arm64: Add test for SVE unwinding from signal handler

The test is skipped if the compiler doesn't support
SVE, otherwise it uses some SVE intrinsics across a
few functions and then sends a signal to take a
backtrace from the sum() function.

Without the previous SVE changes, the unwinding
fails at sum() and the stack looks like:

-> signal_handler()
->   kill()
->     sum()

With the changes the full stack to main can be
unwound and the test passes:

-> signal_handler()
->   kill()
->     sum()
->       square()
->          main()

Currently this test will pass on a Graviton 3 instance
on AWS and with gcc-10.

Co-authored-by: Kent Cheung <Kent.Cheung@arm.com>
Signed-off-by: James Clark <james.clark@arm.com>
Change-Id: Ibe38e6b0fa26276c545f044ffdd26fbdb2789c38

tests/Garm64-test-sve-signal.c

@@ -0,0 +1,121 @@
+/*
+ * Verify that unwinding from a signal handler works when variable width
+ * SVE registers are pushed onto the stack
+ */
+
+#if defined(__ARM_FEATURE_SVE) && defined(__ARM_FEATURE_SVE_VECTOR_OPERATORS)
+
+#include <arm_sve.h>
+#include <libunwind.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+int64_t z[100];
+
+void signal_handler(int signum)
+{
+  unw_cursor_t cursor;
+  unw_context_t context;
+
+  const char* expected[] = {
+    "signal_frame",
+    "kill",
+    "sum",
+    "square",
+    "main",
+  };
+
+  unw_getcontext(&context);
+  unw_init_local(&cursor, &context);
+
+  for (unsigned int depth = 0; depth < sizeof(expected) / sizeof(expected[0]); ++depth)
+    {
+      unw_word_t offset, pc;
+      int unw_rc = unw_step(&cursor);
+      if (unw_rc <= 0) {
+        printf("Frame: %d  unw_step error: %d\n", depth, unw_rc);
+        exit(-1);
+      }
+
+      unw_rc = unw_get_reg(&cursor, UNW_REG_IP, &pc);
+      if (pc == 0 || unw_rc != 0) {
+        printf("Frame: %d  unw_get_reg error: %d\n", depth, unw_rc);
+        exit(-1);
+      }
+
+      char sym[256];
+      unw_rc = unw_is_signal_frame(&cursor);
+      if (unw_rc > 0)
+        {
+          strcpy(sym, "signal_frame");
+        }
+      else if (unw_rc < 0)
+        {
+          printf("Frame: %d  unw_is_signal_frame error: %d\n", depth, unw_rc);
+          exit(-1);
+        }
+      else
+        {
+          unw_rc = unw_get_proc_name(&cursor, sym, sizeof(sym), &offset);
+          if (unw_rc)
+            {
+              printf("Frame: %d  unw_get_proc_name error: %d\n", depth, unw_rc);
+              exit(-1);
+            }
+        }
+
+      if (strcmp(sym, expected[depth]) != 0)
+        {
+          printf("Frame: %d  expected %s but found %s\n", depth, expected[depth], sym);
+          exit(-1);
+        }
+    }
+
+  exit(0); /* PASS */
+}
+
+int64_t sum(svint64_t z0)
+{
+  int64_t ret = svaddv_s64(svptrue_b64(), z0);
+  kill (getpid (), SIGUSR1);
+  return ret;
+}
+
+int64_t square(svint64_t z0)
+{
+  int64_t res = 0;
+  for (int i = 0; i < 100; ++i)
+    {
+      z0 = svmul_s64_z(svptrue_b64(), z0, z0);
+      res += sum(z0);
+    }
+  return res;
+}
+
+int main()
+{
+  signal(SIGUSR1, signal_handler);
+  for (unsigned int i = 0; i < sizeof(z) / sizeof(z[0]); ++i)
+    z[i] = rand();
+
+  svint64_t z0 = svld1(svptrue_b64(), &z[0]);
+  square(z0);
+
+  /*
+   * Shouldn't get here, exit is called from signal handler
+   */
+  printf("Signal handler wasn't called\n");
+  return -1;
+}
+
+#else /* !__ARM_FEATURE_SVE */
+int
+main ()
+{
+  return 77; /* SKIP */
+}
+#endif

tests/Larm64-test-sve-signal.c

@@ -0,0 +1,5 @@
+#define UNW_LOCAL_ONLY
+#include <libunwind.h>
+#if !defined(UNW_REMOTE_ONLY)
+#include "Garm64-test-sve-signal.c"
+#endif

tests/Makefile.am

@@ -46,6 +46,11 @@ if ARCH_X86_64
 endif #ARCH X86_64
 endif #!ARCH_PPC64
 endif #!ARCH_IA64
+
+if ARCH_AARCH64
+  check_PROGRAMS_arch += Garm64-test-sve-signal Larm64-test-sve-signal
+endif
+
  check_PROGRAMS_cdep +=	Gtest-bt Ltest-bt Gtest-exc Ltest-exc		 \
 			Gtest-init Ltest-init				 \
 			Gtest-concurrent Ltest-concurrent		 \
@@ -161,6 +166,10 @@ Gx64_test_dwarf_expressions_SOURCES =  Gx64-test-dwarf-expressions.c \
 Lx64_test_dwarf_expressions_SOURCES =  Lx64-test-dwarf-expressions.c \
 																			 x64-test-dwarf-expressions.S
 
+Garm64_test_sve_signal_SOURCES = Garm64-test-sve-signal.c
+Larm64_test_sve_signal_SOURCES = Larm64-test-sve-signal.c
+Garm64_test_sve_signal_CFLAGS = -fno-inline -march=native
+Larm64_test_sve_signal_CFLAGS = -fno-inline -march=native
 
 Gtest_init_SOURCES = Gtest-init.cxx
 Ltest_init_SOURCES = Ltest-init.cxx
@@ -261,3 +270,6 @@ ppc64_test_altivec_LDADD = $(LIBUNWIND)
 
 Gx64_test_dwarf_expressions_LDADD = $(LIBUNWIND) $(LIBUNWIND_local)
 Lx64_test_dwarf_expressions_LDADD = $(LIBUNWIND_local)
+
+Garm64_test_sve_signal_LDADD = $(LIBUNWIND) $(LIBUNWIND_local)
+Larm64_test_sve_signal_LDADD = $(LIBUNWIND_local)