[PATCH v5 14/17] KVM: arm64: Implement protected nVHE hyp stack unwinder

Kalesh Singh
2022-07-21T05:58:35Z

Implements the common framework necessary for unwind() to work in
the protected nVHE context:
- on_accessible_stack()
- on_overflow_stack()
- unwind_next()

Protected nVHE unwind() is used to unwind and save the hyp stack
addresses to the shared stacktrace buffer. The host reads the
entries in this buffer, symbolizes and dumps the stacktrace (later
patch in the series).

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---
arch/arm64/include/asm/stacktrace/common.h | 2 ++
arch/arm64/include/asm/stacktrace/nvhe.h | 34 ++++++++++++++++++++--
2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/stacktrace/common.h b/arch/arm64/include/asm/stacktrace/common.h
index be7920ba70b0..73fd9e143c4a 100644
--- a/arch/arm64/include/asm/stacktrace/common.h
+++ b/arch/arm64/include/asm/stacktrace/common.h
@@ -34,6 +34,7 @@ enum stack_type {
STACK_TYPE_OVERFLOW,
STACK_TYPE_SDEI_NORMAL,
STACK_TYPE_SDEI_CRITICAL,
+ STACK_TYPE_HYP,
__NR_STACK_TYPES
};

@@ -186,6 +187,7 @@ static inline int unwind_next_common(struct unwind_state *state,
*
* TASK -> IRQ -> OVERFLOW -> SDEI_NORMAL
* TASK -> SDEI_NORMAL -> SDEI_CRITICAL -> OVERFLOW
+ * HYP -> OVERFLOW
*
* ... but the nesting itself is strict. Once we transition from one
* stack to another, it's never valid to unwind back to that first
diff --git a/arch/arm64/include/asm/stacktrace/nvhe.h b/arch/arm64/include/asm/stacktrace/nvhe.h
index 8f02803a005f..c3688e717136 100644
--- a/arch/arm64/include/asm/stacktrace/nvhe.h
+++ b/arch/arm64/include/asm/stacktrace/nvhe.h
@@ -39,10 +39,19 @@ static inline void kvm_nvhe_unwind_init(struct unwind_state *state,
state->pc = pc;
}

+static inline bool on_hyp_stack(unsigned long sp, unsigned long size,
+ struct stack_info *info);
+
static inline bool on_accessible_stack(const struct task_struct *tsk,
unsigned long sp, unsigned long size,
struct stack_info *info)
{
+ if (on_accessible_stack_common(tsk, sp, size, info))
+ return true;
+
+ if (on_hyp_stack(sp, size, info))
+ return true;
+
return false;
}

@@ -60,12 +69,27 @@ DECLARE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);
static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
struct stack_info *info)
{
- return false;
+ unsigned long low = (unsigned long)this_cpu_ptr(overflow_stack);
+ unsigned long high = low + OVERFLOW_STACK_SIZE;
+
+ return on_stack(sp, size, low, high, STACK_TYPE_OVERFLOW, info);
+}
+
+static inline bool on_hyp_stack(unsigned long sp, unsigned long size,
+ struct stack_info *info)
+{
+ struct kvm_nvhe_init_params *params = this_cpu_ptr(&kvm_init_params);
+ unsigned long high = params->stack_hyp_va;
+ unsigned long low = high - PAGE_SIZE;
+
+ return on_stack(sp, size, low, high, STACK_TYPE_HYP, info);
}

static inline int notrace unwind_next(struct unwind_state *state)
{
- return 0;
+ struct stack_info info;
+
+ return unwind_next_common(state, &info, NULL);
}
NOKPROBE_SYMBOL(unwind_next);
#else /* !CONFIG_PROTECTED_NVHE_STACKTRACE */
@@ -75,6 +99,12 @@ static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
return false;
}

+static inline bool on_hyp_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;
--
2.37.0.170.g444d1eabd0-goog