diff mbox series

drm: amd: dc: don't use FP math when Kcov is enabled

Message ID 20171204131031.1418828-1-arnd@arndb.de
State New
Headers show
Series drm: amd: dc: don't use FP math when Kcov is enabled | expand

Commit Message

Arnd Bergmann Dec. 4, 2017, 1:08 p.m. UTC 
Building the DCN 1.0 Raven display driver with CONFIG_KCOV_INSTRUMENT_ALL=y
and CONFIG_KCOV_ENABLE_COMPARISONS=y results in warnings about many functions
that do a comparison of floating-point variables:

drivers/gpu/drm/amd/display/dc/calcs/dcn_calcs.o: In function `dcn_bw_calc_rq_dlg_ttu':
dcn_calcs.c:(.text+0x263): undefined reference to `__sanitizer_cov_trace_cmpf'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calcs.o: In function `hack_force_pipe_split':
dcn_calcs.c:(.text+0x155b): undefined reference to `__sanitizer_cov_trace_cmpf'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calcs.o: In function `dcn_find_dcfclk_suits_all':
dcn_calcs.c:(.text+0x190e): undefined reference to `__sanitizer_cov_trace_cmpf'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calcs.o: In function `dcn_validate_bandwidth':
dcn_calcs.c:(.text+0xe121): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_mod':
dcn_calc_math.c:(.text+0x22): undefined reference to `__sanitizer_cov_trace_cmpf'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_min2':
dcn_calc_math.c:(.text+0xb2): undefined reference to `__sanitizer_cov_trace_cmpf'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_ceil2':
dcn_calc_math.c:(.text+0x2a0): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_max3':
dcn_calc_math.c:(.text+0x325): undefined reference to `__sanitizer_cov_trace_cmpf'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_max5':
dcn_calc_math.c:(.text+0x3c3): undefined reference to `__sanitizer_cov_trace_cmpf'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_log':
dcn_calc_math.c:(.text+0x54e): undefined reference to `__sanitizer_cov_trace_cmpd'
dcn_calc_math.c:(.text+0x57c): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `scaler_settings_calculation':
dcn_calc_auto.c:(.text+0x5c5): undefined reference to `__sanitizer_cov_trace_cmpf'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `mode_support_and_system_configuration':
dcn_calc_auto.c:(.text+0x137c): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `mode_support_and_system_configuration':
dcn_calc_auto.c:(.text+0x9233): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `mode_support_and_system_configuration':
dcn_calc_auto.c:(.text+0xb70f): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `mode_support_and_system_configuration':
dcn_calc_auto.c:(.text+0x121fd): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `display_pipe_configuration':
dcn_calc_auto.c:(.text+0x15a2f): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `dispclkdppclkdcfclk_deep_sleep_prefetch_parameters_watermarks_and_performance_calculation':
dcn_calc_auto.c:(.text+0x17c2d): undefined reference to `__sanitizer_cov_trace_cmpf'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `dispclkdppclkdcfclk_deep_sleep_prefetch_parameters_watermarks_and_performance_calculation':
dcn_calc_auto.c:(.text+0x19362): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `dispclkdppclkdcfclk_deep_sleep_prefetch_parameters_watermarks_and_performance_calculation':
dcn_calc_auto.c:(.text+0x25575): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `dispclkdppclkdcfclk_deep_sleep_prefetch_parameters_watermarks_and_performance_calculation':
dcn_calc_auto.c:(.text+0x27f33): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/dml/display_rq_dlg_calc.o: In function `get_refcyc_per_delivery':
display_rq_dlg_calc.c:(.text+0xb5): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/dml/display_rq_dlg_calc.o: In function `calculate_ttu_cursor.isra.1':
display_rq_dlg_calc.c:(.text+0x9f6): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/dml/display_rq_dlg_calc.o: In function `dml_rq_dlg_get_dlg_params':
display_rq_dlg_calc.c:(.text+0x82cc): undefined reference to `__sanitizer_cov_trace_cmpf'
drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `get_refcyc_per_delivery.isra.0':
dml1_display_rq_dlg_calc.c:(.text+0x6c4): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `get_vratio_pre.isra.2':
dml1_display_rq_dlg_calc.c:(.text+0x957): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `get_swath_need.isra.3':
dml1_display_rq_dlg_calc.c:(.text+0xc8e): undefined reference to `__sanitizer_cov_trace_cmpf'
drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `dml1_extract_rq_regs':
dml1_display_rq_dlg_calc.c:(.text+0x30a8): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `dml1_rq_dlg_get_dlg_params':
dml1_display_rq_dlg_calc.c:(.text+0x41ee): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `dml1_rq_dlg_get_dlg_params':
dml1_display_rq_dlg_calc.c:(.text+0x8f95): undefined reference to `__sanitizer_cov_trace_cmpf'
drivers/gpu/drm/amd/display/dc/dml/dml_common_defs.o: In function `dml_round':
dml_common_defs.c:(.text+0x77): undefined reference to `__sanitizer_cov_trace_cmpd'
drivers/gpu/drm/amd/display/dc/dml/display_mode_vba.o: In function `adjust_ReturnBW':
display_mode_vba.c:(.text+0x4490): undefined reference to `__sanitizer_cov_trace_cmpd'

We already prevent the driver from being built on non-x86 architectures
because of its use of floating-point arithmetic, this extends the
dependency to also cover Kcov-enabled builds, which arguably is a much
more severe limitation.

I tried implementing the two functions in KCOV: __sanitizer_cov_trace_cmpd
and __sanitizer_cov_trace_cmpf, but that fails to build on architectures
that do not support any floating-point functions, or would require making
that code x86 specific as well.  I also looked at what it would take to
convert the code to fixed-point arithmetic, but quickly gave up. This
is probably the right approach, but it requires a non-trivial amount of
work and certainly won't be appropriate as a bugfix.

Fixes: bf2e2e2e0ea9 ("drm/amd/display: Limit DCN to x86 arch")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

---
 drivers/gpu/drm/amd/display/Kconfig | 2 ++
 1 file changed, 2 insertions(+)

-- 
2.9.0

Comments

Arnd Bergmann Dec. 5, 2017, 12:05 p.m. UTC | #1 
On Mon, Dec 4, 2017 at 9:34 PM, Harry Wentland <harry.wentland@amd.com> wrote:
> On 2017-12-04 08:08 AM, Arnd Bergmann wrote:

>> Building the DCN 1.0 Raven display driver with CONFIG_KCOV_INSTRUMENT_ALL=y

>> and CONFIG_KCOV_ENABLE_COMPARISONS=y results in warnings about many functions

>> that do a comparison of floating-point variables:

>>

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calcs.o: In function `dcn_bw_calc_rq_dlg_ttu':

>> dcn_calcs.c:(.text+0x263): undefined reference to `__sanitizer_cov_trace_cmpf'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calcs.o: In function `hack_force_pipe_split':

>> dcn_calcs.c:(.text+0x155b): undefined reference to `__sanitizer_cov_trace_cmpf'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calcs.o: In function `dcn_find_dcfclk_suits_all':

>> dcn_calcs.c:(.text+0x190e): undefined reference to `__sanitizer_cov_trace_cmpf'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calcs.o: In function `dcn_validate_bandwidth':

>> dcn_calcs.c:(.text+0xe121): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_mod':

>> dcn_calc_math.c:(.text+0x22): undefined reference to `__sanitizer_cov_trace_cmpf'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_min2':

>> dcn_calc_math.c:(.text+0xb2): undefined reference to `__sanitizer_cov_trace_cmpf'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_ceil2':

>> dcn_calc_math.c:(.text+0x2a0): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_max3':

>> dcn_calc_math.c:(.text+0x325): undefined reference to `__sanitizer_cov_trace_cmpf'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_max5':

>> dcn_calc_math.c:(.text+0x3c3): undefined reference to `__sanitizer_cov_trace_cmpf'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_log':

>> dcn_calc_math.c:(.text+0x54e): undefined reference to `__sanitizer_cov_trace_cmpd'

>> dcn_calc_math.c:(.text+0x57c): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `scaler_settings_calculation':

>> dcn_calc_auto.c:(.text+0x5c5): undefined reference to `__sanitizer_cov_trace_cmpf'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `mode_support_and_system_configuration':

>> dcn_calc_auto.c:(.text+0x137c): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `mode_support_and_system_configuration':

>> dcn_calc_auto.c:(.text+0x9233): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `mode_support_and_system_configuration':

>> dcn_calc_auto.c:(.text+0xb70f): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `mode_support_and_system_configuration':

>> dcn_calc_auto.c:(.text+0x121fd): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `display_pipe_configuration':

>> dcn_calc_auto.c:(.text+0x15a2f): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `dispclkdppclkdcfclk_deep_sleep_prefetch_parameters_watermarks_and_performance_calculation':

>> dcn_calc_auto.c:(.text+0x17c2d): undefined reference to `__sanitizer_cov_trace_cmpf'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `dispclkdppclkdcfclk_deep_sleep_prefetch_parameters_watermarks_and_performance_calculation':

>> dcn_calc_auto.c:(.text+0x19362): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `dispclkdppclkdcfclk_deep_sleep_prefetch_parameters_watermarks_and_performance_calculation':

>> dcn_calc_auto.c:(.text+0x25575): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `dispclkdppclkdcfclk_deep_sleep_prefetch_parameters_watermarks_and_performance_calculation':

>> dcn_calc_auto.c:(.text+0x27f33): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/dml/display_rq_dlg_calc.o: In function `get_refcyc_per_delivery':

>> display_rq_dlg_calc.c:(.text+0xb5): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/dml/display_rq_dlg_calc.o: In function `calculate_ttu_cursor.isra.1':

>> display_rq_dlg_calc.c:(.text+0x9f6): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/dml/display_rq_dlg_calc.o: In function `dml_rq_dlg_get_dlg_params':

>> display_rq_dlg_calc.c:(.text+0x82cc): undefined reference to `__sanitizer_cov_trace_cmpf'

>> drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `get_refcyc_per_delivery.isra.0':

>> dml1_display_rq_dlg_calc.c:(.text+0x6c4): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `get_vratio_pre.isra.2':

>> dml1_display_rq_dlg_calc.c:(.text+0x957): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `get_swath_need.isra.3':

>> dml1_display_rq_dlg_calc.c:(.text+0xc8e): undefined reference to `__sanitizer_cov_trace_cmpf'

>> drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `dml1_extract_rq_regs':

>> dml1_display_rq_dlg_calc.c:(.text+0x30a8): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `dml1_rq_dlg_get_dlg_params':

>> dml1_display_rq_dlg_calc.c:(.text+0x41ee): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `dml1_rq_dlg_get_dlg_params':

>> dml1_display_rq_dlg_calc.c:(.text+0x8f95): undefined reference to `__sanitizer_cov_trace_cmpf'

>> drivers/gpu/drm/amd/display/dc/dml/dml_common_defs.o: In function `dml_round':

>> dml_common_defs.c:(.text+0x77): undefined reference to `__sanitizer_cov_trace_cmpd'

>> drivers/gpu/drm/amd/display/dc/dml/display_mode_vba.o: In function `adjust_ReturnBW':

>> display_mode_vba.c:(.text+0x4490): undefined reference to `__sanitizer_cov_trace_cmpd'

>>

>

> Is this with clang? I don't seem to get these with gcc.


This was with gcc-8. I just tried other versions and found that gcc-7
and earlier
(i.e. all released versions) don't support CONFIG_KCOV_ENABLE_COMPARISONS
and won't be affected by this.

I've also tried building it with clang-5, but that rejects the
-mpreferred-stack-boundary=4
argument and (once I fixed that) did not have the issue either.
Presumably, clang-6
will do the same thing as gcc-8, but I haven't built a clang-6 snapshot yet.

>> diff --git a/drivers/gpu/drm/amd/display/Kconfig b/drivers/gpu/drm/amd/display/Kconfig

>> index ec3285f65517..5cd5906c9bee 100644

>> --- a/drivers/gpu/drm/amd/display/Kconfig

>> +++ b/drivers/gpu/drm/amd/display/Kconfig

>> @@ -30,6 +30,8 @@ config DRM_AMD_DC_FBC

>>  config DRM_AMD_DC_DCN1_0

>>       bool "DCN 1.0 Raven family"

>>       depends on DRM_AMD_DC && X86

>> +     # x86 floating point math here breaks with KCOV:

>> +     depends on !(KCOV_INSTRUMENT_ALL && KCOV_ENABLE_COMPARISONS) || BROKEN

>

> I don't think it makes sense to make this depend on BROKEN as it works and is quite

> useful to people with Raven systems.


Well, it's clearly broken when using with CONFIG_KCOV_ENABLE_COMPARISONS.
Fortunately that option doesn't do anything unless used with gcc-8, which won't
be released until next spring, so that leaves some time to change the code into
fixed-point arithmetic or find a different workaround.

        Arnd
Harry Wentland Dec. 5, 2017, 5:01 p.m. UTC | #2 
On 2017-12-05 07:05 AM, Arnd Bergmann wrote:
> On Mon, Dec 4, 2017 at 9:34 PM, Harry Wentland <harry.wentland@amd.com> wrote:

>> On 2017-12-04 08:08 AM, Arnd Bergmann wrote:

>>> Building the DCN 1.0 Raven display driver with CONFIG_KCOV_INSTRUMENT_ALL=y

>>> and CONFIG_KCOV_ENABLE_COMPARISONS=y results in warnings about many functions

>>> that do a comparison of floating-point variables:

>>>

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calcs.o: In function `dcn_bw_calc_rq_dlg_ttu':

>>> dcn_calcs.c:(.text+0x263): undefined reference to `__sanitizer_cov_trace_cmpf'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calcs.o: In function `hack_force_pipe_split':

>>> dcn_calcs.c:(.text+0x155b): undefined reference to `__sanitizer_cov_trace_cmpf'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calcs.o: In function `dcn_find_dcfclk_suits_all':

>>> dcn_calcs.c:(.text+0x190e): undefined reference to `__sanitizer_cov_trace_cmpf'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calcs.o: In function `dcn_validate_bandwidth':

>>> dcn_calcs.c:(.text+0xe121): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_mod':

>>> dcn_calc_math.c:(.text+0x22): undefined reference to `__sanitizer_cov_trace_cmpf'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_min2':

>>> dcn_calc_math.c:(.text+0xb2): undefined reference to `__sanitizer_cov_trace_cmpf'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_ceil2':

>>> dcn_calc_math.c:(.text+0x2a0): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_max3':

>>> dcn_calc_math.c:(.text+0x325): undefined reference to `__sanitizer_cov_trace_cmpf'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_max5':

>>> dcn_calc_math.c:(.text+0x3c3): undefined reference to `__sanitizer_cov_trace_cmpf'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_math.o: In function `dcn_bw_log':

>>> dcn_calc_math.c:(.text+0x54e): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> dcn_calc_math.c:(.text+0x57c): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `scaler_settings_calculation':

>>> dcn_calc_auto.c:(.text+0x5c5): undefined reference to `__sanitizer_cov_trace_cmpf'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `mode_support_and_system_configuration':

>>> dcn_calc_auto.c:(.text+0x137c): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `mode_support_and_system_configuration':

>>> dcn_calc_auto.c:(.text+0x9233): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `mode_support_and_system_configuration':

>>> dcn_calc_auto.c:(.text+0xb70f): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `mode_support_and_system_configuration':

>>> dcn_calc_auto.c:(.text+0x121fd): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `display_pipe_configuration':

>>> dcn_calc_auto.c:(.text+0x15a2f): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `dispclkdppclkdcfclk_deep_sleep_prefetch_parameters_watermarks_and_performance_calculation':

>>> dcn_calc_auto.c:(.text+0x17c2d): undefined reference to `__sanitizer_cov_trace_cmpf'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `dispclkdppclkdcfclk_deep_sleep_prefetch_parameters_watermarks_and_performance_calculation':

>>> dcn_calc_auto.c:(.text+0x19362): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `dispclkdppclkdcfclk_deep_sleep_prefetch_parameters_watermarks_and_performance_calculation':

>>> dcn_calc_auto.c:(.text+0x25575): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/calcs/dcn_calc_auto.o: In function `dispclkdppclkdcfclk_deep_sleep_prefetch_parameters_watermarks_and_performance_calculation':

>>> dcn_calc_auto.c:(.text+0x27f33): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/dml/display_rq_dlg_calc.o: In function `get_refcyc_per_delivery':

>>> display_rq_dlg_calc.c:(.text+0xb5): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/dml/display_rq_dlg_calc.o: In function `calculate_ttu_cursor.isra.1':

>>> display_rq_dlg_calc.c:(.text+0x9f6): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/dml/display_rq_dlg_calc.o: In function `dml_rq_dlg_get_dlg_params':

>>> display_rq_dlg_calc.c:(.text+0x82cc): undefined reference to `__sanitizer_cov_trace_cmpf'

>>> drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `get_refcyc_per_delivery.isra.0':

>>> dml1_display_rq_dlg_calc.c:(.text+0x6c4): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `get_vratio_pre.isra.2':

>>> dml1_display_rq_dlg_calc.c:(.text+0x957): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `get_swath_need.isra.3':

>>> dml1_display_rq_dlg_calc.c:(.text+0xc8e): undefined reference to `__sanitizer_cov_trace_cmpf'

>>> drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `dml1_extract_rq_regs':

>>> dml1_display_rq_dlg_calc.c:(.text+0x30a8): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `dml1_rq_dlg_get_dlg_params':

>>> dml1_display_rq_dlg_calc.c:(.text+0x41ee): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/dml/dml1_display_rq_dlg_calc.o: In function `dml1_rq_dlg_get_dlg_params':

>>> dml1_display_rq_dlg_calc.c:(.text+0x8f95): undefined reference to `__sanitizer_cov_trace_cmpf'

>>> drivers/gpu/drm/amd/display/dc/dml/dml_common_defs.o: In function `dml_round':

>>> dml_common_defs.c:(.text+0x77): undefined reference to `__sanitizer_cov_trace_cmpd'

>>> drivers/gpu/drm/amd/display/dc/dml/display_mode_vba.o: In function `adjust_ReturnBW':

>>> display_mode_vba.c:(.text+0x4490): undefined reference to `__sanitizer_cov_trace_cmpd'

>>>

>>

>> Is this with clang? I don't seem to get these with gcc.

> 

> This was with gcc-8. I just tried other versions and found that gcc-7

> and earlier

> (i.e. all released versions) don't support CONFIG_KCOV_ENABLE_COMPARISONS

> and won't be affected by this.

> 

> I've also tried building it with clang-5, but that rejects the

> -mpreferred-stack-boundary=4

> argument and (once I fixed that) did not have the issue either.

> Presumably, clang-6

> will do the same thing as gcc-8, but I haven't built a clang-6 snapshot yet.

> 

>>> diff --git a/drivers/gpu/drm/amd/display/Kconfig b/drivers/gpu/drm/amd/display/Kconfig

>>> index ec3285f65517..5cd5906c9bee 100644

>>> --- a/drivers/gpu/drm/amd/display/Kconfig

>>> +++ b/drivers/gpu/drm/amd/display/Kconfig

>>> @@ -30,6 +30,8 @@ config DRM_AMD_DC_FBC

>>>  config DRM_AMD_DC_DCN1_0

>>>       bool "DCN 1.0 Raven family"

>>>       depends on DRM_AMD_DC && X86

>>> +     # x86 floating point math here breaks with KCOV:

>>> +     depends on !(KCOV_INSTRUMENT_ALL && KCOV_ENABLE_COMPARISONS) || BROKEN

>>

>> I don't think it makes sense to make this depend on BROKEN as it works and is quite

>> useful to people with Raven systems.

> 

> Well, it's clearly broken when using with CONFIG_KCOV_ENABLE_COMPARISONS.

> Fortunately that option doesn't do anything unless used with gcc-8, which won't

> be released until next spring, so that leaves some time to change the code into

> fixed-point arithmetic or find a different workaround.

> 


Thanks, Arnd. This is what I was missing. I'll take another look.

It would still work without KCOV, although I agree that's not ideal by any means.

Harry

>         Arnd

>
diff mbox series

Patch

diff --git a/drivers/gpu/drm/amd/display/Kconfig b/drivers/gpu/drm/amd/display/Kconfig
index ec3285f65517..5cd5906c9bee 100644
--- a/drivers/gpu/drm/amd/display/Kconfig
+++ b/drivers/gpu/drm/amd/display/Kconfig
@@ -30,6 +30,8 @@  config DRM_AMD_DC_FBC
 config DRM_AMD_DC_DCN1_0
 	bool "DCN 1.0 Raven family"
 	depends on DRM_AMD_DC && X86
+	# x86 floating point math here breaks with KCOV:
+	depends on !(KCOV_INSTRUMENT_ALL && KCOV_ENABLE_COMPARISONS) || BROKEN
 	help
 	  Choose this option if you want to have
 	  RV family for display engine