Hi all,
This is v6 of nVHE stacktrace support. The series is based on
arm64 for-next/stacktrace.
The previous versions were posted at:
v5: https://lore.kernel.org/r/[email protected]/
v4: https://lore.kernel.org/r/[email protected]/
v3: https://lore.kernel.org/r/[email protected]/
v2: https://lore.kernel.org/r/[email protected]/
v1: https://lore.kernel.org/r/[email protected]/
This version mainly reorganizes the order of to patches into more coherent
groups, along with addressing the other feedback in v5.
Patches 1 to 6 factor out the common unwinding logic into
into arch/arm64/include/asm/stacktrace/common.h, for reuse by the nVHE
unwinder. No functional change is introduced by these:
[01/17] arm64: stacktrace: Add shared header for common stack unwinding code
[02/17] arm64: stacktrace: Factor out on_accessible_stack_common()
[03/17] arm64: stacktrace: Factor out unwind_next_common()
[04/17] arm64: stacktrace: Handle frame pointer from different address spaces
[05/17] arm64: stacktrace: Factor out common unwind()
[06/17] arm64: stacktrace: Add description of stacktrace/common.h
Patches 7 to 11 implement stacktraces for conventional nVHE (non-protected
mode):
[07/17] KVM: arm64: On stack overflow switch to hyp overflow_stack
[08/17] KVM: arm64: Stub implementation of non-protected nVHE HYP stack
unwinder
[09/17] KVM: arm64: Prepare non-protected nVHE hypervisor stacktrace
[10/17] KVM: arm64: Implement non-protected nVHE hyp stack unwinder
[11/17] KVM: arm64: Introduce hyp_dump_backtrace()
Patches 12 to 17 implement stacktraces for protected-nVHE (pKVM):
[12/17] KVM: arm64: Add PROTECTED_NVHE_STACKTRACE Kconfig
[13/17] KVM: arm64: Allocate shared pKVM hyp stacktrace buffers
[14/17] KVM: arm64: Stub implementation of pKVM HYP stack unwinder
[15/17] KVM: arm64: Save protected-nVHE (pKVM) hyp stacktrace
[16/17] KVM: arm64: Implement protected nVHE hyp stack unwinder
[17/17] KVM: arm64: Introduce pkvm_dump_backtrace()
The updated cover letter is copied below for convenience.
Thanks,
Kalesh
============
KVM nVHE Stack unwinding.
===
nVHE has two modes of operation: protected (pKVM) and unprotected
(conventional nVHE). Depending on the mode, a slightly different approach
is used to dump the hypervisor stacktrace but the core unwinding logic
remains the same.
Protected nVHE (pKVM) stacktraces
====
In protected nVHE mode, the host cannot directly access hypervisor memory.
The hypervisor stack unwinding happens in EL2 and is made accessible to
the host via a shared buffer. Symbolizing and printing the stacktrace
addresses is delegated to the host and happens in EL1.
Non-protected (Conventional) nVHE stacktraces
====
In non-protected mode, the host is able to directly access the hypervisor
stack pages.
The hypervisor stack unwinding and dumping of the stacktrace is performed
by the host in EL1, as this avoids the memory overhead of setting up
shared buffers between the host and hypervisor.
Resuing the Core Unwinding Logic
====
Since the hypervisor cannot link against the kernel code in proteced mode.
The common stack unwinding code is moved to a shared header to allow reuse
in the nVHE hypervisor.
Reducing the memory footprint
====
In this version the below steps were taken to reduce the memory usage of
nVHE stack unwinding:
1) The nVHE overflow stack is reduced from PAGE_SIZE to 4KB; benificial
for configurations with non 4KB pages (16KB or 64KB pages).
2) In protected nVHE mode (pKVM), the shared stacktrace buffers with the
host are reduced from PAGE_SIZE to the minimum size required.
3) In systems other than Android, conventional nVHE makes up the vast
majority of use case. So the pKVM stack tracing is disabled by default
(!CONFIG_PROTECTED_NVHE_STACKTRACE), which avoid the memory usage for
setting up shared buffers.
4) In non-protected nVHE mode (conventional nVHE), the stack unwinding
is done directly in EL1 by the host and no shared buffers with the
hypervisor are needed.
Sample Output
====
The below shows an example output from a simple stack overflow test:
[ 111.623091] kvm [367]: nVHE call trace:
[ 111.623215] kvm [367]: [<ffff8000090a6570>] __kvm_nvhe_hyp_panic+0xac/0xf8
[ 111.623448] kvm [367]: [<ffff8000090a65cc>] __kvm_nvhe_hyp_panic_bad_stack+0x10/0x10
[ 111.623642] kvm [367]: [<ffff8000090a61e4>] __kvm_nvhe_recursive_death+0x24/0x34
. . .
[ 111.640366] kvm [367]: [<ffff8000090a61e4>] __kvm_nvhe_recursive_death+0x24/0x34
[ 111.640467] kvm [367]: [<ffff8000090a61e4>] __kvm_nvhe_recursive_death+0x24/0x34
[ 111.640574] kvm [367]: [<ffff8000090a5de4>] __kvm_nvhe___kvm_vcpu_run+0x30/0x40c
[ 111.640676] kvm [367]: [<ffff8000090a8b64>] __kvm_nvhe_handle___kvm_vcpu_run+0x30/0x48
[ 111.640778] kvm [367]: [<ffff8000090a88b8>] __kvm_nvhe_handle_trap+0xc4/0x128
[ 111.640880] kvm [367]: [<ffff8000090a7864>] __kvm_nvhe___host_exit+0x64/0x64
[ 111.640996] kvm [367]: ---[ end nVHE call trace ]---
============
Kalesh Singh (17):
arm64: stacktrace: Add shared header for common stack unwinding code
arm64: stacktrace: Factor out on_accessible_stack_common()
arm64: stacktrace: Factor out unwind_next_common()
arm64: stacktrace: Handle frame pointer from different address spaces
arm64: stacktrace: Factor out common unwind()
arm64: stacktrace: Add description of stacktrace/common.h
KVM: arm64: On stack overflow switch to hyp overflow_stack
KVM: arm64: Stub implementation of non-protected nVHE HYP stack
unwinder
KVM: arm64: Prepare non-protected nVHE hypervisor stacktrace
KVM: arm64: Implement non-protected nVHE hyp stack unwinder
KVM: arm64: Introduce hyp_dump_backtrace()
KVM: arm64: Add PROTECTED_NVHE_STACKTRACE Kconfig
KVM: arm64: Allocate shared pKVM hyp stacktrace buffers
KVM: arm64: Stub implementation of pKVM HYP stack unwinder
KVM: arm64: Save protected-nVHE (pKVM) hyp stacktrace
KVM: arm64: Implement protected nVHE hyp stack unwinder
KVM: arm64: Introduce pkvm_dump_backtrace()
arch/arm64/include/asm/kvm_asm.h | 16 ++
arch/arm64/include/asm/memory.h | 8 +
arch/arm64/include/asm/stacktrace.h | 92 +++++----
arch/arm64/include/asm/stacktrace/common.h | 230 +++++++++++++++++++++
arch/arm64/include/asm/stacktrace/nvhe.h | 176 ++++++++++++++++
arch/arm64/kernel/stacktrace.c | 157 --------------
arch/arm64/kvm/Kconfig | 15 ++
arch/arm64/kvm/arm.c | 2 +-
arch/arm64/kvm/handle_exit.c | 102 +++++++++
arch/arm64/kvm/hyp/nvhe/Makefile | 2 +-
arch/arm64/kvm/hyp/nvhe/host.S | 9 +-
arch/arm64/kvm/hyp/nvhe/stacktrace.c | 109 ++++++++++
arch/arm64/kvm/hyp/nvhe/switch.c | 6 +
13 files changed, 720 insertions(+), 204 deletions(-)
create mode 100644 arch/arm64/include/asm/stacktrace/common.h
create mode 100644 arch/arm64/include/asm/stacktrace/nvhe.h
create mode 100644 arch/arm64/kvm/hyp/nvhe/stacktrace.c
base-commit: 82a592c13b0aeff94d84d54183dae0b26384c95f
--
2.37.1.359.gd136c6c3e2-goog
Add stub implementations of non-protected nVHE stack unwinder, for
building. These are implemented later in this series.
Signed-off-by: Kalesh Singh <[email protected]>
Reviewed-by: Fuad Tabba <[email protected]>
Tested-by: Fuad Tabba <[email protected]>
---
Changes in v6:
- Add Fuad’s Reviewed-by and Tested-by tags
Changes in v5:
- Mark unwind_next() as inline, per Marc
- Comment !__KVM_NVHE_HYPERVISOR__ unwinder path, per Marc
arch/arm64/include/asm/stacktrace/nvhe.h | 47 ++++++++++++++++++++++++
1 file changed, 47 insertions(+)
create mode 100644 arch/arm64/include/asm/stacktrace/nvhe.h
diff --git a/arch/arm64/include/asm/stacktrace/nvhe.h b/arch/arm64/include/asm/stacktrace/nvhe.h
new file mode 100644
index 000000000000..1192ae0f80c1
--- /dev/null
+++ b/arch/arm64/include/asm/stacktrace/nvhe.h
@@ -0,0 +1,47 @@
+/* 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.
+ *
+ * Copyright (C) 2022 Google LLC
+ */
+#ifndef __ASM_STACKTRACE_NVHE_H
+#define __ASM_STACKTRACE_NVHE_H
+
+#include <asm/stacktrace/common.h>
+
+static inline bool on_accessible_stack(const struct task_struct *tsk,
+ unsigned long sp, unsigned long size,
+ struct stack_info *info)
+{
+ return false;
+}
+
+#ifndef __KVM_NVHE_HYPERVISOR__
+/*
+ * Conventional (non-protected) nVHE HYP stack unwinder
+ *
+ * In non-protected mode, the unwinding is done from kernel proper context
+ * (by the host in EL1).
+ */
+
+static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
+ struct stack_info *info)
+{
+ return false;
+}
+
+static inline int notrace unwind_next(struct unwind_state *state)
+{
+ return 0;
+}
+NOKPROBE_SYMBOL(unwind_next);
+
+#endif /* !__KVM_NVHE_HYPERVISOR__ */
+#endif /* __ASM_STACKTRACE_NVHE_H */
--
2.37.1.359.gd136c6c3e2-goog
On Tue, 26 Jul 2022 00:37:33 -0700, Kalesh Singh wrote:
> This is v6 of nVHE stacktrace support. The series is based on
> arm64 for-next/stacktrace.
>
> The previous versions were posted at:
> v5: https://lore.kernel.org/r/[email protected]/
> v4: https://lore.kernel.org/r/[email protected]/
> v3: https://lore.kernel.org/r/[email protected]/
> v2: https://lore.kernel.org/r/[email protected]/
> v1: https://lore.kernel.org/r/[email protected]/
>
> [...]
Applied to next, thanks!
[01/17] arm64: stacktrace: Add shared header for common stack unwinding code
commit: 6bf212c89c48458d8deef1c973678c62528dab04
[02/17] arm64: stacktrace: Factor out on_accessible_stack_common()
commit: 15a59f19a015185bff90a68f601caec151dea4b4
[03/17] arm64: stacktrace: Factor out unwind_next_common()
commit: be63c647fd28d25484257f5f36a008db7d99991d
[04/17] arm64: stacktrace: Handle frame pointer from different address spaces
commit: 5b1b08619f50422c3e43d1fd7af257595a9e4a67
[05/17] arm64: stacktrace: Factor out common unwind()
commit: f51e7146740514347d6c5526a2c393e224a19c0d
[06/17] arm64: stacktrace: Add description of stacktrace/common.h
commit: 051ece6758cc10c2a6f1700ffe86d23fbb0b2553
[07/17] KVM: arm64: On stack overflow switch to hyp overflow_stack
commit: 548ec3336f323db56260b312c232ab37285f0284
[08/17] KVM: arm64: Stub implementation of non-protected nVHE HYP stack unwinder
commit: 573e1e8275f7167ddd533c6e4e0f500f8be4d974
[09/17] KVM: arm64: Prepare non-protected nVHE hypervisor stacktrace
commit: 879e5ac7b2e4db05799a905b5a07fc9e5dedf651
[10/17] KVM: arm64: Implement non-protected nVHE hyp stack unwinder
commit: db129d486ebdf4e3168282236f9d9008b42cac7e
[11/17] KVM: arm64: Introduce hyp_dump_backtrace()
commit: 314a61dc31845c233e47c53db3fe6f34284034f4
[12/17] KVM: arm64: Add PROTECTED_NVHE_STACKTRACE Kconfig
commit: 72adac1bd234002a65cef738e0eebfd6c2ce2e30
[13/17] KVM: arm64: Allocate shared pKVM hyp stacktrace buffers
commit: 6928bcc84bc4bd9a24a1cb1986418c3de76e1d99
[14/17] KVM: arm64: Stub implementation of pKVM HYP stack unwinder
commit: 25aa73b6db1831527cd4f14bf0ddf8dceadec802
[15/17] KVM: arm64: Save protected-nVHE (pKVM) hyp stacktrace
commit: 871c5d931417d3c0e1aa32c9e04da1dc74703843
[16/17] KVM: arm64: Implement protected nVHE hyp stack unwinder
commit: 75e9459e48d4867caf549e388bd4faabe1dbcbd3
[17/17] KVM: arm64: Introduce pkvm_dump_backtrace()
commit: 3a7e1b55aad45c0cf86bd4e2f212bb9a61905142
Cheers,
M.
--
Marc Zyngier <[email protected]>