From 0100301bfdf56a2a370c7157b5ab0fbf9313e1cd Mon Sep 17 00:00:00 2001 From: Brian Gerst Date: Sat, 13 Aug 2016 12:38:19 -0400 Subject: sched/x86: Rewrite the switch_to() code Move the low-level context switch code to an out-of-line asm stub instead of using complex inline asm. This allows constructing a new stack frame for the child process to make it seamlessly flow to ret_from_fork without an extra test and branch in __switch_to(). It also improves code generation for __schedule() by using the C calling convention instead of clobbering all registers. Signed-off-by: Brian Gerst Reviewed-by: Josh Poimboeuf Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1471106302-10159-5-git-send-email-brgerst@gmail.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/processor.h | 3 --- 1 file changed, 3 deletions(-) (limited to 'arch/x86/include/asm/processor.h') diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 63def9537a2d..6fee8635340b 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -389,9 +389,6 @@ struct thread_struct { unsigned short fsindex; unsigned short gsindex; #endif -#ifdef CONFIG_X86_32 - unsigned long ip; -#endif #ifdef CONFIG_X86_64 unsigned long fsbase; unsigned long gsbase; -- cgit v1.2.3 From ffcb043ba524d3fbd979a9dac2c9ce8ad352000d Mon Sep 17 00:00:00 2001 From: Brian Gerst Date: Sat, 13 Aug 2016 12:38:21 -0400 Subject: sched/x86: Fix thread_saved_pc() thread_saved_pc() was using a completely bogus method to get the return address. Since switch_to() was previously inlined, there was no sane way to know where on the stack the return address was stored. Now with the frame of a sleeping thread well defined, this can be implemented correctly. Signed-off-by: Brian Gerst Reviewed-by: Josh Poimboeuf Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1471106302-10159-7-git-send-email-brgerst@gmail.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/processor.h | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) (limited to 'arch/x86/include/asm/processor.h') diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 6fee8635340b..b22fb5a4ff3c 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -721,8 +721,6 @@ static inline void spin_lock_prefetch(const void *x) .addr_limit = KERNEL_DS, \ } -extern unsigned long thread_saved_pc(struct task_struct *tsk); - /* * 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" @@ -773,17 +771,13 @@ extern unsigned long thread_saved_pc(struct task_struct *tsk); .addr_limit = KERNEL_DS, \ } -/* - * Return saved PC of a blocked thread. - * What is this good for? it will be always the scheduler or ret_from_fork. - */ -#define thread_saved_pc(t) READ_ONCE_NOCHECK(*(unsigned long *)((t)->thread.sp - 8)) - #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 */ +extern unsigned long thread_saved_pc(struct task_struct *tsk); + extern void start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp); -- cgit v1.2.3 From b9d989c7218ac922185d82ad46f3e58b27a4bea9 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Tue, 13 Sep 2016 14:29:21 -0700 Subject: x86/asm: Move the thread_info::status field to thread_struct Because sched.h and thread_info.h are a tangled mess, I turned in_compat_syscall() into a macro. If we had current_thread_struct() or similar and we could use it from thread_info.h, then this would be a bit cleaner. Signed-off-by: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Jann Horn Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/ccc8a1b2f41f9c264a41f771bb4a6539a642ad72.1473801993.git.luto@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/include/asm/processor.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'arch/x86/include/asm/processor.h') diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index b22fb5a4ff3c..984a7bf17f6a 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -389,6 +389,9 @@ struct thread_struct { unsigned short fsindex; unsigned short gsindex; #endif + + u32 status; /* thread synchronous flags */ + #ifdef CONFIG_X86_64 unsigned long fsbase; unsigned long gsbase; @@ -434,6 +437,15 @@ struct thread_struct { */ }; +/* + * Thread-synchronous status. + * + * This is different from the flags in that nobody else + * ever touches our thread-synchronous status, so we don't + * have to worry about atomic accesses. + */ +#define TS_COMPAT 0x0002 /* 32bit syscall active (64BIT)*/ + /* * Set IOPL bits in EFLAGS from given mask */ -- cgit v1.2.3