linux/arch/arm64/kernel/sdei.c
D Scott Phillips 5cd474e573 arm64: sdei: abort running SDEI handlers during crash
Interrupts are blocked in SDEI context, per the SDEI spec: "The client
interrupts cannot preempt the event handler." If we crashed in the SDEI
handler-running context (as with ACPI's AGDI) then we need to clean up the
SDEI state before proceeding to the crash kernel so that the crash kernel
can have working interrupts.

Track the active SDEI handler per-cpu so that we can COMPLETE_AND_RESUME
the handler, discarding the interrupted context.

Fixes: f5df269618 ("arm64: kernel: Add arch-specific SDEI entry code and CPU masking")
Signed-off-by: D Scott Phillips <scott@os.amperecomputing.com>
Cc: stable@vger.kernel.org
Reviewed-by: James Morse <james.morse@arm.com>
Tested-by: Mihai Carabas <mihai.carabas@oracle.com>
Link: https://lore.kernel.org/r/20230627002939.2758-1-scott@os.amperecomputing.com
Signed-off-by: Will Deacon <will@kernel.org>
2023-08-04 17:35:33 +01:00

268 lines
6.2 KiB
C

// 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
DEFINE_PER_CPU(struct sdei_registered_event *, sdei_active_normal_event);
DEFINE_PER_CPU(struct sdei_registered_event *, sdei_active_critical_event);
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 (!scs_is_enabled())
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;
}
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;
}