ptrace: revert "Prepare to fix racy accesses on task breakpoints"

This reverts commit bf26c018490c2fce ("Prepare to fix racy accesses on
task breakpoints").

The patch was fine but we can no longer race with SIGKILL after 9899d11f
("ptrace: ensure arch_ptrace/ptrace_request can never race with SIGKILL"),
the __TASK_TRACED tracee can't be woken up and ->ptrace_bps[] can't go
away.

Now that ptrace_get_breakpoints/ptrace_put_breakpoints have no callers, we
can kill them and remove task->ptrace_bp_refcnt.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Michael Neuling <mikey@neuling.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 89573a33ab3c43ee84cf629d84e5ff3d7f091206..07d0df6bf7687064c0b328dbb316694faa7442cf 100644 (file)
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -142,9 +142,6 @@ static inline void ptrace_init_task(struct task_struct *child, bool ptrace)
 {
        INIT_LIST_HEAD(&child->ptrace_entry);
        INIT_LIST_HEAD(&child->ptraced);
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
-       atomic_set(&child->ptrace_bp_refcnt, 1);
-#endif
        child->jobctl = 0;
        child->ptrace = 0;
        child->parent = child->real_parent;
@@ -351,11 +348,4 @@ extern int task_current_syscall(struct task_struct *target, long *callno,
                                unsigned long args[6], unsigned int maxargs,
                                unsigned long *sp, unsigned long *pc);
 
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
-extern int ptrace_get_breakpoints(struct task_struct *tsk);
-extern void ptrace_put_breakpoints(struct task_struct *tsk);
-#else
-static inline void ptrace_put_breakpoints(struct task_struct *tsk) { }
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
-
 #endif

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1100a5c60b892099cda85bceef2ca4470c35c377..8b10339321de08f92e5216274b70ecfe0e865e2e 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1404,9 +1404,6 @@ struct task_struct {
        } memcg_batch;
        unsigned int memcg_kmem_skip_account;
 #endif
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
-       atomic_t ptrace_bp_refcnt;
-#endif
 #ifdef CONFIG_UPROBES
        struct uprobe_task *utask;
 #endif

diff --git a/kernel/exit.c b/kernel/exit.c
index 6a057750ebbbdee49b9c2c2b578567401fd8540f..2f3be8b6904b25513fe3946e11c3d8a1e824e74d 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -819,7 +819,7 @@ void do_exit(long code)
        /*
         * FIXME: do that only when needed, using sched_exit tracepoint
         */
-       ptrace_put_breakpoints(tsk);
+       flush_ptrace_hw_breakpoint(tsk);
 
        exit_notify(tsk, group_dead);
 #ifdef CONFIG_NUMA

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index aed981a3f69c180dda76bfca76411656842eec01..8cc170b157d73cbda10253014427b0393e0d47f6 100644 (file)
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -1179,19 +1179,3 @@ asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
        return ret;
 }
 #endif /* CONFIG_COMPAT */
-
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
-int ptrace_get_breakpoints(struct task_struct *tsk)
-{
-       if (atomic_inc_not_zero(&tsk->ptrace_bp_refcnt))
-               return 0;
-
-       return -1;
-}
-
-void ptrace_put_breakpoints(struct task_struct *tsk)
-{
-       if (atomic_dec_and_test(&tsk->ptrace_bp_refcnt))
-               flush_ptrace_hw_breakpoint(tsk);
-}
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */