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Martin Kaiser
284928533c
[ Upstream commit206b25c090] For a char * element in an event, the FILTER_PTR_STRING filter type is used. When the event occurs, a pointer is stored in the ringbuffer. If an eprobe references such a char * element of a "base event", the stored pointer is truncated when it's read from the ringbuffer. $ cd /sys/kernel/tracing $ echo 'e rcu.rcu_utilization $s:x64 $s:string' > dynamic_events $ echo 1 > tracing_on $ echo 1 > events/eprobes/enable $ sleep 1 $ echo 0 > events/eprobes/enable $ cat trace <idle>-0 ...: (rcu.rcu_utilization) arg1=0x4f arg2=(fault) <idle>-0 ...: (rcu.rcu_utilization) arg1=0x2 arg2=(fault) The problem is in get_event_field val = (unsigned long)(*(char *)addr); addr points to the position in the ringbuffer where the pointer was stored. The assignment reads only the lowest byte of the pointer. Fix the cast to read the whole pointer. The output of the test above is now <idle>-0 ... arg1=0xffffffff81c7d3f3 arg2="Start scheduler-tick" <idle>-0 ... arg1=0xffffffff81c57340 arg2="End scheduler-tick" Link: https://lore.kernel.org/all/20260620145339.3234726-1-martin@kaiser.cx/ Fixes:f04dec9346("tracing/eprobes: Fix reading of string fields") Signed-off-by: Martin Kaiser <martin@kaiser.cx> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.