Messages in this thread Patch in this message |  | | From | Antonio Borneo <> | Subject | [PATCH] tracing: Fix printing ptrs in preempt/irq enable/disable events | Date | Wed, 27 Nov 2019 16:44:28 +0100 |
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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
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