[Xen-devel] [PATCH] x86/boot: Further minor GDT corrections

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

gdt_boot_descr and gdt_48 disagree on how long trampoline_gdt is.

Introduce an end label and have the linker calculate the 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 remaining GDTs in Xen.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>

The trampoline GDT access bits were actually noticed when trying to clean up
our boot time pagetables and map the trampoline read-only.
---
 xen/arch/x86/boot/head.S          |  2 +-
 xen/arch/x86/boot/trampoline.S    | 15 ++++++++-------
 xen/arch/x86/x86_64/kexec_reloc.S |  4 ++--
 3 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
index 26b680521d..9fdb9b3954 100644
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -129,7 +129,7 @@ multiboot2_header:
 
         .word   0
 gdt_boot_descr:
-        .word   7*8-1
+        .word   .Ltramopline_gdt_end - trampoline_gdt - 1
 gdt_boot_base:
         .long   sym_offs(trampoline_gdt)
         .long   0 /* Needed for 64-bit lgdt */
diff --git a/xen/arch/x86/boot/trampoline.S b/xen/arch/x86/boot/trampoline.S
index 7c6a2328d2..1761fc1213 100644
--- a/xen/arch/x86/boot/trampoline.S
+++ b/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
+.Ltramopline_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   .Ltramopline_gdt_end - trampoline_gdt - 1
         .long   bootsym_rel(trampoline_gdt,4)
 
 /* The first page of trampoline is permanent, the rest boot-time only. */
diff --git a/xen/arch/x86/x86_64/kexec_reloc.S 
b/xen/arch/x86/x86_64/kexec_reloc.S
index 5bf61d5c2d..9e5b7a6ba1 100644
--- a/xen/arch/x86/x86_64/kexec_reloc.S
+++ b/xen/arch/x86/x86_64/kexec_reloc.S
@@ -182,8 +182,8 @@ compat_mode_gdt_desc:
         .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 */
 
 compat_mode_idt:
         .word 0                      /* limit */
-- 
2.11.0


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