| Message ID | 20231102-amdgpu-dml2-increase-frame-size-warning-for-clang-v2-1-b088a718131a@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] drm/amd/display: Increase frame warning limit with KASAN or KCSAN in dml2 | expand |
On Thu, Nov 2, 2023 at 1:41 PM Nathan Chancellor <nathan@kernel.org> wrote: > > When building ARCH=x86_64 allmodconfig with clang, which will typically > have sanitizers enabled, there is a warning about a large stack frame. > > drivers/gpu/drm/amd/amdgpu/../display/dc/dml2/display_mode_core.c:6265:13: error: stack frame size (2520) exceeds limit (2048) in 'dml_prefetch_check' [-Werror,-Wframe-larger-than] > 6265 | static void dml_prefetch_check(struct display_mode_lib_st *mode_lib) > | ^ > 1 error generated. > > Notably, GCC 13.2.0 does not do too much of a better job, as it is right > at the current limit of 2048 (and others have reported being over with > older GCC versions): > > drivers/gpu/drm/amd/amdgpu/../display/dc/dml2/display_mode_core.c: In function 'dml_prefetch_check': > drivers/gpu/drm/amd/amdgpu/../display/dc/dml2/display_mode_core.c:6705:1: error: the frame size of 2048 bytes is larger than 1800 bytes [-Werror=frame-larger-than=] > 6705 | } > | ^ > > In the past, these warnings have been avoided by reducing the number of > parameters to various functions so that not as many arguments need to be > passed on the stack. However, these patches take a good amount of effort > to write despite being mechanical due to code structure and complexity > and they are never carried forward to new generations of the code so > that effort has to be expended every new hardware generation, which > becomes harder to justify as time goes on. > > To avoid having a noticeable or lengthy breakage in all{mod,yes}config, > which are easy testing targets that have -Werror enabled, increase the > limit for configurations that have KASAN or KCSAN enabled by 50% so that > cases of extremely poor code generation can still be caught while not > breaking the majority of builds. CONFIG_KMSAN also causes high stack > usage but the frame limit is already set to zero when it is enabled, > which is accounted for by the check for CONFIG_FRAME_WARN=0 in the dml2 > Makefile. > > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > --- > If there is another DRM pull before 6.7-rc1, it would be much > appreciated if this could make that so that other trees are not > potentially broken by this. If not, no worries, as it was my fault for > not sending this sooner. Applied. Thanks! Will send out a PR this week. Alex > > Changes in v2: > - Adjust workaround to check for either CONFIG_KASAN=y or > CONFIG_KCSAN=y, as the same problem has been reported with older > versions of GCC (Hamza, Alex) > - Link to v1: https://lore.kernel.org/r/20231102-amdgpu-dml2-increase-frame-size-warning-for-clang-v1-1-6eb157352931@kernel.org > --- > drivers/gpu/drm/amd/display/dc/dml2/Makefile | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/gpu/drm/amd/display/dc/dml2/Makefile b/drivers/gpu/drm/amd/display/dc/dml2/Makefile > index 70ae5eba624e..acff3449b8d7 100644 > --- a/drivers/gpu/drm/amd/display/dc/dml2/Makefile > +++ b/drivers/gpu/drm/amd/display/dc/dml2/Makefile > @@ -60,8 +60,12 @@ endif > endif > > ifneq ($(CONFIG_FRAME_WARN),0) > +ifeq ($(filter y,$(CONFIG_KASAN)$(CONFIG_KCSAN)),y) > +frame_warn_flag := -Wframe-larger-than=3072 > +else > frame_warn_flag := -Wframe-larger-than=2048 > endif > +endif > > CFLAGS_$(AMDDALPATH)/dc/dml2/display_mode_core.o := $(dml2_ccflags) $(frame_warn_flag) > CFLAGS_$(AMDDALPATH)/dc/dml2/display_mode_util.o := $(dml2_ccflags) > > --- > base-commit: 21e80f3841c01aeaf32d7aee7bbc87b3db1aa0c6 > change-id: 20231102-amdgpu-dml2-increase-frame-size-warning-for-clang-c93bd2d6a871 > > Best regards, > -- > Nathan Chancellor <nathan@kernel.org> >
diff --git a/drivers/gpu/drm/amd/display/dc/dml2/Makefile b/drivers/gpu/drm/amd/display/dc/dml2/Makefile index 70ae5eba624e..acff3449b8d7 100644 --- a/drivers/gpu/drm/amd/display/dc/dml2/Makefile +++ b/drivers/gpu/drm/amd/display/dc/dml2/Makefile @@ -60,8 +60,12 @@ endif endif ifneq ($(CONFIG_FRAME_WARN),0) +ifeq ($(filter y,$(CONFIG_KASAN)$(CONFIG_KCSAN)),y) +frame_warn_flag := -Wframe-larger-than=3072 +else frame_warn_flag := -Wframe-larger-than=2048 endif +endif CFLAGS_$(AMDDALPATH)/dc/dml2/display_mode_core.o := $(dml2_ccflags) $(frame_warn_flag) CFLAGS_$(AMDDALPATH)/dc/dml2/display_mode_util.o := $(dml2_ccflags)
When building ARCH=x86_64 allmodconfig with clang, which will typically have sanitizers enabled, there is a warning about a large stack frame. drivers/gpu/drm/amd/amdgpu/../display/dc/dml2/display_mode_core.c:6265:13: error: stack frame size (2520) exceeds limit (2048) in 'dml_prefetch_check' [-Werror,-Wframe-larger-than] 6265 | static void dml_prefetch_check(struct display_mode_lib_st *mode_lib) | ^ 1 error generated. Notably, GCC 13.2.0 does not do too much of a better job, as it is right at the current limit of 2048 (and others have reported being over with older GCC versions): drivers/gpu/drm/amd/amdgpu/../display/dc/dml2/display_mode_core.c: In function 'dml_prefetch_check': drivers/gpu/drm/amd/amdgpu/../display/dc/dml2/display_mode_core.c:6705:1: error: the frame size of 2048 bytes is larger than 1800 bytes [-Werror=frame-larger-than=] 6705 | } | ^ In the past, these warnings have been avoided by reducing the number of parameters to various functions so that not as many arguments need to be passed on the stack. However, these patches take a good amount of effort to write despite being mechanical due to code structure and complexity and they are never carried forward to new generations of the code so that effort has to be expended every new hardware generation, which becomes harder to justify as time goes on. To avoid having a noticeable or lengthy breakage in all{mod,yes}config, which are easy testing targets that have -Werror enabled, increase the limit for configurations that have KASAN or KCSAN enabled by 50% so that cases of extremely poor code generation can still be caught while not breaking the majority of builds. CONFIG_KMSAN also causes high stack usage but the frame limit is already set to zero when it is enabled, which is accounted for by the check for CONFIG_FRAME_WARN=0 in the dml2 Makefile. Signed-off-by: Nathan Chancellor <nathan@kernel.org> --- If there is another DRM pull before 6.7-rc1, it would be much appreciated if this could make that so that other trees are not potentially broken by this. If not, no worries, as it was my fault for not sending this sooner. Changes in v2: - Adjust workaround to check for either CONFIG_KASAN=y or CONFIG_KCSAN=y, as the same problem has been reported with older versions of GCC (Hamza, Alex) - Link to v1: https://lore.kernel.org/r/20231102-amdgpu-dml2-increase-frame-size-warning-for-clang-v1-1-6eb157352931@kernel.org --- drivers/gpu/drm/amd/display/dc/dml2/Makefile | 4 ++++ 1 file changed, 4 insertions(+) --- base-commit: 21e80f3841c01aeaf32d7aee7bbc87b3db1aa0c6 change-id: 20231102-amdgpu-dml2-increase-frame-size-warning-for-clang-c93bd2d6a871 Best regards,