[IA64] Synchronize kernel RSE to user-space and back
This is base kernel patch for ptrace RSE bug. It's basically a backport
from the utrace RSE patch I sent out several weeks ago. please review.
when a thread is stopped (ptraced), debugger might change thread's user
stack (change memory directly), and we must avoid the RSE stored in
kernel to override user stack (user space's RSE is newer than kernel's
in the case). To workaround the issue, we copy kernel RSE to user RSE
before the task is stopped, so user RSE has updated data. we then copy
user RSE to kernel after the task is resummed from traced stop and
kernel will use the newer RSE to return to user.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
CC: Roland McGrath <roland@redhat.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c
index 2e96f17..2de5a52 100644
--- a/arch/ia64/kernel/ptrace.c
+++ b/arch/ia64/kernel/ptrace.c
@@ -547,6 +547,72 @@
return 0;
}
+static long
+ia64_sync_kernel_rbs (struct task_struct *child, struct switch_stack *sw,
+ unsigned long user_rbs_start, unsigned long user_rbs_end)
+{
+ unsigned long addr, val;
+ long ret;
+
+ /* now copy word for word from user rbs to kernel rbs: */
+ for (addr = user_rbs_start; addr < user_rbs_end; addr += 8) {
+ if (access_process_vm(child, addr, &val, sizeof(val), 0)
+ != sizeof(val))
+ return -EIO;
+
+ ret = ia64_poke(child, sw, user_rbs_end, addr, val);
+ if (ret < 0)
+ return ret;
+ }
+ return 0;
+}
+
+typedef long (*syncfunc_t)(struct task_struct *, struct switch_stack *,
+ unsigned long, unsigned long);
+
+static void do_sync_rbs(struct unw_frame_info *info, void *arg)
+{
+ struct pt_regs *pt;
+ unsigned long urbs_end;
+ syncfunc_t fn = arg;
+
+ if (unw_unwind_to_user(info) < 0)
+ return;
+ pt = task_pt_regs(info->task);
+ urbs_end = ia64_get_user_rbs_end(info->task, pt, NULL);
+
+ fn(info->task, info->sw, pt->ar_bspstore, urbs_end);
+}
+
+/*
+ * when a thread is stopped (ptraced), debugger might change thread's user
+ * stack (change memory directly), and we must avoid the RSE stored in kernel
+ * to override user stack (user space's RSE is newer than kernel's in the
+ * case). To workaround the issue, we copy kernel RSE to user RSE before the
+ * task is stopped, so user RSE has updated data. we then copy user RSE to
+ * kernel after the task is resummed from traced stop and kernel will use the
+ * newer RSE to return to user. TIF_RESTORE_RSE is the flag to indicate we need
+ * synchronize user RSE to kernel.
+ */
+void ia64_ptrace_stop(void)
+{
+ if (test_and_set_tsk_thread_flag(current, TIF_RESTORE_RSE))
+ return;
+ tsk_set_notify_resume(current);
+ unw_init_running(do_sync_rbs, ia64_sync_user_rbs);
+}
+
+/*
+ * This is called to read back the register backing store.
+ */
+void ia64_sync_krbs(void)
+{
+ clear_tsk_thread_flag(current, TIF_RESTORE_RSE);
+ tsk_clear_notify_resume(current);
+
+ unw_init_running(do_sync_rbs, ia64_sync_kernel_rbs);
+}
+
static inline int
thread_matches (struct task_struct *thread, unsigned long addr)
{
@@ -1422,6 +1488,7 @@
struct task_struct *child;
struct switch_stack *sw;
long ret;
+ struct unw_frame_info info;
lock_kernel();
ret = -EPERM;
@@ -1453,6 +1520,8 @@
if (request == PTRACE_ATTACH) {
ret = ptrace_attach(child);
+ if (!ret)
+ arch_ptrace_attach(child);
goto out_tsk;
}
@@ -1481,6 +1550,11 @@
/* write the word at location addr */
urbs_end = ia64_get_user_rbs_end(child, pt, NULL);
ret = ia64_poke(child, sw, urbs_end, addr, data);
+
+ /* Make sure user RBS has the latest data */
+ unw_init_from_blocked_task(&info, child);
+ do_sync_rbs(&info, ia64_sync_user_rbs);
+
goto out_tsk;
case PTRACE_PEEKUSR:
@@ -1634,6 +1708,10 @@
&& (current->ptrace & PT_PTRACED))
syscall_trace();
+ /* copy user rbs to kernel rbs */
+ if (test_thread_flag(TIF_RESTORE_RSE))
+ ia64_sync_krbs();
+
if (unlikely(current->audit_context)) {
long syscall;
int arch;
@@ -1671,4 +1749,8 @@
|| test_thread_flag(TIF_SINGLESTEP))
&& (current->ptrace & PT_PTRACED))
syscall_trace();
+
+ /* copy user rbs to kernel rbs */
+ if (test_thread_flag(TIF_RESTORE_RSE))
+ ia64_sync_krbs();
}