Merge tag 'Wimplicit-fallthrough-5.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux

torvalds · torvalds · commit 88c508344245 · 2019-07-27T11:04:18.000-07:00
Pull Wimplicit-fallthrough enablement from Gustavo A. R. Silva:
 "This marks switch cases where we are expecting to fall through, and
  globally enables the -Wimplicit-fallthrough option in the main
  Makefile.

  Finally, some missing-break fixes that have been tagged for -stable:

   - drm/amdkfd: Fix missing break in switch statement

   - drm/amdgpu/gfx10: Fix missing break in switch statement

  With these changes, we completely get rid of all the fall-through
  warnings in the kernel"

* tag 'Wimplicit-fallthrough-5.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux:
  Makefile: Globally enable fall-through warning
  drm/i915: Mark expected switch fall-throughs
  drm/amd/display: Mark expected switch fall-throughs
  drm/amdkfd/kfd_mqd_manager_v10: Avoid fall-through warning
  drm/amdgpu/gfx10: Fix missing break in switch statement
  drm/amdkfd: Fix missing break in switch statement
  perf/x86/intel: Mark expected switch fall-throughs
  mtd: onenand_base: Mark expected switch fall-through
  afs: fsclient: Mark expected switch fall-throughs
  afs: yfsclient: Mark expected switch fall-throughs
  can: mark expected switch fall-throughs
  firewire: mark expected switch fall-throughs
diff --git a/Documentation/process/deprecated.rst b/Documentation/process/deprecated.rst
@@ -119,3 +119,17 @@ array may exceed the remaining memory in the stack segment. This could
 lead to a crash, possible overwriting sensitive contents at the end of the
 stack (when built without `CONFIG_THREAD_INFO_IN_TASK=y`), or overwriting
 memory adjacent to the stack (when built without `CONFIG_VMAP_STACK=y`)
+
+Implicit switch case fall-through
+---------------------------------
+The C language allows switch cases to "fall through" when
+a "break" statement is missing at the end of a case. This,
+however, introduces ambiguity in the code, as it's not always
+clear if the missing break is intentional or a bug. As there
+have been a long list of flaws `due to missing "break" statements
+<https://cwe.mitre.org/data/definitions/484.html>`_, we no longer allow
+"implicit fall-through". In order to identify an intentional fall-through
+case, we have adopted the marking used by static analyzers: a comment
+saying `/* Fall through */`. Once the C++17 `__attribute__((fallthrough))`
+is more widely handled by C compilers, static analyzers, and IDEs, we can
+switch to using that instead.
diff --git a/Makefile b/Makefile
@@ -843,6 +843,9 @@ NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
 # warn about C99 declaration after statement
 KBUILD_CFLAGS += -Wdeclaration-after-statement
 
+# Warn about unmarked fall-throughs in switch statement.
+KBUILD_CFLAGS += $(call cc-option,-Wimplicit-fallthrough=3,)
+
 # Variable Length Arrays (VLAs) should not be used anywhere in the kernel
 KBUILD_CFLAGS += -Wvla
 
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
@@ -4955,6 +4955,7 @@ __init int intel_pmu_init(void)
 
 	case INTEL_FAM6_SKYLAKE_X:
 		pmem = true;
+		/* fall through */
 	case INTEL_FAM6_SKYLAKE_MOBILE:
 	case INTEL_FAM6_SKYLAKE_DESKTOP:
 	case INTEL_FAM6_KABYLAKE_MOBILE:
@@ -5004,6 +5005,7 @@ __init int intel_pmu_init(void)
 	case INTEL_FAM6_ICELAKE_X:
 	case INTEL_FAM6_ICELAKE_XEON_D:
 		pmem = true;
+		/* fall through */
 	case INTEL_FAM6_ICELAKE_MOBILE:
 	case INTEL_FAM6_ICELAKE_DESKTOP:
 		x86_pmu.late_ack = true;
diff --git a/drivers/firewire/core-device.c b/drivers/firewire/core-device.c
@@ -957,7 +957,7 @@ static void set_broadcast_channel(struct fw_device *device, int generation)
 				device->bc_implemented = BC_IMPLEMENTED;
 				break;
 			}
-			/* else fall through to case address error */
+			/* else, fall through - to case address error */
 		case RCODE_ADDRESS_ERROR:
 			device->bc_implemented = BC_UNIMPLEMENTED;
 		}
diff --git a/drivers/firewire/core-iso.c b/drivers/firewire/core-iso.c
@@ -284,7 +284,7 @@ static int manage_channel(struct fw_card *card, int irm_id, int generation,
 			if ((data[0] & bit) == (data[1] & bit))
 				continue;
 
-			/* 1394-1995 IRM, fall through to retry. */
+			/* fall through - It's a 1394-1995 IRM, retry. */
 		default:
 			if (retry) {
 				retry--;
diff --git a/drivers/firewire/core-topology.c b/drivers/firewire/core-topology.c
@@ -54,6 +54,7 @@ static u32 *count_ports(u32 *sid, int *total_port_count, int *child_port_count)
 		switch (port_type) {
 		case SELFID_PORT_CHILD:
 			(*child_port_count)++;
+			/* fall through */
 		case SELFID_PORT_PARENT:
 		case SELFID_PORT_NCONN:
 			(*total_port_count)++;
diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c
@@ -4620,6 +4620,7 @@ gfx_v10_0_set_gfx_eop_interrupt_state(struct amdgpu_device *adev,
 		cp_int_cntl = REG_SET_FIELD(cp_int_cntl, CP_INT_CNTL_RING0,
 					    TIME_STAMP_INT_ENABLE, 0);
 		WREG32(cp_int_cntl_reg, cp_int_cntl);
+		break;
 	case AMDGPU_IRQ_STATE_ENABLE:
 		cp_int_cntl = RREG32(cp_int_cntl_reg);
 		cp_int_cntl = REG_SET_FIELD(cp_int_cntl, CP_INT_CNTL_RING0,
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_crat.c b/drivers/gpu/drm/amd/amdkfd/kfd_crat.c
@@ -668,6 +668,7 @@ static int kfd_fill_gpu_cache_info(struct kfd_dev *kdev,
 	case CHIP_RAVEN:
 		pcache_info = raven_cache_info;
 		num_of_cache_types = ARRAY_SIZE(raven_cache_info);
+		break;
 	case CHIP_NAVI10:
 		pcache_info = navi10_cache_info;
 		num_of_cache_types = ARRAY_SIZE(navi10_cache_info);
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v10.c b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v10.c
@@ -429,7 +429,6 @@ struct mqd_manager *mqd_manager_init_v10(enum KFD_MQD_TYPE type,
 
 	switch (type) {
 	case KFD_MQD_TYPE_CP:
-		pr_debug("%s@%i\n", __func__, __LINE__);
 	case KFD_MQD_TYPE_COMPUTE:
 		pr_debug("%s@%i\n", __func__, __LINE__);
 		mqd->allocate_mqd = allocate_mqd;
diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_dccg.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_dccg.c
@@ -102,14 +102,19 @@ void dccg2_init(struct dccg *dccg)
 	switch (dccg_dcn->base.ctx->dc->res_pool->pipe_count) {
 	case 6:
 		REG_UPDATE(DPPCLK_DTO_CTRL, DPPCLK_DTO_DB_EN[5], 1);
+		/* Fall through */
 	case 5:
 		REG_UPDATE(DPPCLK_DTO_CTRL, DPPCLK_DTO_DB_EN[4], 1);
+		/* Fall through */
 	case 4:
 		REG_UPDATE(DPPCLK_DTO_CTRL, DPPCLK_DTO_DB_EN[3], 1);
+		/* Fall through */
 	case 3:
 		REG_UPDATE(DPPCLK_DTO_CTRL, DPPCLK_DTO_DB_EN[2], 1);
+		/* Fall through */
 	case 2:
 		REG_UPDATE(DPPCLK_DTO_CTRL, DPPCLK_DTO_DB_EN[1], 1);
+		/* Fall through */
 	case 1:
 		REG_UPDATE(DPPCLK_DTO_CTRL, DPPCLK_DTO_DB_EN[0], 1);
 		break;
diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
@@ -16,7 +16,6 @@ subdir-ccflags-y := -Wall -Wextra
 subdir-ccflags-y += $(call cc-disable-warning, unused-parameter)
 subdir-ccflags-y += $(call cc-disable-warning, type-limits)
 subdir-ccflags-y += $(call cc-disable-warning, missing-field-initializers)
-subdir-ccflags-y += $(call cc-disable-warning, implicit-fallthrough)
 subdir-ccflags-y += $(call cc-disable-warning, unused-but-set-variable)
 # clang warnings
 subdir-ccflags-y += $(call cc-disable-warning, sign-compare)
diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
@@ -12042,7 +12042,7 @@ static bool check_digital_port_conflicts(struct intel_atomic_state *state)
 		case INTEL_OUTPUT_DDI:
 			if (WARN_ON(!HAS_DDI(to_i915(dev))))
 				break;
-			/* else: fall through */
+			/* else, fall through */
 		case INTEL_OUTPUT_DP:
 		case INTEL_OUTPUT_HDMI:
 		case INTEL_OUTPUT_EDP:
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -231,6 +231,7 @@ static int intel_dp_get_fia_supported_lane_count(struct intel_dp *intel_dp)
 	switch (lane_info) {
 	default:
 		MISSING_CASE(lane_info);
+		/* fall through */
 	case 1:
 	case 2:
 	case 4:
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -341,7 +341,7 @@ vm_fault_t i915_gem_fault(struct vm_fault *vmf)
 		 */
 		if (!i915_terminally_wedged(i915))
 			return VM_FAULT_SIGBUS;
-		/* else: fall through */
+		/* else, fall through */
 	case -EAGAIN:
 		/*
 		 * EAGAIN means the gpu is hung and we'll wait for the error
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
@@ -268,7 +268,7 @@ static void *i915_gem_object_map(const struct drm_i915_gem_object *obj,
 	switch (type) {
 	default:
 		MISSING_CASE(type);
-		/* fallthrough to use PAGE_KERNEL anyway */
+		/* fallthrough - to use PAGE_KERNEL anyway */
 	case I915_MAP_WB:
 		pgprot = PAGE_KERNEL;
 		break;
diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -1194,6 +1194,7 @@ static void error_record_engine_registers(struct i915_gpu_state *error,
 			switch (engine->id) {
 			default:
 				MISSING_CASE(engine->id);
+				/* fall through */
 			case RCS0:
 				mmio = RENDER_HWS_PGA_GEN7;
 				break;
diff --git a/drivers/mtd/nand/onenand/onenand_base.c b/drivers/mtd/nand/onenand/onenand_base.c
@@ -3259,6 +3259,7 @@ static void onenand_check_features(struct mtd_info *mtd)
 	switch (density) {
 	case ONENAND_DEVICE_DENSITY_8Gb:
 		this->options |= ONENAND_HAS_NOP_1;
+		/* fall through */
 	case ONENAND_DEVICE_DENSITY_4Gb:
 		if (ONENAND_IS_DDP(this))
 			this->options |= ONENAND_HAS_2PLANE;
diff --git a/drivers/net/can/at91_can.c b/drivers/net/can/at91_can.c
@@ -898,7 +898,8 @@ static void at91_irq_err_state(struct net_device *dev,
 				CAN_ERR_CRTL_TX_WARNING :
 				CAN_ERR_CRTL_RX_WARNING;
 		}
-	case CAN_STATE_ERROR_WARNING:	/* fallthrough */
+		/* fall through */
+	case CAN_STATE_ERROR_WARNING:
 		/*
 		 * from: ERROR_ACTIVE, ERROR_WARNING
 		 * to  : ERROR_PASSIVE, BUS_OFF
@@ -947,7 +948,8 @@ static void at91_irq_err_state(struct net_device *dev,
 		netdev_dbg(dev, "Error Active\n");
 		cf->can_id |= CAN_ERR_PROT;
 		cf->data[2] = CAN_ERR_PROT_ACTIVE;
-	case CAN_STATE_ERROR_WARNING:	/* fallthrough */
+		/* fall through */
+	case CAN_STATE_ERROR_WARNING:
 		reg_idr = AT91_IRQ_ERRA | AT91_IRQ_WARN | AT91_IRQ_BOFF;
 		reg_ier = AT91_IRQ_ERRP;
 		break;
diff --git a/drivers/net/can/peak_canfd/peak_pciefd_main.c b/drivers/net/can/peak_canfd/peak_pciefd_main.c
@@ -660,7 +660,7 @@ static int pciefd_can_probe(struct pciefd_board *pciefd)
 		pciefd_can_writereg(priv, CANFD_CLK_SEL_80MHZ,
 				    PCIEFD_REG_CAN_CLK_SEL);
 
-		/* fallthough */
+		/* fall through */
 	case CANFD_CLK_SEL_80MHZ:
 		priv->ucan.can.clock.freq = 80 * 1000 * 1000;
 		break;
diff --git a/drivers/net/can/spi/mcp251x.c b/drivers/net/can/spi/mcp251x.c
@@ -860,7 +860,8 @@ static irqreturn_t mcp251x_can_ist(int irq, void *dev_id)
 			if (new_state >= CAN_STATE_ERROR_WARNING &&
 			    new_state <= CAN_STATE_BUS_OFF)
 				priv->can.can_stats.error_warning++;
-		case CAN_STATE_ERROR_WARNING:	/* fallthrough */
+			/* fall through */
+		case CAN_STATE_ERROR_WARNING:
 			if (new_state >= CAN_STATE_ERROR_PASSIVE &&
 			    new_state <= CAN_STATE_BUS_OFF)
 				priv->can.can_stats.error_passive++;
diff --git a/drivers/net/can/usb/peak_usb/pcan_usb.c b/drivers/net/can/usb/peak_usb/pcan_usb.c
@@ -415,7 +415,7 @@ static int pcan_usb_decode_error(struct pcan_usb_msg_context *mc, u8 n,
 			new_state = CAN_STATE_ERROR_WARNING;
 			break;
 		}
-		/* else: fall through */
+		/* fall through */
 
 	case CAN_STATE_ERROR_WARNING:
 		if (n & PCAN_USB_ERROR_BUS_HEAVY) {
diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
diff --git a/fs/afs/yfsclient.c b/fs/afs/yfsclient.c

Original file line number	Diff line number	Diff line change
`@@ -957,7 +957,7 @@ static void set_broadcast_channel(struct fw_device *device, int generation)`
`957`	`957`	`device->bc_implemented = BC_IMPLEMENTED;`
`958`	`958`	`break;`
`959`	`959`	`}`
`960`		`- /* else fall through to case address error */`
	`960`	`+ /* else, fall through - to case address error */`
`961`	`961`	`case RCODE_ADDRESS_ERROR:`
`962`	`962`	`device->bc_implemented = BC_UNIMPLEMENTED;`
`963`	`963`	`}`