[PATCH V2 5/6] x86_32/sysenter: use percpu to get thread.sp0 when sysenter

From: Lai Jiangshan <jiangshanlai@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: Lai Jiangshan <laijs@linux.alibaba.com>,
	Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Joerg Roedel <jroedel@suse.de>,
	Ricardo Neri <ricardo.neri-calderon@linux.intel.com>,
	Reinette Chatre <reinette.chatre@intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Gabriel Krisman Bertazi <krisman@collabora.com>,
	Kees Cook <keescook@chromium.org>,
	Frederic Weisbecker <frederic@kernel.org>,
	Jens Axboe <axboe@kernel.dk>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	Brian Gerst <brgerst@gmail.com>, Ard Biesheuvel <ardb@kernel.org>,
	Andi Kleen <ak@linux.intel.com>, Mike Rapoport <rppt@kernel.org>,
	Mike Hommey <mh@glandium.org>,
	Mark Gross <mgross@linux.intel.com>,
	Fenghua Yu <fenghua.yu@intel.com>,
	Tony Luck <tony.luck@intel.com>,
	Anthony Steinhauser <asteinhauser@google.com>,
	Jay Lang <jaytlang@mit.edu>,
	"Chang S. Bae" <chang.seok.bae@intel.com>
Subject: [PATCH V2 5/6] x86_32/sysenter: use percpu to get thread.sp0 when sysenter
Date: Tue, 26 Jan 2021 01:34:33 +0800	[thread overview]
Message-ID: <20210125173444.22696-6-jiangshanlai@gmail.com> (raw)
In-Reply-To: <20210125173444.22696-1-jiangshanlai@gmail.com>

From: Lai Jiangshan <laijs@linux.alibaba.com>

TSS_entry2task_stack is used to refer to tss.sp1 which is stored the value
of thread.sp0.

At the code where TSS_entry2task_stack is used in sysenter, the CR3 is
already kernel CR3 and kernel segments is loaded.

So that we can directly use percpu for it instead of offset-calculation.

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 a8d2640394f9..3cb42efb3c04 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

