blob: 2c7ca449dd5111206fa8559065fd95ce2858dcf9 [file] [log] [blame]
// 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, 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, low, high, STACK_TYPE_SDEI_NORMAL, info);
}
static bool on_sdei_critical_stack(unsigned long sp, 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, low, high, STACK_TYPE_SDEI_CRITICAL, info);
}
bool _on_sdei_stack(unsigned long sp, struct stack_info *info)
{
if (!IS_ENABLED(CONFIG_VMAP_STACK))
return false;
if (on_sdei_critical_stack(sp, info))
return true;
if (on_sdei_normal_stack(sp, 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_mode_available() && !is_kernel_in_hyp_mode()) {
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;
}
/*
* __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]);
}
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;
}
static void __kprobes notrace __sdei_pstate_entry(void)
{
/*
* The original SDEI spec (ARM DEN 0054A) can be read ambiguously as to
* whether PSTATE bits are inherited unchanged or generated from
* scratch, and the TF-A implementation always clears PAN and always
* clears UAO. There are no other known implementations.
*
* Subsequent revisions (ARM DEN 0054B) follow the usual rules for how
* PSTATE is modified upon architectural exceptions, and so PAN is
* either inherited or set per SCTLR_ELx.SPAN, and UAO is always
* cleared.
*
* We must explicitly reset PAN to the expected state, including
* clearing it when the host isn't using it, in case a VM had it set.
*/
if (system_uses_hw_pan())
set_pstate_pan(1);
else if (cpu_has_pan())
set_pstate_pan(0);
}
asmlinkage noinstr unsigned long
__sdei_handler(struct pt_regs *regs, struct sdei_registered_event *arg)
{
unsigned long ret;
/*
* We didn't take an exception to get here, so the HW hasn't
* set/cleared bits in PSTATE that we may rely on. Initialize PAN.
*/
__sdei_pstate_entry();
arm64_enter_nmi(regs);
ret = _sdei_handler(regs, arg);
arm64_exit_nmi(regs);
return ret;
}