1 files changed, 13 insertions, 24 deletions

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index c8ace880661b..a0a2b5ca9b7d 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -207,19 +207,15 @@ ENTRY(secondary_startup_64)
 
 #ifdef CONFIG_SMP
         /*
-         * early_gdt_base should point to the gdt_page in static percpu init
-         * data area.  Computing this requires two symbols - __per_cpu_load
-         * and per_cpu__gdt_page.  As linker can't do no such relocation, do
-         * it by hand.  As early_gdt_descr is manipulated by C code for
-         * secondary CPUs, this should be done only once for the boot CPU
-         * when early_gdt_descr_base contains zero.
+         * Fix up static pointers that need __per_cpu_load added.  The assembler
+         * is unable to do this directly.  This is only needed for the boot cpu.
+         * These values are set up with the correct base addresses by C code for
+         * secondary cpus.
          */
-        movq    early_gdt_descr_base(%rip), %rax
-        testq   %rax, %rax
-        jnz     1f
-        movq    $__per_cpu_load, %rax
-        addq    $per_cpu__gdt_page, %rax
-        movq    %rax, early_gdt_descr_base(%rip)
+        movq    initial_gs(%rip), %rax
+        cmpl    $0, per_cpu__cpu_number(%rax)
+        jne     1f
+        addq    %rax, early_gdt_descr_base(%rip)
 1:
 #endif
         /*
@@ -246,13 +242,10 @@ ENTRY(secondary_startup_64)
 
         /* Set up %gs.
          *
-         * On SMP, %gs should point to the per-cpu area.  For initial
-         * boot, make %gs point to the init data section.  For a
-         * secondary CPU,initial_gs should be set to its pda address
-         * before the CPU runs this code.
-         *
-         * On UP, initial_gs points to PER_CPU_VAR(__pda) and doesn't
-         * change.
+         * The base of %gs always points to the bottom of the irqstack
+         * union.  If the stack protector canary is enabled, it is
+         * located at %gs:40.  Note that, on SMP, the boot cpu uses
+         * init data section till per cpu areas are set up.
          */
         movl    $MSR_GS_BASE,%ecx
         movq    initial_gs(%rip),%rax
@@ -285,7 +278,7 @@ ENTRY(secondary_startup_64)
 #ifdef CONFIG_SMP
         .quad   __per_cpu_load
 #else
-        .quad   PER_CPU_VAR(__pda)
+        .quad   PER_CPU_VAR(irq_stack_union)
 #endif
         __FINITDATA
 
@@ -431,12 +424,8 @@ NEXT_PAGE(level2_spare_pgt)
         .globl early_gdt_descr
 early_gdt_descr:
         .word   GDT_ENTRIES*8-1
-#ifdef CONFIG_SMP
 early_gdt_descr_base:
-        .quad   0x0000000000000000
-#else
         .quad   per_cpu__gdt_page
-#endif
 
 ENTRY(phys_base)
         /* This must match the first entry in level2_kernel_pgt */