[Crash-utility] [PATCH] Allows to change the error output direction

[Daniel Kwon]

Currently, the error() is always printing the output to the console
through 'stdout'. This does not follow redirection which is good when
you want to know error while redirecting commands output to a file.
However, there are situations that you want to hide error messages or
redirect it into somewhere else.

Using 'set stderr' command, it can be changed to three different
destination - fixed 'stdout', following redirection (fp), or a custom
file path.

        crash> set stderr
        stderr: stdout
        crash> sym 0x523 > /dev/null
        sym: invalid address: 0x523
        crash> set stderr fp
        stderr: fp
        crash> sym 0x523 > /dev/null
        crash> set stderr /tmp/err.log
        stderr: /tmp/err.log
        crash> sym 0x523 > /dev/null
        crash> set stderr stdout
        stderr: stdout
        crash> sym 0x523 > /dev/null
        sym: invalid address: 0x523
---
 defs.h  |  2 ++
 help.c  |  5 +++++
 main.c  |  2 ++
 tools.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++---
 4 files changed, 61 insertions(+), 3 deletions(-)

diff --git a/defs.h b/defs.h
index ccffe58..57850c6 100644
--- a/defs.h
+++ b/defs.h
@@ -553,6 +553,8 @@ struct program_context {
  ulong scope; /* optional text context address */
  ulong nr_hash_queues; /* hash queue head count */
  char *(*read_vmcoreinfo)(const char *);
+        FILE *stderr;                   /* error() message direction */
+        char stderr_path[PATH_MAX];     /* stderr path information */
 };

 #define READMEM  pc->readmem
diff --git a/help.c b/help.c
index 581e616..ddc8e86 100644
--- a/help.c
+++ b/help.c
@@ -1093,6 +1093,10 @@ char *help_set[] = {
 "         redzone  on | off     if on, CONFIG_SLUB object addresses
displayed by",
 "                               the kmem command will point to the
SLAB_RED_ZONE",
 "                               padding inserted at the beginning of
the object.",
+" stderr  stdout | fp | <path>  set the direction of error put.
'stdout' always",
+"                               print on console. 'fp' follows the
redirection",
+"                               or pipe command. '<path>' can be any
file path",
+"                               in the filesystem which can save the output",
 " ",
 "  Internal variables may be set in four manners:\n",
 "    1. entering the set command in $HOME/.%src.",
@@ -1144,6 +1148,7 @@ char *help_set[] = {
 "             scope: (not set)",
 "           offline: show",
 "           redzone: on",
+"            stderr: stdout",
 " ",
 "  Show the current context:\n",
 "    %s> set",
diff --git a/main.c b/main.c
index 83ccd31..68bdec4 100644
--- a/main.c
+++ b/main.c
@@ -1085,6 +1085,8 @@ setup_environment(int argc, char **argv)
  *  to pipes or output files.
  */
  fp = stdout;
+        pc->stderr = stdout;
+        strcpy(pc->stderr_path, "stdout");

  /*
  *  Start populating the program_context structure.  It's used so
diff --git a/tools.c b/tools.c
index 2d95c3a..840d07c 100644
--- a/tools.c
+++ b/tools.c
@@ -58,6 +58,9 @@ __error(int type, char *fmt, ...)
         void *retaddr[NUMBER_STACKFRAMES] = { 0 };
  va_list ap;

+        if (!strcmp(pc->stderr_path, "fp"))
+                pc->stderr = fp;
+
  if (CRASHDEBUG(1) || (pc->flags & DROP_CORE)) {
  SAVE_RETURN_ADDRESS(retaddr);
  console("error() trace: %lx => %lx => %lx => %lx\n",
@@ -69,7 +72,7 @@ __error(int type, char *fmt, ...)
         va_end(ap);

  if (!fmt && FATAL_ERROR(type)) {
- fprintf(stdout, "\n");
+ fprintf(pc->stderr, "\n");
  clean_exit(1);
  }

@@ -95,14 +98,14 @@ __error(int type, char *fmt, ...)
  buf);
  fflush(pc->stdpipe);
  } else {
- fprintf(stdout, "%s%s%s %s%s",
+ fprintf(pc->stderr, "%s%s%s %s%s",
  new_line || end_of_line ? "\n" : "",
  type == WARNING ? "WARNING" :
  type == NOTE ? "NOTE" :
  type == CONT ? spacebuf : pc->curcmd,
  type == CONT ? " " : ":",
  buf, end_of_line ? "\n" : "");
- fflush(stdout);
+ fflush(pc->stderr);
  }

         if ((fp != stdout) && (fp != pc->stdpipe) && (fp != pc->tmpfile)) {
@@ -2483,6 +2486,51 @@ cmd_set(void)
  }
  return;

+                } else if (STREQ(args[optind], "stderr")) {
+                        if (args[optind+1]) {
+                                FILE *tmp_fp = NULL;
+                                char tmp_path[PATH_MAX];
+
+                                optind++;
+                                if (STREQ(args[optind], "stdout")) {
+                                        tmp_fp = stdout;
+                                        strcpy(tmp_path, "stdout");
+                                } else if (STREQ(args[optind], "fp")) {
+                                        tmp_fp = fp;
+                                        strcpy(tmp_path, "fp");
+                                } else {
+                                        if (strlen(args[optind]) >= PATH_MAX) {
+                                                error(INFO, "path
length %d is too long. (max=%d)\n",
+
strlen(args[optind]), PATH_MAX);
+                                                return;
+                                        }
+                                        tmp_fp = fopen(args[optind], "a");
+                                        if (tmp_fp != NULL) {
+                                                strcpy(tmp_path, args[optind]);
+                                        } else {
+                                                error(INFO, "invalid
path: %s\n",
+                                                      args[optind]);
+                                                return;
+                                        }
+
+                                }
+
+                                if (strcmp(pc->stderr_path, tmp_path)) {
+                                        if (strcmp(pc->stderr_path, "stdout")
+                                            && strcmp(pc->stderr_path, "fp")) {
+                                                fclose(pc->stderr);
+                                        }
+                                        pc->stderr = tmp_fp;
+                                        strcpy(pc->stderr_path, tmp_path);
+                                }
+                        }
+
+                        if (runtime) {
+                                fprintf(fp, "stderr: %s\n",
+                                        pc->stderr_path);
+                        }
+                        return;
+
  } else if (XEN_HYPER_MODE()) {
  error(FATAL, "invalid argument for the Xen hypervisor\n");
  } else if (pc->flags & MINIMAL_MODE) {
@@ -2590,6 +2638,7 @@ show_options(void)
  fprintf(fp, "(not set)\n");
  fprintf(fp, "       offline: %s\n", pc->flags2 & OFFLINE_HIDE ?
"hide" : "show");
  fprintf(fp, "       redzone: %s\n", pc->flags2 & REDZONE ? "on" : "off");
+ fprintf(fp, "        stderr: %s\n", pc->stderr_path);
 }


--
1.8.3.1