[Bug 1367832] Re: gdbserver gets conditionals wrong on ppc64le

[bugproxy]

** Tags removed: targetmilestone-inin---
** Tags added: targetmilestone-inin1410

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https://bugs.launchpad.net/bugs/1367832

Title:
  gdbserver gets conditionals wrong on ppc64le

Status in “gdb” package in Ubuntu:
  New

Bug description:
  ---Problem Description---
  Single stepping has issues with conditionals when debugging with gdbserver, taking the wrong path through the code.
   
  Machine Type = Power8 LE 
   
  ---Steps to Reproduce---
   ubuntu at ubuntu:~$ cat > test.c
  #include <stdio.h>
  #include <stdlib.h>

  typedef enum {
    Success = 0,
    Failure,
  } dev_status_t;

  dev_status_t getDeviceCount(int *countp)
  { 
    *countp = 1;
    return Success;
  }

  int
  main(int argc, char **argv)
  { 
    int count = 0;
    dev_status_t status = getDeviceCount(&count);

    if (status != Success)
      { 
        printf("getDeviceCount returned %d\n", (int)status);
        printf("Result = FAIL\n");
        exit(EXIT_FAILURE);
      }

    if (count == 0)
      { 
        printf("There are no devices\n");
      }
    else
      { 
        printf("Detected %d device(s)\n", count);
      }

    exit(EXIT_SUCCESS);
  }

  ubuntu at ubuntu:~$ gcc -g test.c -o test
  ubuntu at ubuntu:~$ gdbserver :9999 ./test
  Process ./test created; pid = 25600
  Listening on port 9999
  Remote debugging from host 127.0.0.1

  In another terminal, run gdb:

  ubuntu at ubuntu:~$ gdb ./test 
  GNU gdb (Ubuntu 7.8-0ubuntu1) 7.8
  Copyright (C) 2014 Free Software Foundation, Inc.
  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
  This is free software: you are free to change and redistribute it.
  There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
  and "show warranty" for details.
  This GDB was configured as "powerpc64le-linux-gnu".
  Type "show configuration" for configuration details.
  For bug reporting instructions, please see:
  <http://www.gnu.org/software/gdb/bugs/>.
  Find the GDB manual and other documentation resources online at:
  <http://www.gnu.org/software/gdb/documentation/>.
  For help, type "help".
  Type "apropos word" to search for commands related to "word"...
  Reading symbols from ./test...done.
  (gdb) target remote :9999
  Remote debugging using :9999
  Reading symbols from /lib64/ld64.so.2...(no debugging symbols found)...done.
  Loaded symbols for /lib64/ld64.so.2
  Can't read symbols from system-supplied DSO at 0x3fffb7fa0000: File truncated
  0x00003fffb7fc1a60 in ?? () from /lib64/ld64.so.2
  (gdb) b main
  Breakpoint 1 at 0x100006d4: file test.c, line 17.
  (gdb) cont
  Continuing.

  Breakpoint 1, main (argc=1, argv=0x3ffffffff088) at test.c:17
  17      {
  (gdb) next
  18        int count = 0;
  (gdb) next
  19        dev_status_t status = getDeviceCount(&count);
  (gdb) next
  21        if (status != Success)
  (gdb) next
  23            printf("getDeviceCount returned %d\n", (int)status);
  (gdb) print status
  $1 = Success

  Notice the program took the wrong direction on if() block.
   
  ---uname output---
  Linux ubuntu 3.16.0-14-generic #20-Ubuntu SMP Sat Sep 6 23:45:12 UTC 2014 ppc64le ppc64le ppc64le GNU/Linux
   
  Userspace tool common name: gdbserver

  The root cause of this issue was a routine that collect/supply ptrace
  registers on gdbserver, originally developed for BE only.

  The attached patch against gdb 7.8-0ubuntu1 sources fixes this problem
  on gdbserver. It was already accepted and committed upstream:

  https://sourceware.org/ml/gdb-patches/2014-09/msg00181.html

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