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Date: Sun, 18 Jan 2015 02:17:41 +0100
From: Alexander van Heukelum <heukelum@...tmail.fm>
To: Andy Lutomirski <luto@...capital.net>, x86@...nel.org,
linux-kernel@...r.kernel.org
Cc: Frederic Weisbecker <fweisbec@...il.com>,
Oleg Nesterov <oleg@...hat.com>, Borislav Petkov <bp@...e.de>,
Rik van Riel <riel@...hat.com>
Subject: [PATCH 2/3] x86_64: don't use KERNEL_STACK_OFFSET for syscall and sysenter
The syscall and sysenter code use KERNEL_STACK_OFFSET to set the
initial stack pointer a bit below the top of the kernel stack page.
Stop doing that.
Signed-off-by: Alexander van Heukelum <heukelum@...tmail.fm>
---
arch/x86/ia32/ia32entry.S | 4 ++--
arch/x86/include/asm/thread_info.h | 6 ++----
arch/x86/kernel/cpu/common.c | 2 +-
arch/x86/kernel/entry_64.S | 3 ++-
arch/x86/kernel/process_64.c | 3 +--
arch/x86/kernel/smpboot.c | 3 +--
arch/x86/xen/smp.c | 3 +--
7 files changed, 10 insertions(+), 14 deletions(-)
diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 1c74f39..93b30a1 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -122,7 +122,6 @@ ENTRY(ia32_sysenter_target)
CFI_REGISTER rsp,rbp
SWAPGS_UNSAFE_STACK
movq PER_CPU_VAR(kernel_stack), %rsp
- addq $(KERNEL_STACK_OFFSET),%rsp
/*
* No need to follow this irqs on/off section: the syscall
* disabled irqs, here we enable it straight after entry:
@@ -292,13 +291,14 @@ ENDPROC(ia32_sysenter_target)
ENTRY(ia32_cstar_target)
CFI_STARTPROC32 simple
CFI_SIGNAL_FRAME
- CFI_DEF_CFA rsp,KERNEL_STACK_OFFSET
+ CFI_DEF_CFA rsp,0
CFI_REGISTER rip,rcx
/*CFI_REGISTER rflags,r11*/
SWAPGS_UNSAFE_STACK
movl %esp,%r8d
CFI_REGISTER rsp,r8
movq PER_CPU_VAR(kernel_stack),%rsp
+ sub $(PTREGS_SIZE-RIP),%rsp
/*
* No need to follow this irqs on/off section: the syscall
* disabled irqs and here we enable it straight after entry:
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 471037d..2caaaf2 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -149,7 +149,6 @@ struct thread_info {
#define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW)
#define STACK_WARN (THREAD_SIZE/8)
-#define KERNEL_STACK_OFFSET (5*(BITS_PER_LONG/8))
/*
* macros/functions for gaining access to the thread information structure
@@ -163,8 +162,7 @@ DECLARE_PER_CPU(unsigned long, kernel_stack);
static inline struct thread_info *current_thread_info(void)
{
struct thread_info *ti;
- ti = (void *)(this_cpu_read_stable(kernel_stack) +
- KERNEL_STACK_OFFSET - THREAD_SIZE);
+ ti = (void *)(this_cpu_read_stable(kernel_stack) - THREAD_SIZE);
return ti;
}
@@ -184,7 +182,7 @@ static inline unsigned long current_stack_pointer(void)
/* how to get the thread information struct from ASM */
#define GET_THREAD_INFO(reg) \
_ASM_MOV PER_CPU_VAR(kernel_stack),reg ; \
- _ASM_SUB $(THREAD_SIZE-KERNEL_STACK_OFFSET),reg ;
+ _ASM_SUB $THREAD_SIZE,reg ;
/*
* Same if PER_CPU_VAR(kernel_stack) is, perhaps with some offset, already in
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index c604965..aa76c69 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1116,7 +1116,7 @@ static __init int setup_disablecpuid(char *arg)
__setup("clearcpuid=", setup_disablecpuid);
DEFINE_PER_CPU(unsigned long, kernel_stack) =
- (unsigned long)&init_thread_union - KERNEL_STACK_OFFSET + THREAD_SIZE;
+ (unsigned long)&init_thread_union + THREAD_SIZE;
EXPORT_PER_CPU_SYMBOL(kernel_stack);
#ifdef CONFIG_X86_64
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 9f9ca20..7adff94 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -321,7 +321,7 @@ END(ret_from_fork)
ENTRY(system_call)
CFI_STARTPROC simple
CFI_SIGNAL_FRAME
- CFI_DEF_CFA rsp,KERNEL_STACK_OFFSET
+ CFI_DEF_CFA rsp,0
CFI_REGISTER rip,rcx
/*CFI_REGISTER rflags,r11*/
SWAPGS_UNSAFE_STACK
@@ -334,6 +334,7 @@ GLOBAL(system_call_after_swapgs)
movq %rsp,PER_CPU_VAR(old_rsp)
movq PER_CPU_VAR(kernel_stack),%rsp
+ sub $(PTREGS_SIZE-RIP),%rsp
/*
* No need to follow this irqs off/on section - it's straight
* and short:
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 5a2c029..0747dbf 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -414,8 +414,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
this_cpu_write(__preempt_count, task_thread_info(next_p)->saved_preempt_count);
this_cpu_write(kernel_stack,
- (unsigned long)task_stack_page(next_p) +
- THREAD_SIZE - KERNEL_STACK_OFFSET);
+ (unsigned long)task_stack_page(next_p) + THREAD_SIZE);
/*
* Now maybe reload the debug registers and handle I/O bitmaps
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 6d7022c..66fd449 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -776,8 +776,7 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
initial_gs = per_cpu_offset(cpu);
#endif
per_cpu(kernel_stack, cpu) =
- (unsigned long)task_stack_page(idle) -
- KERNEL_STACK_OFFSET + THREAD_SIZE;
+ (unsigned long)task_stack_page(idle) + THREAD_SIZE;
early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);
initial_code = (unsigned long)start_secondary;
stack_start = idle->thread.sp;
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 4c071ae..4e71a3b 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -452,8 +452,7 @@ static int xen_cpu_up(unsigned int cpu, struct task_struct *idle)
clear_tsk_thread_flag(idle, TIF_FORK);
#endif
per_cpu(kernel_stack, cpu) =
- (unsigned long)task_stack_page(idle) -
- KERNEL_STACK_OFFSET + THREAD_SIZE;
+ (unsigned long)task_stack_page(idle) + THREAD_SIZE;
xen_setup_runstate_info(cpu);
xen_setup_timer(cpu);
--
2.1.0
--
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