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Subject[PATCH 04/10] x86: set %fs to __KERNEL_PERCPU unconditionally for x86_32
Date
From: Brian Gerst <brgerst@gmail.com>

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>
---
arch/x86/kernel/cpu/common.c | 2 +-
arch/x86/kernel/head_32.S | 6 +++---
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index a8f0ded..fbebbce 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 e835b4e..24c0e5c 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 */
--
1.6.0.2


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