pc-bios/s390-ccw: Move the stack array into start.S

The stack array is only referenced from the start-up code (which is
shared between the s390-ccw.img and the s390-netboot.img), but it is
currently declared twice, once in main.c and once in netmain.c.
It makes more sense to declare this in start.S instead - which will
also be helpful in the next patch, since we need to mention the .bss
section in start.S in that patch.

While we're at it, let's also drop the huge alignment of the stack,
since there is no technical requirement for aligning it to page
boundaries.

Message-Id: <20230627074703.99608-4-thuth@redhat.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

pc-bios/s390-ccw/main.c

@@ -17,7 +17,6 @@
 #include "virtio-scsi.h"
 #include "dasd-ipl.h"
 
-char stack[PAGE_SIZE * 8] __attribute__((__aligned__(PAGE_SIZE)));
 static SubChannelId blk_schid = { .one = 1 };
 static char loadparm_str[LOADPARM_LEN + 1];
 QemuIplParameters qipl;

pc-bios/s390-ccw/netmain.c

@@ -50,7 +50,6 @@ void write_iplb_location(void) {}
 /* STSI 3.2.2 offset of first vmdb + offset of uuid inside vmdb */
 #define STSI322_VMDB_UUID_OFFSET ((8 + 12) * 4)
 
-char stack[PAGE_SIZE * 8] __attribute__((aligned(PAGE_SIZE)));
 IplParameterBlock iplb __attribute__((aligned(PAGE_SIZE)));
 static char cfgbuf[2048];
 

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

@@ -50,7 +50,6 @@ void consume_io_int(void);
 /* main.c */
 void write_subsystem_identification(void);
 void write_iplb_location(void);
-extern char stack[PAGE_SIZE * 8] __attribute__((__aligned__(PAGE_SIZE)));
 unsigned int get_loadparm_index(void);
 void main(void);
 

pc-bios/s390-ccw/start.S

@@ -121,3 +121,9 @@ external_new_mask:
     .quad   0x0000000180000000
 io_new_mask:
     .quad   0x0000000180000000
+
+.bss
+    .align  8
+stack:
+    .space  STACK_SIZE
+    .size   stack,STACK_SIZE

tests/tcg/s390x/head64.S

@@ -8,6 +8,8 @@
 #include "../../../pc-bios/s390-ccw/start.S"
 #undef main
 
+.text
+
 main_pre:
     aghi %r15,-160                     /* reserve stack for C code */
     brasl %r14,sclp_setup
@@ -24,8 +26,3 @@ success_psw:
     .quad 0x2000180000000,0xfff        /* see is_special_wait_psw() */
 failure_psw:
     .quad 0x2000180000000,0            /* disabled wait */
-
-    .section .bss
-    .align 0x1000
-stack:
-    .skip 0x8000