KVM: arm64: Log source when panicking from nVHE hyp

To aid with debugging, add details of the source of a panic from nVHE
hyp. This is done by having nVHE hyp exit to nvhe_hyp_panic_handler()
rather than directly to panic(). The handler will then add the extra
details for debugging before panicking the kernel.

If the panic was due to a BUG(), look up the metadata to log the file
and line, if available, otherwise log an address that can be looked up
in vmlinux. The hyp offset is also logged to allow other hyp VAs to be
converted, similar to how the kernel offset is logged during a panic.

__hyp_panic_string is now inlined since it no longer needs to be
referenced as a symbol and the message is free to diverge between VHE
and nVHE.

The following is an example of the logs generated by a BUG in nVHE hyp.

[   46.754840] kvm [307]: nVHE hyp BUG at: arch/arm64/kvm/hyp/nvhe/switch.c:242!
[   46.755357] kvm [307]: Hyp Offset: 0xfffea6c58e1e0000
[   46.755824] Kernel panic - not syncing: HYP panic:
[   46.755824] PS:400003c9 PC:0000d93a82c705ac ESR:f2000800
[   46.755824] FAR:0000000080080000 HPFAR:0000000000800800 PAR:0000000000000000
[   46.755824] VCPU:0000d93a880d0000
[   46.756960] CPU: 3 PID: 307 Comm: kvm-vcpu-0 Not tainted 5.12.0-rc3-00005-gc572b99cf65b-dirty #133
[   46.757459] Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015
[   46.758366] Call trace:
[   46.758601]  dump_backtrace+0x0/0x1b0
[   46.758856]  show_stack+0x18/0x70
[   46.759057]  dump_stack+0xd0/0x12c
[   46.759236]  panic+0x16c/0x334
[   46.759426]  arm64_kernel_unmapped_at_el0+0x0/0x30
[   46.759661]  kvm_arch_vcpu_ioctl_run+0x134/0x750
[   46.759936]  kvm_vcpu_ioctl+0x2f0/0x970
[   46.760156]  __arm64_sys_ioctl+0xa8/0xec
[   46.760379]  el0_svc_common.constprop.0+0x60/0x120
[   46.760627]  do_el0_svc+0x24/0x90
[   46.760766]  el0_svc+0x2c/0x54
[   46.760915]  el0_sync_handler+0x1a4/0x1b0
[   46.761146]  el0_sync+0x170/0x180
[   46.761889] SMP: stopping secondary CPUs
[   46.762786] Kernel Offset: 0x3e1cd2820000 from 0xffff800010000000
[   46.763142] PHYS_OFFSET: 0xffffa9f680000000
[   46.763359] CPU features: 0x00240022,61806008
[   46.763651] Memory Limit: none
[   46.813867] ---[ end Kernel panic - not syncing: HYP panic:
[   46.813867] PS:400003c9 PC:0000d93a82c705ac ESR:f2000800
[   46.813867] FAR:0000000080080000 HPFAR:0000000000800800 PAR:0000000000000000
[   46.813867] VCPU:0000d93a880d0000 ]---

Signed-off-by: Andrew Scull <ascull@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210318143311.839894-6-ascull@google.com

7 files changed, 56 insertions, 20 deletions

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 90873851f677..7c17a67d2291 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -121,6 +121,8 @@ void kvm_update_va_mask(struct alt_instr *alt,
 void kvm_compute_layout(void);
 void kvm_apply_hyp_relocations(void);
 
+#define __hyp_pa(x) (((phys_addr_t)(x)) + hyp_physvirt_offset)
+
 static __always_inline unsigned long __kern_hyp_va(unsigned long v)
 {
 	asm volatile(ALTERNATIVE_CB("and %0, %0, #1\n"
diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
index 5aa9ed1e9ec6..5ff2b6909387 100644
--- a/arch/arm64/kernel/image-vars.h
+++ b/arch/arm64/kernel/image-vars.h
@@ -70,8 +70,7 @@ KVM_NVHE_ALIAS(kvm_get_kimage_voffset);
 KVM_NVHE_ALIAS(kvm_vgic_global_state);
 
 /* Kernel symbols used to call panic() from nVHE hyp code (via ERET). */
-KVM_NVHE_ALIAS(__hyp_panic_string);
-KVM_NVHE_ALIAS(panic);
+KVM_NVHE_ALIAS(nvhe_hyp_panic_handler);
 
 /* Vectors installed by hyp-init on reset HVC. */
 KVM_NVHE_ALIAS(__hyp_stub_vectors);
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index cebe39f3b1b6..6f48336b1d86 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -291,3 +291,48 @@ void handle_exit_early(struct kvm_vcpu *vcpu, int exception_index)
 	if (exception_index == ARM_EXCEPTION_EL1_SERROR)
 		kvm_handle_guest_serror(vcpu, kvm_vcpu_get_esr(vcpu));
 }
+
+void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr, u64 elr,
+					      u64 par, uintptr_t vcpu,
+					      u64 far, u64 hpfar) {
+	u64 elr_in_kimg = __phys_to_kimg(__hyp_pa(elr));
+	u64 hyp_offset = elr_in_kimg - kaslr_offset() - elr;
+	u64 mode = spsr & PSR_MODE_MASK;
+
+	/*
+	 * The nVHE hyp symbols are not included by kallsyms to avoid issues
+	 * with aliasing. That means that the symbols cannot be printed with the
+	 * "%pS" format specifier, so fall back to the vmlinux address if
+	 * there's no better option.
+	 */
+	if (mode != PSR_MODE_EL2t && mode != PSR_MODE_EL2h) {
+		kvm_err("Invalid host exception to nVHE hyp!\n");
+	} else if (ESR_ELx_EC(esr) == ESR_ELx_EC_BRK64 &&
+		   (esr & ESR_ELx_BRK64_ISS_COMMENT_MASK) == BUG_BRK_IMM) {
+		struct bug_entry *bug = find_bug(elr_in_kimg);
+		const char *file = NULL;
+		unsigned int line = 0;
+
+		/* All hyp bugs, including warnings, are treated as fatal. */
+		if (bug)
+			bug_get_file_line(bug, &file, &line);
+
+		if (file)
+			kvm_err("nVHE hyp BUG at: %s:%u!\n", file, line);
+		else
+			kvm_err("nVHE hyp BUG at: %016llx!\n", elr + hyp_offset);
+	} else {
+		kvm_err("nVHE hyp panic at: %016llx!\n", elr + 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
+	 * also safe to reveal the hyp offset as a debugging aid for translating
+	 * hyp VAs to vmlinux addresses.
+	 */
+	kvm_err("Hyp Offset: 0x%llx\n", hyp_offset);
+
+	panic("HYP panic:\nPS:%08llx PC:%016llx ESR:%08llx\nFAR:%016llx HPFAR:%016llx PAR:%016llx\nVCPU:%016lx\n",
+	      spsr, elr, esr, far, hpfar, par, vcpu);
+}
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 6c1f51f25eb3..32d0c036c050 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -30,8 +30,6 @@
 #include <asm/processor.h>
 #include <asm/thread_info.h>
 
-extern const char __hyp_panic_string[];
-
 extern struct exception_table_entry __start___kvm_ex_table;
 extern struct exception_table_entry __stop___kvm_ex_table;
 
diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S
index 5d94584840cc..2b23400e0fb3 100644
--- a/arch/arm64/kvm/hyp/nvhe/host.S
+++ b/arch/arm64/kvm/hyp/nvhe/host.S
@@ -79,22 +79,18 @@ SYM_FUNC_START(__hyp_do_panic)
 	mov	lr, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\
 		      PSR_MODE_EL1h)
 	msr	spsr_el2, lr
-	ldr	lr, =panic
+	ldr	lr, =nvhe_hyp_panic_handler
 	hyp_kimg_va lr, x6
 	msr	elr_el2, lr
 
 	mov	x29, x0
 
-	/* Load the format string into x0 and arguments into x1-7 */
-	ldr	x0, =__hyp_panic_string
-	hyp_kimg_va x0, x6
-
-	/* Load the format arguments into x1-7. */
-	mov	x6, x3
-	get_vcpu_ptr x7, x3
-	mrs	x3, esr_el2
-	mrs	x4, far_el2
-	mrs	x5, hpfar_el2
+	/* Load the panic arguments into x0-7 */
+	mrs	x0, esr_el2
+	get_vcpu_ptr x4, x5
+	mrs	x5, far_el2
+	mrs	x6, hpfar_el2
+	mov	x7, xzr			// Unused argument
 
 	/* Enter the host, conditionally restoring the host context. */
 	cbz	x29, __host_enter_without_restoring
diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
index 63de71c0481e..ca630896476d 100644
--- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c
+++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
@@ -22,8 +22,6 @@ void __noreturn __host_enter(struct kvm_cpu_context *host_ctxt);
 struct kvm_host_psci_config __ro_after_init kvm_host_psci_config;
 s64 __ro_after_init hyp_physvirt_offset;
 
-#define __hyp_pa(x) ((phys_addr_t)((x)) + hyp_physvirt_offset)
-
 #define INVALID_CPU_ID	UINT_MAX
 
 struct psci_boot_args {
diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index af8e940d0f03..7b8f7db5c1ed 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -27,8 +27,6 @@
 #include <asm/processor.h>
 #include <asm/thread_info.h>
 
-const char __hyp_panic_string[] = "HYP panic:\nPS:%08llx PC:%016llx ESR:%08llx\nFAR:%016llx HPFAR:%016llx PAR:%016llx\nVCPU:%p\n";
-
 /* VHE specific context */
 DEFINE_PER_CPU(struct kvm_host_data, kvm_host_data);
 DEFINE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt);
@@ -207,7 +205,7 @@ static void __hyp_call_panic(u64 spsr, u64 elr, u64 par)
 	__deactivate_traps(vcpu);
 	sysreg_restore_host_state_vhe(host_ctxt);
 
-	panic(__hyp_panic_string,
+	panic("HYP panic:\nPS:%08llx PC:%016llx ESR:%08llx\nFAR:%016llx HPFAR:%016llx PAR:%016llx\nVCPU:%p\n",
 	      spsr, elr,
 	      read_sysreg_el2(SYS_ESR), read_sysreg_el2(SYS_FAR),
 	      read_sysreg(hpfar_el2), par, vcpu);