1 files changed, 124 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/dexcr.c b/arch/powerpc/kernel/dexcr.c
new file mode 100644
index 000000000000..3a0358e91c60
--- /dev/null
+++ b/arch/powerpc/kernel/dexcr.c
@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/capability.h>
+#include <linux/cpu.h>
+#include <linux/init.h>
+#include <linux/prctl.h>
+#include <linux/sched.h>
+
+#include <asm/cpu_has_feature.h>
+#include <asm/cputable.h>
+#include <asm/processor.h>
+#include <asm/reg.h>
+
+static int __init init_task_dexcr(void)
+{
+	if (!early_cpu_has_feature(CPU_FTR_ARCH_31))
+		return 0;
+
+	current->thread.dexcr_onexec = mfspr(SPRN_DEXCR);
+
+	return 0;
+}
+early_initcall(init_task_dexcr)
+
+/* Allow thread local configuration of these by default */
+#define DEXCR_PRCTL_EDITABLE ( \
+	DEXCR_PR_IBRTPD | \
+	DEXCR_PR_SRAPD | \
+	DEXCR_PR_NPHIE)
+
+static int prctl_to_aspect(unsigned long which, unsigned int *aspect)
+{
+	switch (which) {
+	case PR_PPC_DEXCR_SBHE:
+		*aspect = DEXCR_PR_SBHE;
+		break;
+	case PR_PPC_DEXCR_IBRTPD:
+		*aspect = DEXCR_PR_IBRTPD;
+		break;
+	case PR_PPC_DEXCR_SRAPD:
+		*aspect = DEXCR_PR_SRAPD;
+		break;
+	case PR_PPC_DEXCR_NPHIE:
+		*aspect = DEXCR_PR_NPHIE;
+		break;
+	default:
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+int get_dexcr_prctl(struct task_struct *task, unsigned long which)
+{
+	unsigned int aspect;
+	int ret;
+
+	ret = prctl_to_aspect(which, &aspect);
+	if (ret)
+		return ret;
+
+	if (aspect & DEXCR_PRCTL_EDITABLE)
+		ret |= PR_PPC_DEXCR_CTRL_EDITABLE;
+
+	if (aspect & mfspr(SPRN_DEXCR))
+		ret |= PR_PPC_DEXCR_CTRL_SET;
+	else
+		ret |= PR_PPC_DEXCR_CTRL_CLEAR;
+
+	if (aspect & task->thread.dexcr_onexec)
+		ret |= PR_PPC_DEXCR_CTRL_SET_ONEXEC;
+	else
+		ret |= PR_PPC_DEXCR_CTRL_CLEAR_ONEXEC;
+
+	return ret;
+}
+
+int set_dexcr_prctl(struct task_struct *task, unsigned long which, unsigned long ctrl)
+{
+	unsigned long dexcr;
+	unsigned int aspect;
+	int err = 0;
+
+	err = prctl_to_aspect(which, &aspect);
+	if (err)
+		return err;
+
+	if (!(aspect & DEXCR_PRCTL_EDITABLE))
+		return -EPERM;
+
+	if (ctrl & ~PR_PPC_DEXCR_CTRL_MASK)
+		return -EINVAL;
+
+	if (ctrl & PR_PPC_DEXCR_CTRL_SET && ctrl & PR_PPC_DEXCR_CTRL_CLEAR)
+		return -EINVAL;
+
+	if (ctrl & PR_PPC_DEXCR_CTRL_SET_ONEXEC && ctrl & PR_PPC_DEXCR_CTRL_CLEAR_ONEXEC)
+		return -EINVAL;
+
+	/*
+	 * We do not want an unprivileged process being able to disable
+	 * a setuid process's hash check instructions
+	 */
+	if (aspect == DEXCR_PR_NPHIE &&
+	    ctrl & PR_PPC_DEXCR_CTRL_CLEAR_ONEXEC &&
+	    !capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	dexcr = mfspr(SPRN_DEXCR);
+
+	if (ctrl & PR_PPC_DEXCR_CTRL_SET)
+		dexcr |= aspect;
+	else if (ctrl & PR_PPC_DEXCR_CTRL_CLEAR)
+		dexcr &= ~aspect;
+
+	if (ctrl & PR_PPC_DEXCR_CTRL_SET_ONEXEC)
+		task->thread.dexcr_onexec |= aspect;
+	else if (ctrl & PR_PPC_DEXCR_CTRL_CLEAR_ONEXEC)
+		task->thread.dexcr_onexec &= ~aspect;
+
+	mtspr(SPRN_DEXCR, dexcr);
+
+	return 0;
+}