diff mbox series

[v2,3/4] Revert "tracing: Add "(fault)" name injection to kernel probes"

Message ID 168873727209.2687993.6806850187024303094.stgit@mhiramat.roam.corp.google.com
State New
Headers
Series tracing/probes: Fix bugs in process_fetch_insn |

Commit Message

Masami Hiramatsu (Google) July 7, 2023, 1:41 p.m. UTC 
  From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

This reverts commit 2e9906f84fc7c99388bb7123ade167250d50f1c0.

It was turned out that commit 2e9906f84fc7 ("tracing: Add "(fault)"
name injection to kernel probes") did not work correctly and probe
events still show just '(fault)' (instead of '"(fault)"').
Also, current '(fault)' is more explicit that it faulted.

Link: https://lore.kernel.org/all/20230706230642.3793a593@rorschach.local.home/

Cc: stable@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 kernel/trace/trace_events_synth.c |    2 +-
 kernel/trace/trace_probe_kernel.h |   31 ++++++-------------------------
 2 files changed, 7 insertions(+), 26 deletions(-)

Comments

Steven Rostedt July 7, 2023, 2:14 p.m. UTC | #1 
On Fri,  7 Jul 2023 22:41:12 +0900
"Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:

> diff --git a/kernel/trace/trace_probe_kernel.h b/kernel/trace/trace_probe_kernel.h
> index c4e1d4c03a85..6deae2ce34f8 100644
> --- a/kernel/trace/trace_probe_kernel.h
> +++ b/kernel/trace/trace_probe_kernel.h
> @@ -2,8 +2,6 @@
>  #ifndef __TRACE_PROBE_KERNEL_H_
>  #define __TRACE_PROBE_KERNEL_H_
>  
> -#define FAULT_STRING "(fault)"
> -

Instead of deleting this, why not use it in both places? After applying
your patch, we have:

 $ git grep '(fault)' kernel/trace
kernel/trace/trace_events_synth.c:                      strcpy(str_field, "(fault)");
kernel/trace/trace_probe.c:             trace_seq_puts(s, "(fault)");

We could make that consistent with:

kernel/trace/trace_events_synth.c:                      strcpy(str_field, FAULT_STRING);
kernel/trace/trace_probe.c:             trace_seq_puts(s, FAULT_STRING);

-- Steve
Masami Hiramatsu (Google) July 7, 2023, 3:46 p.m. UTC | #2 
On Fri, 7 Jul 2023 10:14:20 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Fri,  7 Jul 2023 22:41:12 +0900
> "Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:
> 
> > diff --git a/kernel/trace/trace_probe_kernel.h b/kernel/trace/trace_probe_kernel.h
> > index c4e1d4c03a85..6deae2ce34f8 100644
> > --- a/kernel/trace/trace_probe_kernel.h
> > +++ b/kernel/trace/trace_probe_kernel.h
> > @@ -2,8 +2,6 @@
> >  #ifndef __TRACE_PROBE_KERNEL_H_
> >  #define __TRACE_PROBE_KERNEL_H_
> >  
> > -#define FAULT_STRING "(fault)"
> > -
> 
> Instead of deleting this, why not use it in both places? After applying
> your patch, we have:
> 
>  $ git grep '(fault)' kernel/trace
> kernel/trace/trace_events_synth.c:                      strcpy(str_field, "(fault)");
> kernel/trace/trace_probe.c:             trace_seq_puts(s, "(fault)");
> 
> We could make that consistent with:
> 
> kernel/trace/trace_events_synth.c:                      strcpy(str_field, FAULT_STRING);
> kernel/trace/trace_probe.c:             trace_seq_puts(s, FAULT_STRING);

Indeed. So can I tweak the revert patch more for this?

I would like to move the definition to trace.h.

Thanks,

> 
> -- Steve
>
Steven Rostedt July 7, 2023, 3:48 p.m. UTC | #3 
On Sat, 8 Jul 2023 00:46:43 +0900
Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:

> Indeed. So can I tweak the revert patch more for this?
> 
> I would like to move the definition to trace.h.

Sure.

-- Steve
Masami Hiramatsu (Google) July 8, 2023, 1:30 a.m. UTC | #4 
On Fri, 7 Jul 2023 11:48:17 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Sat, 8 Jul 2023 00:46:43 +0900
> Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:
> 
> > Indeed. So can I tweak the revert patch more for this?
> > 
> > I would like to move the definition to trace.h.
> 
> Sure.

OK, let me update the patch. Thanks!

> 
> -- Steve
diff mbox series

Patch

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index d6a70aff2410..23416ec8e1da 100644
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -478,7 +478,7 @@  static unsigned int trace_string(struct synth_trace_event *entry,
 			ret = strncpy_from_kernel_nofault(str_field, str_val, STR_VAR_LEN_MAX);
 
 		if (ret < 0)
-			strcpy(str_field, FAULT_STRING);
+			strcpy(str_field, "(fault)");
 
 		(*n_u64) += STR_VAR_LEN_MAX / sizeof(u64);
 	}
diff --git a/kernel/trace/trace_probe_kernel.h b/kernel/trace/trace_probe_kernel.h
index c4e1d4c03a85..6deae2ce34f8 100644
--- a/kernel/trace/trace_probe_kernel.h
+++ b/kernel/trace/trace_probe_kernel.h
@@ -2,8 +2,6 @@ 
 #ifndef __TRACE_PROBE_KERNEL_H_
 #define __TRACE_PROBE_KERNEL_H_
 
-#define FAULT_STRING "(fault)"
-
 /*
  * This depends on trace_probe.h, but can not include it due to
  * the way trace_probe_tmpl.h is used by trace_kprobe.c and trace_eprobe.c.
@@ -15,16 +13,8 @@  static nokprobe_inline int
 fetch_store_strlen_user(unsigned long addr)
 {
 	const void __user *uaddr =  (__force const void __user *)addr;
-	int ret;
 
-	ret = strnlen_user_nofault(uaddr, MAX_STRING_SIZE);
-	/*
-	 * strnlen_user_nofault returns zero on fault, insert the
-	 * FAULT_STRING when that occurs.
-	 */
-	if (ret <= 0)
-		return strlen(FAULT_STRING) + 1;
-	return ret;
+	return strnlen_user_nofault(uaddr, MAX_STRING_SIZE);
 }
 
 /* Return the length of string -- including null terminal byte */
@@ -44,18 +34,7 @@  fetch_store_strlen(unsigned long addr)
 		len++;
 	} while (c && ret == 0 && len < MAX_STRING_SIZE);
 
-	/* For faults, return enough to hold the FAULT_STRING */
-	return (ret < 0) ? strlen(FAULT_STRING) + 1 : len;
-}
-
-static nokprobe_inline void set_data_loc(int ret, void *dest, void *__dest, void *base, int len)
-{
-	if (ret >= 0) {
-		*(u32 *)dest = make_data_loc(ret, __dest - base);
-	} else {
-		strscpy(__dest, FAULT_STRING, len);
-		ret = strlen(__dest) + 1;
-	}
+	return (ret < 0) ? ret : len;
 }
 
 /*
@@ -76,7 +55,8 @@  fetch_store_string_user(unsigned long addr, void *dest, void *base)
 	__dest = get_loc_data(dest, base);
 
 	ret = strncpy_from_user_nofault(__dest, uaddr, maxlen);
-	set_data_loc(ret, dest, __dest, base, maxlen);
+	if (ret >= 0)
+		*(u32 *)dest = make_data_loc(ret, __dest - base);
 
 	return ret;
 }
@@ -107,7 +87,8 @@  fetch_store_string(unsigned long addr, void *dest, void *base)
 	 * probing.
 	 */
 	ret = strncpy_from_kernel_nofault(__dest, (void *)addr, maxlen);
-	set_data_loc(ret, dest, __dest, base, maxlen);
+	if (ret >= 0)
+		*(u32 *)dest = make_data_loc(ret, __dest - base);
 
 	return ret;
 }