6a3 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn21/Makefile
+++ b/drivers/gpu/drm/amd/display/dc/dcn21/Makefile
@@ -6,6 +6,15 @@ DCN21 = dcn21_hubp.o dcn21_hubbub.o dcn21_resource.o dcn21_hwseq.o dcn21_link_en
CFLAGS_dcn21_resource.o := -mhard-float -msse
ifdef CONFIG_CC_IS_GCC
+ifeq ($(call cc-ifversion, -lt, 0701, y), y)
+IS_OLD_GCC = 1
+endif
+endif
+
+ifdef IS_OLD_GCC
+# Stack alignment mismatch, proceed with caution.
+# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
+# (8B stack alignment).
CFLAGS_dcn21_resource.o += -mpreferred-stack-boundary=4
endif
diff --git a/drivers/gpu/drm/amd/display/dc/dml/Makefile b/drivers/gpu/drm/amd/display/dc/dml/Makefile
index b3db0900b473..f85f2bb1b0c7 100644
--- a/drivers/gpu/drm/amd/display/dc/dml/Makefile
+++ b/drivers/gpu/drm/amd/display/dc/dml/Makefile
@@ -27,6 +27,15 @@
dml_ccflags := -mhard-float -msse
ifdef CONFIG_CC_IS_GCC
+ifeq ($(call cc-ifversion, -lt, 0701, y), y)
+IS_OLD_GCC = 1
+endif
+endif
+
+ifdef IS_OLD_GCC
+# Stack alignment mismatch, proceed with caution.
+# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
+# (8B stack alignment).
dml_ccflags += -mpreferred-stack-boundary=4
endif
diff --git a/drivers/gpu/drm/amd/display/dc/dsc/Makefile b/drivers/gpu/drm/amd/display/dc/dsc/Makefile
index 4d18e2b60223..ec2ebee0078f 100644
--- a/drivers/gpu/drm/amd/display/dc/dsc/Makefile
+++ b/drivers/gpu/drm/amd/display/dc/dsc/Makefile
@@ -4,6 +4,15 @@
dsc_ccflags := -mhard-float -msse
ifdef CONFIG_CC_IS_GCC
+ifeq ($(call cc-ifversion, -lt, 0701, y), y)
+IS_OLD_GCC = 1
+endif
+endif
+
+ifdef IS_OLD_GCC
+# Stack alignment mismatch, proceed with caution.
+# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
+# (8B stack alignment).
dsc_ccflags += -mpreferred-stack-boundary=4
endif
--
2.17.1
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