diff options
Diffstat (limited to 'arch/x86/kernel/process_64.c')
-rw-r--r-- | arch/x86/kernel/process_64.c | 65 |
1 files changed, 51 insertions, 14 deletions
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index ebefb5407b9d..72edac026a78 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -52,12 +52,11 @@ #include <asm/idle.h> #include <asm/syscalls.h> #include <asm/ds.h> +#include <asm/debugreg.h> +#include <asm/hw_breakpoint.h> asmlinkage extern void ret_from_fork(void); -DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task; -EXPORT_PER_CPU_SYMBOL(current_task); - DEFINE_PER_CPU(unsigned long, old_rsp); static DEFINE_PER_CPU(unsigned char, is_idle); @@ -245,6 +244,8 @@ void release_thread(struct task_struct *dead_task) BUG(); } } + if (unlikely(dead_task->thread.debugreg7)) + flush_thread_hw_breakpoint(dead_task); } static inline void set_32bit_tls(struct task_struct *t, int tls, u32 addr) @@ -300,12 +301,18 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, p->thread.fs = me->thread.fs; p->thread.gs = me->thread.gs; + p->thread.io_bitmap_ptr = NULL; savesegment(gs, p->thread.gsindex); savesegment(fs, p->thread.fsindex); savesegment(es, p->thread.es); savesegment(ds, p->thread.ds); + err = -ENOMEM; + if (unlikely(test_tsk_thread_flag(me, TIF_DEBUG))) + if (copy_thread_hw_breakpoint(me, p, clone_flags)) + goto out; + if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) { p->thread.io_bitmap_ptr = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL); if (!p->thread.io_bitmap_ptr) { @@ -344,6 +351,9 @@ out: kfree(p->thread.io_bitmap_ptr); p->thread.io_bitmap_max = 0; } + if (err) + flush_thread_hw_breakpoint(p); + return err; } @@ -386,9 +396,17 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) int cpu = smp_processor_id(); struct tss_struct *tss = &per_cpu(init_tss, cpu); unsigned fsindex, gsindex; + bool preload_fpu; + + /* + * If the task has used fpu the last 5 timeslices, just do a full + * restore of the math state immediately to avoid the trap; the + * chances of needing FPU soon are obviously high now + */ + preload_fpu = tsk_used_math(next_p) && next_p->fpu_counter > 5; /* we're going to use this soon, after a few expensive things */ - if (next_p->fpu_counter > 5) + if (preload_fpu) prefetch(next->xstate); /* @@ -419,6 +437,13 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) load_TLS(next, cpu); + /* Must be after DS reload */ + unlazy_fpu(prev_p); + + /* Make sure cpu is ready for new context */ + if (preload_fpu) + clts(); + /* * Leave lazy mode, flushing any hypercalls made here. * This must be done before restoring TLS segments so @@ -459,9 +484,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) wrmsrl(MSR_KERNEL_GS_BASE, next->gs); prev->gsindex = gsindex; - /* Must be after DS reload */ - unlazy_fpu(prev_p); - /* * Switch the PDA and FPU contexts. */ @@ -480,15 +502,30 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV)) __switch_to_xtra(prev_p, next_p, tss); - /* If the task has used fpu the last 5 timeslices, just do a full - * restore of the math state immediately to avoid the trap; the - * chances of needing FPU soon are obviously high now + /* + * Preload the FPU context, now that we've determined that the + * task is likely to be using it. + */ + if (preload_fpu) + __math_state_restore(); + /* + * There's a problem with moving the arch_install_thread_hw_breakpoint() + * call before current is updated. Suppose a kernel breakpoint is + * triggered in between the two, the hw-breakpoint handler will see that + * the 'current' task does not have TIF_DEBUG flag set and will think it + * is leftover from an old task (lazy switching) and will erase it. Then + * until the next context switch, no user-breakpoints will be installed. * - * tsk_used_math() checks prevent calling math_state_restore(), - * which can sleep in the case of !tsk_used_math() + * The real problem is that it's impossible to update both current and + * physical debug registers at the same instant, so there will always be + * a window in which they disagree and a breakpoint might get triggered. + * Since we use lazy switching, we are forced to assume that a + * disagreement means that current is correct and the exception is due + * to lazy debug register switching. */ - if (tsk_used_math(next_p) && next_p->fpu_counter > 5) - math_state_restore(); + if (unlikely(test_tsk_thread_flag(next_p, TIF_DEBUG))) + arch_install_thread_hw_breakpoint(next_p); + return prev_p; } |