diff options
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/i386/kernel/process.c | 73 |
1 files changed, 39 insertions, 34 deletions
diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c index 06dfa65ad18..6c49acb9698 100644 --- a/arch/i386/kernel/process.c +++ b/arch/i386/kernel/process.c @@ -538,8 +538,31 @@ int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs) return 1; } -static noinline void __switch_to_xtra(struct task_struct *next_p, - struct tss_struct *tss) +#ifdef CONFIG_SECCOMP +void hard_disable_TSC(void) +{ + write_cr4(read_cr4() | X86_CR4_TSD); +} +void disable_TSC(void) +{ + preempt_disable(); + if (!test_and_set_thread_flag(TIF_NOTSC)) + /* + * Must flip the CPU state synchronously with + * TIF_NOTSC in the current running context. + */ + hard_disable_TSC(); + preempt_enable(); +} +void hard_enable_TSC(void) +{ + write_cr4(read_cr4() & ~X86_CR4_TSD); +} +#endif /* CONFIG_SECCOMP */ + +static noinline void +__switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p, + struct tss_struct *tss) { struct thread_struct *next; @@ -555,6 +578,17 @@ static noinline void __switch_to_xtra(struct task_struct *next_p, set_debugreg(next->debugreg[7], 7); } +#ifdef CONFIG_SECCOMP + if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^ + test_tsk_thread_flag(next_p, TIF_NOTSC)) { + /* prev and next are different */ + if (test_tsk_thread_flag(next_p, TIF_NOTSC)) + hard_disable_TSC(); + else + hard_enable_TSC(); + } +#endif + if (!test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) { /* * Disable the bitmap via an invalid offset. We still cache @@ -586,33 +620,6 @@ static noinline void __switch_to_xtra(struct task_struct *next_p, } /* - * This function selects if the context switch from prev to next - * has to tweak the TSC disable bit in the cr4. - */ -static inline void disable_tsc(struct task_struct *prev_p, - struct task_struct *next_p) -{ - struct thread_info *prev, *next; - - /* - * gcc should eliminate the ->thread_info dereference if - * has_secure_computing returns 0 at compile time (SECCOMP=n). - */ - prev = task_thread_info(prev_p); - next = task_thread_info(next_p); - - if (has_secure_computing(prev) || has_secure_computing(next)) { - /* slow path here */ - if (has_secure_computing(prev) && - !has_secure_computing(next)) { - write_cr4(read_cr4() & ~X86_CR4_TSD); - } else if (!has_secure_computing(prev) && - has_secure_computing(next)) - write_cr4(read_cr4() | X86_CR4_TSD); - } -} - -/* * switch_to(x,yn) should switch tasks from x to y. * * We fsave/fwait so that an exception goes off at the right time @@ -689,11 +696,9 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas /* * Now maybe handle debug registers and/or IO bitmaps */ - if (unlikely((task_thread_info(next_p)->flags & _TIF_WORK_CTXSW) - || test_tsk_thread_flag(prev_p, TIF_IO_BITMAP))) - __switch_to_xtra(next_p, tss); - - disable_tsc(prev_p, next_p); + 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); /* * Leave lazy mode, flushing any hypercalls made here. |