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>

1 files changed, 0 insertions, 2 deletions

diff --git a/arch/powerpc/include/asm/signal.h b/arch/powerpc/include/asm/signal.h
index 9322c28aebd2..5ff77722a52d 100644
--- a/arch/powerpc/include/asm/signal.h
+++ b/arch/powerpc/include/asm/signal.h
@@ -5,6 +5,4 @@
 #include <uapi/asm/signal.h>
 #include <uapi/asm/ptrace.h>
 
-extern unsigned long get_tm_stackpointer(struct pt_regs *regs);
-
 #endif /* _ASM_POWERPC_SIGNAL_H */