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drm/amdgpu: fix stack alignment ABI mismatch for Clang 

The x86 kernel is compiled with an 8B stack alignment via
`-mpreferred-stack-boundary=3` for GCC since 3.6-rc1 via
commit d9b0cde91c ("x86-64, gcc: Use -mpreferred-stack-boundary=3 if supported")
or `-mstack-alignment=8` for Clang. Parts of the AMDGPU driver are
compiled with 16B stack alignment.

Generally, the stack alignment is part of the ABI. Linking together two
different translation units with differing stack alignment is dangerous,
particularly when the translation unit with the smaller stack alignment
makes calls into the translation unit with the larger stack alignment.
While 8B aligned stacks are sometimes also 16B aligned, they are not
always.

Multiple users have reported General Protection Faults (GPF) when using
the AMDGPU driver compiled with Clang. Clang is placing objects in stack
slots assuming the stack is 16B aligned, and selecting instructions that
require 16B aligned memory operands.

At runtime, syscall handlers with 8B aligned stack call into code that
assumes 16B stack alignment.  When the stack is a multiple of 8B but not
16B, these instructions result in a GPF.

Remove the code that added compatibility between the differing compiler
flags, as it will result in runtime GPFs when built with Clang. Cleanups
for GCC will be sent in later patches in the series.

Link: https://github.com/ClangBuiltLinux/linux/issues/735
Debugged-by: Yuxuan Shui <yshuiv7@gmail.com>
Reported-by: Shirish S <shirish.s@amd.com>
Reported-by: Yuxuan Shui <yshuiv7@gmail.com>
Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Nick Desaulniers 2019-10-16 16:02:07 -07:00 committed by Alex Deucher
parent 722608433c
commit c868868f6b
5 changed files with 20 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
drivers/gpu/drm/amd/display/dc/calcs/Makefile
View File

@ -24,13 +24,11 @@
# It calculates Bandwidth and Watermarks values for HW programming
#
ifneq ($(call cc-option, -mpreferred-stack-boundary=4),)
cc_stack_align := -mpreferred-stack-boundary=4
else ifneq ($(call cc-option, -mstack-alignment=16),)
cc_stack_align := -mstack-alignment=16
endif
calcs_ccflags := -mhard-float -msse
calcs_ccflags := -mhard-float -msse $(cc_stack_align)
ifdef CONFIG_CC_IS_GCC
calcs_ccflags += -mpreferred-stack-boundary=4
endif
ifdef CONFIG_CC_IS_CLANG
calcs_ccflags += -msse2

10
drivers/gpu/drm/amd/display/dc/dcn20/Makefile
View File

@ -10,13 +10,11 @@ ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
DCN20 += dcn20_dsc.o
endif
ifneq ($(call cc-option, -mpreferred-stack-boundary=4),)
cc_stack_align := -mpreferred-stack-boundary=4
else ifneq ($(call cc-option, -mstack-alignment=16),)
cc_stack_align := -mstack-alignment=16
endif
CFLAGS_$(AMDDALPATH)/dc/dcn20/dcn20_resource.o := -mhard-float -msse
CFLAGS_$(AMDDALPATH)/dc/dcn20/dcn20_resource.o := -mhard-float -msse $(cc_stack_align)
ifdef CONFIG_CC_IS_GCC
CFLAGS_$(AMDDALPATH)/dc/dcn20/dcn20_resource.o += -mpreferred-stack-boundary=4
endif
ifdef CONFIG_CC_IS_CLANG
CFLAGS_$(AMDDALPATH)/dc/dcn20/dcn20_resource.o += -msse2

10
drivers/gpu/drm/amd/display/dc/dcn21/Makefile
View File

@ -3,13 +3,11 @@
DCN21 = dcn21_hubp.o dcn21_hubbub.o dcn21_resource.o
ifneq ($(call cc-option, -mpreferred-stack-boundary=4),)
cc_stack_align := -mpreferred-stack-boundary=4
else ifneq ($(call cc-option, -mstack-alignment=16),)
cc_stack_align := -mstack-alignment=16
endif
CFLAGS_$(AMDDALPATH)/dc/dcn21/dcn21_resource.o := -mhard-float -msse
CFLAGS_$(AMDDALPATH)/dc/dcn21/dcn21_resource.o := -mhard-float -msse $(cc_stack_align)
ifdef CONFIG_CC_IS_GCC
CFLAGS_$(AMDDALPATH)/dc/dcn21/dcn21_resource.o += -mpreferred-stack-boundary=4
endif
ifdef CONFIG_CC_IS_CLANG
CFLAGS_$(AMDDALPATH)/dc/dcn21/dcn21_resource.o += -msse2

10
drivers/gpu/drm/amd/display/dc/dml/Makefile
View File

@ -24,13 +24,11 @@
# It provides the general basic services required by other DAL
# subcomponents.
ifneq ($(call cc-option, -mpreferred-stack-boundary=4),)
cc_stack_align := -mpreferred-stack-boundary=4
else ifneq ($(call cc-option, -mstack-alignment=16),)
cc_stack_align := -mstack-alignment=16
endif
dml_ccflags := -mhard-float -msse
dml_ccflags := -mhard-float -msse $(cc_stack_align)
ifdef CONFIG_CC_IS_GCC
dml_ccflags += -mpreferred-stack-boundary=4
endif
ifdef CONFIG_CC_IS_CLANG
dml_ccflags += -msse2

10
drivers/gpu/drm/amd/display/dc/dsc/Makefile
View File

@ -1,13 +1,11 @@
#
# Makefile for the 'dsc' sub-component of DAL.
ifneq ($(call cc-option, -mpreferred-stack-boundary=4),)
cc_stack_align := -mpreferred-stack-boundary=4
else ifneq ($(call cc-option, -mstack-alignment=16),)
cc_stack_align := -mstack-alignment=16
endif
dsc_ccflags := -mhard-float -msse
dsc_ccflags := -mhard-float -msse $(cc_stack_align)
ifdef CONFIG_CC_IS_GCC
dsc_ccflags += -mpreferred-stack-boundary=4
endif
ifdef CONFIG_CC_IS_CLANG
dsc_ccflags += -msse2