linux-kernel - Re: [PATCH v8-RESEND 22/33] dyndbg: split multi-query strings with %

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Date: Tue, 21 May 2024 13:58:15 +0200
From: Łukasz Bartosik <ukaszb@...omium.org>
To: Jim Cromie <jim.cromie@...il.com>
Cc: jbaron@...mai.com, gregkh@...uxfoundation.org, 
	linux-kernel@...r.kernel.org, linux@...musvillemoes.dk, joe@...ches.com, 
	mcgrof@...nel.org, daniel.vetter@...ll.ch, tvrtko.ursulin@...ux.intel.com, 
	jani.nikula@...el.com, ville.syrjala@...ux.intel.com, seanpaul@...omium.org, 
	robdclark@...il.com, groeck@...gle.com, yanivt@...gle.com, bleung@...gle.com
Subject: Re: [PATCH v8-RESEND 22/33] dyndbg: split multi-query strings with %

On Thu, May 16, 2024 at 7:45 PM Jim Cromie <jim.cromie@...il.com> wrote:
>
> Multi-query strings have long allowed:

Missing been ?

>
>   modprobe drm dyndbg="class DRM_UT_CORE +p; class DRM_UT_KMS +p"
>   modprobe drm dyndbg=<<EOX
>      class DRM_UT_CORE +p
>      class DRM_UT_KMS +p
>   EOX
>
> More recently, the need for quoting was avoided by treating a comma
> like a space/token-terminator:
>
>   modprobe drm dyndbg=class,DRM_UT_CORE,+p\;class,DRM_UT_KMS,+p
>
> That worked, but it left unfinished business; the semicolon in the
> example above is a shell special-char (one of the bash control
> operators), so it is brittle when passed in/down/around scripts.  In
> particular, it fails when passed to vng (virtme-ng).
>
> So this patch adds '%' to the existing ';' and '\n' multi-cmd
> separators, which is more shell-friendly, and also avoids quoting and
> escaping hassles.
>
> NOTE: it does break format matching on '%' patterns:
>
> bash-5.2# ddcmd 'format "find-me: %foo" +p'
> [  203.900581] dyndbg: read 26 bytes from userspace
> [  203.900883] dyndbg: query 0: "format "find-me: " mod:*
> [  203.901118] dyndbg: unclosed quote: find-me:
> [  203.901355] dyndbg: tokenize failed
> [  203.901529] dyndbg: query 1: "foo" +p" mod:*
> [  203.901957] dyndbg: split into words: "foo"" "+p"
> [  203.902243] dyndbg: op='+' flags=0x1 maskp=0xffffffff
> [  203.902458] dyndbg: expecting pairs of match-spec <value>
> [  203.902703] dyndbg: query parse failed
> [  203.902871] dyndbg: processed 2 queries, with 0 matches, 2 errs
> bash: echo: write error: Invalid argument
>
> The '%' splits the input into 2 queries, and both fail.  Given the
> limited utility of matching against the working parts of a format
> string "foo: %d bar %s", nothing is actually lost here.
>
> Signed-off-by: Jim Cromie <jim.cromie@...il.com>
> ---
>  lib/dynamic_debug.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
> index c1bc728cb050..625838bd74aa 100644
> --- a/lib/dynamic_debug.c
> +++ b/lib/dynamic_debug.c
> @@ -596,7 +596,7 @@ static int ddebug_exec_queries(char *query, const char *modname)
>         int i, errs = 0, exitcode = 0, rc, nfound = 0;
>
>         for (i = 0; query; query = split) {
> -               split = strpbrk(query, ";\n");
> +               split = strpbrk(query, "%;\n");
>                 if (split)
>                         *split++ = '\0';
>
> --
> 2.45.0
>