8 files changed, 66 insertions, 25 deletions

diff --git a/Documentation/powerpc/transactional_memory.txt b/Documentation/powerpc/transactional_memory.txt
index ded69794a5c0..ba0a2a4a54ba 100644
--- a/Documentation/powerpc/transactional_memory.txt
+++ b/Documentation/powerpc/transactional_memory.txt
@@ -74,22 +74,23 @@ Causes of transaction aborts
 Syscalls
 ========
 
-Performing syscalls from within transaction is not recommended, and can lead
-to unpredictable results.
+Syscalls made from within an active transaction will not be performed and the
+transaction will be doomed by the kernel with the failure code TM_CAUSE_SYSCALL
+| TM_CAUSE_PERSISTENT.
 
-Syscalls do not by design abort transactions, but beware: The kernel code will
-not be running in transactional state.  The effect of syscalls will always
-remain visible, but depending on the call they may abort your transaction as a
-side-effect, read soon-to-be-aborted transactional data that should not remain
-invisible, etc.  If you constantly retry a transaction that constantly aborts
-itself by calling a syscall, you'll have a livelock & make no progress.
+Syscalls made from within a suspended transaction are performed as normal and
+the transaction is not explicitly doomed by the kernel.  However, what the
+kernel does to perform the syscall may result in the transaction being doomed
+by the hardware.  The syscall is performed in suspended mode so any side
+effects will be persistent, independent of transaction success or failure.  No
+guarantees are provided by the kernel about which syscalls will affect
+transaction success.
 
-Simple syscalls (e.g. sigprocmask()) "could" be OK.  Even things like write()
-from, say, printf() should be OK as long as the kernel does not access any
-memory that was accessed transactionally.
-
-Consider any syscalls that happen to work as debug-only -- not recommended for
-production use.  Best to queue them up till after the transaction is over.
+Care must be taken when relying on syscalls to abort during active transactions
+if the calls are made via a library.  Libraries may cache values (which may
+give the appearance of success) or perform operations that cause transaction
+failure before entering the kernel (which may produce different failure codes).
+Examples are glibc's getpid() and lazy symbol resolution.
 
 
 Signals
@@ -176,8 +177,7 @@ kernel aborted a transaction:
  TM_CAUSE_RESCHED       Thread was rescheduled.
  TM_CAUSE_TLBI          Software TLB invalid.
  TM_CAUSE_FAC_UNAV      FP/VEC/VSX unavailable trap.
- TM_CAUSE_SYSCALL       Currently unused; future syscalls that must abort
-                        transactions for consistency will use this.
+ TM_CAUSE_SYSCALL       Syscall from active transaction.
  TM_CAUSE_SIGNAL        Signal delivered.
  TM_CAUSE_MISC          Currently unused.
  TM_CAUSE_ALIGNMENT     Alignment fault.
diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
index 6367b8347dad..4994648b9265 100644
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -242,11 +242,13 @@ enum {
 
 /* We only set the TM feature if the kernel was compiled with TM supprt */
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
-#define CPU_FTR_TM_COMP         CPU_FTR_TM
-#define PPC_FEATURE2_HTM_COMP   PPC_FEATURE2_HTM
+#define CPU_FTR_TM_COMP                 CPU_FTR_TM
+#define PPC_FEATURE2_HTM_COMP           PPC_FEATURE2_HTM
+#define PPC_FEATURE2_HTM_NOSC_COMP      PPC_FEATURE2_HTM_NOSC
 #else
-#define CPU_FTR_TM_COMP         0
-#define PPC_FEATURE2_HTM_COMP   0
+#define CPU_FTR_TM_COMP                 0
+#define PPC_FEATURE2_HTM_COMP           0
+#define PPC_FEATURE2_HTM_NOSC_COMP      0
 #endif
 
 /* We need to mark all pages as being coherent if we're SMP or we have a
diff --git a/arch/powerpc/include/uapi/asm/cputable.h b/arch/powerpc/include/uapi/asm/cputable.h
index de2c0e4ee1aa..43686043e297 100644
--- a/arch/powerpc/include/uapi/asm/cputable.h
+++ b/arch/powerpc/include/uapi/asm/cputable.h
@@ -42,5 +42,6 @@
 #define PPC_FEATURE2_ISEL               0x08000000
 #define PPC_FEATURE2_TAR                0x04000000
 #define PPC_FEATURE2_VEC_CRYPTO         0x02000000
+#define PPC_FEATURE2_HTM_NOSC           0x01000000
 
 #endif /* _UAPI__ASM_POWERPC_CPUTABLE_H */
diff --git a/arch/powerpc/include/uapi/asm/tm.h b/arch/powerpc/include/uapi/asm/tm.h
index 5d836b7c1176..5047659815a5 100644
--- a/arch/powerpc/include/uapi/asm/tm.h
+++ b/arch/powerpc/include/uapi/asm/tm.h
@@ -11,7 +11,7 @@
 #define TM_CAUSE_RESCHED        0xde
 #define TM_CAUSE_TLBI           0xdc
 #define TM_CAUSE_FAC_UNAV       0xda
-#define TM_CAUSE_SYSCALL        0xd8  /* future use */
+#define TM_CAUSE_SYSCALL        0xd8
 #define TM_CAUSE_MISC           0xd6  /* future use */
 #define TM_CAUSE_SIGNAL         0xd4
 #define TM_CAUSE_ALIGNMENT      0xd2
diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c
index 60262fdf35ba..7d80bfdfb15e 100644
--- a/arch/powerpc/kernel/cputable.c
+++ b/arch/powerpc/kernel/cputable.c
@@ -108,7 +108,9 @@ extern void __restore_cpu_e6500(void);
                                  PPC_FEATURE_TRUE_LE | \
                                  PPC_FEATURE_PSERIES_PERFMON_COMPAT)
 #define COMMON_USER2_POWER8     (PPC_FEATURE2_ARCH_2_07 | \
-                                 PPC_FEATURE2_HTM_COMP | PPC_FEATURE2_DSCR | \
+                                 PPC_FEATURE2_HTM_COMP | \
+                                 PPC_FEATURE2_HTM_NOSC_COMP | \
+                                 PPC_FEATURE2_DSCR | \
                                  PPC_FEATURE2_ISEL | PPC_FEATURE2_TAR | \
                                  PPC_FEATURE2_VEC_CRYPTO)
 #define COMMON_USER_PA6T        (COMMON_USER_PPC64 | PPC_FEATURE_PA6T |\
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 278888e89acc..579e0f9a2d57 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -34,6 +34,7 @@
 #include <asm/ftrace.h>
 #include <asm/hw_irq.h>
 #include <asm/context_tracking.h>
+#include <asm/tm.h>
 
 /*
  * System calls.
@@ -51,6 +52,12 @@ exception_marker:
 
         .globl system_call_common
 system_call_common:
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+BEGIN_FTR_SECTION
+        extrdi. r10, r12, 1, (63-MSR_TS_T_LG) /* transaction active? */
+        bne     tabort_syscall
+END_FTR_SECTION_IFSET(CPU_FTR_TM)
+#endif
         andi.   r10,r12,MSR_PR
         mr      r10,r1
         addi    r1,r1,-INT_FRAME_SIZE
@@ -311,6 +318,34 @@ syscall_exit_work:
         bl      do_syscall_trace_leave
         b       ret_from_except
 
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+tabort_syscall:
+        /* Firstly we need to enable TM in the kernel */
+        mfmsr   r10
+        li      r13, 1
+        rldimi  r10, r13, MSR_TM_LG, 63-MSR_TM_LG
+        mtmsrd  r10, 0
+
+        /* tabort, this dooms the transaction, nothing else */
+        li      r13, (TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT)
+        TABORT(R13)
+
+        /*
+         * Return directly to userspace. We have corrupted user register state,
+         * but userspace will never see that register state. Execution will
+         * resume after the tbegin of the aborted transaction with the
+         * checkpointed register state.
+         */
+        li      r13, MSR_RI
+        andc    r10, r10, r13
+        mtmsrd  r10, 1
+        mtspr   SPRN_SRR0, r11
+        mtspr   SPRN_SRR1, r12
+
+        rfid
+        b       .       /* prevent speculative execution */
+#endif
+
 /* Save non-volatile GPRs, if not already saved. */
 _GLOBAL(save_nvgprs)
         ld      r11,_TRAP(r1)
diff --git a/tools/testing/selftests/powerpc/tm/Makefile b/tools/testing/selftests/powerpc/tm/Makefile
index 6bff955e1d55..4bea62a319dc 100644
--- a/tools/testing/selftests/powerpc/tm/Makefile
+++ b/tools/testing/selftests/powerpc/tm/Makefile
@@ -1,11 +1,11 @@
-TEST_PROGS := tm-resched-dscr
+TEST_PROGS := tm-resched-dscr tm-syscall
 
 all: $(TEST_PROGS)
 
 $(TEST_PROGS): ../harness.c
 
 tm-syscall: tm-syscall-asm.S
-tm-syscall: CFLAGS += -mhtm
+tm-syscall: CFLAGS += -mhtm -I../../../../../usr/include
 
 include ../../lib.mk
 
diff --git a/tools/testing/selftests/powerpc/tm/tm-syscall.c b/tools/testing/selftests/powerpc/tm/tm-syscall.c
index 3ed8d4b252fa..1276e23da63b 100644
--- a/tools/testing/selftests/powerpc/tm/tm-syscall.c
+++ b/tools/testing/selftests/powerpc/tm/tm-syscall.c
@@ -82,7 +82,8 @@ int tm_syscall(void)
         unsigned count = 0;
         struct timeval end, now;
 
-        SKIP_IF(!((long)get_auxv_entry(AT_HWCAP2) & PPC_FEATURE2_HTM));
+        SKIP_IF(!((long)get_auxv_entry(AT_HWCAP2)
+                  & PPC_FEATURE2_HTM_NOSC));
         setbuf(stdout, NULL);
 
         printf("Testing transactional syscalls for %d seconds...\n", TEST_DURATION);