hw-breakpoints: Rewrite the hw-breakpoints layer on top of perf events

[linux-2.6-block.git] / arch / x86 / kernel / process_64.c

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 72edac026a78f71cbbf4d0e32d1557b2272735e3..5bafdec344415387f94b7a344bbba75b3b457950 100644 (file)
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -53,7 +53,6 @@
 #include <asm/syscalls.h>
 #include <asm/ds.h>
 #include <asm/debugreg.h>
-#include <asm/hw_breakpoint.h>
 
 asmlinkage extern void ret_from_fork(void);
 
@@ -244,8 +243,6 @@ 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)
@@ -309,9 +306,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
        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;
+       memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
 
        if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) {
                p->thread.io_bitmap_ptr = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
@@ -351,8 +346,6 @@ out:
                kfree(p->thread.io_bitmap_ptr);
                p->thread.io_bitmap_max = 0;
        }
-       if (err)
-               flush_thread_hw_breakpoint(p);
 
        return err;
 }
@@ -508,23 +501,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
         */
        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.
-        *
-        * 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 (unlikely(test_tsk_thread_flag(next_p, TIF_DEBUG)))
-               arch_install_thread_hw_breakpoint(next_p);
 
        return prev_p;
 }