* [PATCH 3/5] powerpc/tm: Abort on emulation and alignment faults
2013-05-27 4:09 [PATCH 0/5] powerpc/tm: Various transactional memory fixes Michael Neuling
2013-05-27 4:09 ` [PATCH 1/5] powerpc/tm: Make room for hypervisor in abort cause codes Michael Neuling
2013-05-27 4:09 ` [PATCH 2/5] powerpc/tm: Update cause codes documentation Michael Neuling
@ 2013-05-27 4:09 ` Michael Neuling
2013-05-27 4:09 ` [PATCH 4/5] powerpc/tm: Move TM abort cause codes to uapi Michael Neuling
2013-05-27 4:09 ` [PATCH 5/5] powerpc/tm: Fix userspace stack corruption on signal delivery for active transactions Michael Neuling
4 siblings, 0 replies; 7+ messages in thread
From: Michael Neuling @ 2013-05-27 4:09 UTC (permalink / raw)
To: Benjamin Herrenschmidt; +Cc: Michael Neuling, linuxppc-dev, Matt Evans
If we are emulating an instruction inside an active user transaction that
touches memory, the kernel can't emulate it as it operates in transactional
suspend context. We need to abort these transactions and send them back to
userspace for the hardware to rollback.
We can service these if the user transaction is in suspend mode, since the
kernel will operate in the same suspend context.
This adds a check to all alignment faults and to specific instruction
emulations (only string instructions for now). If the user process is in an
active (non-suspended) transaction, we abort the transaction go back to
userspace allowing the HW to roll back the transaction and tell the user of the
failure. This also adds new tm abort cause codes to report the reason of the
persistent error to the user.
Crappy test case here http://neuling.org/devel/junkcode/aligntm.c
Signed-off-by: Michael Neuling <mikey@neuling.org>
Cc: <stable@vger.kernel.org> # v3.9
---
Documentation/powerpc/transactional_memory.txt | 7 ++++--
arch/powerpc/include/asm/reg.h | 2 ++
arch/powerpc/kernel/traps.c | 29 ++++++++++++++++++++++++
3 files changed, 36 insertions(+), 2 deletions(-)
diff --git a/Documentation/powerpc/transactional_memory.txt b/Documentation/powerpc/transactional_memory.txt
index 84e04a0..c54bf31 100644
--- a/Documentation/powerpc/transactional_memory.txt
+++ b/Documentation/powerpc/transactional_memory.txt
@@ -161,9 +161,12 @@ kernel aborted a transaction:
transactions for consistency will use this.
TM_CAUSE_SIGNAL Signal delivered.
TM_CAUSE_MISC Currently unused.
+ TM_CAUSE_ALIGNMENT Alignment fault.
+ TM_CAUSE_EMULATE Emulation that touched memory.
-These can be checked by the user program's abort handler as TEXASR[0:7].
-
+These can be checked by the user program's abort handler as TEXASR[0:7]. If
+bit 7 is set, it indicates that the error is consider persistent. For example
+a TM_CAUSE_ALIGNMENT will be persistent while a TM_CAUSE_RESCHED will not.q
GDB
===
diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 8f6a94b..d0528e0 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -122,6 +122,8 @@
#define TM_CAUSE_SYSCALL 0xd8 /* future use */
#define TM_CAUSE_MISC 0xd6 /* future use */
#define TM_CAUSE_SIGNAL 0xd4
+#define TM_CAUSE_ALIGNMENT 0xd2
+#define TM_CAUSE_EMULATE 0xd0
#if defined(CONFIG_PPC_BOOK3S_64)
#define MSR_64BIT MSR_SF
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index a7a648f..f18c79c 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -53,6 +53,7 @@
#ifdef CONFIG_PPC64
#include <asm/firmware.h>
#include <asm/processor.h>
+#include <asm/tm.h>
#endif
#include <asm/kexec.h>
#include <asm/ppc-opcode.h>
@@ -932,6 +933,28 @@ static int emulate_isel(struct pt_regs *regs, u32 instword)
return 0;
}
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+static inline bool tm_abort_check(struct pt_regs *regs, int cause)
+{
+ /* If we're emulating a load/store in an active transaction, we cannot
+ * emulate it as the kernel operates in transaction suspended context.
+ * We need to abort the transaction. This creates a persistent TM
+ * abort so tell the user what caused it with a new code.
+ */
+ if (MSR_TM_TRANSACTIONAL(regs->msr)) {
+ tm_enable();
+ tm_abort(cause);
+ return true;
+ }
+ return false;
+}
+#else
+static inline bool tm_abort_check(struct pt_regs *regs, int reason)
+{
+ return false;
+}
+#endif
+
static int emulate_instruction(struct pt_regs *regs)
{
u32 instword;
@@ -971,6 +994,9 @@ static int emulate_instruction(struct pt_regs *regs)
/* Emulate load/store string insn. */
if ((instword & PPC_INST_STRING_GEN_MASK) == PPC_INST_STRING) {
+ if (tm_abort_check(regs,
+ TM_CAUSE_EMULATE | TM_CAUSE_PERSISTENT))
+ return -EINVAL;
PPC_WARN_EMULATED(string, regs);
return emulate_string_inst(regs, instword);
}
@@ -1148,6 +1174,9 @@ void alignment_exception(struct pt_regs *regs)
if (!arch_irq_disabled_regs(regs))
local_irq_enable();
+ if (tm_abort_check(regs, TM_CAUSE_ALIGNMENT | TM_CAUSE_PERSISTENT))
+ goto bail;
+
/* we don't implement logging of alignment exceptions */
if (!(current->thread.align_ctl & PR_UNALIGN_SIGBUS))
fixed = fix_alignment(regs);
--
1.7.10.4
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH 5/5] powerpc/tm: Fix userspace stack corruption on signal delivery for active transactions
2013-05-27 4:09 [PATCH 0/5] powerpc/tm: Various transactional memory fixes Michael Neuling
` (3 preceding siblings ...)
2013-05-27 4:09 ` [PATCH 4/5] powerpc/tm: Move TM abort cause codes to uapi Michael Neuling
@ 2013-05-27 4:09 ` Michael Neuling
4 siblings, 0 replies; 7+ messages in thread
From: Michael Neuling @ 2013-05-27 4:09 UTC (permalink / raw)
To: Benjamin Herrenschmidt; +Cc: Michael Neuling, linuxppc-dev, Matt Evans
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.
Tested with 64 and 32 bit signals
Signed-off-by: Michael Neuling <mikey@neuling.org>
Cc: <stable@vger.kernel.org> # v3.9
---
Documentation/powerpc/transactional_memory.txt | 19 +++++++++++
arch/powerpc/include/asm/processor.h | 13 +++-----
arch/powerpc/include/asm/signal.h | 3 ++
arch/powerpc/kernel/signal.c | 40 ++++++++++++++++++++++--
arch/powerpc/kernel/signal.h | 2 +-
arch/powerpc/kernel/signal_32.c | 10 ++----
arch/powerpc/kernel/signal_64.c | 23 +++++---------
7 files changed, 74 insertions(+), 36 deletions(-)
diff --git a/Documentation/powerpc/transactional_memory.txt b/Documentation/powerpc/transactional_memory.txt
index c54bf31..dc23e58 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 594db6b..14a6583 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 fbe66c4..9322c28 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 577a8aa..457e97a 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(¤t->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 ec84c90..c69b9ae 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 95068bf..201385c 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(¤t->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 c179428..3459473 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(¤t->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;
--
1.7.10.4
^ permalink raw reply related [flat|nested] 7+ messages in thread