Commit 314a61dc authored by Kalesh Singh's avatar Kalesh Singh Committed by Marc Zyngier
Browse files

KVM: arm64: Introduce hyp_dump_backtrace() 



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: default avatarKalesh Singh <kaleshsingh@google.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220726073750.3219117-12-kaleshsingh@google.com
parent db129d48

arch/arm64/include/asm/stacktrace/nvhe.h

+17 −0
Original line number Diff line number Diff line
@@ -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);

arch/arm64/kvm/handle_exit.c

+69 −0
Original line number Diff line number Diff line
@@ -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