From: Thomas Gleixner tglx@linutronix.de
commit ff16701a29cba3aafa0bd1656d766813b2d0a811 upstream.
Move the conditional invocation of __switch_to_xtra() into an inline function so the logic can be shared between 32 and 64 bit.
Remove the handthrough of the TSS pointer and retrieve the pointer directly in the bitmap handling function. Use this_cpu_ptr() instead of the per_cpu() indirection.
This is a preparatory change so integration of conditional indirect branch speculation optimization happens only in one place.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Ingo Molnar mingo@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: Andy Lutomirski luto@kernel.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Jiri Kosina jkosina@suse.cz Cc: Tom Lendacky thomas.lendacky@amd.com Cc: Josh Poimboeuf jpoimboe@redhat.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: David Woodhouse dwmw@amazon.co.uk Cc: Tim Chen tim.c.chen@linux.intel.com Cc: Andi Kleen ak@linux.intel.com Cc: Dave Hansen dave.hansen@intel.com Cc: Casey Schaufler casey.schaufler@intel.com Cc: Asit Mallick asit.k.mallick@intel.com Cc: Arjan van de Ven arjan@linux.intel.com Cc: Jon Masters jcm@redhat.com Cc: Waiman Long longman9394@gmail.com Cc: Greg KH gregkh@linuxfoundation.org Cc: Dave Stewart david.c.stewart@intel.com Cc: Kees Cook keescook@chromium.org Link: https://lkml.kernel.org/r/20181125185005.280855518@linutronix.de [bwh: Backported to 4.4: - Use cpu_tss instead of cpu_tss_rw - __switch_to() still uses the tss variable, so don't delete it - Adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/include/asm/switch_to.h | 3 --- arch/x86/kernel/process.c | 12 +++++++----- arch/x86/kernel/process.h | 24 ++++++++++++++++++++++++ arch/x86/kernel/process_32.c | 9 +++------ arch/x86/kernel/process_64.c | 9 +++------ 5 files changed, 37 insertions(+), 20 deletions(-) create mode 100644 arch/x86/kernel/process.h
--- a/arch/x86/include/asm/switch_to.h +++ b/arch/x86/include/asm/switch_to.h @@ -6,9 +6,6 @@ struct task_struct; /* one of the stranger aspects of C forward declarations */ __visible struct task_struct *__switch_to(struct task_struct *prev, struct task_struct *next); -struct tss_struct; -void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p, - struct tss_struct *tss);
#ifdef CONFIG_X86_32
--- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -33,6 +33,8 @@ #include <asm/vm86.h> #include <asm/spec-ctrl.h>
+#include "process.h" + /* * per-CPU TSS segments. Threads are completely 'soft' on Linux, * no more per-task TSS's. The TSS size is kept cacheline-aligned @@ -179,11 +181,12 @@ int set_tsc_mode(unsigned int val) return 0; }
-static inline void switch_to_bitmap(struct tss_struct *tss, - struct thread_struct *prev, +static inline void switch_to_bitmap(struct thread_struct *prev, struct thread_struct *next, unsigned long tifp, unsigned long tifn) { + struct tss_struct *tss = this_cpu_ptr(&cpu_tss); + if (tifn & _TIF_IO_BITMAP) { /* * Copy the relevant range of the IO bitmap. @@ -370,8 +373,7 @@ void speculation_ctrl_update(unsigned lo preempt_enable(); }
-void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p, - struct tss_struct *tss) +void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p) { struct thread_struct *prev, *next; unsigned long tifp, tifn; @@ -381,7 +383,7 @@ void __switch_to_xtra(struct task_struct
tifn = READ_ONCE(task_thread_info(next_p)->flags); tifp = READ_ONCE(task_thread_info(prev_p)->flags); - switch_to_bitmap(tss, prev, next, tifp, tifn); + switch_to_bitmap(prev, next, tifp, tifn);
propagate_user_return_notify(prev_p, next_p);
--- /dev/null +++ b/arch/x86/kernel/process.h @@ -0,0 +1,24 @@ +// SPDX-License-Identifier: GPL-2.0 +// +// Code shared between 32 and 64 bit + +void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p); + +/* + * This needs to be inline to optimize for the common case where no extra + * work needs to be done. + */ +static inline void switch_to_extra(struct task_struct *prev, + struct task_struct *next) +{ + unsigned long next_tif = task_thread_info(next)->flags; + unsigned long prev_tif = task_thread_info(prev)->flags; + + /* + * __switch_to_xtra() handles debug registers, i/o bitmaps, + * speculation mitigations etc. + */ + if (unlikely(next_tif & _TIF_WORK_CTXSW_NEXT || + prev_tif & _TIF_WORK_CTXSW_PREV)) + __switch_to_xtra(prev, next); +} --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -55,6 +55,8 @@ #include <asm/switch_to.h> #include <asm/vm86.h>
+#include "process.h" + asmlinkage void ret_from_fork(void) __asm__("ret_from_fork"); asmlinkage void ret_from_kernel_thread(void) __asm__("ret_from_kernel_thread");
@@ -279,12 +281,7 @@ __switch_to(struct task_struct *prev_p, if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl)) set_iopl_mask(next->iopl);
- /* - * Now maybe handle debug registers and/or IO bitmaps - */ - if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV || - task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT)) - __switch_to_xtra(prev_p, next_p, tss); + switch_to_extra(prev_p, next_p);
/* * Leave lazy mode, flushing any hypercalls made here. --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -50,6 +50,8 @@ #include <asm/switch_to.h> #include <asm/xen/hypervisor.h>
+#include "process.h" + asmlinkage extern void ret_from_fork(void);
__visible DEFINE_PER_CPU(unsigned long, rsp_scratch); @@ -406,12 +408,7 @@ __switch_to(struct task_struct *prev_p, /* Reload esp0 and ss1. This changes current_thread_info(). */ load_sp0(tss, next);
- /* - * Now maybe reload the debug registers and handle I/O bitmaps - */ - if (unlikely(task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT || - task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV)) - __switch_to_xtra(prev_p, next_p, tss); + switch_to_extra(prev_p, next_p);
#ifdef CONFIG_XEN /*