On Thu, Feb 20, 2020 at 12:21:14PM +0200, Jani Nikula wrote: > On Wed, 19 Feb 2020, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > Variables declared in a switch statement before any case statements > > cannot be automatically initialized with compiler instrumentation (as > > they are not part of any execution flow). With GCC's proposed automatic > > stack variable initialization feature, this triggers a warning (and they > > don't get initialized). Clang's automatic stack variable initialization > > (via CONFIG_INIT_STACK_ALL=y) doesn't throw a warning, but it also > > doesn't initialize such variables[1]. Note that these warnings (or silent > > skipping) happen before the dead-store elimination optimization phase, > > so even when the automatic initializations are later elided in favor of > > direct initializations, the warnings remain. > > > > To avoid these problems, move such variables into the "case" where > > they're used or lift them up into the main function body. > > > > drivers/gpu/drm/i915/display/intel_display.c: In function ‘check_digital_port_conflicts’: > > drivers/gpu/drm/i915/display/intel_display.c:12963:17: warning: statement will never be executed [-Wswitch-unreachable] > > 12963 | unsigned int port_mask; > > | ^~~~~~~~~ > > > > drivers/gpu/drm/i915/intel_pm.c: In function ‘vlv_get_fifo_size’: > > drivers/gpu/drm/i915/intel_pm.c:474:7: warning: statement will never be executed [-Wswitch-unreachable] > > 474 | u32 dsparb, dsparb2, dsparb3; > > | ^~~~~~ > > drivers/gpu/drm/i915/intel_pm.c: In function ‘vlv_atomic_update_fifo’: > > drivers/gpu/drm/i915/intel_pm.c:1997:7: warning: statement will never be executed [-Wswitch-unreachable] > > 1997 | u32 dsparb, dsparb2, dsparb3; > > | ^~~~~~ > > > > [1] https://bugs.llvm.org/show_bug.cgi?id=44916 > > > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > > Reviewed-by: Jani Nikula <jani.nikula@xxxxxxxxx> Thanks! > > If you look at i915/Makefile, you'll see that we don't shy away from > enabling lots of extra warnings, and we run our CI with -Werror to keep > it clean. It does not seem like -Wswitch-unreachable does me any good, > though... is it new? It's already enabled by default, but the GCC feature that tweaks it doesn't exist yet. But it points out a problem that exists for Clang today, but Clang doesn't actually warn on (yet). So this is a fix to avoid the silent Clang problem and fix future warnings before they happen. -Kees > > BR, > Jani. > > > > --- > > drivers/gpu/drm/i915/display/intel_display.c | 6 ++++-- > > drivers/gpu/drm/i915/intel_pm.c | 4 ++-- > > 2 files changed, 6 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c > > index 064dd99bbc49..c829cd26f99e 100644 > > --- a/drivers/gpu/drm/i915/display/intel_display.c > > +++ b/drivers/gpu/drm/i915/display/intel_display.c > > @@ -12960,14 +12960,15 @@ static bool check_digital_port_conflicts(struct intel_atomic_state *state) > > WARN_ON(!connector_state->crtc); > > > > switch (encoder->type) { > > - unsigned int port_mask; > > case INTEL_OUTPUT_DDI: > > if (WARN_ON(!HAS_DDI(to_i915(dev)))) > > break; > > /* else, fall through */ > > case INTEL_OUTPUT_DP: > > case INTEL_OUTPUT_HDMI: > > - case INTEL_OUTPUT_EDP: > > + case INTEL_OUTPUT_EDP: { > > + unsigned int port_mask; > > + > > port_mask = 1 << encoder->port; > > > > /* the same port mustn't appear more than once */ > > @@ -12976,6 +12977,7 @@ static bool check_digital_port_conflicts(struct intel_atomic_state *state) > > > > used_ports |= port_mask; > > break; > > + } > > case INTEL_OUTPUT_DP_MST: > > used_mst_ports |= > > 1 << encoder->port; > > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c > > index bd2d30ecc030..17d8833787c4 100644 > > --- a/drivers/gpu/drm/i915/intel_pm.c > > +++ b/drivers/gpu/drm/i915/intel_pm.c > > @@ -469,9 +469,9 @@ static void vlv_get_fifo_size(struct intel_crtc_state *crtc_state) > > struct vlv_fifo_state *fifo_state = &crtc_state->wm.vlv.fifo_state; > > enum pipe pipe = crtc->pipe; > > int sprite0_start, sprite1_start; > > + u32 dsparb, dsparb2, dsparb3; > > > > switch (pipe) { > > - u32 dsparb, dsparb2, dsparb3; > > case PIPE_A: > > dsparb = I915_READ(DSPARB); > > dsparb2 = I915_READ(DSPARB2); > > @@ -1969,6 +1969,7 @@ static void vlv_atomic_update_fifo(struct intel_atomic_state *state, > > const struct vlv_fifo_state *fifo_state = > > &crtc_state->wm.vlv.fifo_state; > > int sprite0_start, sprite1_start, fifo_size; > > + u32 dsparb, dsparb2, dsparb3; > > > > if (!crtc_state->fifo_changed) > > return; > > @@ -1994,7 +1995,6 @@ static void vlv_atomic_update_fifo(struct intel_atomic_state *state, > > spin_lock(&uncore->lock); > > > > switch (crtc->pipe) { > > - u32 dsparb, dsparb2, dsparb3; > > case PIPE_A: > > dsparb = intel_uncore_read_fw(uncore, DSPARB); > > dsparb2 = intel_uncore_read_fw(uncore, DSPARB2); > > > > -- > Jani Nikula, Intel Open Source Graphics Center -- Kees Cook _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
