[PATCH v3 05/11] ptrace: Remove arch_ptrace_attach

Eric W. Biederman
2022-05-04T22:40:52Z

The last remaining implementation of arch_ptrace_attach is ia64's
ptrace_attach_sync_user_rbs which was added at the end of 2007 in
commit aa91a2e90044 ("[IA64] Synchronize RBS on PTRACE_ATTACH").

Reading the comments and examining the code ptrace_attach_sync_user_rbs
has the sole purpose of saving registers to the stack when ptrace_attach
changes TASK_STOPPED to TASK_TRACED. In all other cases arch_ptrace_stop
takes care of the register saving.

In commit d79fdd6d96f4 ("ptrace: Clean transitions between TASK_STOPPED and TRACED")
modified ptrace_attach to wake up the thread and enter ptrace_stop normally even
when the thread starts out stopped.

This makes ptrace_attach_sync_user_rbs completely unnecessary. So just
remove it.

Cc: linux-ia64@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
arch/ia64/include/asm/ptrace.h | 4 ---
arch/ia64/kernel/ptrace.c | 57 ----------------------------------
kernel/ptrace.c | 18 -----------
3 files changed, 79 deletions(-)

diff --git a/arch/ia64/include/asm/ptrace.h b/arch/ia64/include/asm/ptrace.h
index a10a498eede1..402874489890 100644
--- a/arch/ia64/include/asm/ptrace.h
+++ b/arch/ia64/include/asm/ptrace.h
@@ -139,10 +139,6 @@ static inline long regs_return_value(struct pt_regs *regs)
#define arch_ptrace_stop_needed() \
(!test_thread_flag(TIF_RESTORE_RSE))

- extern void ptrace_attach_sync_user_rbs (struct task_struct *);
- #define arch_ptrace_attach(child) \
- ptrace_attach_sync_user_rbs(child)
-
#define arch_has_single_step() (1)
#define arch_has_block_step() (1)

diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c
index a19acd9f5e1f..a45f529046c3 100644
--- a/arch/ia64/kernel/ptrace.c
+++ b/arch/ia64/kernel/ptrace.c
@@ -617,63 +617,6 @@ void ia64_sync_krbs(void)
unw_init_running(do_sync_rbs, ia64_sync_kernel_rbs);
}

-/*
- * After PTRACE_ATTACH, a thread's register backing store area in user
- * space is assumed to contain correct data whenever the thread is
- * stopped. arch_ptrace_stop takes care of this on tracing stops.
- * But if the child was already stopped for job control when we attach
- * to it, then it might not ever get into ptrace_stop by the time we
- * want to examine the user memory containing the RBS.
- */
-void
-ptrace_attach_sync_user_rbs (struct task_struct *child)
-{
- int stopped = 0;
- struct unw_frame_info info;
-
- /*
- * If the child is in TASK_STOPPED, we need to change that to
- * TASK_TRACED momentarily while we operate on it. This ensures
- * that the child won't be woken up and return to user mode while
- * we are doing the sync. (It can only be woken up for SIGKILL.)
- */
-
- read_lock(&tasklist_lock);
- if (child->sighand) {
- spin_lock_irq(&child->sighand->siglock);
- if (READ_ONCE(child->__state) = TASK_STOPPED &&
- !test_and_set_tsk_thread_flag(child, TIF_RESTORE_RSE)) {
- set_notify_resume(child);
-
- WRITE_ONCE(child->__state, TASK_TRACED);
- stopped = 1;
- }
- spin_unlock_irq(&child->sighand->siglock);
- }
- read_unlock(&tasklist_lock);
-
- if (!stopped)
- return;
-
- unw_init_from_blocked_task(&info, child);
- do_sync_rbs(&info, ia64_sync_user_rbs);
-
- /*
- * Now move the child back into TASK_STOPPED if it should be in a
- * job control stop, so that SIGCONT can be used to wake it up.
- */
- read_lock(&tasklist_lock);
- if (child->sighand) {
- spin_lock_irq(&child->sighand->siglock);
- if (READ_ONCE(child->__state) = TASK_TRACED &&
- (child->signal->flags & SIGNAL_STOP_STOPPED)) {
- WRITE_ONCE(child->__state, TASK_STOPPED);
- }
- spin_unlock_irq(&child->sighand->siglock);
- }
- read_unlock(&tasklist_lock);
-}
-
/*
* Write f32-f127 back to task->thread.fph if it has been modified.
*/
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index ccc4b465775b..da30dcd477a0 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -1285,10 +1285,6 @@ int ptrace_request(struct task_struct *child, long request,
return ret;
}

-#ifndef arch_ptrace_attach
-#define arch_ptrace_attach(child) do { } while (0)
-#endif
-
SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr,
unsigned long, data)
{
@@ -1297,8 +1293,6 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr,

if (request = PTRACE_TRACEME) {
ret = ptrace_traceme();
- if (!ret)
- arch_ptrace_attach(current);
goto out;
}

@@ -1310,12 +1304,6 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr,

if (request = PTRACE_ATTACH || request = PTRACE_SEIZE) {
ret = ptrace_attach(child, request, addr, data);
- /*
- * Some architectures need to do book-keeping after
- * a ptrace attach.
- */
- if (!ret)
- arch_ptrace_attach(child);
goto out_put_task_struct;
}

@@ -1455,12 +1443,6 @@ COMPAT_SYSCALL_DEFINE4(ptrace, compat_long_t, request, compat_long_t, pid,

if (request = PTRACE_ATTACH || request = PTRACE_SEIZE) {
ret = ptrace_attach(child, request, addr, data);
- /*
- * Some architectures need to do book-keeping after
- * a ptrace attach.
- */
- if (!ret)
- arch_ptrace_attach(child);
goto out_put_task_struct;
}

--
2.35.3