x86: set %fs to __KERNEL_PERCPU unconditionally for x86_32

Impact: cleanup

%fs is currently set to __KERNEL_DS at boot, and conditionally
switched to __KERNEL_PERCPU for secondary cpus.  Instead, initialize
GDT_ENTRY_PERCPU to the same attributes as GDT_ENTRY_KERNEL_DS and
set %fs to __KERNEL_PERCPU unconditionally.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

2 files changed, 4 insertions, 4 deletions

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index a8f0dedcb0cc..fbebbcec001b 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -111,7 +111,7 @@ DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = {
         [GDT_ENTRY_APMBIOS_BASE+2] = { { { 0x0000ffff, 0x00409200 } } },
 
         [GDT_ENTRY_ESPFIX_SS] = { { { 0x00000000, 0x00c09200 } } },
-        [GDT_ENTRY_PERCPU] = { { { 0x00000000, 0x00000000 } } },
+        [GDT_ENTRY_PERCPU] = { { { 0x0000ffff, 0x00cf9200 } } },
 #endif
 } };
 EXPORT_PER_CPU_SYMBOL_GPL(gdt_page);
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index e835b4eea70b..24c0e5cd71e3 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -429,12 +429,14 @@ is386:	movl $2,%ecx		# set MP
         ljmp $(__KERNEL_CS),$1f
 1:      movl $(__KERNEL_DS),%eax        # reload all the segment registers
         movl %eax,%ss                   # after changing gdt.
-        movl %eax,%fs                   # gets reset once there's real percpu
 
         movl $(__USER_DS),%eax          # DS/ES contains default USER segment
         movl %eax,%ds
         movl %eax,%es
 
+        movl $(__KERNEL_PERCPU), %eax
+        movl %eax,%fs                   # set this cpu's percpu
+
         xorl %eax,%eax                  # Clear GS and LDT
         movl %eax,%gs
         lldt %ax
@@ -446,8 +448,6 @@ is386:	movl $2,%ecx		# set MP
         movb $1, ready
         cmpb $0,%cl             # the first CPU calls start_kernel
         je   1f
-        movl $(__KERNEL_PERCPU), %eax
-        movl %eax,%fs           # set this cpu's percpu
         movl (stack_start), %esp
 1:
 #endif /* CONFIG_SMP */