[tip:x86/asm] x86/entry/64: Pass SP0 directly to load_sp0()

From: tip-bot for Andy Lutomirski
Date: Thu Nov 02 2017 - 06:58:38 EST

Commit-ID: da51da189a24bb9b7e2d5a123be096e51a4695a5
Gitweb: https://git.kernel.org/tip/da51da189a24bb9b7e2d5a123be096e51a4695a5
Author: Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate: Thu, 2 Nov 2017 00:59:10 -0700
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 2 Nov 2017 11:04:44 +0100

x86/entry/64: Pass SP0 directly to load_sp0()

load_sp0() had an odd signature:

void load_sp0(struct tss_struct *tss, struct thread_struct *thread);

Simplify it to:

void load_sp0(unsigned long sp0);

Also simplify a few get_cpu()/put_cpu() sequences to
preempt_disable()/preempt_enable().

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Cc: Borislav Petkov <bpetkov@xxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/2655d8b42ed940aa384fe18ee1129bbbcf730a08.1509609304.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/include/asm/paravirt.h | 5 ++---
arch/x86/include/asm/paravirt_types.h | 2 +-
arch/x86/include/asm/processor.h | 9 ++++-----
arch/x86/kernel/cpu/common.c | 4 ++--
arch/x86/kernel/process_32.c | 2 +-
arch/x86/kernel/process_64.c | 2 +-
arch/x86/kernel/vm86_32.c | 14 ++++++--------
arch/x86/xen/enlighten_pv.c | 7 +++----
8 files changed, 20 insertions(+), 25 deletions(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 12deec7..43d4f90 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -15,10 +15,9 @@
#include <linux/cpumask.h>
#include <asm/frame.h>

-static inline void load_sp0(struct tss_struct *tss,
- struct thread_struct *thread)
+static inline void load_sp0(unsigned long sp0)
{
- PVOP_VCALL2(pv_cpu_ops.load_sp0, tss, thread);
+ PVOP_VCALL1(pv_cpu_ops.load_sp0, sp0);
}

/* The paravirtualized CPUID instruction. */
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 280d94c..a916788 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -133,7 +133,7 @@ struct pv_cpu_ops {
void (*alloc_ldt)(struct desc_struct *ldt, unsigned entries);
void (*free_ldt)(struct desc_struct *ldt, unsigned entries);

- void (*load_sp0)(struct tss_struct *tss, struct thread_struct *t);
+ void (*load_sp0)(unsigned long sp0);

void (*set_iopl_mask)(unsigned mask);

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 0167e3e..064b847 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -517,9 +517,9 @@ static inline void native_set_iopl_mask(unsigned mask)
}

static inline void
-native_load_sp0(struct tss_struct *tss, struct thread_struct *thread)
+native_load_sp0(unsigned long sp0)
{
- tss->x86_tss.sp0 = thread->sp0;
+ this_cpu_write(cpu_tss.x86_tss.sp0, sp0);
}

static inline void native_swapgs(void)
@@ -544,10 +544,9 @@ static inline unsigned long current_top_of_stack(void)
#else
#define __cpuid native_cpuid

-static inline void load_sp0(struct tss_struct *tss,
- struct thread_struct *thread)
+static inline void load_sp0(unsigned long sp0)
{
- native_load_sp0(tss, thread);
+ native_load_sp0(sp0);
}

#define set_iopl_mask native_set_iopl_mask
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 03bb004..4e7fb9c 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1570,7 +1570,7 @@ void cpu_init(void)
initialize_tlbstate_and_flush();
enter_lazy_tlb(&init_mm, me);

- load_sp0(t, &current->thread);
+ load_sp0(current->thread.sp0);
set_tss_desc(cpu, t);
load_TR_desc();
load_mm_ldt(&init_mm);
@@ -1625,7 +1625,7 @@ void cpu_init(void)
initialize_tlbstate_and_flush();
enter_lazy_tlb(&init_mm, curr);

- load_sp0(t, thread);
+ load_sp0(thread->sp0);
set_tss_desc(cpu, t);
load_TR_desc();
load_mm_ldt(&init_mm);
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 0936ed3..40b8587 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -287,7 +287,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
* current_thread_info(). Refresh the SYSENTER configuration in
* case prev or next is vm86.
*/
- load_sp0(tss, next);
+ load_sp0(next->sp0);
refresh_sysenter_cs(next);
this_cpu_write(cpu_current_top_of_stack,
(unsigned long)task_stack_page(next_p) +
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index a6ff6d1..2124304 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -465,7 +465,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
this_cpu_write(current_task, next_p);

/* Reload sp0. */
- load_sp0(tss, next);
+ load_sp0(next->sp0);

/*
* Now maybe reload the debug registers and handle I/O bitmaps
diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
index 5bc1c3a..0f1d92c 100644
--- a/arch/x86/kernel/vm86_32.c
+++ b/arch/x86/kernel/vm86_32.c
@@ -94,7 +94,6 @@

void save_v86_state(struct kernel_vm86_regs *regs, int retval)
{
- struct tss_struct *tss;
struct task_struct *tsk = current;
struct vm86plus_struct __user *user;
struct vm86 *vm86 = current->thread.vm86;
@@ -146,13 +145,13 @@ void save_v86_state(struct kernel_vm86_regs *regs, int retval)
do_exit(SIGSEGV);
}

- tss = &per_cpu(cpu_tss, get_cpu());
+ preempt_disable();
tsk->thread.sp0 = vm86->saved_sp0;
tsk->thread.sysenter_cs = __KERNEL_CS;
- load_sp0(tss, &tsk->thread);
+ load_sp0(tsk->thread.sp0);
refresh_sysenter_cs(&tsk->thread);
vm86->saved_sp0 = 0;
- put_cpu();
+ preempt_enable();

memcpy(&regs->pt, &vm86->regs32, sizeof(struct pt_regs));

@@ -238,7 +237,6 @@ SYSCALL_DEFINE2(vm86, unsigned long, cmd, unsigned long, arg)

static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
{
- struct tss_struct *tss;
struct task_struct *tsk = current;
struct vm86 *vm86 = tsk->thread.vm86;
struct kernel_vm86_regs vm86regs;
@@ -366,8 +364,8 @@ static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
vm86->saved_sp0 = tsk->thread.sp0;
lazy_save_gs(vm86->regs32.gs);

- tss = &per_cpu(cpu_tss, get_cpu());
/* make room for real-mode segments */
+ preempt_disable();
tsk->thread.sp0 += 16;

if (static_cpu_has(X86_FEATURE_SEP)) {
@@ -375,8 +373,8 @@ static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
refresh_sysenter_cs(&tsk->thread);
}

- load_sp0(tss, &tsk->thread);
- put_cpu();
+ load_sp0(tsk->thread.sp0);
+ preempt_enable();

if (vm86->flags & VM86_SCREEN_BITMAP)
mark_screen_rdonly(tsk->mm);
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 8da4eff..e7b2130 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -810,15 +810,14 @@ static void __init xen_write_gdt_entry_boot(struct desc_struct *dt, int entry,
}
}

-static void xen_load_sp0(struct tss_struct *tss,
- struct thread_struct *thread)
+static void xen_load_sp0(unsigned long sp0)
{
struct multicall_space mcs;

mcs = xen_mc_entry(0);
- MULTI_stack_switch(mcs.mc, __KERNEL_DS, thread->sp0);
+ MULTI_stack_switch(mcs.mc, __KERNEL_DS, sp0);
xen_mc_issue(PARAVIRT_LAZY_CPU);
- tss->x86_tss.sp0 = thread->sp0;
+ this_cpu_write(cpu_tss.x86_tss.sp0, sp0);
}

void xen_set_iopl_mask(unsigned mask)