[binutils-gdb] Skip gdb.base/relativedebug.exp if libc doesn't have debug info

[Yao Qi <qiyao at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=42d38f42dc1cdee90052db9aab54da8149ea2ee3

commit 42d38f42dc1cdee90052db9aab54da8149ea2ee3
Author: Yao Qi <yao.qi@linaro.org>
Date:   Thu Apr 30 09:55:06 2015 +0100

    Skip gdb.base/relativedebug.exp if libc doesn't have debug info
    
    Hi,
    I see the fail in gdb.base/relativedebug.exp on aarch64 box on which
    glibc doesn't have debug info,
    
     bt^M
     #0 0x0000002000061a88 in raise () from /lib/aarch64-linux-gnu/libc.so.6^M
     #1 0x0000002000064efc in abort () from /lib/aarch64-linux-gnu/libc.so.6^M
     #2 0x0000000000400640 in handler (signo=14) at ../../../binutils-gdb/gdb/testsuite/gdb.base/relativedebug.c:25^M
     #3 <signal handler called>^M
     #4 0x00000020000cc478 in ?? () from /lib/aarch64-linux-gnu/libc.so.6^M
     #5 0x0000000000400664 in main () at ../../../binutils-gdb/gdb/testsuite/gdb.base/relativedebug.c:32^M
     (gdb) FAIL: gdb.base/relativedebug.exp: pause found in backtrace
    
    if glibc has debug info, this test doesn't fail.
    
    In sysdeps/unix/sysv/linux/generic/pause.c, __libc_pause calls
    __syscall_pause,
    
      static int
      __syscall_pause (void)
      {
        sigset_t set;
    
        int rc =
          INLINE_SYSCALL (rt_sigprocmask, 4, SIG_BLOCK, NULL, &set, _NSIG / 8);
        if (rc == 0)
          rc = INLINE_SYSCALL (rt_sigsuspend, 2, &set, _NSIG / 8);
    
        return rc;
      }
    
      int
      __libc_pause (void)
      {
        if (SINGLE_THREAD_P)
          return __syscall_pause ();     <--- tail call
    
        int oldtype = LIBC_CANCEL_ASYNC ();
    
        int result = __syscall_pause ();
    
        LIBC_CANCEL_RESET (oldtype);
    
        return result;
      }
    
    and GDB unwinder is confused by the GCC optimized code,
    
    (gdb) disassemble pause
    Dump of assembler code for function pause:
       0x0000007fb7f274c4 <+0>:     stp     x29, x30, [sp,#-32]!
       0x0000007fb7f274c8 <+4>:     mov     x29, sp
       0x0000007fb7f274cc <+8>:     adrp    x0, 0x7fb7fd2000
       0x0000007fb7f274d0 <+12>:    ldr     w0, [x0,#364]
       0x0000007fb7f274d4 <+16>:    stp     x19, x20, [sp,#16]
       0x0000007fb7f274d8 <+20>:    cbnz    w0, 0x7fb7f274e8 <pause+36>
    
       0x0000007fb7f274dc <+24>:    ldp     x19, x20, [sp,#16]
       0x0000007fb7f274e0 <+28>:    ldp     x29, x30, [sp],#32
       0x0000007fb7f274e4 <+32>:    b       0x7fb7f27434    <---- __syscall_pause
    
       0x0000007fb7f274e8 <+36>:    bl      0x7fb7f5e080
    
    Note that the program stops in __syscall_pause, but its symbol is
    stripped in glibc, so GDB doesn't know where the program stops.
    __syscall_pause is a tail call in __libc_pause, so it returns to main
    instead of __libc_pause.  As a result, the backtrace is like,
    
     #0  0x0000007fb7ebca88 in raise () from /lib/aarch64-linux-gnu/libc.so.6
     #1  0x0000007fb7ebfefc in abort () from /lib/aarch64-linux-gnu/libc.so.6
     #2  0x0000000000400640 in handler (signo=14) at ../../../binutils-gdb/gdb/testsuite/gdb.base/relativedebug.c:25
     #3  <signal handler called>
     #4  0x0000007fb7f27478 in ?? () from /lib/aarch64-linux-gnu/libc.so.6   <-- [in __syscall_pause]
     #5  0x0000000000400664 in main () at ../../../binutils-gdb/gdb/testsuite/gdb.base/relativedebug.c:32
    
    looks GDB does nothing wrong here.  I looked back at the test case
    gdb.base/relativedebug.exp, which was added
    https://sourceware.org/ml/gdb-patches/2006-10/msg00305.html
    This test was indented to test the problem that "backtraces no longer
    display some libc functions" after separate debug info is installed.
    IOW, it makes few sense to test against libc which doesn't have debug
    info at all, such as my case.
    
    This patch is to tweak the test case to catch the output of
    "info shared", if "(*)" is found for libc.so, which means libc doesn't
    have debug info, then skip the test.
    
    gdb/testsuite:
    
    2015-04-30  Yao Qi  <yao.qi@linaro.org>
    
    	* gdb.base/relativedebug.exp: Invoke gdb command
    	"info sharedlibrary", and if libc.so doesn't have debug info,
    	skip the test.

Diff:
---
 gdb/testsuite/ChangeLog                  |  6 ++++++
 gdb/testsuite/gdb.base/relativedebug.exp | 11 +++++++++++
 2 files changed, 17 insertions(+)

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index a9a0757..1e48f98 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2015-04-30  Yao Qi  <yao.qi@linaro.org>
+
+	* gdb.base/relativedebug.exp: Invoke gdb command
+	"info sharedlibrary", and if libc.so doesn't have debug info,
+	skip the test.
+
 2015-04-29  Doug Evans  <dje@google.com>
 
 	* gdb.python/py-xmethods.exp: Add ptype tests.
diff --git a/gdb/testsuite/gdb.base/relativedebug.exp b/gdb/testsuite/gdb.base/relativedebug.exp
index 621226b..b42dbf9 100644
--- a/gdb/testsuite/gdb.base/relativedebug.exp
+++ b/gdb/testsuite/gdb.base/relativedebug.exp
@@ -31,6 +31,17 @@ clean_restart ${binfile}
 
 runto_main
 
+set test "info sharedlibrary"
+gdb_test_multiple $test $test {
+    -re ".*\(\\*\)\[^\r\n\]*/libc\.so.*$gdb_prompt $" {
+	# Skip the test below if libc doesn't have debug info.
+	unsupported "libc doesn't have debug info"
+	return -1
+    }
+    -re ".*$gdb_prompt $" {
+    }
+}
+
 # pause () -> SIGALRM -> handler () -> abort ()
 gdb_test "continue" "Program received signal SIGABRT.*"