* Make the s390-ccw bios compilable with Clang

* Fix ECKD booting with null block numbers in the chain
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Merge remote-tracking branch 'remotes/thuth-gitlab/tags/s390-ccw-bios-2021-05-10' into staging

* Make the s390-ccw bios compilable with Clang
* Fix ECKD booting with null block numbers in the chain

# gpg: Signature made Mon 10 May 2021 08:27:34 BST
# gpg:                using RSA key 27B88847EEE0250118F3EAB92ED9D774FE702DB5
# gpg:                issuer "thuth@redhat.com"
# gpg: Good signature from "Thomas Huth <th.huth@gmx.de>" [full]
# gpg:                 aka "Thomas Huth <thuth@redhat.com>" [full]
# gpg:                 aka "Thomas Huth <huth@tuxfamily.org>" [full]
# gpg:                 aka "Thomas Huth <th.huth@posteo.de>" [unknown]
# Primary key fingerprint: 27B8 8847 EEE0 2501 18F3  EAB9 2ED9 D774 FE70 2DB5

* remotes/thuth-gitlab/tags/s390-ccw-bios-2021-05-10:
  pc-bios/s390: Update the s390-ccw bios binaries with the Clang and other fixes
  pc-bios/s390-ccw: Allow building with Clang, too
  pc-bios/s390-ccw: Silence GCC 11 stringop-overflow warning
  pc-bios/s390-ccw: Fix the cc-option macro in the Makefile
  pc-bios/s390-ccw: Silence warning from Clang by marking panic() as noreturn
  pc-bios/s390-ccw/netboot: Use "-Wl," prefix to pass parameter to the linker
  pc-bios/s390-ccw: Use reset_psw pointer instead of hard-coded null pointer
  pc-bios/s390-ccw/bootmap: Silence compiler warning from Clang
  pc-bios/s390-ccw: don't try to read the next block if end of chunk is reached

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

configure

@@ -5440,9 +5440,16 @@ if { test "$cpu" = "i386" || test "$cpu" = "x86_64"; } && \
 fi
 
 # Only build s390-ccw bios if we're on s390x and the compiler has -march=z900
+# or -march=z10 (which is the lowest architecture level that Clang supports)
 if test "$cpu" = "s390x" ; then
   write_c_skeleton
-  if compile_prog "-march=z900" ""; then
+  compile_prog "-march=z900" ""
+  has_z900=$?
+  if [ $has_z900 = 0 ] || compile_prog "-march=z10" ""; then
+    if [ $has_z900 != 0 ]; then
+      echo "WARNING: Your compiler does not support the z900!"
+      echo "         The s390-ccw bios will only work with guest CPUs >= z10."
+    fi
     roms="$roms s390-ccw"
     # SLOF is required for building the s390-ccw firmware on s390x,
     # since it is using the libnet code from SLOF for network booting.

pc-bios/s390-ccw/Makefile

@@ -6,8 +6,8 @@ include ../../config-host.mak
 CFLAGS = -O2 -g
 
 quiet-command = $(if $(V),$1,$(if $(2),@printf "  %-7s %s\n" $2 $3 && $1, @$1))
-cc-option = $(if $(shell $(CC) $1 -S -o /dev/null -xc /dev/null > /dev/null \
-	      2>&1 && echo OK), $1, $2)
+cc-option = $(if $(shell $(CC) $1 $2 -S -o /dev/null -xc /dev/null \
+			 >/dev/null 2>&1 && echo OK),$2,$3)
 
 VPATH_SUFFIXES = %.c %.h %.S %.m %.mak %.sh %.rc Kconfig% %.json.in
 set-vpath = $(if $1,$(foreach PATTERN,$(VPATH_SUFFIXES),$(eval vpath $(PATTERN) $1)))
@@ -30,10 +30,12 @@ OBJECTS = start.o main.o bootmap.o jump2ipl.o sclp.o menu.o \
 	  virtio.o virtio-scsi.o virtio-blkdev.o libc.o cio.o dasd-ipl.o
 
 QEMU_CFLAGS := -Wall $(filter -W%, $(QEMU_CFLAGS))
+QEMU_CFLAGS += $(call cc-option,-Werror $(QEMU_CFLAGS),-Wno-stringop-overflow)
 QEMU_CFLAGS += -ffreestanding -fno-delete-null-pointer-checks -fno-common -fPIE
 QEMU_CFLAGS += -fwrapv -fno-strict-aliasing -fno-asynchronous-unwind-tables
 QEMU_CFLAGS += $(call cc-option, $(QEMU_CFLAGS), -fno-stack-protector)
-QEMU_CFLAGS += -msoft-float -march=z900
+QEMU_CFLAGS += -msoft-float
+QEMU_CFLAGS += $(call cc-option, $(QEMU_CFLAGS),-march=z900,-march=z10)
 QEMU_CFLAGS += -std=gnu99
 LDFLAGS += -Wl,-pie -nostdlib
 

pc-bios/s390-ccw/bootmap.c

@@ -213,7 +213,7 @@ static int eckd_get_boot_menu_index(block_number_t s1b_block_nr)
                 next_block_nr = eckd_block_num(&s1b->seek[i + 1].chs);
             }
 
-            if (next_block_nr) {
+            if (next_block_nr && !is_null_block_number(next_block_nr)) {
                 read_block(next_block_nr, s2_next_blk,
                            "Cannot read stage2 boot loader");
             }
@@ -299,7 +299,7 @@ static void ipl_eckd_cdl(void)
         sclp_print("Bad block size in zIPL section of IPL2 record.\n");
         return;
     }
-    if (!mbr->dev_type == DEV_TYPE_ECKD) {
+    if (mbr->dev_type != DEV_TYPE_ECKD) {
         sclp_print("Non-ECKD device type in zIPL section of IPL2 record.\n");
         return;
     }

pc-bios/s390-ccw/jump2ipl.c

@@ -82,8 +82,8 @@ void jump_to_low_kernel(void)
         jump_to_IPL_code(KERN_IMAGE_START);
     }
 
-    /* Trying to get PSW at zero address */
-    if (*((uint64_t *)0) & RESET_PSW_MASK) {
+    /* Trying to get PSW at zero address (pointed to by reset_psw) */
+    if (*reset_psw & RESET_PSW_MASK) {
         /*
          * Surely nobody will try running directly from lowcore, so
          * let's use 0 as an indication that we want to load the reset

pc-bios/s390-ccw/netboot.mak

@@ -6,7 +6,7 @@ NETOBJS := start.o sclp.o cio.o virtio.o virtio-net.o jump2ipl.o netmain.o
 LIBC_INC := -nostdinc -I$(SLOF_DIR)/lib/libc/include
 LIBNET_INC := -I$(SLOF_DIR)/lib/libnet
 
-NETLDFLAGS := $(LDFLAGS) -Ttext=0x7800000
+NETLDFLAGS := $(LDFLAGS) -Wl,-Ttext=0x7800000
 
 $(NETOBJS): QEMU_CFLAGS += $(LIBC_INC) $(LIBNET_INC)
 

pc-bios/s390-ccw/s390-ccw.h

@@ -89,6 +89,7 @@ bool menu_is_enabled_enum(void);
 
 #define MAX_BOOT_ENTRIES  31
 
+__attribute__ ((__noreturn__))
 static inline void panic(const char *string)
 {
     sclp_print(string);