i386, x86_64, ppc: fix switch fallthrough cases with GCC7

In util/getroot and efidisk slightly modify exitsing comment to mostly
retain it but still make GCC7 compliant with respect to fall through
annotation.

In grub-core/lib/xzembed/xz_dec_lzma2.c it adds same comments as
upstream.

In grub-core/tests/setjmp_tets.c declare functions as "noreturn" to
suppress GCC7 warning.

In grub-core/gnulib/regexec.c use new __attribute__, because existing
annotation is not recognized by GCC7 parser (which requires that comment
immediately precedes case statement).

Otherwise add FALLTHROUGH comment.

Closes: 50598

grub-core/commands/hdparm.c

@@ -328,6 +328,7 @@ grub_cmd_hdparm (grub_extcmd_context_t ctxt, int argc, char **args)
 	  ata = ((struct grub_scsi *) disk->data)->data;
 	  break;
 	}
+      /* FALLTHROUGH */
     default:
       grub_disk_close (disk);
       return grub_error (GRUB_ERR_IO, "not an ATA device");

grub-core/commands/nativedisk.c

@@ -79,6 +79,7 @@ get_uuid (const char *name, char **uuid, int getnative)
     case GRUB_DISK_DEVICE_XEN:
       if (getnative)
 	break;
+      /* FALLTHROUGH */
 
       /* Virtual disks.  */
       /* GRUB dynamically generated files.  */

grub-core/disk/cryptodisk.c

@@ -282,6 +282,7 @@ grub_cryptodisk_endecrypt (struct grub_cryptodisk *dev,
 	  break;
 	case GRUB_CRYPTODISK_MODE_IV_PLAIN64:
 	  iv[1] = grub_cpu_to_le32 (sector >> 32);
+	  /* FALLTHROUGH */
 	case GRUB_CRYPTODISK_MODE_IV_PLAIN:
 	  iv[0] = grub_cpu_to_le32 (sector & 0xFFFFFFFF);
 	  break;

grub-core/disk/efi/efidisk.c

@@ -224,7 +224,7 @@ name_devices (struct grub_efidisk_data *devices)
 	    {
 	    case GRUB_EFI_HARD_DRIVE_DEVICE_PATH_SUBTYPE:
 	      is_hard_drive = 1;
-	      /* Fall through by intention.  */
+	      /* Intentionally fall through.  */
 	    case GRUB_EFI_CDROM_DEVICE_PATH_SUBTYPE:
 	      {
 		struct grub_efidisk_data *parent, *parent2;

grub-core/efiemu/mm.c

@@ -417,6 +417,7 @@ fill_hook (grub_uint64_t addr, grub_uint64_t size, grub_memory_type_t type,
       default:
 	grub_dprintf ("efiemu",
 		      "Unknown memory type %d. Assuming unusable\n", type);
+	/* FALLTHROUGH */
       case GRUB_MEMORY_RESERVED:
 	return grub_efiemu_add_to_mmap (addr, size,
 					GRUB_EFI_UNUSABLE_MEMORY);

grub-core/gdb/cstub.c

@@ -336,6 +336,7 @@ grub_gdb_trap (int trap_no)
 	/* sAA..AA: Step one instruction from AA..AA(optional).  */
 	case 's':
 	  stepping = 1;
+	  /* FALLTHROUGH */
 
 	/* cAA..AA: Continue at address AA..AA(optional).  */
 	case 'c':

grub-core/gnulib/regexec.c

@@ -4099,6 +4099,9 @@ check_node_accept (const re_match_context_t *mctx, const re_token_t *node,
     case OP_UTF8_PERIOD:
       if (ch >= ASCII_CHARS)
         return false;
+#if defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((fallthrough));
+#endif
       /* FALLTHROUGH */
 #endif
     case OP_PERIOD:

grub-core/lib/xzembed/xz_dec_lzma2.c

@@ -1044,6 +1044,8 @@ enum xz_ret xz_dec_lzma2_run(
 
 			s->lzma2.sequence = SEQ_LZMA_PREPARE;
 
+		/* Fall through */
+
 		case SEQ_LZMA_PREPARE:
 			if (s->lzma2.compressed < RC_INIT_BYTES)
 				return XZ_DATA_ERROR;
@@ -1054,6 +1056,8 @@ enum xz_ret xz_dec_lzma2_run(
 			s->lzma2.compressed -= RC_INIT_BYTES;
 			s->lzma2.sequence = SEQ_LZMA_RUN;
 
+		/* Fall through */
+
 		case SEQ_LZMA_RUN:
 			/*
 			 * Set dictionary limit to indicate how much we want

grub-core/lib/xzembed/xz_dec_stream.c

@@ -750,6 +750,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 
 			s->sequence = SEQ_BLOCK_START;
 
+			/* FALLTHROUGH */
 		case SEQ_BLOCK_START:
 			/* We need one byte of input to continue. */
 			if (b->in_pos == b->in_size)
@@ -773,6 +774,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 			s->temp.pos = 0;
 			s->sequence = SEQ_BLOCK_HEADER;
 
+			/* FALLTHROUGH */
 		case SEQ_BLOCK_HEADER:
 			if (!fill_temp(s, b))
 				return XZ_OK;
@@ -783,6 +785,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 
 			s->sequence = SEQ_BLOCK_UNCOMPRESS;
 
+			/* FALLTHROUGH */
 		case SEQ_BLOCK_UNCOMPRESS:
 			ret = dec_block(s, b);
 			if (ret != XZ_STREAM_END)
@@ -810,6 +813,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 
 			s->sequence = SEQ_BLOCK_CHECK;
 
+			/* FALLTHROUGH */
 		case SEQ_BLOCK_CHECK:
 			ret = hash_validate(s, b, 0);
 			if (ret != XZ_STREAM_END)
@@ -858,6 +862,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 
 			s->sequence = SEQ_INDEX_CRC32;
 
+			/* FALLTHROUGH */
 		case SEQ_INDEX_CRC32:
 			ret = hash_validate(s, b, 1);
 			if (ret != XZ_STREAM_END)
@@ -866,6 +871,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 			s->temp.size = STREAM_HEADER_SIZE;
 			s->sequence = SEQ_STREAM_FOOTER;
 
+			/* FALLTHROUGH */
 		case SEQ_STREAM_FOOTER:
 			if (!fill_temp(s, b))
 				return XZ_OK;

grub-core/loader/i386/linux.c

@@ -984,10 +984,13 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
 	      {
 	      case 'g':
 		shift += 10;
+		/* FALLTHROUGH */
 	      case 'm':
 		shift += 10;
+		/* FALLTHROUGH */
 	      case 'k':
 		shift += 10;
+		/* FALLTHROUGH */
 	      default:
 		break;
 	      }

grub-core/tests/setjmp_test.c

@@ -25,7 +25,10 @@ GRUB_MOD_LICENSE ("GPLv3+");
 static grub_jmp_buf jmp_point;
 static int expected, ctr;
 
-#pragma GCC diagnostic ignored "-Wmissing-noreturn"
+/* This fixes GCC7 "unintentional fallthrough" warning */
+static void jmp0 (void) __attribute__ ((noreturn));
+static void jmp1 (void) __attribute__ ((noreturn));
+static void jmp2 (void) __attribute__ ((noreturn));
 
 static void
 jmp0 (void)

grub-core/video/ieee1275.c

@@ -181,6 +181,7 @@ grub_video_ieee1275_fill_mode_info (grub_ieee1275_phandle_t dev,
     case 32:
       out->reserved_mask_size = 8;
       out->reserved_field_pos = 24;
+      /* FALLTHROUGH */
 
     case 24:
       out->red_mask_size = 8;

grub-core/video/readers/jpeg.c

@@ -736,6 +736,7 @@ grub_jpeg_decode_jpeg (struct grub_jpeg_data *data)
 	case JPEG_MARKER_SOS:	/* Start Of Scan.  */
 	  if (grub_jpeg_decode_sos (data))
 	    break;
+	  /* FALLTHROUGH */
 	case JPEG_MARKER_RST0:	/* Restart.  */
 	case JPEG_MARKER_RST1:
 	case JPEG_MARKER_RST2:

util/getroot.c

@@ -99,7 +99,7 @@ grub_util_pull_device (const char *os_dev)
     {
     case GRUB_DEV_ABSTRACTION_LVM:
       grub_util_pull_lvm_by_command (os_dev);
-      /* Fallthrough in case that lvm-tools are unavailable.  */
+      /* Fallthrough - in case that lvm-tools are unavailable.  */
     case GRUB_DEV_ABSTRACTION_LUKS:
       grub_util_pull_devmapper (os_dev);
       return;

util/grub-install.c

@@ -1851,6 +1851,7 @@ main (int argc, char *argv[])
 	  free (mach_kernel);
 	  break;
 	}
+      /* FALLTHROUGH */
     case GRUB_INSTALL_PLATFORM_ARM_EFI:
     case GRUB_INSTALL_PLATFORM_ARM64_EFI:
     case GRUB_INSTALL_PLATFORM_IA64_EFI:

util/grub-mkimagexx.c

@@ -907,6 +907,7 @@ SUFFIX (relocate_addresses) (Elf_Ehdr *e, Elf_Shdr *sections,
 									    + sym->st_value
 									    - image_target->vaddr_offset));
 		  }
+		/* FALLTHROUGH */
 		case R_IA64_LTOFF_FPTR22:
 		  *gpptr = grub_host_to_target64 (addend + sym_addr);
 		  grub_ia64_add_value_to_slot_21 ((grub_addr_t) target,

util/grub-mount.c

@@ -530,6 +530,7 @@ argp_parser (int key, char *arg, struct argp_state *state)
       if (arg[0] != '-')
 	break;
 
+    /* FALLTHROUGH */
     default:
       if (!arg)
 	return 0;