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authorJeremy Fitzhardinge <jeremy@goop.org>2006-12-07 02:14:02 +0100
committerAndi Kleen <andi@basil.nowhere.org>2006-12-07 02:14:02 +0100
commitf95d47caae5302a63d92be9a0292abc90e2a14e1 (patch)
treecfa963975d104c56aba28df6c941759175ed4b98 /include/asm-i386/processor.h
parent62111195800d80c66cdc69063ea3145878c99fbf (diff)
[PATCH] i386: Use %gs as the PDA base-segment in the kernel
This patch is the meat of the PDA change. This patch makes several related changes: 1: Most significantly, %gs is now used in the kernel. This means that on entry, the old value of %gs is saved away, and it is reloaded with __KERNEL_PDA. 2: entry.S constructs the stack in the shape of struct pt_regs, and this is passed around the kernel so that the process's saved register state can be accessed. Unfortunately struct pt_regs doesn't currently have space for %gs (or %fs). This patch extends pt_regs to add space for gs (no space is allocated for %fs, since it won't be used, and it would just complicate the code in entry.S to work around the space). 3: Because %gs is now saved on the stack like %ds, %es and the integer registers, there are a number of places where it no longer needs to be handled specially; namely context switch, and saving/restoring the register state in a signal context. 4: And since kernel threads run in kernel space and call normal kernel code, they need to be created with their %gs == __KERNEL_PDA. Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Signed-off-by: Andi Kleen <ak@suse.de> Cc: Chuck Ebbert <76306.1226@compuserve.com> Cc: Zachary Amsden <zach@vmware.com> Cc: Jan Beulich <jbeulich@novell.com> Cc: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org>
Diffstat (limited to 'include/asm-i386/processor.h')
-rw-r--r--include/asm-i386/processor.h4
1 files changed, 3 insertions, 1 deletions
diff --git a/include/asm-i386/processor.h b/include/asm-i386/processor.h
index a9f2041c7c87..f73cf836e649 100644
--- a/include/asm-i386/processor.h
+++ b/include/asm-i386/processor.h
@@ -473,6 +473,7 @@ struct thread_struct {
.vm86_info = NULL, \
.sysenter_cs = __KERNEL_CS, \
.io_bitmap_ptr = NULL, \
+ .gs = __KERNEL_PDA, \
}
/*
@@ -500,7 +501,8 @@ static inline void load_esp0(struct tss_struct *tss, struct thread_struct *threa
}
#define start_thread(regs, new_eip, new_esp) do { \
- __asm__("movl %0,%%fs ; movl %0,%%gs": :"r" (0)); \
+ __asm__("movl %0,%%fs": :"r" (0)); \
+ regs->xgs = 0; \
set_fs(USER_DS); \
regs->xds = __USER_DS; \
regs->xes = __USER_DS; \