x86, bts: add fork and exit handling

Impact: introduce new ptrace facility

Add arch_ptrace_untrace() function that is called when the tracer
detaches (either voluntarily or when the tracing task dies);
ptrace_disable() is only called on a voluntary detach.

Add ptrace_fork() and arch_ptrace_fork(). They are called when a
traced task is forked.

Clear DS and BTS related fields on fork.

Release DS resources and reclaim memory in ptrace_untrace(). This
releases resources already when the tracing task dies. We used to do
that when the traced task dies.

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 9 insertions, 11 deletions

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 1cfd2a4bf853..416fb9282f4f 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -53,6 +53,7 @@
 #include <asm/ia32.h>
 #include <asm/idle.h>
 #include <asm/syscalls.h>
+#include <asm/ds.h>
 
 asmlinkage extern void ret_from_fork(void);
 
@@ -236,17 +237,8 @@ void exit_thread(void)
                 t->io_bitmap_max = 0;
                 put_cpu();
         }
-#ifdef CONFIG_X86_DS
-        /* Free any BTS tracers that have not been properly released. */
-        if (unlikely(current->bts)) {
-                ds_release_bts(current->bts);
-                current->bts = NULL;
-
-                kfree(current->bts_buffer);
-                current->bts_buffer = NULL;
-                current->bts_size = 0;
-        }
-#endif /* CONFIG_X86_DS */
+
+        ds_exit_thread(current);
 }
 
 void flush_thread(void)
@@ -376,6 +368,12 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long sp,
                 if (err)
                         goto out;
         }
+
+        ds_copy_thread(p, me);
+
+        clear_tsk_thread_flag(p, TIF_DEBUGCTLMSR);
+        p->thread.debugctlmsr = 0;
+
         err = 0;
 out:
         if (err && p->thread.io_bitmap_ptr) {