On 23.02.2023 10:57, Dmitry Baryshkov wrote: > The rewritten dpu_hw_ctl_setup_blendstage() can lightly smash the stack > when setting the SSPP_NONE pipe. However it was unnoticed until the > kernel was tested under AOSP (with some kind of stack protection/check). > > This fixes the following backtrace: > > Unexpected kernel BRK exception at EL1 > Internal error: BRK handler: 00000000f20003e8 [#1] PREEMPT SMP > Hardware name: Thundercomm Dragonboard 845c (DT) > pstate: a0400005 (NzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : dpu_hw_ctl_setup_blendstage+0x26c/0x278 [msm] > lr : _dpu_crtc_blend_setup+0x4b4/0x5a0 [msm] > sp : ffffffc00bdcb720 > x29: ffffffc00bdcb720 x28: ffffff8085debac0 x27: 0000000000000002 > x26: ffffffd74af18320 x25: ffffff8083af75a0 x24: ffffffc00bdcb878 > x23: 0000000000000001 x22: 0000000000000000 x21: ffffff8085a70000 > x20: ffffff8083012dc0 x19: 0000000000000001 x18: 0000000000000000 > x17: 000000040044ffff x16: 045000f4b5593519 x15: 0000000000000000 > x14: 000000000000000b x13: 0000000000000001 x12: 0000000000000000 > x11: 0000000000000001 x10: ffffffc00bdcb764 x9 : ffffffd74af06a08 > x8 : 0000000000000001 x7 : 0000000000000001 x6 : 0000000000000000 > x5 : ffffffc00bdcb878 x4 : 0000000000000002 x3 : ffffffffffffffff > x2 : ffffffc00bdcb878 x1 : 0000000000000000 x0 : 0000000000000002 > Call trace: > dpu_hw_ctl_setup_blendstage+0x26c/0x278 [msm] > _dpu_crtc_blend_setup+0x4b4/0x5a0 [msm] > dpu_crtc_atomic_begin+0xd8/0x22c [msm] > drm_atomic_helper_commit_planes+0x80/0x208 [drm_kms_helper] > msm_atomic_commit_tail+0x134/0x6f0 [msm] > commit_tail+0xa4/0x1a4 [drm_kms_helper] > drm_atomic_helper_commit+0x170/0x184 [drm_kms_helper] > drm_atomic_commit+0xac/0xe8 > drm_mode_atomic_ioctl+0xbf0/0xdac > drm_ioctl_kernel+0xc4/0x178 > drm_ioctl+0x2c8/0x608 > __arm64_sys_ioctl+0xa8/0xec > invoke_syscall+0x44/0x104 > el0_svc_common.constprop.0+0x44/0xec > do_el0_svc+0x38/0x98 > el0_svc+0x2c/0xb4 > el0t_64_sync_handler+0xb8/0xbc > el0t_64_sync+0x1a0/0x1a4 > Code: 52800016 52800017 52800018 17ffffc7 (d4207d00) > > Fixes: 4488f71f6373 ("drm/msm/dpu: simplify blend configuration") > Reported-by: Amit Pundir <amit.pundir@xxxxxxxxxx> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> > --- > drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c > index b88a2f3724e6..6c53ea560ffa 100644 > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c > @@ -446,7 +446,9 @@ static void dpu_hw_ctl_setup_blendstage(struct dpu_hw_ctl *ctx, > * CTL_LAYER has 3-bit field (and extra bits in EXT register), > * all EXT registers has 4-bit fields. > */ > - if (cfg->idx == 0) { > + if (cfg->idx == -1) { if (cfg->idx == ctl_blend_config[SSPP_NONE][0].idx)? Konrad > + continue; > + } else if (cfg->idx == 0) { > mixercfg[0] |= mix << cfg->shift; > mixercfg[1] |= ext << cfg->ext_shift; > } else { >