From: Andy Lutomirski <luto@kernel.org>
To: x86@kernel.org
Cc: linux-kernel@vger.kernel.org, Borislav Petkov <bp@alien8.de>,
Brian Gerst <brgerst@gmail.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Juergen Gross <jgross@suse.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Kees Cook <keescook@chromium.org>,
Andy Lutomirski <luto@kernel.org>
Subject: [RFC 16/17] x86/asm/64: Remove thread_struct::sp0
Date: Wed, 6 Sep 2017 14:37:01 -0700 [thread overview]
Message-ID: <e3800c2ca04d89516b58f625e55dc4636ab0f65c.1504733277.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1504733277.git.luto@kernel.org>
In-Reply-To: <cover.1504733277.git.luto@kernel.org>
On x86_64, we can easily calculate sp0 when needed instead of
storing it in thread_struct.
On x86_32, a similar cleanup would be possible, but it would require
cleaning up the vm86 code first, and that can wait for a later
cleanup series.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/include/asm/compat.h | 1 +
arch/x86/include/asm/processor.h | 33 +++++++++++++++------------------
arch/x86/include/asm/switch_to.h | 6 ++++++
arch/x86/kernel/process_64.c | 1 -
4 files changed, 22 insertions(+), 19 deletions(-)
diff --git a/arch/x86/include/asm/compat.h b/arch/x86/include/asm/compat.h
index 5343c19814b3..948b6d8ec46f 100644
--- a/arch/x86/include/asm/compat.h
+++ b/arch/x86/include/asm/compat.h
@@ -6,6 +6,7 @@
*/
#include <linux/types.h>
#include <linux/sched.h>
+#include <linux/sched/task_stack.h>
#include <asm/processor.h>
#include <asm/user32.h>
#include <asm/unistd.h>
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index f83fbf1b6dd9..4c137472f530 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -423,7 +423,9 @@ typedef struct {
struct thread_struct {
/* Cached TLS descriptors: */
struct desc_struct tls_array[GDT_ENTRY_TLS_ENTRIES];
+#ifdef CONFIG_X86_32
unsigned long sp0;
+#endif
unsigned long sp;
#ifdef CONFIG_X86_32
unsigned long sysenter_cs;
@@ -790,6 +792,13 @@ static inline void spin_lock_prefetch(const void *x)
#define task_top_of_stack(task) ((unsigned long)(task_pt_regs(task) + 1))
+#define task_pt_regs(task) \
+({ \
+ unsigned long __ptr = (unsigned long)task_stack_page(task); \
+ __ptr += THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING; \
+ ((struct pt_regs *)__ptr) - 1; \
+})
+
#ifdef CONFIG_X86_32
/*
* User space process size: 3GB (default).
@@ -807,23 +816,6 @@ static inline void spin_lock_prefetch(const void *x)
.addr_limit = KERNEL_DS, \
}
-/*
- * TOP_OF_KERNEL_STACK_PADDING reserves 8 bytes on top of the ring0 stack.
- * This is necessary to guarantee that the entire "struct pt_regs"
- * is accessible even if the CPU haven't stored the SS/ESP registers
- * on the stack (interrupt gate does not save these registers
- * when switching to the same priv ring).
- * Therefore beware: accessing the ss/esp fields of the
- * "struct pt_regs" is possible, but they may contain the
- * completely wrong values.
- */
-#define task_pt_regs(task) \
-({ \
- unsigned long __ptr = (unsigned long)task_stack_page(task); \
- __ptr += THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING; \
- ((struct pt_regs *)__ptr) - 1; \
-})
-
#define KSTK_ESP(task) (task_pt_regs(task)->sp)
#else
@@ -852,12 +844,17 @@ static inline void spin_lock_prefetch(const void *x)
#define STACK_TOP TASK_SIZE
#define STACK_TOP_MAX TASK_SIZE_MAX
+#ifdef CONFIG_X86_32
#define INIT_THREAD { \
.sp0 = TOP_OF_INIT_STACK, \
.addr_limit = KERNEL_DS, \
}
+#else
+#define INIT_THREAD { \
+ .addr_limit = KERNEL_DS, \
+}
+#endif
-#define task_pt_regs(tsk) ((struct pt_regs *)(tsk)->thread.sp0 - 1)
extern unsigned long KSTK_ESP(struct task_struct *task);
#endif /* CONFIG_X86_64 */
diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
index d9bb491ba45c..c557b7526cc7 100644
--- a/arch/x86/include/asm/switch_to.h
+++ b/arch/x86/include/asm/switch_to.h
@@ -1,6 +1,8 @@
#ifndef _ASM_X86_SWITCH_TO_H
#define _ASM_X86_SWITCH_TO_H
+#include <linux/sched/task_stack.h>
+
struct task_struct; /* one of the stranger aspects of C forward declarations */
struct task_struct *__switch_to_asm(struct task_struct *prev,
@@ -86,7 +88,11 @@ static inline void refresh_sysenter_cs(struct thread_struct *thread)
/* This is used when switching tasks or entering/exiting vm86 mode. */
static inline void update_sp0(struct task_struct *task)
{
+#ifdef CONFIG_X86_32
load_sp0(task->thread.sp0);
+#else
+ load_sp0(task_top_of_stack(task));
+#endif
}
#endif /* _ASM_X86_SWITCH_TO_H */
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index c33f8ad297bb..6d9d11ee42ec 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -158,7 +158,6 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
struct inactive_task_frame *frame;
struct task_struct *me = current;
- p->thread.sp0 = (unsigned long)task_stack_page(p) + THREAD_SIZE;
childregs = task_pt_regs(p);
fork_frame = container_of(childregs, struct fork_frame, regs);
frame = &fork_frame->frame;
--
2.13.5
next prev parent reply other threads:[~2017-09-06 21:37 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-06 21:36 [RFC 00/17] Pile o' entry stack changes Andy Lutomirski
2017-09-06 21:36 ` [RFC 01/17] x86/asm/64: Remove the restore_c_regs_and_iret label Andy Lutomirski
2017-09-07 9:40 ` Borislav Petkov
2017-09-07 9:46 ` Ingo Molnar
2017-09-07 9:49 ` Ingo Molnar
2017-09-07 9:57 ` Borislav Petkov
2017-09-07 10:29 ` Ingo Molnar
2017-09-06 21:36 ` [RFC 02/17] x86/asm/64: Split the iret-to-user and iret-to-kernel paths Andy Lutomirski
2017-09-06 21:36 ` [RFC 03/17] x86/asm/64: Move SWAPGS into the common iret-to-usermode path Andy Lutomirski
2017-09-06 21:36 ` [RFC 04/17] x86/asm/64: Simplify reg restore code in the standard IRET paths Andy Lutomirski
2017-09-12 20:05 ` Josh Poimboeuf
2017-09-06 21:36 ` [RFC 05/17] x86/asm/64: Shrink paranoid_exit_restore and make labels local Andy Lutomirski
2017-09-06 21:36 ` [RFC 06/17] x86/asm/64: Use pop instead of movq in syscall_return_via_sysret Andy Lutomirski
2017-09-06 21:36 ` [RFC 07/17] x86/asm/64: Merge the fast and slow SYSRET paths Andy Lutomirski
2017-09-06 21:36 ` [RFC 08/17] x86/asm/64: De-Xen-ify our NMI code Andy Lutomirski
2017-09-07 9:34 ` Juergen Gross
2017-09-07 18:38 ` Andy Lutomirski
2017-09-08 4:26 ` Juergen Gross
2017-09-06 21:36 ` [RFC 09/17] x86/asm/32: Pull MSR_IA32_SYSENTER_CS update code out of native_load_sp0() Andy Lutomirski
2017-09-12 20:06 ` Josh Poimboeuf
2017-09-06 21:36 ` [RFC 10/17] x86/asm/64: Pass sp0 directly to load_sp0() Andy Lutomirski
2017-09-06 21:36 ` [RFC 11/17] x86/asm: Add task_top_of_stack() to find the top of a task's stack Andy Lutomirski
2017-09-06 21:36 ` [RFC 12/17] x86/xen/64: Clean up SP code in cpu_initialize_context() Andy Lutomirski
2017-09-12 20:09 ` Josh Poimboeuf
2017-09-06 21:36 ` [RFC 13/17] x86/boot/64: Stop initializing TSS.sp0 at boot Andy Lutomirski
2017-09-06 21:36 ` [RFC 14/17] x86/asm/64: Remove all remaining direct thread_struct::sp0 reads Andy Lutomirski
2017-09-06 21:37 ` [RFC 15/17] x86/boot/32: Fix cpu_current_top_of_stack initialization at boot Andy Lutomirski
2017-09-06 21:37 ` Andy Lutomirski [this message]
2017-09-06 21:37 ` [RFC 17/17] x86/traps: Use a new on_thread_stack() helper to clean up an assertion Andy Lutomirski
2017-09-12 20:11 ` Josh Poimboeuf
2017-09-12 20:25 ` Andrew Cooper
2017-09-06 22:16 ` [RFC 00/17] Pile o' entry stack changes Andi Kleen
2017-09-07 0:01 ` Andy Lutomirski
2017-09-07 7:04 ` Ingo Molnar
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