[PATCH v2 8/8] arm64: stacktrace: track hyp stacks in unwinder's address space

Mark Rutland
2022-08-05T12:49:02Z

Currently unwind_next_frame_record() has an optional callback to convert
the address space of the FP. This is necessary for the NVHE unwinder,
which tracks the stacks in the hyp VA space, but accesses the frame
records in the kernel VA space.

This is a bit unfortunate since it clutters unwind_next_frame_record(),
which will get in the way of future rework.

Instead, this patch changes the NVHE unwinder to track the stacks in the
kernel's VA space and translate to FP prior to calling
unwind_next_frame_record(). This removes the need for the translate_fp()
callback, as all unwinders consistently track stacks in the native
address space of the unwinder.

At the same time, this patch consolidates the generation of the stack
addresses behind the stackinfo_get_*() helpers.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Kalesh Singh <kaleshsingh@google.com>
Cc: Fuad Tabba <tabba@google.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
---
arch/arm64/include/asm/stacktrace/common.h | 28 ++--------
arch/arm64/kernel/stacktrace.c | 2 +-
arch/arm64/kvm/hyp/nvhe/stacktrace.c | 2 +-
arch/arm64/kvm/stacktrace.c | 62 ++++++++++++++--------
4 files changed, 46 insertions(+), 48 deletions(-)

diff --git a/arch/arm64/include/asm/stacktrace/common.h b/arch/arm64/include/asm/stacktrace/common.h
index c594f332bb946..0f634bb14ceb3 100644
--- a/arch/arm64/include/asm/stacktrace/common.h
+++ b/arch/arm64/include/asm/stacktrace/common.h
@@ -78,17 +78,6 @@ static inline void unwind_init_common(struct unwind_state *state,
state->stack = stackinfo_get_unknown();
}

-/*
- * stack_trace_translate_fp_fn() - Translates a non-kernel frame pointer to
- * a kernel address.
- *
- * @fp: the frame pointer to be updated to its kernel address.
- *
- * Returns true and success and @fp is updated to the corresponding
- * kernel virtual address; otherwise returns false.
- */
-typedef bool (*stack_trace_translate_fp_fn)(unsigned long *fp);
-
static struct stack_info *unwind_find_next_stack(const struct unwind_state *state,
unsigned long sp,
unsigned long size)
@@ -159,13 +148,11 @@ static inline int unwind_consume_stack(struct unwind_state *state,
* @state->fp.
*
* @state: the current unwind state.
- * @translate_fp: translates the fp prior to access (may be NULL)
*/
static inline int
-unwind_next_frame_record(struct unwind_state *state,
- stack_trace_translate_fp_fn translate_fp)
+unwind_next_frame_record(struct unwind_state *state)
{
- unsigned long fp = state->fp, kern_fp = fp;
+ unsigned long fp = state->fp;
int err;

if (fp & 0x7)
@@ -175,18 +162,11 @@ unwind_next_frame_record(struct unwind_state *state,
if (err)
return err;

- /*
- * If fp is not from the current address space perform the necessary
- * translation before dereferencing it to get the next fp.
- */
- if (translate_fp && !translate_fp(&kern_fp))
- return -EINVAL;
-
/*
* Record this frame record's values.
*/
- state->fp = READ_ONCE(*(unsigned long *)(kern_fp));
- state->pc = READ_ONCE(*(unsigned long *)(kern_fp + 8));
+ state->fp = READ_ONCE(*(unsigned long *)(fp));
+ state->pc = READ_ONCE(*(unsigned long *)(fp + 8));

return 0;
}
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 9c8820f242625..634279b3b03d1 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -84,7 +84,7 @@ static int notrace unwind_next(struct unwind_state *state)
if (fp == (unsigned long)task_pt_regs(tsk)->stackframe)
return -ENOENT;

- err = unwind_next_frame_record(state, NULL);
+ err = unwind_next_frame_record(state);
if (err)
return err;

diff --git a/arch/arm64/kvm/hyp/nvhe/stacktrace.c b/arch/arm64/kvm/hyp/nvhe/stacktrace.c
index 08e1325ead73f..ed6b58b19cfa5 100644
--- a/arch/arm64/kvm/hyp/nvhe/stacktrace.c
+++ b/arch/arm64/kvm/hyp/nvhe/stacktrace.c
@@ -64,7 +64,7 @@ static struct stack_info stackinfo_get_hyp(void)

static int unwind_next(struct unwind_state *state)
{
- return unwind_next_frame_record(state, NULL);
+ return unwind_next_frame_record(state);
}

static void notrace unwind(struct unwind_state *state,
diff --git a/arch/arm64/kvm/stacktrace.c b/arch/arm64/kvm/stacktrace.c
index 8295e132da2f0..108a7501be7a0 100644
--- a/arch/arm64/kvm/stacktrace.c
+++ b/arch/arm64/kvm/stacktrace.c
@@ -34,6 +34,17 @@ static struct stack_info stackinfo_get_overflow(void)
};
}

+static struct stack_info stackinfo_get_overflow_kern_va(void)
+{
+ unsigned long low = (unsigned long)this_cpu_ptr_nvhe_sym(overflow_stack);
+ unsigned long high = low + OVERFLOW_STACK_SIZE;
+
+ return (struct stack_info) {
+ .low = low,
+ .high = high,
+ };
+}
+
static struct stack_info stackinfo_get_hyp(void)
{
struct kvm_nvhe_stacktrace_info *stacktrace_info
@@ -47,6 +58,17 @@ static struct stack_info stackinfo_get_hyp(void)
};
}

+static struct stack_info stackinfo_get_hyp_kern_va(void)
+{
+ unsigned long low = (unsigned long)*this_cpu_ptr(&kvm_arm_hyp_stack_page);
+ unsigned long high = low + PAGE_SIZE;
+
+ return (struct stack_info) {
+ .low = low,
+ .high = high,
+ };
+}
+
/*
* kvm_nvhe_stack_kern_va - Convert KVM nVHE HYP stack addresses to a kernel VAs
*
@@ -62,39 +84,35 @@ static struct stack_info stackinfo_get_hyp(void)
*/
static bool kvm_nvhe_stack_kern_va(unsigned long *addr)
{
- struct kvm_nvhe_stacktrace_info *stacktrace_info;
- unsigned long hyp_base, kern_base, hyp_offset;
- struct stack_info stack;
+ struct stack_info stack_hyp, stack_kern;

- stacktrace_info = this_cpu_ptr_nvhe_sym(kvm_stacktrace_info);
-
- stack = stackinfo_get_hyp();
- if (stackinfo_on_stack(&stack, *addr, 1)) {
- kern_base = (unsigned long)*this_cpu_ptr(&kvm_arm_hyp_stack_page);
- hyp_base = (unsigned long)stacktrace_info->stack_base;
+ stack_hyp = stackinfo_get_hyp();
+ stack_kern = stackinfo_get_hyp_kern_va();
+ if (stackinfo_on_stack(&stack_hyp, *addr, 1))
goto found;
- }

- stack = stackinfo_get_overflow();
- if (stackinfo_on_stack(&stack, *addr, 1)) {
- kern_base = (unsigned long)this_cpu_ptr_nvhe_sym(overflow_stack);
- hyp_base = (unsigned long)stacktrace_info->overflow_stack_base;
+ stack_hyp = stackinfo_get_overflow();
+ stack_kern = stackinfo_get_overflow_kern_va();
+ if (stackinfo_on_stack(&stack_hyp, *addr, 1))
goto found;
- }

return false;

found:
- hyp_offset = *addr - hyp_base;
-
- *addr = kern_base + hyp_offset;
-
+ *addr = *addr - stack_hyp.low + stack_kern.low;
return true;
}

static int unwind_next(struct unwind_state *state)
{
- return unwind_next_frame_record(state, kvm_nvhe_stack_kern_va);
+ /*
+ * The FP is in the hypervisor VA space. Convert it to the kernel VA
+ * space so it can be unwound by the regular unwind functions.
+ */
+ if (!kvm_nvhe_stack_kern_va(&state->fp))
+ return -EINVAL;
+
+ return unwind_next_frame_record(state);
}

static void unwind(struct unwind_state *state,
@@ -153,8 +171,8 @@ static void hyp_dump_backtrace(unsigned long hyp_offset)
{
struct kvm_nvhe_stacktrace_info *stacktrace_info;
struct stack_info stacks[] = {
- stackinfo_get_overflow(),
- stackinfo_get_hyp(),
+ stackinfo_get_overflow_kern_va(),
+ stackinfo_get_hyp_kern_va(),
};
struct unwind_state state = {
.stacks = stacks,
--
2.30.2