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Date: Tue, 29 Mar 2022 09:51:15 +0100
From: Fuad Tabba <tabba@...gle.com>
To: Kalesh Singh <kaleshsingh@...gle.com>
Cc: will@...nel.org, maz@...nel.org, qperret@...gle.com,
surenb@...gle.com, kernel-team@...roid.com,
James Morse <james.morse@....com>,
Alexandru Elisei <alexandru.elisei@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Catalin Marinas <catalin.marinas@....com>,
Mark Rutland <mark.rutland@....com>,
Mark Brown <broonie@...nel.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Peter Collingbourne <pcc@...gle.com>,
"Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>,
Peter Zijlstra <peterz@...radead.org>,
Andrew Scull <ascull@...gle.com>,
Andrew Jones <drjones@...hat.com>,
Ard Biesheuvel <ardb@...nel.org>,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 8/8] KVM: arm64: Symbolize the nVHE HYP backtrace
Hi Kalesh,
On Mon, Mar 14, 2022 at 8:07 PM Kalesh Singh <kaleshsingh@...gle.com> wrote:
>
> Reintroduce the __kvm_nvhe_ symbols in kallsyms, ignoring the local
> symbols in this namespace. The local symbols are not informative and
> can cause aliasing issues when symbolizing the addresses.
>
> With the necessary symbols now in kallsyms we can symbolize nVHE
> stacktrace addresses using the %pB print format specifier.
>
> Example call trace:
>
> [ 98.916444][ T426] kvm [426]: nVHE hyp panic at: [<ffffffc0096156fc>] __kvm_nvhe_overflow_stack+0x8/0x34!
> [ 98.918360][ T426] nVHE HYP call trace:
> [ 98.918692][ T426] kvm [426]: [<ffffffc009615aac>] __kvm_nvhe_cpu_prepare_nvhe_panic_info+0x4c/0x68
> [ 98.919545][ T426] kvm [426]: [<ffffffc0096159a4>] __kvm_nvhe_hyp_panic+0x2c/0xe8
> [ 98.920107][ T426] kvm [426]: [<ffffffc009615ad8>] __kvm_nvhe_hyp_panic_bad_stack+0x10/0x10
> [ 98.920665][ T426] kvm [426]: [<ffffffc009610a4c>] __kvm_nvhe___kvm_hyp_host_vector+0x24c/0x794
> [ 98.921292][ T426] kvm [426]: [<ffffffc009615718>] __kvm_nvhe_overflow_stack+0x24/0x34
> . . .
>
> [ 98.973382][ T426] kvm [426]: [<ffffffc009615718>] __kvm_nvhe_overflow_stack+0x24/0x34
> [ 98.973816][ T426] kvm [426]: [<ffffffc0096152f4>] __kvm_nvhe___kvm_vcpu_run+0x38/0x438
> [ 98.974255][ T426] kvm [426]: [<ffffffc009616f80>] __kvm_nvhe_handle___kvm_vcpu_run+0x1c4/0x364
> [ 98.974719][ T426] kvm [426]: [<ffffffc009616928>] __kvm_nvhe_handle_trap+0xa8/0x130
> [ 98.975152][ T426] kvm [426]: [<ffffffc009610064>] __kvm_nvhe___host_exit+0x64/0x64
> [ 98.975588][ T426] ---- end of nVHE HYP call trace ----
>
> Signed-off-by: Kalesh Singh <kaleshsingh@...gle.com>
Tested-by: Fuad Tabba <tabba@...gle.com>
Reviewed-by: Fuad Tabba <tabba@...gle.com>
Thanks,
/fuad
> ---
>
> Changes in v2:
> - Fix printk warnings - %p expects (void *)
>
>
> arch/arm64/kvm/handle_exit.c | 13 +++++--------
> scripts/kallsyms.c | 2 +-
> 2 files changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
> index ff69dff33700..3a5c32017c6b 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -296,13 +296,8 @@ void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr,
> u64 elr_in_kimg = __phys_to_kimg(elr_phys);
> u64 hyp_offset = elr_in_kimg - kaslr_offset() - elr_virt;
> u64 mode = spsr & PSR_MODE_MASK;
> + u64 panic_addr = elr_virt + hyp_offset;
>
> - /*
> - * 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 &&
> @@ -322,9 +317,11 @@ void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr,
> if (file)
> kvm_err("nVHE hyp BUG at: %s:%u!\n", file, line);
> else
> - kvm_err("nVHE hyp BUG at: %016llx!\n", elr_virt + hyp_offset);
> + kvm_err("nVHE hyp BUG at: [<%016llx>] %pB!\n", panic_addr,
> + (void *)panic_addr);
> } else {
> - kvm_err("nVHE hyp panic at: %016llx!\n", elr_virt + hyp_offset);
> + kvm_err("nVHE hyp panic at: [<%016llx>] %pB!\n", panic_addr,
> + (void *)panic_addr);
> }
>
> kvm_nvhe_dump_backtrace(hyp_offset);
> diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
> index 54ad86d13784..19aba43d9da4 100644
> --- a/scripts/kallsyms.c
> +++ b/scripts/kallsyms.c
> @@ -111,7 +111,7 @@ static bool is_ignored_symbol(const char *name, char type)
> ".LASANPC", /* s390 kasan local symbols */
> "__crc_", /* modversions */
> "__efistub_", /* arm64 EFI stub namespace */
> - "__kvm_nvhe_", /* arm64 non-VHE KVM namespace */
> + "__kvm_nvhe_$", /* arm64 local symbols in non-VHE KVM namespace */
> "__AArch64ADRPThunk_", /* arm64 lld */
> "__ARMV5PILongThunk_", /* arm lld */
> "__ARMV7PILongThunk_",
> --
> 2.35.1.723.g4982287a31-goog
>
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