drm/amd/display: Increase frame warning limit with KASAN or KCSAN in dml2

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>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/display/dc/dml2/Makefile b/drivers/gpu/drm/amd/display/dc/dml2/Makefile
index 70ae5eba624e5aa8c7405077ce1e267f97cb544a..acff3449b8d78754b004a15f9b1c7351a33612d2 100644 (file)
--- 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)