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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 /arch/i386/kernel/asm-offsets.c
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 'arch/i386/kernel/asm-offsets.c')
-rw-r--r--arch/i386/kernel/asm-offsets.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/i386/kernel/asm-offsets.c b/arch/i386/kernel/asm-offsets.c
index 70b19807acf..9620872d353 100644
--- a/arch/i386/kernel/asm-offsets.c
+++ b/arch/i386/kernel/asm-offsets.c
@@ -72,6 +72,7 @@ void foo(void)
OFFSET(PT_EAX, pt_regs, eax);
OFFSET(PT_DS, pt_regs, xds);
OFFSET(PT_ES, pt_regs, xes);
+ OFFSET(PT_GS, pt_regs, xgs);
OFFSET(PT_ORIG_EAX, pt_regs, orig_eax);
OFFSET(PT_EIP, pt_regs, eip);
OFFSET(PT_CS, pt_regs, xcs);