x86/pvh: Use fixed_percpu_data for early boot GSBASE

Instead of having a private area for the stack canary, use
fixed_percpu_data for GSBASE like the native kernel.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250123190747.745588-5-brgerst@gmail.com

diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
index 4733a5f467b81253f90d22104f7c28ed93077dbb..723f181b222ababdfd013ec11751784e34100a3c 100644 (file)
--- a/arch/x86/platform/pvh/head.S
+++ b/arch/x86/platform/pvh/head.S
@@ -173,10 +173,15 @@ SYM_CODE_START(pvh_start_xen)
 1:
        UNWIND_HINT_END_OF_STACK
 
-       /* Set base address in stack canary descriptor. */
-       mov $MSR_GS_BASE,%ecx
-       leal canary(%rip), %eax
-       xor %edx, %edx
+       /*
+        * Set up GSBASE.
+        * Note that on SMP the boot CPU uses the init data section until
+        * the per-CPU areas are set up.
+        */
+       movl $MSR_GS_BASE,%ecx
+       leaq INIT_PER_CPU_VAR(fixed_percpu_data)(%rip), %rdx
+       movq %edx, %eax
+       shrq $32, %rdx
        wrmsr
 
        /* Call xen_prepare_pvh() via the kernel virtual mapping */
@@ -238,8 +243,6 @@ SYM_DATA_START_LOCAL(gdt_start)
 SYM_DATA_END_LABEL(gdt_start, SYM_L_LOCAL, gdt_end)
 
        .balign 16
-SYM_DATA_LOCAL(canary, .fill 48, 1, 0)
-
 SYM_DATA_START_LOCAL(early_stack)
        .fill BOOT_STACK_SIZE, 1, 0
 SYM_DATA_END_LABEL(early_stack, SYM_L_LOCAL, early_stack_end)