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From: Steven Rostedt <rostedt@goodmis.org>
To: Chuck Lever III <chuck.lever@oracle.com>
Cc: Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
	David Wysochanski <dwysocha@redhat.com>,
	Bruce Fields <bfields@fieldses.org>
Subject: Re: [PATCH v2 01/25] NFSD: Fix TP_printk() format specifier in trace_nfsd_dirent()
Date: Thu, 13 May 2021 10:50:18 -0400	[thread overview]
Message-ID: <20210513105018.7539996a@gandalf.local.home> (raw)
In-Reply-To: <238C0E2D-C2A4-4578-ADD2-C565B3B99842@oracle.com>

On Wed, 12 May 2021 16:52:05 +0000
Chuck Lever III <chuck.lever@oracle.com> wrote:

> The underlying need is to support non-NUL-terminated C strings.
> 
> I assumed that since the commentary around 9a6944fee68e claims
> the proper way to trace C strings is to use __string and friends,
> and those do not support non-NUL-terminated strings, that such
> strings are really not first-class citizens. Thus I concluded
> that my use of '%.*s' was incorrect.
> 
> Having some __string-style helpers that can deal with such
> strings would be valuable.

I guess the best I can do is a strncpy version, that will add the '\0' in
the ring buffer. That way we don't need to save the length as well (length
would need to be at least 4 bytes, where as '\0' is one).

Something like this?

I added "__string_len()" and "__assign_str_len()". You use them just like
__string() and __assign_str() but add a max length that you want to use
(although, it will always allocate "len" regardless if the string is
smaller). Then use __get_str() just like you use __string().

Would something like that work?

-- Steve

diff --git a/include/trace/trace_events.h b/include/trace/trace_events.h
index 8268bf747d6f..7ab23535a0c8 100644
--- a/include/trace/trace_events.h
+++ b/include/trace/trace_events.h
@@ -102,6 +102,9 @@ TRACE_MAKE_SYSTEM_STR();
 #undef __string
 #define __string(item, src) __dynamic_array(char, item, -1)
 
+#undef __string_len
+#define __string_len(item, src, len) __dynamic_array(char, item, -1)
+
 #undef __bitmask
 #define __bitmask(item, nr_bits) __dynamic_array(char, item, -1)
 
@@ -197,6 +200,9 @@ TRACE_MAKE_SYSTEM_STR();
 #undef __string
 #define __string(item, src) __dynamic_array(char, item, -1)
 
+#undef __string_len
+#define __string_len(item, src, len) __dynamic_array(char, item, -1)
+
 #undef __bitmask
 #define __bitmask(item, nr_bits) __dynamic_array(unsigned long, item, -1)
 
@@ -444,6 +450,9 @@ static struct trace_event_functions trace_event_type_funcs_##call = {	\
 #undef __string
 #define __string(item, src) __dynamic_array(char, item, -1)
 
+#undef __string_len
+#define __string_len(item, src, len) __dynamic_array(char, item, -1)
+
 #undef __bitmask
 #define __bitmask(item, nr_bits) __dynamic_array(unsigned long, item, -1)
 
@@ -492,6 +501,9 @@ static struct trace_event_fields trace_event_fields_##call[] = {	\
 #define __string(item, src) __dynamic_array(char, item,			\
 		    strlen((src) ? (const char *)(src) : "(null)") + 1)
 
+#undef __string_len
+#define __string_len(item, src, len) __dynamic_array(char, item, (len) + 1)
+
 /*
  * __bitmask_size_in_bytes_raw is the number of bytes needed to hold
  * num_possible_cpus().
@@ -655,10 +667,18 @@ static inline notrace int trace_event_get_offsets_##call(		\
 #undef __string
 #define __string(item, src) __dynamic_array(char, item, -1)
 
+#undef __string_len
+#define __string_len(item, src, len) __dynamic_array(char, item, -1)
+
 #undef __assign_str
 #define __assign_str(dst, src)						\
 	strcpy(__get_str(dst), (src) ? (const char *)(src) : "(null)");
 
+#undef __assign_str_len
+#define __assign_str_len(dst, src, len)						\
+	strncpy(__get_str(dst), (src) ? (const char *)(src) : "(null)", len);	\
+	__get_str(dst)[len] = '\0';
+
 #undef __bitmask
 #define __bitmask(item, nr_bits) __dynamic_array(unsigned long, item, -1)
 



  reply	other threads:[~2021-05-13 14:52 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-12 15:34 [PATCH v2 00/25] NFSD callback and lease management observability Chuck Lever
2021-05-12 15:35 ` [PATCH v2 01/25] NFSD: Fix TP_printk() format specifier in trace_nfsd_dirent() Chuck Lever
2021-05-12 16:26   ` Steven Rostedt
2021-05-12 16:52     ` Chuck Lever III
2021-05-13 14:50       ` Steven Rostedt [this message]
2021-05-13 14:53         ` Chuck Lever III
2021-05-13 15:02           ` Steven Rostedt
2021-05-13 15:10         ` Chuck Lever III
2021-05-13 18:43           ` Chuck Lever III
2021-05-13 19:00             ` Steven Rostedt
2021-05-13 19:08               ` Chuck Lever III
2021-05-13 19:17                 ` Steven Rostedt
2021-05-13 20:01                   ` Chuck Lever III
2021-07-12 15:18         ` Chuck Lever III
2021-07-12 17:09           ` Steven Rostedt
2021-05-12 16:53     ` Steven Rostedt
2021-05-12 15:35 ` [PATCH v2 02/25] NFSD: Fix TP_printk() format specifier in nfsd_clid_class Chuck Lever
2021-05-12 15:35 ` [PATCH v2 03/25] NFSD: Add nfsd_clid_cred_mismatch tracepoint Chuck Lever
2021-05-12 15:35 ` [PATCH v2 04/25] NFSD: Add nfsd_clid_verf_mismatch tracepoint Chuck Lever
2021-05-12 15:35 ` [PATCH v2 05/25] NFSD: Remove trace_nfsd_clid_inuse_err Chuck Lever
2021-05-12 15:35 ` [PATCH v2 06/25] NFSD: Add nfsd_clid_confirmed tracepoint Chuck Lever
2021-05-12 15:35 ` [PATCH v2 07/25] NFSD: Add nfsd_clid_reclaim_complete tracepoint Chuck Lever
2021-05-12 15:35 ` [PATCH v2 08/25] NFSD: Add nfsd_clid_destroyed tracepoint Chuck Lever
2021-05-12 15:35 ` [PATCH v2 09/25] NFSD: Add a couple more nfsd_clid_expired call sites Chuck Lever
2021-05-13 16:42   ` David Wysochanski
2021-05-13 17:05     ` Chuck Lever III
2021-05-12 15:36 ` [PATCH v2 10/25] NFSD: Add an RPC authflavor tracepoint display helper Chuck Lever
2021-05-12 15:36 ` [PATCH v2 11/25] NFSD: Add tracepoints for SETCLIENTID edge cases Chuck Lever
2021-05-12 15:36 ` [PATCH v2 12/25] NFSD: Add tracepoints for EXCHANGEID " Chuck Lever
2021-05-12 15:36 ` [PATCH v2 13/25] NFSD: Constify @fh argument of knfsd_fh_hash() Chuck Lever
2021-05-12 15:36 ` [PATCH v2 14/25] NFSD: Capture every CB state transition Chuck Lever
2021-05-12 15:36 ` [PATCH v2 15/25] NFSD: Drop TRACE_DEFINE_ENUM for NFSD4_CB_<state> macros Chuck Lever
2021-05-12 15:36 ` [PATCH v2 16/25] NFSD: Add cb_lost tracepoint Chuck Lever
2021-05-12 15:36 ` [PATCH v2 17/25] NFSD: Adjust cb_shutdown tracepoint Chuck Lever
2021-05-12 15:36 ` [PATCH v2 18/25] NFSD: Remove spurious cb_setup_err tracepoint Chuck Lever
2021-05-12 15:37 ` [PATCH v2 19/25] NFSD: Enhance the nfsd_cb_setup tracepoint Chuck Lever
2021-05-12 15:37 ` [PATCH v2 20/25] NFSD: Add an nfsd_cb_lm_notify tracepoint Chuck Lever
2021-05-12 15:37 ` [PATCH v2 21/25] NFSD: Add an nfsd_cb_offload tracepoint Chuck Lever
2021-05-12 15:37 ` [PATCH v2 22/25] NFSD: Replace the nfsd_deleg_break tracepoint Chuck Lever
2021-05-12 15:37 ` [PATCH v2 23/25] NFSD: Add an nfsd_cb_probe tracepoint Chuck Lever
2021-05-12 15:37 ` [PATCH v2 24/25] NFSD: Remove the nfsd_cb_work and nfsd_cb_done tracepoints Chuck Lever
2021-05-12 15:37 ` [PATCH v2 25/25] NFSD: Update nfsd_cb_args tracepoint Chuck Lever

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