linuxdebug/arch/arm64/kvm/stacktrace.c

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2024-07-16 15:50:57 +02:00
/* SPDX-License-Identifier: GPL-2.0-only */
/*
* KVM nVHE hypervisor stack tracing support.
*
* The unwinder implementation depends on the nVHE mode:
*
* 1) Non-protected nVHE mode - the host can directly access the
* HYP stack pages and unwind the HYP stack in EL1. This saves having
* to allocate shared buffers for the host to read the unwinded
* stacktrace.
*
* 2) pKVM (protected nVHE) mode - the host cannot directly access
* the HYP memory. The stack is unwinded in EL2 and dumped to a shared
* buffer where the host can read and print the stacktrace.
*
* Copyright (C) 2022 Google LLC
*/
#include <linux/kvm.h>
#include <linux/kvm_host.h>
#include <asm/stacktrace/nvhe.h>
static struct stack_info stackinfo_get_overflow(void)
{
struct kvm_nvhe_stacktrace_info *stacktrace_info
= this_cpu_ptr_nvhe_sym(kvm_stacktrace_info);
unsigned long low = (unsigned long)stacktrace_info->overflow_stack_base;
unsigned long high = low + OVERFLOW_STACK_SIZE;
return (struct stack_info) {
.low = low,
.high = high,
};
}
static struct stack_info stackinfo_get_overflow_kern_va(void)
{
unsigned long low = (unsigned long)this_cpu_ptr_nvhe_sym(overflow_stack);
unsigned long high = low + OVERFLOW_STACK_SIZE;
return (struct stack_info) {
.low = low,
.high = high,
};
}
static struct stack_info stackinfo_get_hyp(void)
{
struct kvm_nvhe_stacktrace_info *stacktrace_info
= this_cpu_ptr_nvhe_sym(kvm_stacktrace_info);
unsigned long low = (unsigned long)stacktrace_info->stack_base;
unsigned long high = low + PAGE_SIZE;
return (struct stack_info) {
.low = low,
.high = high,
};
}
static struct stack_info stackinfo_get_hyp_kern_va(void)
{
unsigned long low = (unsigned long)*this_cpu_ptr(&kvm_arm_hyp_stack_page);
unsigned long high = low + PAGE_SIZE;
return (struct stack_info) {
.low = low,
.high = high,
};
}
/*
* kvm_nvhe_stack_kern_va - Convert KVM nVHE HYP stack addresses to a kernel VAs
*
* The nVHE hypervisor stack is mapped in the flexible 'private' VA range, to
* allow for guard pages below the stack. Consequently, the fixed offset address
* translation macros won't work here.
*
* The kernel VA is calculated as an offset from the kernel VA of the hypervisor
* stack base.
*
* Returns true on success and updates @addr to its corresponding kernel VA;
* otherwise returns false.
*/
static bool kvm_nvhe_stack_kern_va(unsigned long *addr, unsigned long size)
{
struct stack_info stack_hyp, stack_kern;
stack_hyp = stackinfo_get_hyp();
stack_kern = stackinfo_get_hyp_kern_va();
if (stackinfo_on_stack(&stack_hyp, *addr, size))
goto found;
stack_hyp = stackinfo_get_overflow();
stack_kern = stackinfo_get_overflow_kern_va();
if (stackinfo_on_stack(&stack_hyp, *addr, size))
goto found;
return false;
found:
*addr = *addr - stack_hyp.low + stack_kern.low;
return true;
}
/*
* Convert a KVN nVHE HYP frame record address to a kernel VA
*/
static bool kvm_nvhe_stack_kern_record_va(unsigned long *addr)
{
return kvm_nvhe_stack_kern_va(addr, 16);
}
static int unwind_next(struct unwind_state *state)
{
/*
* The FP is in the hypervisor VA space. Convert it to the kernel VA
* space so it can be unwound by the regular unwind functions.
*/
if (!kvm_nvhe_stack_kern_record_va(&state->fp))
return -EINVAL;
return unwind_next_frame_record(state);
}
static void unwind(struct unwind_state *state,
stack_trace_consume_fn consume_entry, void *cookie)
{
while (1) {
int ret;
if (!consume_entry(cookie, state->pc))
break;
ret = unwind_next(state);
if (ret < 0)
break;
}
}
/*
* kvm_nvhe_dump_backtrace_entry - Symbolize and print an nVHE backtrace entry
*
* @arg : the hypervisor offset, used for address translation
* @where : the program counter corresponding to the stack frame
*/
static bool kvm_nvhe_dump_backtrace_entry(void *arg, unsigned long where)
{
unsigned long va_mask = GENMASK_ULL(vabits_actual - 1, 0);
unsigned long hyp_offset = (unsigned long)arg;
/* Mask tags and convert to kern addr */
where = (where & va_mask) + hyp_offset;
kvm_err(" [<%016lx>] %pB\n", where, (void *)(where + kaslr_offset()));
return true;
}
static void kvm_nvhe_dump_backtrace_start(void)
{
kvm_err("nVHE call trace:\n");
}
static void kvm_nvhe_dump_backtrace_end(void)
{
kvm_err("---[ end nVHE call trace ]---\n");
}
/*
* hyp_dump_backtrace - Dump the non-protected nVHE backtrace.
*
* @hyp_offset: hypervisor offset, used for address translation.
*
* The host can directly access HYP stack pages in non-protected
* mode, so the unwinding is done directly from EL1. This removes
* the need for shared buffers between host and hypervisor for
* the stacktrace.
*/
static void hyp_dump_backtrace(unsigned long hyp_offset)
{
struct kvm_nvhe_stacktrace_info *stacktrace_info;
struct stack_info stacks[] = {
stackinfo_get_overflow_kern_va(),
stackinfo_get_hyp_kern_va(),
};
struct unwind_state state = {
.stacks = stacks,
.nr_stacks = ARRAY_SIZE(stacks),
};
stacktrace_info = this_cpu_ptr_nvhe_sym(kvm_stacktrace_info);
kvm_nvhe_unwind_init(&state, stacktrace_info->fp, stacktrace_info->pc);
kvm_nvhe_dump_backtrace_start();
unwind(&state, kvm_nvhe_dump_backtrace_entry, (void *)hyp_offset);
kvm_nvhe_dump_backtrace_end();
}
#ifdef CONFIG_PROTECTED_NVHE_STACKTRACE
DECLARE_KVM_NVHE_PER_CPU(unsigned long [NVHE_STACKTRACE_SIZE/sizeof(long)],
pkvm_stacktrace);
/*
* pkvm_dump_backtrace - Dump the protected nVHE HYP backtrace.
*
* @hyp_offset: hypervisor offset, used for address translation.
*
* Dumping of the pKVM HYP backtrace is done by reading the
* stack addresses from the shared stacktrace buffer, since the
* host cannot directly access hypervisor memory in protected
* mode.
*/
static void pkvm_dump_backtrace(unsigned long hyp_offset)
{
unsigned long *stacktrace
= (unsigned long *) this_cpu_ptr_nvhe_sym(pkvm_stacktrace);
int i;
kvm_nvhe_dump_backtrace_start();
/* The saved stacktrace is terminated by a null entry */
for (i = 0;
i < ARRAY_SIZE(kvm_nvhe_sym(pkvm_stacktrace)) && stacktrace[i];
i++)
kvm_nvhe_dump_backtrace_entry((void *)hyp_offset, stacktrace[i]);
kvm_nvhe_dump_backtrace_end();
}
#else /* !CONFIG_PROTECTED_NVHE_STACKTRACE */
static void pkvm_dump_backtrace(unsigned long hyp_offset)
{
kvm_err("Cannot dump pKVM nVHE stacktrace: !CONFIG_PROTECTED_NVHE_STACKTRACE\n");
}
#endif /* CONFIG_PROTECTED_NVHE_STACKTRACE */
/*
* kvm_nvhe_dump_backtrace - Dump KVM nVHE hypervisor backtrace.
*
* @hyp_offset: hypervisor offset, used for address translation.
*/
void kvm_nvhe_dump_backtrace(unsigned long hyp_offset)
{
if (is_protected_kvm_enabled())
pkvm_dump_backtrace(hyp_offset);
else
hyp_dump_backtrace(hyp_offset);
}