[Crash-utility] [PATCH] Allows to change the error output direction
Daniel Kwon
dkwon at redhat.com
Tue Jun 25 06:51:33 UTC 2019
Hi Dave,
It looks like __error() function has an extra output which can cause of
confusion. I rewrote the code to cover that as well as the changes you had
asked. Please let me know how it goes.
Kind regards,
Daniel Kwon
On Tue, Jun 25, 2019 at 2:06 AM Dave Anderson <anderson at redhat.com> wrote:
>
> ----- Original Message -----
> > Hi Dave,
> >
> > Here I attach as a file for the patch. Thanks.
> >
> > Kind regards,
> > Daniel
>
> Hi Daniel,
>
> As I mentioned before, the concept seems reasonable, which I thought
> was to allow a user to prevent error() messages from being intermingled
> with command output by redirecting them somewhere else. But that's
> apparently not the case, as a few simple examples show otherwise.
>
> Here's the default setting, and a sample command generating an error:
>
> crash> set -v
> scroll: on (/usr/bin/less)
> radix: 10 (decimal)
> refresh: on
> print_max: 256
> print_array: off
> console: (not assigned)
> debug: 0
> core: off
> hash: on
> silent: off
> edit: vi
> namelist:
> /usr/lib/debug/lib/modules/3.10.0-957.21.2.el7.x86_64/vmlinux
> dumpfile: (null)
> unwind: off
> zero_excluded: off
> null-stop: off
> gdb: off
> scope: 0 (not set)
> offline: show
> redzone: on
> stderr: stdout
> crash> bt 33333
> bt: invalid task or pid value: 33333
> crash>
>
> Here I set stderr to /dev/null, which sets the new pc->stderr,
> but the behavior is still the same:
>
> crash> set stderr /dev/null
> stderr: /dev/null
> crash> set -v
> scroll: on (/usr/bin/less)
> radix: 10 (decimal)
> refresh: on
> print_max: 256
> print_array: off
> console: (not assigned)
> debug: 0
> core: off
> hash: on
> silent: off
> edit: vi
> namelist:
> /usr/lib/debug/lib/modules/3.10.0-957.21.2.el7.x86_64/vmlinux
> dumpfile: (null)
> unwind: off
> zero_excluded: off
> null-stop: off
> gdb: off
> scope: 0 (not set)
> offline: show
> redzone: on
> stderr: /dev/null
> crash> bt 33333
> bt: invalid task or pid value: 33333
> crash>
>
> Or if I set it to a file, the same thing happens:
>
> crash> set stderr /tmp/junk
> stderr: /tmp/junk
> crash> set -v
> scroll: on (/usr/bin/less)
> radix: 10 (decimal)
> refresh: on
> print_max: 256
> print_array: off
> console: (not assigned)
> debug: 0
> core: off
> hash: on
> silent: off
> edit: vi
> namelist:
> /usr/lib/debug/lib/modules/3.10.0-957.21.2.el7.x86_64/vmlinux
> dumpfile: (null)
> unwind: off
> zero_excluded: off
> null-stop: off
> gdb: off
> scope: 0 (not set)
> offline: show
> redzone: on
> stderr: /tmp/junk
> crash> bt 33333
> bt: invalid task or pid value: 33333
> crash>
>
> With your patch applied, the help page indicates:
>
> 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
>
> Is states that "<path>" can be any file path in the filesystem which can
> save
> the output. But even I redirect a command, it still doesn't seem to do
> what
> it states:
>
> crash> set stderr /dev/null
> stderr: /dev/null
> crash> bt 33333 > /tmp/junk
> crash> !cat /tmp/junk
> bt: invalid task or pid value: 33333
> crash>
>
> Or if I pipe it:
>
> crash> bt 33333 | cat
> bt: invalid task or pid value: 33333
> crash>
>
> What am I missing?
>
> And also, a couple more things...
>
> Please make pc->stderr_path a pointer:
>
> --- 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 */
> };
>
> Since it's typically going to contain a handful of bytes, it's kind of
> wasteful
> to use PATH_MAX (4096). Just use malloc/free to get a buffer of the
> correct
> length.
>
> And please display pc->stderr and pc->stderr_path to dump_program_context()
> for use by "help -p".
>
> Thanks,
> Dave
>
>
>
>
>
> >
> >
> > On Sat, Jun 22, 2019 at 5:24 AM Dave Anderson < anderson at redhat.com >
> wrote:
> >
> >
> >
> > Hi Daniel,
> >
> > The idea seems reasonable, but the patch below is malformed:
> >
> > $ patch -p1 < error.patch
> > checking file defs.h
> > Hunk #1 FAILED at 553.
> > 1 out of 1 hunk FAILED
> > checking file help.c
> > patch: **** malformed patch at line 52: displayed by",
> >
> > $
> >
> > You can see that there are a quite a few unintended line wraps
> > in the patch below.
> >
> > Can you make the patch a discrete attachment to your email?
> >
> > Thanks,
> > Dave
> >
> >
> > ----- Original Message -----
> > > 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
> > >
> > > --
> > > Crash-utility mailing list
> > > Crash-utility at redhat.com
> > > https://www.redhat.com/mailman/listinfo/crash-utility
> > >
> >
> > --
> > Crash-utility mailing list
> > Crash-utility at redhat.com
> > https://www.redhat.com/mailman/listinfo/crash-utility
> >
> > --
> > Crash-utility mailing list
> > Crash-utility at redhat.com
> > https://www.redhat.com/mailman/listinfo/crash-utility
>
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