On 2023/05/30 14:09, Hsin-Yi Wang wrote:
> On Tue, May 30, 2023 at 10:31 AM HAGIO KAZUHITO(萩尾 一仁)
> <k-hagio-ab@xxxxxxx> wrote:
>>
>> On 2023/05/28 5:17, Hsin-Yi Wang wrote:
>>> hi crash-utility community,
>>>
>>> When stdin is not a TTY, but all the other flags remain the same,
>>> prompt ("crash> ") won't be displayed. An example use case is, the
>>> stdin of crash is replaced by a piped fd connected to another process.
>>>
>>> In process_command_line(), it checks if pc->flags does NOT have any of
>>> the flag: READLINE|SILENT|CMDLINE_IFILE|RCHOME_IFILE|RCLOCAL_IFILE, a
>>> prompt should be printed.
>>>
>>> But in setup_environment(), pc->flags is set to have READLINE flag[2],
>>> the above check will not be true at all.
>>>
>>> Should READLINE be set for all cases in setup_environment()?
>>> - If true, should the check in process_command_line() look for TTY
>>> instead of READLINE? Since if pc->flags has TTY, [2] won't be true and
>>> the prompt will be printed later in TTY's case[3].
>>> - If false, where should be a proper place and conditions to set READLINE?
>>>
>>> Or is the current behavior intended? I may not fully understand the
>>> design logic. Any explanations are appreciated.
>>
>> I don't know the full history of crash, but my impression of the flag is
>> that probably it's an ancient code and almost meaningless now, but the
>> current behavior is intended.
>>
>> What you want to do is displaying the prompt and command without a tty?
>
> Interact with crash through another process that piped stdin/stdout
> with crash to do additional input/output processing, so the filemode
> won't work.
Ah, got it. So the prompt can be used as a delimiter or something? It
might be useful.
>
>> This is also my imagination, but probably they wanted only command
>> output like this without the prompt and command:
>>
>> # echo sys | crash -s
>> KERNEL: /usr/lib/debug/lib/modules/4.18.0-305.el8.x86_64/vmlinux
>> DUMPFILE: /proc/kcore
>> CPUS: 16
>> DATE: Tue May 30 11:15:41 JST 2023
>> UPTIME: 19 days, 23:23:48
>> LOAD AVERAGE: 0.18, 0.12, 0.09
>> TASKS: 555
>> NODENAME: r110j-1
>> RELEASE: 4.18.0-305.el8.x86_64
>> VERSION: #1 SMP Thu Apr 29 08:54:30 EDT 2021
>> MACHINE: x86_64 (3400 Mhz)
>> MEMORY: 63.9 GB
>> #
>
> But I wonder if the current behavior is intended, wouldn't [1] never
> be run because of [2]?
> [1] https://github.com/crash-utility/crash/blob/05a3a328fcd8920e49926b6d1c9c81ce0b6acbca/cmdline.c#L67
> [2] https://github.com/crash-utility/crash/blob/8246dce99dd23457e8c7a3fe9609c706694d1959/main.c#L1182
Right, I guessed that it ultimately became so after changes, although it
should have got removed. But maybe not.
>
> Another not necessarily related data point is, I compared the gdb tool
> and it will also give the prompt if no tty presented.
>
>>
>> Because if they wanted the prompt and command, it would be easily done
>> like this...
>>
>> --- a/cmdline.c
>> +++ b/cmdline.c
>> @@ -139,6 +139,7 @@ process_command_line(void)
>> } else {
>> if (fgets(pc->command_line, BUFSIZE-1, stdin) == NULL)
>> clean_exit(1);
>> + fprintf(fp, "%s%s", pc->prompt, pc->command_line);
>> clean_line(pc->command_line);
>> strcpy(pc->orig_line, pc->command_line);
>> }
>
> Yeah, maybe print this before the fgets with fflush()? similar to [1],
> or does the following make sense?
>
> diff --git a/cmdline.c b/cmdline.c
> index ded6551..181800a 100644
> --- a/cmdline.c
> +++ b/cmdline.c
> @@ -65,7 +65,7 @@ process_command_line(void)
> BZERO(pc->command_line, BUFSIZE);
>
> if (!(pc->flags &
> - (READLINE|SILENT|CMDLINE_IFILE|RCHOME_IFILE|RCLOCAL_IFILE)))
> + (TTY|SILENT|CMDLINE_IFILE|RCHOME_IFILE|RCLOCAL_IFILE)))
> fprintf(fp, "%s", pc->prompt);
> fflush(fp);
It does not print the input command line only with this, I would like to
also print it if we print the prompt. How about this?
--- a/cmdline.c
+++ b/cmdline.c
@@ -65,7 +65,7 @@ process_command_line(void)
BZERO(pc->command_line, BUFSIZE);
if (!(pc->flags &
- (READLINE|SILENT|CMDLINE_IFILE|RCHOME_IFILE|RCLOCAL_IFILE)))
+ (TTY|SILENT|CMDLINE_IFILE|RCHOME_IFILE|RCLOCAL_IFILE)))
fprintf(fp, "%s", pc->prompt);
fflush(fp);
@@ -139,6 +139,11 @@ process_command_line(void)
} else {
if (fgets(pc->command_line, BUFSIZE-1, stdin) == NULL)
clean_exit(1);
+
+ if (!(pc->flags & SILENT)) {
+ fprintf(fp, "%s", pc->command_line);
+ fflush(fp);
+ }
clean_line(pc->command_line);
strcpy(pc->orig_line, pc->command_line);
}
This looks consistent with the other types of crash session.
And we can still get only a command output with -s option.
# echo sys | crash -s
Thanks,
Kazu
>
>>
>> If you want the prompt and command with pre-generated crash commands,
>> you can use "crash -i" option. How about this?
>
> Filemode is not ideal if we want to pipe crash with another process
> that users interact with, since we will have to load vmlinux and
> dumpfile every time.
>
> But if this still looks like working as intended, I will close this issue.
>
> Thanks for your reply.
>
>>
>> # echo sys > cmd
>> # crash -i cmd
>>
>> Thanks,
>> Kazu
>>
>>>
>>> Thanks!
>>>
>>> [1] https://github.com/crash-utility/crash/blob/05a3a328fcd8920e49926b6d1c9c81ce0b6acbca/cmdline.c#L67
>>> [2] https://github.com/crash-utility/crash/blob/8246dce99dd23457e8c7a3fe9609c706694d1959/main.c#L1182
>>> [3] https://github.com/crash-utility/crash/blob/05a3a328fcd8920e49926b6d1c9c81ce0b6acbca/cmdline.c#L120
>>>
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