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Message-ID: <tip-a6b744f3ce9d017dd86b28355de2d8e0d36496d4@git.kernel.org>
Date: Thu, 19 Jul 2018 16:19:55 -0700
From: tip-bot for Joerg Roedel <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: peterz@...radead.org, jroedel@...e.de, luto@...nel.org,
aarcange@...hat.com, llong@...hat.com, pavel@....cz,
dave.hansen@...el.com, mingo@...nel.org, will.deacon@....com,
eduval@...zon.com, dvlasenk@...hat.com,
linux-kernel@...r.kernel.org, David.Laight@...lab.com,
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jgross@...e.com, jkosina@...e.cz, hpa@...or.com,
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Subject: [tip:x86/pti] x86/entry/32: Load task stack from x86_tss.sp1 in
SYSENTER handler
Commit-ID: a6b744f3ce9d017dd86b28355de2d8e0d36496d4
Gitweb: https://git.kernel.org/tip/a6b744f3ce9d017dd86b28355de2d8e0d36496d4
Author: Joerg Roedel <jroedel@...e.de>
AuthorDate: Wed, 18 Jul 2018 11:40:40 +0200
Committer: Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 20 Jul 2018 01:11:36 +0200
x86/entry/32: Load task stack from x86_tss.sp1 in SYSENTER handler
x86_tss.sp0 will be used to point to the entry stack later to use it as a
trampoline stack for other kernel entry points besides SYSENTER.
So store the real task stack pointer in x86_tss.sp1, which is otherwise
unused by the hardware, as Linux doesn't make use of Ring 1.
Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Pavel Machek <pavel@....cz>
Cc: "H . Peter Anvin" <hpa@...or.com>
Cc: linux-mm@...ck.org
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Jiri Kosina <jkosina@...e.cz>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Brian Gerst <brgerst@...il.com>
Cc: David Laight <David.Laight@...lab.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Eduardo Valentin <eduval@...zon.com>
Cc: Greg KH <gregkh@...uxfoundation.org>
Cc: Will Deacon <will.deacon@....com>
Cc: aliguori@...zon.com
Cc: daniel.gruss@...k.tugraz.at
Cc: hughd@...gle.com
Cc: keescook@...gle.com
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Waiman Long <llong@...hat.com>
Cc: "David H . Gutteridge" <dhgutteridge@...patico.ca>
Cc: joro@...tes.org
Link: https://lkml.kernel.org/r/1531906876-13451-4-git-send-email-joro@8bytes.org
---
arch/x86/kernel/asm-offsets_32.c | 9 +++++++--
arch/x86/kernel/process_32.c | 2 ++
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c
index 15b3f45b69cd..82826f2275cc 100644
--- a/arch/x86/kernel/asm-offsets_32.c
+++ b/arch/x86/kernel/asm-offsets_32.c
@@ -46,9 +46,14 @@ void foo(void)
OFFSET(saved_context_gdt_desc, saved_context, gdt_desc);
BLANK();
- /* Offset from the entry stack to task stack stored in TSS */
+ /*
+ * 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.sp0) -
+ offsetof(struct cpu_entry_area, tss.x86_tss.sp1) -
offsetofend(struct cpu_entry_area, entry_stack_page.stack));
#ifdef CONFIG_STACKPROTECTOR
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 0ae659de21eb..ec62cc77388d 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -290,6 +290,8 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
this_cpu_write(cpu_current_top_of_stack,
(unsigned long)task_stack_page(next_p) +
THREAD_SIZE);
+ /* SYSENTER reads the task-stack from tss.sp1 */
+ this_cpu_write(cpu_tss_rw.x86_tss.sp1, next_p->thread.sp0);
/*
* Restore %gs if needed (which is common)
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