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Subject[PATCH V4 5/6] x86/entry/32: Use percpu to get thread.sp0 in SYSENTER
Date
From: Lai Jiangshan <laijs@linux.alibaba.com>

TSS_entry2task_stack is used to refer to tss.sp1 which is a copy of
thread.sp0.

When TSS_entry2task_stack is used in entry_SYSENTER_32, the CR3 is
already kernel CR3 and the kernel %fs is loaded.

So it directly uses percpu instead of offset-calculation via
TSS_entry2task_stack.

And we remove the unused TSS_entry2task_stack.

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
arch/x86/entry/entry_32.S | 2 +-
arch/x86/kernel/asm-offsets_32.c | 10 ----------
2 files changed, 1 insertion(+), 11 deletions(-)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 01f098c5b017..d5b5b43fd0c0 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -916,7 +916,7 @@ SYM_FUNC_START(entry_SYSENTER_32)

/* Switch to task stack */
movl %esp, %eax
- movl (3*4+TSS_entry2task_stack)(%esp), %esp
+ movl PER_CPU_VAR(cpu_tss_rw + TSS_sp1), %esp

.Lsysenter_past_esp:
pushl $__USER_DS /* pt_regs->ss */
diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c
index 6e043f295a60..6d4143cfbf03 100644
--- a/arch/x86/kernel/asm-offsets_32.c
+++ b/arch/x86/kernel/asm-offsets_32.c
@@ -43,16 +43,6 @@ void foo(void)
OFFSET(saved_context_gdt_desc, saved_context, gdt_desc);
BLANK();

- /*
- * Offset from the entry stack to task stack stored in TSS. Kernel entry
- * happens on the per-cpu entry-stack, and the asm code switches to the
- * task-stack pointer stored in x86_tss.sp1, which is a copy of
- * task->thread.sp0 where entry code can find it.
- */
- DEFINE(TSS_entry2task_stack,
- offsetof(struct cpu_entry_area, tss.x86_tss.sp1) -
- offsetofend(struct cpu_entry_area, entry_stack_page.stack));
-
#ifdef CONFIG_STACKPROTECTOR
BLANK();
OFFSET(stack_canary_offset, stack_canary, canary);
--
2.19.1.6.gb485710b
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