x86/boot: Further minor GDT corrections

gdt_boot_descr and gdt_48 disagree on how long trampoline_gdt is.

Introduce an end label for each GDT and have the linker calculate their size,
rather than hard coding it.

Also, just as with c/s af292b41e9, there is no point forcing the CPU to set
Access bits.  Fix all affected GDTs.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/boot/head.S

@@ -129,7 +129,7 @@ multiboot2_header:
 
         .word   0
 gdt_boot_descr:
-        .word   7*8-1
+        .word   .Ltrampoline_gdt_end - trampoline_gdt - 1
 gdt_boot_base:
         .long   sym_offs(trampoline_gdt)
         .long   0 /* Needed for 64-bit lgdt */

xen/arch/x86/boot/trampoline.S

@@ -63,22 +63,23 @@ trampoline_gdt:
         /* 0x0000: unused */
         .quad   0x0000000000000000
         /* 0x0008: ring 0 code, 32-bit mode */
-        .quad   0x00cf9a000000ffff
+        .quad   0x00cf9b000000ffff
         /* 0x0010: ring 0 code, 64-bit mode */
-        .quad   0x00af9a000000ffff
+        .quad   0x00af9b000000ffff
         /* 0x0018: ring 0 data */
-        .quad   0x00cf92000000ffff
+        .quad   0x00cf93000000ffff
         /* 0x0020: real-mode code @ BOOT_TRAMPOLINE */
         .long   0x0000ffff
-        .long   0x00009a00
+        .long   0x00009b00
         /* 0x0028: real-mode data @ BOOT_TRAMPOLINE */
         .long   0x0000ffff
-        .long   0x00009200
+        .long   0x00009300
         /*
          * 0x0030: ring 0 Xen data, 16 MiB size, base
          * address is computed at runtime.
          */
-        .quad   0x00c0920000000fff
+        .quad   0x00c0930000000fff
+.Ltrampoline_gdt_end:
 
         .pushsection .trampoline_rel, "a"
         .long   trampoline_gdt + BOOT_PSEUDORM_CS + 2 - .
@@ -182,7 +183,7 @@ start64:
         .word   0
 idt_48: .word   0, 0, 0 # base = limit = 0
         .word   0
-gdt_48: .word   6*8-1
+gdt_48: .word   .Ltrampoline_gdt_end - trampoline_gdt - 1
         .long   bootsym_rel(trampoline_gdt,4)
 
 /* The first page of trampoline is permanent, the rest boot-time only. */

xen/arch/x86/x86_64/kexec_reloc.S

@@ -176,14 +176,15 @@ compatibility_mode_far:
         .word 0x0010
 
 compat_mode_gdt_desc:
-        .word (3*8)-1
+        .word .Lcompat_mode_gdt_end - compat_mode_gdt -1
         .quad 0x0000000000000000     /* set in call_32_bit above */
 
         .align 8
 compat_mode_gdt:
         .quad 0x0000000000000000     /* null                              */
-        .quad 0x00cf92000000ffff     /* 0x0008 ring 0 data                */
-        .quad 0x00cf9a000000ffff     /* 0x0010 ring 0 code, compatibility */
+        .quad 0x00cf93000000ffff     /* 0x0008 ring 0 data                */
+        .quad 0x00cf9b000000ffff     /* 0x0010 ring 0 code, compatibility */
+.Lcompat_mode_gdt_end:
 
 compat_mode_idt:
         .word 0                      /* limit */