linux-kernel - [PATCH V4 5/6] x86/entry/32: Use percpu to get thread.sp0 in SYSENTER

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Message-Id: <20210210133917.2414-6-jiangshanlai@gmail.com>
Date:   Wed, 10 Feb 2021 21:39:16 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>
Cc:     Lai Jiangshan <laijs@...ux.alibaba.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Joerg Roedel <jroedel@...e.de>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Balbir Singh <sblbir@...zon.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        Kees Cook <keescook@...omium.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Jens Axboe <axboe@...nel.dk>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Brian Gerst <brgerst@...il.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Mike Rapoport <rppt@...nel.org>, Mike Hommey <mh@...ndium.org>,
        Mark Gross <mgross@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Anthony Steinhauser <asteinhauser@...gle.com>,
        Jay Lang <jaytlang@....edu>,
        "Chang S. Bae" <chang.seok.bae@...el.com>
Subject: [PATCH V4 5/6] x86/entry/32: Use percpu to get thread.sp0 in SYSENTER

From: Lai Jiangshan <laijs@...ux.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@...ux.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