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
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.
/* 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
#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 */
#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
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 |\
#include <asm/ftrace.h>
#include <asm/hw_irq.h>
#include <asm/context_tracking.h>
+#include <asm/tm.h>
/*
* System calls.
.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
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)
-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
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);
projects / GitHub / LineageOS / android_kernel_motorola_exynos9610.git / commitdiff