[kvm-unit-tests PATCH v3 3/6] arm64: enable frame pointer and support stack unwinding

Nadav Amit
2023-06-28T00:14:46Z

Enable frame pointers for arm64 and perform stack unwinding based on
arm64 convention.

Signed-off-by: Nadav Amit <namit@vmware.com>

---
v1->v2:
* Adding SPDX [checkpatch]
* Moving some unused declarations to next patch [Andrew]
* Adding recursion prevention
---
arm/Makefile.arm | 3 ---
arm/Makefile.arm64 | 1 +
arm/Makefile.common | 3 +++
lib/arm64/asm/stack.h | 3 +++
lib/arm64/stack.c | 44 +++++++++++++++++++++++++++++++++++++++++++
5 files changed, 51 insertions(+), 3 deletions(-)
create mode 100644 lib/arm64/stack.c

diff --git a/arm/Makefile.arm b/arm/Makefile.arm
index 2ce00f5..7fd39f3 100644
--- a/arm/Makefile.arm
+++ b/arm/Makefile.arm
@@ -11,9 +11,6 @@ ifeq ($(CONFIG_EFI),y)
$(error Cannot build arm32 tests as EFI apps)
endif

-# stack.o relies on frame pointers.
-KEEP_FRAME_POINTER := y
-
CFLAGS += $(machine)
CFLAGS += -mcpu=$(PROCESSOR)
CFLAGS += -mno-unaligned-access
diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
index 85b3348..960880f 100644
--- a/arm/Makefile.arm64
+++ b/arm/Makefile.arm64
@@ -22,6 +22,7 @@ define arch_elf_check =
endef

cstart.o = $(TEST_DIR)/cstart64.o
+cflatobjs += lib/arm64/stack.o
cflatobjs += lib/arm64/processor.o
cflatobjs += lib/arm64/spinlock.o
cflatobjs += lib/arm64/gic-v3-its.o lib/arm64/gic-v3-its-cmd.o
diff --git a/arm/Makefile.common b/arm/Makefile.common
index 9b45a8f..bc86e44 100644
--- a/arm/Makefile.common
+++ b/arm/Makefile.common
@@ -22,6 +22,9 @@ $(TEST_DIR)/sieve.elf: AUXFLAGS = 0x1
##################################################################
AUXFLAGS ?= 0x0

+# stack.o relies on frame pointers.
+KEEP_FRAME_POINTER := y
+
CFLAGS += -std=gnu99
CFLAGS += -ffreestanding
CFLAGS += -O2
diff --git a/lib/arm64/asm/stack.h b/lib/arm64/asm/stack.h
index d000624..be486cf 100644
--- a/lib/arm64/asm/stack.h
+++ b/lib/arm64/asm/stack.h
@@ -5,4 +5,7 @@
#error Do not directly include <asm/stack.h>. Just use <stack.h>.
#endif

+#define HAVE_ARCH_BACKTRACE_FRAME
+#define HAVE_ARCH_BACKTRACE
+
#endif
diff --git a/lib/arm64/stack.c b/lib/arm64/stack.c
new file mode 100644
index 0000000..a2024e8
--- /dev/null
+++ b/lib/arm64/stack.c
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Backtrace support.
+ */
+#include <libcflat.h>
+#include <stdbool.h>
+#include <stack.h>
+
+int backtrace_frame(const void *frame, const void **return_addrs, int max_depth)
+{
+ const void *fp = frame;
+ static bool walking;
+ void *lr;
+ int depth;
+
+ if (walking) {
+ printf("RECURSIVE STACK WALK!!!\n");
+ return 0;
+ }
+ walking = true;
+
+ /*
+ * ARM64 stack grows down. fp points to the previous fp on the stack,
+ * and lr is just above it
+ */
+ for (depth = 0; fp && depth < max_depth; ++depth) {
+
+ asm volatile ("ldp %0, %1, [%2]"
+ : "=r" (fp), "=r" (lr)
+ : "r" (fp)
+ : );
+
+ return_addrs[depth] = lr;
+ }
+
+ walking = false;
+ return depth;
+}
+
+int backtrace(const void **return_addrs, int max_depth)
+{
+ return backtrace_frame(__builtin_frame_address(0),
+ return_addrs, max_depth);
+}
--
2.34.1