7 files changed, 74 insertions, 36 deletions

diff --git a/Documentation/powerpc/transactional_memory.txt b/Documentation/powerpc/transactional_memory.txt
index c54bf3127651..dc23e58ae264 100644
--- a/Documentation/powerpc/transactional_memory.txt
+++ b/Documentation/powerpc/transactional_memory.txt
@@ -147,6 +147,25 @@ Example signal handler:
       fix_the_problem(ucp->dar);
     }
 
+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 up after the tbegin.
+The obvious case here is when the tbegin is called inside a function that
+returns before a tend.  In this case, the stack is part of the checkpointed
+transactional memory state.  If we write over this non transactionally or in
+suspend, we are in trouble because if we get a tm abort, the program counter and
+stack pointer will be back at the tbegin but our in memory stack won't be valid
+anymore.
+
+To avoid this, when taking a signal in an active transaction, we need to use
+the stack pointer from the checkpointed state, rather than the speculated
+state.  This ensures that the signal context (written tm suspended) will be
+written below the stack required for the rollback.  The transaction is aborted
+becuase of the treclaim, so any memory written between the tbegin and the
+signal will be rolled back anyway.
+
+For signals taken in non-TM or suspended mode, we use the
+normal/non-checkpointed stack pointer.
+
 
 Failure cause codes used by kernel
 ==================================
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index 594db6bc093c..14a658363698 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -409,21 +409,16 @@ static inline void prefetchw(const void *x)
 #endif
 
 #ifdef CONFIG_PPC64
-static inline unsigned long get_clean_sp(struct pt_regs *regs, int is_32)
+static inline unsigned long get_clean_sp(unsigned long sp, int is_32)
 {
-        unsigned long sp;
-
         if (is_32)
-                sp = regs->gpr[1] & 0x0ffffffffUL;
-        else
-                sp = regs->gpr[1];
-
+                return sp & 0x0ffffffffUL;
         return sp;
 }
 #else
-static inline unsigned long get_clean_sp(struct pt_regs *regs, int is_32)
+static inline unsigned long get_clean_sp(unsigned long sp, int is_32)
 {
-        return regs->gpr[1];
+        return sp;
 }
 #endif
 
diff --git a/arch/powerpc/include/asm/signal.h b/arch/powerpc/include/asm/signal.h
index fbe66c463891..9322c28aebd2 100644
--- a/arch/powerpc/include/asm/signal.h
+++ b/arch/powerpc/include/asm/signal.h
@@ -3,5 +3,8 @@
 
 #define __ARCH_HAS_SA_RESTORER
 #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 */
diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
index 577a8aa69c6e..457e97aa2945 100644
--- a/arch/powerpc/kernel/signal.c
+++ b/arch/powerpc/kernel/signal.c
@@ -18,6 +18,7 @@
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
 #include <asm/debug.h>
+#include <asm/tm.h>
 
 #include "signal.h"
 
@@ -30,13 +31,13 @@ int show_unhandled_signals = 1;
 /*
  * Allocate space for the signal frame
  */
-void __user * get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
+void __user * get_sigframe(struct k_sigaction *ka, unsigned long sp,
                            size_t frame_size, int is_32)
 {
         unsigned long oldsp, newsp;
 
         /* Default to using normal stack */
-        oldsp = get_clean_sp(regs, is_32);
+        oldsp = get_clean_sp(sp, is_32);
 
         /* Check for alt stack */
         if ((ka->sa.sa_flags & SA_ONSTACK) &&
@@ -175,3 +176,38 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
 
         user_enter();
 }
+
+unsigned long get_tm_stackpointer(struct pt_regs *regs)
+{
+        /* 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
+         * up after the tbegin.  The obvious case here is when the tbegin is
+         * called inside a function that returns before a tend.  In this case,
+         * the stack is part of the checkpointed transactional memory state.
+         * If we write over this non transactionally or in suspend, we are in
+         * trouble because if we get a tm abort, the program counter and stack
+         * pointer will be back at the tbegin but our in memory stack won't be
+         * valid anymore.
+         *
+         * To avoid this, when taking a signal in an active transaction, we
+         * need to use the stack pointer from the checkpointed state, rather
+         * than the speculated state.  This ensures that the signal context
+         * (written tm suspended) will be written below the stack required for
+         * the rollback.  The transaction is aborted becuase of the treclaim,
+         * so any memory written between the tbegin and the signal will be
+         * rolled back anyway.
+         *
+         * For signals taken in non-TM or suspended mode, we use the
+         * normal/non-checkpointed stack pointer.
+         */
+
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+        if (MSR_TM_ACTIVE(regs->msr)) {
+                tm_enable();
+                tm_reclaim(&current->thread, regs->msr, TM_CAUSE_SIGNAL);
+                if (MSR_TM_TRANSACTIONAL(regs->msr))
+                        return current->thread.ckpt_regs.gpr[1];
+        }
+#endif
+        return regs->gpr[1];
+}
diff --git a/arch/powerpc/kernel/signal.h b/arch/powerpc/kernel/signal.h
index ec84c901ceab..c69b9aeb9f23 100644
--- a/arch/powerpc/kernel/signal.h
+++ b/arch/powerpc/kernel/signal.h
@@ -12,7 +12,7 @@
 
 extern void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags);
 
-extern void __user * get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
+extern void __user * get_sigframe(struct k_sigaction *ka, unsigned long sp,
                                   size_t frame_size, int is_32);
 
 extern int handle_signal32(unsigned long sig, struct k_sigaction *ka,
diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index 95068bf569ad..201385c3a1ae 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -503,12 +503,6 @@ static int save_tm_user_regs(struct pt_regs *regs,
 {
         unsigned long msr = regs->msr;
 
-        /* tm_reclaim rolls back all reg states, updating thread.ckpt_regs,
-         * thread.transact_fpr[], thread.transact_vr[], etc.
-         */
-        tm_enable();
-        tm_reclaim(&current->thread, msr, TM_CAUSE_SIGNAL);
-
         /* Make sure floating point registers are stored in regs */
         flush_fp_to_thread(current);
 
@@ -965,7 +959,7 @@ int handle_rt_signal32(unsigned long sig, struct k_sigaction *ka,
 
         /* Set up Signal Frame */
         /* Put a Real Time Context onto stack */
-        rt_sf = get_sigframe(ka, regs, sizeof(*rt_sf), 1);
+        rt_sf = get_sigframe(ka, get_tm_stackpointer(regs), sizeof(*rt_sf), 1);
         addr = rt_sf;
         if (unlikely(rt_sf == NULL))
                 goto badframe;
@@ -1403,7 +1397,7 @@ int handle_signal32(unsigned long sig, struct k_sigaction *ka,
         unsigned long tramp;
 
         /* Set up Signal Frame */
-        frame = get_sigframe(ka, regs, sizeof(*frame), 1);
+        frame = get_sigframe(ka, get_tm_stackpointer(regs), sizeof(*frame), 1);
         if (unlikely(frame == NULL))
                 goto badframe;
         sc = (struct sigcontext __user *) &frame->sctx;
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index c1794286098c..345947367ec0 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -154,11 +154,12 @@ static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
  * As above, but Transactional Memory is in use, so deliver sigcontexts
  * containing checkpointed and transactional register states.
  *
- * To do this, we treclaim to gather both sets of registers and set up the
- * 'normal' sigcontext registers with rolled-back register values such that a
- * simple signal handler sees a correct checkpointed register state.
- * If interested, a TM-aware sighandler can examine the transactional registers
- * in the 2nd sigcontext to determine the real origin of the signal.
+ * To do this, we treclaim (done before entering here) to gather both sets of
+ * registers and set up the 'normal' sigcontext registers with rolled-back
+ * register values such that a simple signal handler sees a correct
+ * checkpointed register state.  If interested, a TM-aware sighandler can
+ * examine the transactional registers in the 2nd sigcontext to determine the
+ * real origin of the signal.
  */
 static long setup_tm_sigcontexts(struct sigcontext __user *sc,
                                  struct sigcontext __user *tm_sc,
@@ -184,16 +185,6 @@ static long setup_tm_sigcontexts(struct sigcontext __user *sc,
 
         BUG_ON(!MSR_TM_ACTIVE(regs->msr));
 
-        /* tm_reclaim rolls back all reg states, saving checkpointed (older)
-         * GPRs to thread.ckpt_regs and (if used) FPRs to (newer)
-         * thread.transact_fp and/or VRs to (newer) thread.transact_vr.
-         * THEN we save out FP/VRs, if necessary, to the checkpointed (older)
-         * thread.fr[]/vr[]s.  The transactional (newer) GPRs are on the
-         * stack, in *regs.
-         */
-        tm_enable();
-        tm_reclaim(&current->thread, msr, TM_CAUSE_SIGNAL);
-
         flush_fp_to_thread(current);
 
 #ifdef CONFIG_ALTIVEC
@@ -711,7 +702,7 @@ int handle_rt_signal64(int signr, struct k_sigaction *ka, siginfo_t *info,
         unsigned long newsp = 0;
         long err = 0;
 
-        frame = get_sigframe(ka, regs, sizeof(*frame), 0);
+        frame = get_sigframe(ka, get_tm_stackpointer(regs), sizeof(*frame), 0);
         if (unlikely(frame == NULL))
                 goto badframe;