powerpc: signals: Stop using current in signal code
Much of the signal code takes a pt_regs on which it operates. Over
time the signal code has needed to know more about the thread than
what pt_regs can supply, this information is obtained as needed by
using 'current'.
This approach is not strictly incorrect however it does mean that
there is now a hard requirement that the pt_regs being passed around
does belong to current, this is never checked. A safer approach is for
the majority of the signal functions to take a task_struct from which
they can obtain pt_regs and any other information they need. The
caveat that the task_struct they are passed must be current doesn't go
away but can more easily be checked for.
Functions called from outside powerpc signal code are passed a pt_regs
and they can confirm that the pt_regs is that of current and pass
current to other functions, furthurmore, powerpc signal functions can
check that the task_struct they are passed is the same as current
avoiding possible corruption of current (or the task they are passed)
if this assertion ever fails.
CC: paulus@samba.org
Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
index cb64d6f..bbe77ae 100644
--- a/arch/powerpc/kernel/signal.c
+++ b/arch/powerpc/kernel/signal.c
@@ -99,22 +99,24 @@
}
}
-static void do_signal(struct pt_regs *regs)
+static void do_signal(struct task_struct *tsk)
{
sigset_t *oldset = sigmask_to_save();
struct ksignal ksig;
int ret;
int is32 = is_32bit_task();
+ BUG_ON(tsk != current);
+
get_signal(&ksig);
/* Is there any syscall restart business here ? */
- check_syscall_restart(regs, &ksig.ka, ksig.sig > 0);
+ check_syscall_restart(tsk->thread.regs, &ksig.ka, ksig.sig > 0);
if (ksig.sig <= 0) {
/* No signal to deliver -- put the saved sigmask back */
restore_saved_sigmask();
- regs->trap = 0;
+ tsk->thread.regs->trap = 0;
return; /* no signals delivered */
}
@@ -124,23 +126,22 @@
* user space. The DABR will have been cleared if it
* triggered inside the kernel.
*/
- if (current->thread.hw_brk.address &&
- current->thread.hw_brk.type)
- __set_breakpoint(¤t->thread.hw_brk);
+ if (tsk->thread.hw_brk.address && tsk->thread.hw_brk.type)
+ __set_breakpoint(&tsk->thread.hw_brk);
#endif
/* Re-enable the breakpoints for the signal stack */
- thread_change_pc(current, regs);
+ thread_change_pc(tsk, tsk->thread.regs);
if (is32) {
if (ksig.ka.sa.sa_flags & SA_SIGINFO)
- ret = handle_rt_signal32(&ksig, oldset, regs);
+ ret = handle_rt_signal32(&ksig, oldset, tsk);
else
- ret = handle_signal32(&ksig, oldset, regs);
+ ret = handle_signal32(&ksig, oldset, tsk);
} else {
- ret = handle_rt_signal64(&ksig, oldset, regs);
+ ret = handle_rt_signal64(&ksig, oldset, tsk);
}
- regs->trap = 0;
+ tsk->thread.regs->trap = 0;
signal_setup_done(ret, &ksig, test_thread_flag(TIF_SINGLESTEP));
}
@@ -151,8 +152,10 @@
if (thread_info_flags & _TIF_UPROBE)
uprobe_notify_resume(regs);
- if (thread_info_flags & _TIF_SIGPENDING)
- do_signal(regs);
+ if (thread_info_flags & _TIF_SIGPENDING) {
+ BUG_ON(regs != current->thread.regs);
+ do_signal(current);
+ }
if (thread_info_flags & _TIF_NOTIFY_RESUME) {
clear_thread_flag(TIF_NOTIFY_RESUME);
@@ -162,7 +165,7 @@
user_enter();
}
-unsigned long get_tm_stackpointer(struct pt_regs *regs)
+unsigned long get_tm_stackpointer(struct task_struct *tsk)
{
/* When in an active transaction that takes a signal, we need to be
* careful with the stack. It's possible that the stack has moved back
@@ -187,11 +190,13 @@
*/
#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
- if (MSR_TM_ACTIVE(regs->msr)) {
+ BUG_ON(tsk != current);
+
+ if (MSR_TM_ACTIVE(tsk->thread.regs->msr)) {
tm_reclaim_current(TM_CAUSE_SIGNAL);
- if (MSR_TM_TRANSACTIONAL(regs->msr))
- return current->thread.ckpt_regs.gpr[1];
+ if (MSR_TM_TRANSACTIONAL(tsk->thread.regs->msr))
+ return tsk->thread.ckpt_regs.gpr[1];
}
#endif
- return regs->gpr[1];
+ return tsk->thread.regs->gpr[1];
}