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-rw-r--r--arch/powerpc/kernel/syscall.c189
1 files changed, 189 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c
new file mode 100644
index 000000000..18b9d3253
--- /dev/null
+++ b/arch/powerpc/kernel/syscall.c
@@ -0,0 +1,189 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/compat.h>
+#include <linux/context_tracking.h>
+#include <linux/randomize_kstack.h>
+
+#include <asm/interrupt.h>
+#include <asm/kup.h>
+#include <asm/syscall.h>
+#include <asm/time.h>
+#include <asm/tm.h>
+#include <asm/unistd.h>
+
+
+/* Has to run notrace because it is entered not completely "reconciled" */
+notrace long system_call_exception(struct pt_regs *regs, unsigned long r0)
+{
+ long ret;
+ syscall_fn f;
+
+ kuap_lock();
+
+ add_random_kstack_offset();
+
+ if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
+ BUG_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED);
+
+ trace_hardirqs_off(); /* finish reconciling */
+
+ CT_WARN_ON(ct_state() == CONTEXT_KERNEL);
+ user_exit_irqoff();
+
+ BUG_ON(regs_is_unrecoverable(regs));
+ BUG_ON(!(regs->msr & MSR_PR));
+ BUG_ON(arch_irq_disabled_regs(regs));
+
+#ifdef CONFIG_PPC_PKEY
+ if (mmu_has_feature(MMU_FTR_PKEY)) {
+ unsigned long amr, iamr;
+ bool flush_needed = false;
+ /*
+ * When entering from userspace we mostly have the AMR/IAMR
+ * different from kernel default values. Hence don't compare.
+ */
+ amr = mfspr(SPRN_AMR);
+ iamr = mfspr(SPRN_IAMR);
+ regs->amr = amr;
+ regs->iamr = iamr;
+ if (mmu_has_feature(MMU_FTR_BOOK3S_KUAP)) {
+ mtspr(SPRN_AMR, AMR_KUAP_BLOCKED);
+ flush_needed = true;
+ }
+ if (mmu_has_feature(MMU_FTR_BOOK3S_KUEP)) {
+ mtspr(SPRN_IAMR, AMR_KUEP_BLOCKED);
+ flush_needed = true;
+ }
+ if (flush_needed)
+ isync();
+ } else
+#endif
+ kuap_assert_locked();
+
+ booke_restore_dbcr0();
+
+ account_cpu_user_entry();
+
+ account_stolen_time();
+
+ /*
+ * This is not required for the syscall exit path, but makes the
+ * stack frame look nicer. If this was initialised in the first stack
+ * frame, or if the unwinder was taught the first stack frame always
+ * returns to user with IRQS_ENABLED, this store could be avoided!
+ */
+ irq_soft_mask_regs_set_state(regs, IRQS_ENABLED);
+
+ /*
+ * If system call is called with TM active, set _TIF_RESTOREALL to
+ * prevent RFSCV being used to return to userspace, because POWER9
+ * TM implementation has problems with this instruction returning to
+ * transactional state. Final register values are not relevant because
+ * the transaction will be aborted upon return anyway. Or in the case
+ * of unsupported_scv SIGILL fault, the return state does not much
+ * matter because it's an edge case.
+ */
+ if (IS_ENABLED(CONFIG_PPC_TRANSACTIONAL_MEM) &&
+ unlikely(MSR_TM_TRANSACTIONAL(regs->msr)))
+ set_bits(_TIF_RESTOREALL, &current_thread_info()->flags);
+
+ /*
+ * If the system call was made with a transaction active, doom it and
+ * return without performing the system call. Unless it was an
+ * unsupported scv vector, in which case it's treated like an illegal
+ * instruction.
+ */
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+ if (unlikely(MSR_TM_TRANSACTIONAL(regs->msr)) &&
+ !trap_is_unsupported_scv(regs)) {
+ /* Enable TM in the kernel, and disable EE (for scv) */
+ hard_irq_disable();
+ mtmsr(mfmsr() | MSR_TM);
+
+ /* tabort, this dooms the transaction, nothing else */
+ asm volatile(".long 0x7c00071d | ((%0) << 16)"
+ :: "r"(TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT));
+
+ /*
+ * Userspace will never see the return value. Execution will
+ * resume after the tbegin. of the aborted transaction with the
+ * checkpointed register state. A context switch could occur
+ * or signal delivered to the process before resuming the
+ * doomed transaction context, but that should all be handled
+ * as expected.
+ */
+ return -ENOSYS;
+ }
+#endif // CONFIG_PPC_TRANSACTIONAL_MEM
+
+ local_irq_enable();
+
+ if (unlikely(read_thread_flags() & _TIF_SYSCALL_DOTRACE)) {
+ if (unlikely(trap_is_unsupported_scv(regs))) {
+ /* Unsupported scv vector */
+ _exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
+ return regs->gpr[3];
+ }
+ /*
+ * We use the return value of do_syscall_trace_enter() as the
+ * syscall number. If the syscall was rejected for any reason
+ * do_syscall_trace_enter() returns an invalid syscall number
+ * and the test against NR_syscalls will fail and the return
+ * value to be used is in regs->gpr[3].
+ */
+ r0 = do_syscall_trace_enter(regs);
+ if (unlikely(r0 >= NR_syscalls))
+ return regs->gpr[3];
+
+ } else if (unlikely(r0 >= NR_syscalls)) {
+ if (unlikely(trap_is_unsupported_scv(regs))) {
+ /* Unsupported scv vector */
+ _exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
+ return regs->gpr[3];
+ }
+ return -ENOSYS;
+ }
+
+ /* May be faster to do array_index_nospec? */
+ barrier_nospec();
+
+#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
+ // No COMPAT if we have SYSCALL_WRAPPER, see Kconfig
+ f = (void *)sys_call_table[r0];
+ ret = f(regs);
+#else
+ if (unlikely(is_compat_task())) {
+ unsigned long r3, r4, r5, r6, r7, r8;
+
+ f = (void *)compat_sys_call_table[r0];
+
+ r3 = regs->gpr[3] & 0x00000000ffffffffULL;
+ r4 = regs->gpr[4] & 0x00000000ffffffffULL;
+ r5 = regs->gpr[5] & 0x00000000ffffffffULL;
+ r6 = regs->gpr[6] & 0x00000000ffffffffULL;
+ r7 = regs->gpr[7] & 0x00000000ffffffffULL;
+ r8 = regs->gpr[8] & 0x00000000ffffffffULL;
+
+ ret = f(r3, r4, r5, r6, r7, r8);
+ } else {
+ f = (void *)sys_call_table[r0];
+
+ ret = f(regs->gpr[3], regs->gpr[4], regs->gpr[5],
+ regs->gpr[6], regs->gpr[7], regs->gpr[8]);
+ }
+#endif
+
+ /*
+ * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(),
+ * so the maximum stack offset is 1k bytes (10 bits).
+ *
+ * The actual entropy will be further reduced by the compiler when
+ * applying stack alignment constraints: the powerpc architecture
+ * may have two kinds of stack alignment (16-bytes and 8-bytes).
+ *
+ * So the resulting 6 or 7 bits of entropy is seen in SP[9:4] or SP[9:3].
+ */
+ choose_random_kstack_offset(mftb());
+
+ return ret;
+}