Messages in this thread | | | From | Masami Hiramatsu <> | Subject | [PATCH -tip v8 0/6] tracing/probes: uaccess: Add support user-space access | Date | Fri, 10 May 2019 00:12:49 +0900 |
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Hi,
Here is the v8 series of probe-event to support user-space access. Previous version is here.
https://lkml.kernel.org/r/155732230159.12756.15040196512285621636.stgit@devnote2
In this version, I fixed some typos/style issues and renamed fields according to Ingo's comment, and added Ack from Steve.
Also this version is rebased on the latest -tip/master tree.
Changes in v8: [2/6] Fix style issues and typos according to Ingo's comment. [3/6] Fix style issues according to Ingo's comment. [6/6] Fix a typo and rename user field to user_access field.
In summary, strncpy_from_user() should work as below
- strncpy_from_user() can access user memory with set_fs(USER_DS) in task context
- strncpy_from_user() can access kernel memory with set_fs(KERNEL_DS) in task context (e.g. devtmpfsd and init)
- strncpy_from_user() can access user/kernel memory (depends on DS) in IRQ context if pagefault is disabled. (both verified)
Note that this changes the warning behavior when CONFIG_DEBUG_ATOMIC_SLEEP=y, it still warns when __copy_from_user_inatomic() is called in IRQ context, but don't warn if pagefault is disabled because it will not sleep in atomic.
==== Kprobe event user-space memory access features:
For user-space access extension, this series adds 2 features, "ustring" type and user-space dereference syntax. "ustring" is used for recording a null-terminated string in user-space from kprobe events.
"ustring" type is easy, it is able to use instead of "string" type, so if you want to record a user-space string via "__user char *", you can use ustring type instead of string. For example,
echo 'p do_sys_open path=+0($arg2):ustring' >> kprobe_events
will record the path string from user-space.
The user-space dereference syntax is also simple. Thi just adds 'u' prefix before an offset value.
+|-u<OFFSET>(<FETCHARG>)
e.g. +u8(%ax), +u0(+0(%si))
This is more generic. If you want to refer the variable in user- space from its address or access a field in data structure in user-space, you need to use this.
For example, if you probe do_sched_setscheduler(pid, policy, param) and record param->sched_priority, you can add new probe as below; p do_sched_setscheduler priority=+u0($arg3)
Actually, with this feature, "ustring" type is not absolutely necessary, because these are same meanings.
+0($arg2):ustring == +u0($arg2):string
Note that kprobe event provides these methods, but it doesn't change it from kernel to user automatically because we do not know whether the given address is in userspace or kernel on some arch.
Thank you,
---
Masami Hiramatsu (6): x86/uaccess: Allow access_ok() in irq context if pagefault_disabled uaccess: Add non-pagefault user-space read functions tracing/probe: Add ustring type for user-space string tracing/probe: Support user-space dereference selftests/ftrace: Add user-memory access syntax testcase perf-probe: Add user memory access attribute support
Documentation/trace/kprobetrace.rst | 28 ++++- Documentation/trace/uprobetracer.rst | 10 +- arch/x86/include/asm/uaccess.h | 4 - include/linux/uaccess.h | 19 +++ kernel/trace/trace.c | 7 + kernel/trace/trace_kprobe.c | 37 ++++++ kernel/trace/trace_probe.c | 37 +++++- kernel/trace/trace_probe.h | 3 kernel/trace/trace_probe_tmpl.h | 37 +++++- kernel/trace/trace_uprobe.c | 19 +++ mm/maccess.c | 122 +++++++++++++++++++- tools/perf/Documentation/perf-probe.txt | 3 tools/perf/util/probe-event.c | 11 ++ tools/perf/util/probe-event.h | 2 tools/perf/util/probe-file.c | 7 + tools/perf/util/probe-file.h | 1 tools/perf/util/probe-finder.c | 19 ++- .../ftrace/test.d/kprobe/kprobe_args_user.tc | 32 +++++ 18 files changed, 357 insertions(+), 41 deletions(-) create mode 100644 tools/testing/selftests/ftrace/test.d/kprobe/kprobe_args_user.tc
-- Masami Hiramatsu (Linaro) <mhiramat@kernel.org>
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