arch/arm64/kernel/sdei.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 // Copyright (C) 2017 Arm Ltd.
 #define pr_fmt(fmt) "sdei: " fmt

 #include <linux/arm-smccc.h>
 #include <linux/arm_sdei.h>
 #include <linux/hardirq.h>
 #include <linux/irqflags.h>
 #include <linux/sched/task_stack.h>
 #include <linux/scs.h>
 #include <linux/uaccess.h>

 #include <asm/alternative.h>
 #include <asm/exception.h>
 #include <asm/kprobes.h>
 #include <asm/mmu.h>
 #include <asm/ptrace.h>
 #include <asm/sections.h>
 #include <asm/stacktrace.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

 DECLARE_PER_CPU(unsigned long *, sdei_shadow_call_stack_normal_ptr);
 DECLARE_PER_CPU(unsigned long *, sdei_shadow_call_stack_critical_ptr);

 #ifdef CONFIG_SHADOW_CALL_STACK
 DEFINE_PER_CPU(unsigned long *, sdei_shadow_call_stack_normal_ptr);
 DEFINE_PER_CPU(unsigned long *, sdei_shadow_call_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;

 	if (!IS_ENABLED(CONFIG_VMAP_STACK))
 		return;

 	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;

 	if (!IS_ENABLED(CONFIG_VMAP_STACK))
 		return 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;
 }

 static void _free_sdei_scs(unsigned long * __percpu *ptr, int cpu)
 {
 	void *s;

 	s = per_cpu(*ptr, cpu);
 	if (s) {
 		per_cpu(*ptr, cpu) = NULL;
 		scs_free(s);
 	}
 }

 static void free_sdei_scs(void)
 {
 	int cpu;

 	for_each_possible_cpu(cpu) {
 		_free_sdei_scs(&sdei_shadow_call_stack_normal_ptr, cpu);
 		_free_sdei_scs(&sdei_shadow_call_stack_critical_ptr, cpu);
 	}
 }

 static int _init_sdei_scs(unsigned long * __percpu *ptr, int cpu)
 {
 	void *s;

 	s = scs_alloc(cpu_to_node(cpu));
 	if (!s)
 		return -ENOMEM;
 	per_cpu(*ptr, cpu) = s;

 	return 0;
 }

 static int init_sdei_scs(void)
 {
 	int cpu;
 	int err = 0;

 	if (!IS_ENABLED(CONFIG_SHADOW_CALL_STACK))
 		return 0;

 	for_each_possible_cpu(cpu) {
 		err = _init_sdei_scs(&sdei_shadow_call_stack_normal_ptr, cpu);
 		if (err)
 			break;
 		err = _init_sdei_scs(&sdei_shadow_call_stack_critical_ptr, cpu);
 		if (err)
 			break;
 	}

 	if (err)
 		free_sdei_scs();

 	return err;
 }

 static bool on_sdei_normal_stack(unsigned long sp, unsigned long size,
 				 struct stack_info *info)
 {
 	unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_normal_ptr);
 	unsigned long high = low + SDEI_STACK_SIZE;

 	return on_stack(sp, size, low, high, STACK_TYPE_SDEI_NORMAL, info);
 }

 static bool on_sdei_critical_stack(unsigned long sp, unsigned long size,
 				   struct stack_info *info)
 {
 	unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_critical_ptr);
 	unsigned long high = low + SDEI_STACK_SIZE;

 	return on_stack(sp, size, low, high, STACK_TYPE_SDEI_CRITICAL, info);
 }

 bool _on_sdei_stack(unsigned long sp, unsigned long size, struct stack_info *info)
 {
 	if (!IS_ENABLED(CONFIG_VMAP_STACK))
 		return false;

 	if (on_sdei_critical_stack(sp, size, info))
 		return true;

 	if (on_sdei_normal_stack(sp, size, info))
 		return true;

 	return false;
 }

 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_nvhe()) {
 		pr_err("Not supported on this hardware/boot configuration\n");
 		goto out_err;
 	}

 	if (init_sdei_stacks())
 		goto out_err;

 	if (init_sdei_scs())
 		goto out_err_free_stacks;

 	sdei_exit_mode = (conduit == SMCCC_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;

 out_err_free_stacks:
 	free_sdei_stacks();
 out_err:
 	return 0;
 }

 /*
  * do_sdei_event() 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.
  */
 unsigned long __kprobes do_sdei_event(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]);
 	}

 	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;
 }
	// SPDX-License-Identifier: GPL-2.0
	// Copyright (C) 2017 Arm Ltd.
	#define pr_fmt(fmt) "sdei: " fmt

	#include <linux/arm-smccc.h>
	#include <linux/arm_sdei.h>
	#include <linux/hardirq.h>
	#include <linux/irqflags.h>
	#include <linux/sched/task_stack.h>
	#include <linux/scs.h>
	#include <linux/uaccess.h>

	#include <asm/alternative.h>
	#include <asm/exception.h>
	#include <asm/kprobes.h>
	#include <asm/mmu.h>
	#include <asm/ptrace.h>
	#include <asm/sections.h>
	#include <asm/stacktrace.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

	DECLARE_PER_CPU(unsigned long *, sdei_shadow_call_stack_normal_ptr);
	DECLARE_PER_CPU(unsigned long *, sdei_shadow_call_stack_critical_ptr);

	#ifdef CONFIG_SHADOW_CALL_STACK
	DEFINE_PER_CPU(unsigned long *, sdei_shadow_call_stack_normal_ptr);
	DEFINE_PER_CPU(unsigned long *, sdei_shadow_call_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;

	if (!IS_ENABLED(CONFIG_VMAP_STACK))
	return;

	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;

	if (!IS_ENABLED(CONFIG_VMAP_STACK))
	return 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;
	}

	static void _free_sdei_scs(unsigned long * __percpu *ptr, int cpu)
	{
	void *s;

	s = per_cpu(*ptr, cpu);
	if (s) {
	per_cpu(*ptr, cpu) = NULL;
	scs_free(s);
	}
	}

	static void free_sdei_scs(void)
	{
	int cpu;

	for_each_possible_cpu(cpu) {
	_free_sdei_scs(&sdei_shadow_call_stack_normal_ptr, cpu);
	_free_sdei_scs(&sdei_shadow_call_stack_critical_ptr, cpu);
	}
	}

	static int _init_sdei_scs(unsigned long * __percpu *ptr, int cpu)
	{
	void *s;

	s = scs_alloc(cpu_to_node(cpu));
	if (!s)
	return -ENOMEM;
	per_cpu(*ptr, cpu) = s;

	return 0;
	}

	static int init_sdei_scs(void)
	{
	int cpu;
	int err = 0;

	if (!IS_ENABLED(CONFIG_SHADOW_CALL_STACK))
	return 0;

	for_each_possible_cpu(cpu) {
	err = _init_sdei_scs(&sdei_shadow_call_stack_normal_ptr, cpu);
	if (err)
	break;
	err = _init_sdei_scs(&sdei_shadow_call_stack_critical_ptr, cpu);
	if (err)
	break;
	}

	if (err)
	free_sdei_scs();

	return err;
	}

	static bool on_sdei_normal_stack(unsigned long sp, unsigned long size,
	struct stack_info *info)
	{
	unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_normal_ptr);
	unsigned long high = low + SDEI_STACK_SIZE;

	return on_stack(sp, size, low, high, STACK_TYPE_SDEI_NORMAL, info);
	}

	static bool on_sdei_critical_stack(unsigned long sp, unsigned long size,
	struct stack_info *info)
	{
	unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_critical_ptr);
	unsigned long high = low + SDEI_STACK_SIZE;

	return on_stack(sp, size, low, high, STACK_TYPE_SDEI_CRITICAL, info);
	}

	bool _on_sdei_stack(unsigned long sp, unsigned long size, struct stack_info *info)
	{
	if (!IS_ENABLED(CONFIG_VMAP_STACK))
	return false;

	if (on_sdei_critical_stack(sp, size, info))
	return true;

	if (on_sdei_normal_stack(sp, size, info))
	return true;

	return false;
	}

	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_nvhe()) {
	pr_err("Not supported on this hardware/boot configuration\n");
	goto out_err;
	}

	if (init_sdei_stacks())
	goto out_err;

	if (init_sdei_scs())
	goto out_err_free_stacks;

	sdei_exit_mode = (conduit == SMCCC_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;

	out_err_free_stacks:
	free_sdei_stacks();
	out_err:
	return 0;
	}

	/*
	* do_sdei_event() 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.
	*/
	unsigned long __kprobes do_sdei_event(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]);
	}

	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;
	}