src/patches/suse-2.6.27.31/patches.arch/ppc64-xmon-dmesg-printing.patch

   1 Subject: [PATCH] add syslog printing to xmon debugger.
   2 From: Linas Vepstas <linas@austin.ibm.com>
   3
   4
   5 This patch 'dmesg'/printk log buffer printing to xmon.  I find this
   6 useful because crashes are almost always preceeded by interesting
   7 printk's.   This patch is simple & straightforward, except for one
   8 possibly controversial aspect: it embeds a small snippet in
   9 kernel/printk.c to return the location of the syslog.  This is
  10 needed because kallsyms and even CONFIG_KALLSYMS_ALL is not enough
  11 to reveal the location of log_buf.   This code is about 90%
  12 cut-n-paste of earlier code from Keith Owens.
  13
  14 Signed-off-by: Olaf Hering <olh@suse.de>
  15
  16  arch/powerpc/xmon/xmon.c |   57 +++++++++++++++++++++++++++++++++++++++++++++++
  17  kernel/printk.c          |   15 ++++++++++++
  18  2 files changed, 72 insertions(+)
  19
  20 --- a/arch/powerpc/xmon/xmon.c
  21 +++ b/arch/powerpc/xmon/xmon.c
  22 @@ -136,6 +136,7 @@ static struct bpt *in_breakpoint_table(u
  23  static int  do_step(struct pt_regs *);
  24  static void bpt_cmds(void);
  25  static void cacheflush(void);
  26 +static void xmon_show_dmesg(void);
  27  static int  cpu_cmd(void);
  28  static void csum(void);
  29  static void bootcmds(void);
  30 @@ -194,6 +195,7 @@ Commands:\n\
  31  #endif
  32    "\
  33    C    checksum\n\
  34 +  D    show dmesg (printk) buffer\n\
  35    d    dump bytes\n\
  36    di   dump instructions\n\
  37    df   dump float values\n\
  38 @@ -808,6 +810,9 @@ cmds(struct pt_regs *excp)
  39                 case 'd':
  40                         dump();
  41                         break;
  42 +               case 'D':
  43 +                       xmon_show_dmesg();
  44 +                       break;
  45                 case 'l':
  46                         symbol_lookup();
  47                         break;
  48 @@ -2522,6 +2527,58 @@ static void xmon_print_symbol(unsigned l
  49         printf("%s", after);
  50  }
  51
  52 +extern void debugger_syslog_data(char *syslog_data[4]);
  53 +#define SYSLOG_WRAP(p) if (p < syslog_data[0]) p = syslog_data[1]-1; \
  54 +       else if (p >= syslog_data[1]) p = syslog_data[0];
  55 +
  56 +static void xmon_show_dmesg(void)
  57 +{
  58 +       char *syslog_data[4], *start, *end, c;
  59 +       int logsize;
  60 +
  61 +       /* syslog_data[0,1] physical start, end+1.
  62 +        * syslog_data[2,3] logical start, end+1.
  63 +        */
  64 +       debugger_syslog_data(syslog_data);
  65 +       if (syslog_data[2] == syslog_data[3])
  66 +               return;
  67 +       logsize = syslog_data[1] - syslog_data[0];
  68 +       start = syslog_data[0] + (syslog_data[2] - syslog_data[0]) % logsize;
  69 +       end = syslog_data[0] + (syslog_data[3] - syslog_data[0]) % logsize;
  70 +
  71 +       /* Do a line at a time (max 200 chars) to reduce overhead */
  72 +       c = '\0';
  73 +       while(1) {
  74 +               char *p;
  75 +               int chars = 0;
  76 +               if (!*start) {
  77 +                       while (!*start) {
  78 +                               ++start;
  79 +                               SYSLOG_WRAP(start);
  80 +                               if (start == end)
  81 +                                       break;
  82 +                       }
  83 +                       if (start == end)
  84 +                               break;
  85 +               }
  86 +               p = start;
  87 +               while (*start && chars < 200) {
  88 +                       c = *start;
  89 +                       ++chars;
  90 +                       ++start;
  91 +                       SYSLOG_WRAP(start);
  92 +                       if (start == end || c == '\n')
  93 +                               break;
  94 +               }
  95 +               if (chars)
  96 +                       printf("%.*s", chars, p);
  97 +               if (start == end)
  98 +                       break;
  99 +       }
 100 +       if (c != '\n')
 101 +               printf("\n");
 102 +}
 103 +
 104  #ifdef CONFIG_PPC64
 105  static void dump_slb(void)
 106  {
 107 --- a/kernel/printk.c
 108 +++ b/kernel/printk.c
 109 @@ -426,6 +426,21 @@ asmlinkage long sys_syslog(int type, cha
 110         return do_syslog(type, buf, len);
 111  }
 112
 113 +#ifdef CONFIG_DEBUG_KERNEL
 114 +/* Its very handy to be able to view the syslog buffer during debug.
 115 + * But do_syslog() uses locks so it cannot be used during debugging.
 116 + * Instead, provide the start and end of the physical and logical logs.
 117 + * This is equivalent to do_syslog(3).
 118 + */
 119 +void debugger_syslog_data(char *syslog_data[4])
 120 +{
 121 +       syslog_data[0] = log_buf;
 122 +       syslog_data[1] = log_buf + log_buf_len;
 123 +       syslog_data[2] = log_buf + log_end - (logged_chars < log_buf_len ? logged_chars : log_buf_len);
 124 +       syslog_data[3] = log_buf + log_end;
 125 +}
 126 +#endif   /* CONFIG_DEBUG_KERNEL */
 127 +
 128  /*
 129   * Call the console drivers on a range of log_buf
 130   */