1 files changed, 235 insertions, 0 deletions
diff --git a/arch/arm64/kernel/sdei.c b/arch/arm64/kernel/sdei.c
new file mode 100644
index 000000000000..6b8d90d5ceae
--- /dev/null
+++ b/arch/arm64/kernel/sdei.c
@@ -0,0 +1,235 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2017 Arm Ltd.
+#define pr_fmt(fmt) "sdei: " fmt
+
+#include <linux/arm_sdei.h>
+#include <linux/hardirq.h>
+#include <linux/irqflags.h>
+#include <linux/sched/task_stack.h>
+#include <linux/uaccess.h>
+
+#include <asm/alternative.h>
+#include <asm/kprobes.h>
+#include <asm/mmu.h>
+#include <asm/ptrace.h>
+#include <asm/sections.h>
+#include <asm/sysreg.h>
+#include <asm/vmap_stack.h>
+
+unsigned long sdei_exit_mode;
+
+/*
+ * VMAP'd stacks checking for stack overflow on exception using sp as a scratch
+ * register, meaning SDEI has to switch to its own stack. We need two stacks as
+ * a critical event may interrupt a normal event that has just taken a
+ * synchronous exception, and is using sp as scratch register. For a critical
+ * event interrupting a normal event, we can't reliably tell if we were on the
+ * sdei stack.
+ * For now, we allocate stacks when the driver is probed.
+ */
+DECLARE_PER_CPU(unsigned long *, sdei_stack_normal_ptr);
+DECLARE_PER_CPU(unsigned long *, sdei_stack_critical_ptr);
+
+#ifdef CONFIG_VMAP_STACK
+DEFINE_PER_CPU(unsigned long *, sdei_stack_normal_ptr);
+DEFINE_PER_CPU(unsigned long *, sdei_stack_critical_ptr);
+#endif
+
+static void _free_sdei_stack(unsigned long * __percpu *ptr, int cpu)
+{
+	unsigned long *p;
+
+	p = per_cpu(*ptr, cpu);
+	if (p) {
+		per_cpu(*ptr, cpu) = NULL;
+		vfree(p);
+	}
+}
+
+static void free_sdei_stacks(void)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		_free_sdei_stack(&sdei_stack_normal_ptr, cpu);
+		_free_sdei_stack(&sdei_stack_critical_ptr, cpu);
+	}
+}
+
+static int _init_sdei_stack(unsigned long * __percpu *ptr, int cpu)
+{
+	unsigned long *p;
+
+	p = arch_alloc_vmap_stack(SDEI_STACK_SIZE, cpu_to_node(cpu));
+	if (!p)
+		return -ENOMEM;
+	per_cpu(*ptr, cpu) = p;
+
+	return 0;
+}
+
+static int init_sdei_stacks(void)
+{
+	int cpu;
+	int err = 0;
+
+	for_each_possible_cpu(cpu) {
+		err = _init_sdei_stack(&sdei_stack_normal_ptr, cpu);
+		if (err)
+			break;
+		err = _init_sdei_stack(&sdei_stack_critical_ptr, cpu);
+		if (err)
+			break;
+	}
+
+	if (err)
+		free_sdei_stacks();
+
+	return err;
+}
+
+bool _on_sdei_stack(unsigned long sp)
+{
+	unsigned long low, high;
+
+	if (!IS_ENABLED(CONFIG_VMAP_STACK))
+		return false;
+
+	low = (unsigned long)raw_cpu_read(sdei_stack_critical_ptr);
+	high = low + SDEI_STACK_SIZE;
+
+	if (low <= sp && sp < high)
+		return true;
+
+	low = (unsigned long)raw_cpu_read(sdei_stack_normal_ptr);
+	high = low + SDEI_STACK_SIZE;
+
+	return (low <= sp && sp < high);
+}
+
+unsigned long sdei_arch_get_entry_point(int conduit)
+{
+	/*
+	 * SDEI works between adjacent exception levels. If we booted at EL1 we
+	 * assume a hypervisor is marshalling events. If we booted at EL2 and
+	 * dropped to EL1 because we don't support VHE, then we can't support
+	 * SDEI.
+	 */
+	if (is_hyp_mode_available() && !is_kernel_in_hyp_mode()) {
+		pr_err("Not supported on this hardware/boot configuration\n");
+		return 0;
+	}
+
+	if (IS_ENABLED(CONFIG_VMAP_STACK)) {
+		if (init_sdei_stacks())
+			return 0;
+	}
+
+	sdei_exit_mode = (conduit == CONDUIT_HVC) ? SDEI_EXIT_HVC : SDEI_EXIT_SMC;
+
+#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
+	if (arm64_kernel_unmapped_at_el0()) {
+		unsigned long offset;
+
+		offset = (unsigned long)__sdei_asm_entry_trampoline -
+			 (unsigned long)__entry_tramp_text_start;
+		return TRAMP_VALIAS + offset;
+	} else
+#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
+		return (unsigned long)__sdei_asm_handler;
+
+}
+
+/*
+ * __sdei_handler() returns one of:
+ *  SDEI_EV_HANDLED -  success, return to the interrupted context.
+ *  SDEI_EV_FAILED  -  failure, return this error code to firmare.
+ *  virtual-address -  success, return to this address.
+ */
+static __kprobes unsigned long _sdei_handler(struct pt_regs *regs,
+					     struct sdei_registered_event *arg)
+{
+	u32 mode;
+	int i, err = 0;
+	int clobbered_registers = 4;
+	u64 elr = read_sysreg(elr_el1);
+	u32 kernel_mode = read_sysreg(CurrentEL) | 1;	/* +SPSel */
+	unsigned long vbar = read_sysreg(vbar_el1);
+
+	if (arm64_kernel_unmapped_at_el0())
+		clobbered_registers++;
+
+	/* Retrieve the missing registers values */
+	for (i = 0; i < clobbered_registers; i++) {
+		/* from within the handler, this call always succeeds */
+		sdei_api_event_context(i, &regs->regs[i]);
+	}
+
+	/*
+	 * We didn't take an exception to get here, set PAN. UAO will be cleared
+	 * by sdei_event_handler()s set_fs(USER_DS) call.
+	 */
+	__uaccess_enable_hw_pan();
+
+	err = sdei_event_handler(regs, arg);
+	if (err)
+		return SDEI_EV_FAILED;
+
+	if (elr != read_sysreg(elr_el1)) {
+		/*
+		 * We took a synchronous exception from the SDEI handler.
+		 * This could deadlock, and if you interrupt KVM it will
+		 * hyp-panic instead.
+		 */
+		pr_warn("unsafe: exception during handler\n");
+	}
+
+	mode = regs->pstate & (PSR_MODE32_BIT | PSR_MODE_MASK);
+
+	/*
+	 * If we interrupted the kernel with interrupts masked, we always go
+	 * back to wherever we came from.
+	 */
+	if (mode == kernel_mode && !interrupts_enabled(regs))
+		return SDEI_EV_HANDLED;
+
+	/*
+	 * Otherwise, we pretend this was an IRQ. This lets user space tasks
+	 * receive signals before we return to them, and KVM to invoke it's
+	 * world switch to do the same.
+	 *
+	 * See DDI0487B.a Table D1-7 'Vector offsets from vector table base
+	 * address'.
+	 */
+	if (mode == kernel_mode)
+		return vbar + 0x280;
+	else if (mode & PSR_MODE32_BIT)
+		return vbar + 0x680;
+
+	return vbar + 0x480;
+}
+
+
+asmlinkage __kprobes notrace unsigned long
+__sdei_handler(struct pt_regs *regs, struct sdei_registered_event *arg)
+{
+	unsigned long ret;
+	bool do_nmi_exit = false;
+
+	/*
+	 * nmi_enter() deals with printk() re-entrance and use of RCU when
+	 * RCU believed this CPU was idle. Because critical events can
+	 * interrupt normal events, we may already be in_nmi().
+	 */
+	if (!in_nmi()) {
+		nmi_enter();
+		do_nmi_exit = true;
+	}
+
+	ret = _sdei_handler(regs, arg);
+
+	if (do_nmi_exit)
+		nmi_exit();
+
+	return ret;
+}