From: Antonio Borneo <antonio.borneo@st.com>
To: Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@redhat.com>
Cc: Antonio Borneo <antonio.borneo@st.com>,
Joel Fernandes <joelaf@google.com>,
Joel Fernandes <joel@joelfernandes.org>,
<linux-kernel@vger.kernel.org>,
<linux-stm32@st-md-mailman.stormreply.com>
Subject: [PATCH] tracing: Fix printing ptrs in preempt/irq enable/disable events
Date: Wed, 27 Nov 2019 16:44:28 +0100 [thread overview]
Message-ID: <20191127154428.191095-1-antonio.borneo@st.com> (raw)
This tracing event class is the only instance in kernel that logs
in the trace buffer the instruction pointer as offset to _stext,
instead of logging the full pointer.
This looks like a nice optimization for 64 bits platforms, where a
32 bit offset can take less space than a full 64 bits pointer. But
the symbol _stext is incorrectly resolved as zero in the expansion
of TP_printk(), which then prints only the hex offset instead of
the name of the caller function. Plus, on arm arch the kernel
modules are loaded at address lower than _stext, causing the u32
offset arithmetics to overflow and wrap at 32 bits.
I did not identified a 64 bit arch where the modules are loaded at
offset from _stext that exceed u32 range, but I also did not
identified any constraint to feel safe with a u32 offset.
Log directly the instruction pointer instead of the offset to
_stext.
Signed-off-by: Antonio Borneo <antonio.borneo@st.com>
Fixes: d59158162e03 ("tracing: Add support for preempt and irq enable/disable events")
---
include/trace/events/preemptirq.h | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/include/trace/events/preemptirq.h b/include/trace/events/preemptirq.h
index 95fba0471e5b..d548a6aafa18 100644
--- a/include/trace/events/preemptirq.h
+++ b/include/trace/events/preemptirq.h
@@ -18,18 +18,18 @@ DECLARE_EVENT_CLASS(preemptirq_template,
TP_ARGS(ip, parent_ip),
TP_STRUCT__entry(
- __field(u32, caller_offs)
- __field(u32, parent_offs)
+ __field(unsigned long, caller_ip)
+ __field(unsigned long, parent_ip)
),
TP_fast_assign(
- __entry->caller_offs = (u32)(ip - (unsigned long)_stext);
- __entry->parent_offs = (u32)(parent_ip - (unsigned long)_stext);
+ __entry->caller_ip = ip;
+ __entry->parent_ip = parent_ip;
),
TP_printk("caller=%pS parent=%pS",
- (void *)((unsigned long)(_stext) + __entry->caller_offs),
- (void *)((unsigned long)(_stext) + __entry->parent_offs))
+ (void *)__entry->caller_ip,
+ (void *)__entry->parent_ip)
);
#ifdef CONFIG_TRACE_IRQFLAGS
--
2.24.0
next reply other threads:[~2019-11-27 15:45 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 15:44 Antonio Borneo [this message]
2019-12-04 14:21 ` [PATCH] tracing: Fix printing ptrs in preempt/irq enable/disable events Steven Rostedt
2019-12-04 16:04 ` Joel Fernandes
2019-12-21 23:47 ` Joel Fernandes
2019-12-23 20:13 ` Steven Rostedt
2019-12-23 20:18 ` Steven Rostedt
2020-01-02 19:53 ` Joel Fernandes
2020-01-07 9:21 ` Antonio Borneo
2020-01-07 14:22 ` Steven Rostedt
2019-12-04 16:04 ` Joel Fernandes
2019-12-07 0:00 ` Antonio Borneo
2019-12-19 18:45 ` Valentin Schneider
2019-12-21 23:27 ` Joel Fernandes
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