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Message-Id: <ddf4847e6f114c522fefb24c16fc7a1d75138f9f.1466974736.git.luto@kernel.org>
Date: Sun, 26 Jun 2016 14:55:49 -0700
From: Andy Lutomirski <luto@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
Borislav Petkov <bp@...en8.de>,
Nadav Amit <nadav.amit@...il.com>,
Kees Cook <keescook@...omium.org>,
Brian Gerst <brgerst@...il.com>,
"kernel-hardening@...ts.openwall.com"
<kernel-hardening@...ts.openwall.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Jann Horn <jann@...jh.net>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Andy Lutomirski <luto@...nel.org>
Subject: [PATCH v4 27/29] x86: Move thread_info into task_struct
Now that most of the thread_info users have been cleaned up,
this is straightforward.
Most of this code was written by Linus.
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
arch/x86/Kconfig | 1 +
arch/x86/entry/entry_64.S | 9 +++++---
arch/x86/include/asm/switch_to.h | 6 ++---
arch/x86/include/asm/thread_info.h | 46 --------------------------------------
arch/x86/kernel/asm-offsets.c | 4 +---
arch/x86/kernel/irq_64.c | 3 +--
arch/x86/kernel/process.c | 6 ++---
7 files changed, 13 insertions(+), 62 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index afdcf96ef109..b3002c8efde2 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -155,6 +155,7 @@ config X86
select SPARSE_IRQ
select SRCU
select SYSCTL_EXCEPTION_TRACE
+ select THREAD_INFO_IN_TASK
select USER_STACKTRACE_SUPPORT
select VIRT_TO_BUS
select X86_DEV_DMA_OPS if X86_64
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index b846875aeea6..efeb1c9f64f4 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -179,7 +179,8 @@ GLOBAL(entry_SYSCALL_64_after_swapgs)
* If we need to do entry work or if we guess we'll need to do
* exit work, go straight to the slow path.
*/
- testl $_TIF_WORK_SYSCALL_ENTRY|_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
+ movq %gs:current_task, %r11
+ testl $_TIF_WORK_SYSCALL_ENTRY|_TIF_ALLWORK_MASK, TASK_TI_flags(%r11)
jnz entry_SYSCALL64_slow_path
entry_SYSCALL_64_fastpath:
@@ -217,7 +218,8 @@ entry_SYSCALL_64_fastpath:
*/
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
- testl $_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
+ movq %gs:current_task, %r11
+ testl $_TIF_ALLWORK_MASK, TASK_TI_flags(%r11)
jnz 1f
LOCKDEP_SYS_EXIT
@@ -368,9 +370,10 @@ END(ptregs_\func)
* A newly forked process directly context switches into this address.
*
* rdi: prev task we switched from
+ * rsi: task we're switching to
*/
ENTRY(ret_from_fork)
- LOCK ; btr $TIF_FORK, TI_flags(%r8)
+ LOCK ; btr $TIF_FORK, TASK_TI_flags(%rsi)
call schedule_tail /* rdi: 'prev' task parameter */
diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
index 14e4b20f0aaf..5194f4a680ab 100644
--- a/arch/x86/include/asm/switch_to.h
+++ b/arch/x86/include/asm/switch_to.h
@@ -136,18 +136,16 @@ do { \
"call __switch_to\n\t" \
"movq "__percpu_arg([current_task])",%%rsi\n\t" \
__switch_canary \
- "movq %P[thread_info](%%rsi),%%r8\n\t" \
"movq %%rax,%%rdi\n\t" \
- "testl %[_tif_fork],%P[ti_flags](%%r8)\n\t" \
+ "testl %[_tif_fork],%P[ti_flags](%%rsi)\n\t" \
"jnz ret_from_fork\n\t" \
RESTORE_CONTEXT \
: "=a" (last) \
__switch_canary_oparam \
: [next] "S" (next), [prev] "D" (prev), \
[threadrsp] "i" (offsetof(struct task_struct, thread.sp)), \
- [ti_flags] "i" (offsetof(struct thread_info, flags)), \
+ [ti_flags] "i" (offsetof(struct task_struct, thread_info.flags)), \
[_tif_fork] "i" (_TIF_FORK), \
- [thread_info] "i" (offsetof(struct task_struct, stack)), \
[current_task] "m" (current_task) \
__switch_canary_iparam \
: "memory", "cc" __EXTRA_CLOBBER)
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 7b42c1e462ac..0afc37654ad1 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -52,20 +52,6 @@ struct task_struct;
#include <asm/cpufeature.h>
#include <linux/atomic.h>
-struct thread_info {
- struct task_struct *task; /* main task structure */
- __u32 flags; /* low level flags */
- __u32 cpu; /* current CPU */
-};
-
-#define INIT_THREAD_INFO(tsk) \
-{ \
- .task = &tsk, \
- .flags = 0, \
- .cpu = 0, \
-}
-
-#define init_thread_info (init_thread_union.thread_info)
#define init_stack (init_thread_union.stack)
#else /* !__ASSEMBLY__ */
@@ -159,11 +145,6 @@ struct thread_info {
*/
#ifndef __ASSEMBLY__
-static inline struct thread_info *current_thread_info(void)
-{
- return (struct thread_info *)(current_top_of_stack() - THREAD_SIZE);
-}
-
static inline unsigned long current_stack_pointer(void)
{
unsigned long sp;
@@ -181,33 +162,6 @@ static inline unsigned long current_stack_pointer(void)
# define cpu_current_top_of_stack (cpu_tss + TSS_sp0)
#endif
-/*
- * ASM operand which evaluates to a 'thread_info' address of
- * the current task, if it is known that "reg" is exactly "off"
- * bytes below the top of the stack currently.
- *
- * ( The kernel stack's size is known at build time, it is usually
- * 2 or 4 pages, and the bottom of the kernel stack contains
- * the thread_info structure. So to access the thread_info very
- * quickly from assembly code we can calculate down from the
- * top of the kernel stack to the bottom, using constant,
- * build-time calculations only. )
- *
- * For example, to fetch the current thread_info->flags value into %eax
- * on x86-64 defconfig kernels, in syscall entry code where RSP is
- * currently at exactly SIZEOF_PTREGS bytes away from the top of the
- * stack:
- *
- * mov ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS), %eax
- *
- * will translate to:
- *
- * 8b 84 24 b8 c0 ff ff mov -0x3f48(%rsp), %eax
- *
- * which is below the current RSP by almost 16K.
- */
-#define ASM_THREAD_INFO(field, reg, off) ((field)+(off)-THREAD_SIZE)(reg)
-
#endif
#ifndef __ASSEMBLY__
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index a91a6ead24a2..e900f5e13f22 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -29,9 +29,7 @@
void common(void) {
BLANK();
- OFFSET(TI_flags, thread_info, flags);
-
- BLANK();
+ OFFSET(TASK_TI_flags, task_struct, thread_info.flags);
OFFSET(TASK_addr_limit, task_struct, thread.addr_limit);
BLANK();
diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
index 206d0b90a3ab..38f9f5678dc8 100644
--- a/arch/x86/kernel/irq_64.c
+++ b/arch/x86/kernel/irq_64.c
@@ -41,8 +41,7 @@ static inline void stack_overflow_check(struct pt_regs *regs)
if (user_mode(regs))
return;
- if (regs->sp >= curbase + sizeof(struct thread_info) +
- sizeof(struct pt_regs) + STACK_TOP_MARGIN &&
+ if (regs->sp >= curbase + sizeof(struct pt_regs) + STACK_TOP_MARGIN &&
regs->sp <= curbase + THREAD_SIZE)
return;
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 96becbbb52e0..8f60f810a9e7 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -536,9 +536,7 @@ unsigned long get_wchan(struct task_struct *p)
* PADDING
* ----------- top = topmax - TOP_OF_KERNEL_STACK_PADDING
* stack
- * ----------- bottom = start + sizeof(thread_info)
- * thread_info
- * ----------- start
+ * ----------- bottom = start
*
* The tasks stack pointer points at the location where the
* framepointer is stored. The data on the stack is:
@@ -549,7 +547,7 @@ unsigned long get_wchan(struct task_struct *p)
*/
top = start + THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING;
top -= 2 * sizeof(unsigned long);
- bottom = start + sizeof(struct thread_info);
+ bottom = start;
sp = READ_ONCE(p->thread.sp);
if (sp < bottom || sp > top)
--
2.7.4
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