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

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(a)redhat.com&gt; 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 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Kind regards, > > Daniel Kwon > > > > On Tue, Jun 25, 2019 at 2:06 AM Dave Anderson <anderson(a)redhat.com&gt; > > 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(a)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(a)redhat.com > > > > > https://www.redhat.com/mailman/listinfo/crash-utility > > > > > > > > > > > > > -- > > > > Crash-utility mailing list > > > > Crash-utility(a)redhat.com > > > > https://www.redhat.com/mailman/listinfo/crash-utility > > > > > > > > -- > > > > Crash-utility mailing list > > > > Crash-utility(a)redhat.com > > > > https://www.redhat.com/mailman/listinfo/crash-utility > > > > >