[Crash-utility] [PATCH] Allows to change the error output direction
Daniel Kwon
dkwon at redhat.com
Fri Jun 28 06:10:31 UTC 2019
Hi Dave,
Yes, that is violating the default behaviour. I recheck how it should
be handled and made the below rules.
- 'default' : Working just like the 'crash' before this 'stderr' implementation.
- 'fp' : Only goes into one destination. It can be console in normal
command, but will go into target file if redirection or pipe is used.
- '<path>' : It will go into the specified file only and no console output.
Below is the test I have done for the test. Hope this behaviour is reasonable.
---------------------------
## default: standard error handling behaviour.
normal command: error prints on console
crash> set stderr default
stderr: default
crash> sym 0x123
sym: invalid address: 0x123
redirect: goes into both console and redirected file.
crash> sym 0x123 > /tmp/output
sym: invalid address: 0x123
crash> !cat /tmp/output
sym: invalid address: 0x123
pipe: goes into both console and piped direction.
crash> sym 0x123 | cat
sym: invalid address: 0x123
sym: invalid address: 0x123
crash> sym 0x123 | cat > /tmp/output
sym: invalid address: 0x123
crash> !cat /tmp/output
sym: invalid address: 0x123
## fp: Only to the one target such as stdout, pipe, or redirected file
normal command: error prints on console
crash> set stderr fp
stderr: fp
crash> sym 0x123
sym: invalid address: 0x123
redirect: goes into redirected file only.
crash> sym 0x123 > /tmp/output
crash> !cat /tmp/output
sym: invalid address: 0x123
pipe: goes into piped direction only.
crash> sym 0x123 | cat
sym: invalid address: 0x123
crash> sym 0x123 | cat > /tmp/output
crash> !cat /tmp/output
sym: invalid address: 0x123
## <file path>: Only to the specified file.
normal command: error goes into the specified file only.
crash> set stderr /tmp/stderr
stderr: /tmp/stderr
crash> sym 0x123
crash> !cat /tmp/stderr
sym: invalid address: 0x123
redirect: error goes into the specified file only.
crash> sym 0x124 > /tmp/output
crash> !cat /tmp/output
crash> !cat /tmp/stderr
sym: invalid address: 0x123
sym: invalid address: 0x124
pipe: error goes into the specified file only.
crash> sym 0x125 | cat
crash> sym 0x126 | cat > /tmp/output
crash> !cat /tmp/output
crash> !cat /tmp/stderr
sym: invalid address: 0x123
sym: invalid address: 0x124
sym: invalid address: 0x125
sym: invalid address: 0x126
---------------------------
Regards,
Daniel Kwon
Kind regards,
Daniel Kwon, RHCA
Principle Software Maintenance Engineer, CEE
Red Hat APAC
On Fri, Jun 28, 2019 at 5:27 AM Dave Anderson <anderson at redhat.com> wrote:
>
>
>
> ----- Original Message -----
> > 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.
>
> Hi Daniel,
>
> Upon initial testing, I note that your patch changes the default behavior,
> which is unacceptable.
>
> By default, the idea is to get all error() messages out so that they are
> seen by the user regardless of how the command's output may be piped or
> redirected. So if a command's output is redirected to a file or pipe,
> the error message goes both to the console as well as being intermingled
> in the pipe/file command output.
>
> Taking your simple example, by default, command output and error messages
> are piped (behind the scenes) to /usr/bin/less:
>
> crash> sym 0x523
> sym: invalid address: 0x523
> crash>
>
> If the default piping is turned off, command output and error messages
> go to stdout:
>
> crash> set scroll off
> scroll: off (/usr/bin/less)
> crash> sym 0x523
> sym: invalid address: 0x523
> crash>
>
> However, if the command is redirected to a file, any command output and error
> messages go to the file, but error messages also go to the console:
>
> crash> sym 0x523 > /tmp/output
> sym: invalid address: 0x523
> crash> !cat /tmp/output
> sym: invalid address: 0x523
> crash>
>
> Similarly, if the command is piped to a command, command output and error messages
> go to the pipe, and error messages also go to the console:
>
> crash> sym 0x523 | cat
> sym: invalid address: 0x523
> sym: invalid address: 0x523
> crash>
>
> So with your patch applied, and the new stderr variable set to the default
> of "stdout":
>
> crash> set stderr
> stderr: stdout
> crash>
>
> Let's run the same set of commands as above:
>
> crash> sym 0x523
> sym: invalid address: 0x523
> crash> set scroll off
> scroll: off (/usr/bin/less)
> crash> sym 0x523
> sym: invalid address: 0x523
> crash>
>
> Same behavior as always. However, if a command is redirected to a file,
> the error message only goes to the console, but it is not sent to the
> output file:
>
> crash> sym 0x523 > /tmp/output
> sym: invalid address: 0x523
> crash> !cat /tmp/output
> crash>
>
> Similarly, when piped to a command, the error message is only going to
> one of the destinations:
>
> crash> sym 0x523 | cat
> sym: invalid address: 0x523
> crash>
>
> So there's no way I'm going to change behavior from what it has
> been forever.
>
> While I didn't test your alternative settings, it's not entirely clear
> what you're trying to accomplish. Seemingly it would make sense to have
> a binary setting for the new "stderr":
>
> (1) the current default behavior, or
> (2) a setting allowing you to redirect all error() messages to a
> designated file.
>
> Option (2) would *not* send them to the console *or* intermingle them
> with command output. But that's just me...
>
> Also, here's a minor compiler complaint:
>
> $ make warn
> ...
> cc -c -g -DX86_64 -DLZO -DSNAPPY -DGDB_7_6 main.c -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector -Wformat-security
> main.c: In function ‘setup_environment’:
> main.c:1088:9: warning: implicit declaration of function ‘set_stderr’ [-Wimplicit-function-declaration]
> set_stderr("stdout");
> ^
> cc -c -g -DX86_64 -DLZO -DSNAPPY -DGDB_7_6 tools.c -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector -Wformat-security
> tools.c:42:1: warning: no previous prototype for ‘set_stderr’ [-Wmissing-prototypes]
> set_stderr(char *target)
> ^
> ...
>
> Thanks,
> Dave
>
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> >
> > 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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