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Re: PING: [PATCH 2/2] tests/tcg/s390x: Test unwinding from signal handle


From: Laurent Vivier
Subject: Re: PING: [PATCH 2/2] tests/tcg/s390x: Test unwinding from signal handlers
Date: Tue, 24 May 2022 18:07:14 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0

Le 24/05/2022 à 11:56, Thomas Huth a écrit :
On 19/05/2022 13.34, Ilya Leoshkevich wrote:
On Wed, 2022-05-04 at 00:51 +0200, Ilya Leoshkevich wrote:
Add a small test to prevent regressions.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
  tests/tcg/s390x/signals-s390x.c | 69 ++++++++++++++++++++++++++-----
--
  1 file changed, 55 insertions(+), 14 deletions(-)

diff --git a/tests/tcg/s390x/signals-s390x.c
b/tests/tcg/s390x/signals-s390x.c
index dc2f8ee59a..48c3b6cdfd 100644
--- a/tests/tcg/s390x/signals-s390x.c
+++ b/tests/tcg/s390x/signals-s390x.c
@@ -1,4 +1,5 @@
  #include <assert.h>
+#include <execinfo.h>
  #include <signal.h>
  #include <string.h>
  #include <sys/mman.h>
@@ -11,22 +12,28 @@
   * inline asm is used instead.
   */
+#define DEFINE_ASM_FUNCTION(name, body) \
+    asm(".globl " #name "\n" \
+        #name ":\n" \
+        ".cfi_startproc\n" \
+        body "\n" \
+        "br %r14\n" \
+        ".cfi_endproc");
+
  void illegal_op(void);
-void after_illegal_op(void);
-asm(".globl\tillegal_op\n"
-    "illegal_op:\t.byte\t0x00,0x00\n"
-    "\t.globl\tafter_illegal_op\n"
-    "after_illegal_op:\tbr\t%r14");
+extern const char after_illegal_op;
+DEFINE_ASM_FUNCTION(illegal_op,
+    ".byte 0x00,0x00\n"
+    ".globl after_illegal_op\n"
+    "after_illegal_op:")
  void stg(void *dst, unsigned long src);
-asm(".globl\tstg\n"
-    "stg:\tstg\t%r3,0(%r2)\n"
-    "\tbr\t%r14");
+DEFINE_ASM_FUNCTION(stg, "stg %r3,0(%r2)")
  void mvc_8(void *dst, void *src);
-asm(".globl\tmvc_8\n"
-    "mvc_8:\tmvc\t0(8,%r2),0(%r3)\n"
-    "\tbr\t%r14");
+DEFINE_ASM_FUNCTION(mvc_8, "mvc 0(8,%r2),0(%r3)")
+
+extern const char return_from_main_1;
  static void safe_puts(const char *s)
  {
@@ -49,8 +56,9 @@ static struct {
  static void handle_signal(int sig, siginfo_t *info, void *ucontext)
  {
+    int err, i, n_frames;
+    void *frames[16];
      void *page;
-    int err;
      if (sig != expected.sig) {
          safe_puts("[  FAILED  ] wrong signal");
@@ -86,6 +94,17 @@ static void handle_signal(int sig, siginfo_t
*info, void *ucontext)
      default:
          break;
      }
+
+    n_frames = backtrace(frames, sizeof(frames) /
sizeof(frames[0]));
+    for (i = 0; i < n_frames; i++) {
+        if (frames[i] == &return_from_main_1) {
+            break;
+        }
+    }
+    if (i == n_frames) {
+        safe_puts("[  FAILED  ] backtrace() is broken");
+        _exit(1);
+    }
  }
  static void check_sigsegv(void *func, enum exception exception,
@@ -122,7 +141,7 @@ static void check_sigsegv(void *func, enum
exception exception,
      assert(err == 0);
  }
-int main(void)
+int main_1(void)
  {
      struct sigaction act;
      int err;
@@ -138,7 +157,7 @@ int main(void)
      safe_puts("[ RUN      ] Operation exception");
      expected.sig = SIGILL;
      expected.addr = illegal_op;
-    expected.psw_addr = (unsigned long)after_illegal_op;
+    expected.psw_addr = (unsigned long)&after_illegal_op;
      expected.exception = exception_operation;
      illegal_op();
      safe_puts("[       OK ]");
@@ -163,3 +182,25 @@ int main(void)
      _exit(0);
  }
+
+/*
+ * Define main() in assembly in order to test that unwinding from
signal
+ * handlers until main() works. This way we can define a specific
point that
+ * the unwinder should reach. This is also better than defining
main() in C
+ * and using inline assembly to call main_1(), since it's not easy
to get all
+ * the clobbers right.
+ */
+
+DEFINE_ASM_FUNCTION(main,
+    "stmg %r14,%r15,112(%r15)\n"
+    ".cfi_offset 14,-48\n"
+    ".cfi_offset 15,-40\n"
+    "lay %r15,-160(%r15)\n"
+    ".cfi_def_cfa_offset 320\n"
+    "brasl %r14,main_1\n"
+    ".globl return_from_main_1\n"
+    "return_from_main_1:\n"
+    "lmg %r14,%r15,272(%r15)\n"
+    ".cfi_restore 15\n"
+    ".cfi_restore 14\n"
+    ".cfi_def_cfa_offset 160");

Ping.

Acked-by: Thomas Huth <thuth@redhat.com>

Laurent, do you want to take these two patches through your linux-user branch, or shall I take them via the s390x branch?

I will take both.

Thanks,
Laurent




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