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KVM: arm64: Introduce hyp_dump_backtrace()

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In non-protected nVHE mode, unwinds and dumps the hypervisor backtrace
from EL1. This is possible beacause the host can directly access the
hypervisor stack pages in non-protected mode.

The nVHE backtrace is dumped on hyp_panic(), before panicking the host.

[  101.498183] kvm [377]: nVHE call trace:
[  101.498363] kvm [377]:  [<ffff8000090a6570>] __kvm_nvhe_hyp_panic+0xac/0xf8
[  101.499045] kvm [377]:  [<ffff8000090a65cc>] __kvm_nvhe_hyp_panic_bad_stack+0x10/0x10
[  101.499498] kvm [377]:  [<ffff8000090a61e4>] __kvm_nvhe_recursive_death+0x24/0x34
. . .
[  101.524929] kvm [377]:  [<ffff8000090a61e4>] __kvm_nvhe_recursive_death+0x24/0x34
[  101.525062] kvm [377]:  [<ffff8000090a61e4>] __kvm_nvhe_recursive_death+0x24/0x34
[  101.525195] kvm [377]:  [<ffff8000090a5de4>] __kvm_nvhe___kvm_vcpu_run+0x30/0x40c
[  101.525333] kvm [377]:  [<ffff8000090a8b64>] __kvm_nvhe_handle___kvm_vcpu_run+0x30/0x48
[  101.525468] kvm [377]:  [<ffff8000090a88b8>] __kvm_nvhe_handle_trap+0xc4/0x128
[  101.525602] kvm [377]:  [<ffff8000090a7864>] __kvm_nvhe___host_exit+0x64/0x64
[  101.525745] kvm [377]: ---[ end nVHE call trace ]---

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220726073750.3219117-12-kaleshsingh@google.com
This commit is contained in:
Kalesh Singh 2022-07-26 00:37:44 -07:00 committed by Marc Zyngier
parent db129d486e
commit 314a61dc31
2 changed files with 86 additions and 0 deletions
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17
arch/arm64/include/asm/stacktrace/nvhe.h
View file

@ -16,6 +16,23 @@
#include <asm/stacktrace/common.h>
/*
* kvm_nvhe_unwind_init - Start an unwind from the given nVHE HYP fp and pc
*
* @state : unwind_state to initialize
* @fp : frame pointer at which to start the unwinding.
* @pc : program counter at which to start the unwinding.
*/
static inline void kvm_nvhe_unwind_init(struct unwind_state *state,
unsigned long fp,
unsigned long pc)
{
unwind_init_common(state, NULL);
state->fp = fp;
state->pc = pc;
}
static inline bool on_hyp_stack(unsigned long sp, unsigned long size,
struct stack_info *info);

69
arch/arm64/kvm/handle_exit.c
View file

@ -17,6 +17,7 @@
#include <asm/kvm_emulate.h>
#include <asm/kvm_mmu.h>
#include <asm/debug-monitors.h>
#include <asm/stacktrace/nvhe.h>
#include <asm/traps.h>
#include <kvm/arm_hypercalls.h>
@ -318,6 +319,71 @@ void handle_exit_early(struct kvm_vcpu *vcpu, int exception_index)
kvm_handle_guest_serror(vcpu, kvm_vcpu_get_esr(vcpu));
}
/*
* 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 inline void kvm_nvhe_dump_backtrace_start(void)
{
kvm_err("nVHE call trace:\n");
}
static inline 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 unwind_state state;
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();
}
/*
* kvm_nvhe_dump_backtrace - Dump KVM nVHE hypervisor backtrace.
*
* @hyp_offset: hypervisor offset, used for address translation.
*/
static void kvm_nvhe_dump_backtrace(unsigned long hyp_offset)
{
if (is_protected_kvm_enabled())
return;
else
hyp_dump_backtrace(hyp_offset);
}
void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr,
u64 elr_virt, u64 elr_phys,
u64 par, uintptr_t vcpu,
@ -353,6 +419,9 @@ void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr,
(void *)panic_addr);
}
/* Dump the nVHE hypervisor backtrace */
kvm_nvhe_dump_backtrace(hyp_offset);
/*
* Hyp has panicked and we're going to handle that by panicking the
* kernel. The kernel offset will be revealed in the panic so we're