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Fix to allocate fprobe::entry_data_size buffer with rethook instances.
If fprobe doesn't allocate entry_data_size buffer for each rethook instance,
fprobe entry handler can cause a buffer overrun when storing entry data in
entry handler.
Link: https://lore.kernel.org/all/170920576727.107552.638161246679734051.stgit@devnote2/
Reported-by: Jiri Olsa <olsajiri@gmail.com>
Closes: https://lore.kernel.org/all/Zd9eBn2FTQzYyg7L@krava/
Fixes: 4bbd93455659 ("kprobes: kretprobe scalability improvement")
Cc: stable@vger.kernel.org
Tested-by: Jiri Olsa <olsajiri@gmail.com>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull probes updates from Masami Hiramatsu:
"Cleanups:
- kprobes: Fixes typo in kprobes samples
- tracing/eprobes: Remove 'break' after return
kretprobe/fprobe performance improvements:
- lib: Introduce new `objpool`, which is a high performance lockless
object queue. This uses per-cpu ring array to allocate/release
objects from the pre-allocated object pool.
Since the index of ring array is a 32bit sequential counter, we can
retry to push/pop the object pointer from the ring without lock (as
seq-lock does)
- lib: Add an objpool test module to test the functionality and
evaluate the performance under some circumstances
- kprobes/fprobe: Improve kretprobe and rethook scalability
performance with objpool.
This improves both legacy kretprobe and fprobe exit handler (which
is based on rethook) to be scalable on SMP systems. Even with
8-threads parallel test, it shows a great scalability improvement
- Remove unneeded freelist.h which is replaced by objpool
- objpool: Add maintainers entry for the objpool
- objpool: Fix to remove unused include header lines"
* tag 'probes-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
kprobes: unused header files removed
MAINTAINERS: objpool added
kprobes: freelist.h removed
kprobes: kretprobe scalability improvement
lib: objpool test module added
lib: objpool added: ring-array based lockless MPMC
tracing/eprobe: drop unneeded breaks
samples: kprobes: Fixes a typo
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kretprobe is using freelist to manage return-instances, but freelist,
as LIFO queue based on singly linked list, scales badly and reduces
the overall throughput of kretprobed routines, especially for high
contention scenarios.
Here's a typical throughput test of sys_prctl (counts in 10 seconds,
measured with perf stat -a -I 10000 -e syscalls:sys_enter_prctl):
OS: Debian 10 X86_64, Linux 6.5rc7 with freelist
HW: XEON 8336C x 2, 64 cores/128 threads, DDR4 3200MT/s
1T 2T 4T 8T 16T 24T
24150045 29317964 15446741 12494489 18287272 17708768
32T 48T 64T 72T 96T 128T
16200682 13737658 11645677 11269858 10470118 9931051
This patch introduces objpool to replace freelist. objpool is a
high performance queue, which can bring near-linear scalability
to kretprobed routines. Tests of kretprobe throughput show the
biggest ratio as 159x of original freelist. Here's the result:
1T 2T 4T 8T 16T
native: 41186213 82336866 164250978 328662645 658810299
freelist: 24150045 29317964 15446741 12494489 18287272
objpool: 23926730 48010314 96125218 191782984 385091769
32T 48T 64T 96T 128T
native: 1330338351 1969957941 2512291791 2615754135 2671040914
freelist: 16200682 13737658 11645677 10470118 9931051
objpool: 764481096 1147149781 1456220214 1502109662 1579015050
Testings on 96-core ARM64 output similarly, but with the biggest
ratio up to 448x:
OS: Debian 10 AARCH64, Linux 6.5rc7
HW: Kunpeng-920 96 cores/2 sockets/4 NUMA nodes, DDR4 2933 MT/s
1T 2T 4T 8T 16T
native: . 30066096 63569843 126194076 257447289 505800181
freelist: 16152090 11064397 11124068 7215768 5663013
objpool: 13997541 28032100 55726624 110099926 221498787
24T 32T 48T 64T 96T
native: 763305277 1015925192 1521075123 2033009392 3021013752
freelist: 5015810 4602893 3766792 3382478 2945292
objpool: 328192025 439439564 668534502 887401381 1319972072
Link: https://lore.kernel.org/all/20231017135654.82270-4-wuqiang.matt@bytedance.com/
Signed-off-by: wuqiang.matt <wuqiang.matt@bytedance.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
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The number of active retprobes can be zero but it is not acceptable,
so return EINVAL error if detected.
Link: https://lore.kernel.org/all/169750018550.186853.11198884812017796410.stgit@devnote2/
Reported-by: wuqiang.matt <wuqiang.matt@bytedance.com>
Closes: https://lore.kernel.org/all/20231016222103.cb9f426edc60220eabd8aa6a@kernel.org/
Fixes: 5b0ab78998e3 ("fprobe: Add exit_handler support")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull probe fixes from Masami Hiramatsu:
- fprobe: Add a comment why fprobe will be skipped if another kprobe is
running in fprobe_kprobe_handler().
- probe-events: Fix some issues related to fetch-arguments:
- Fix double counting of the string length for user-string and
symstr. This will require longer buffer in the array case.
- Fix not to count error code (minus value) for the total used
length in array argument. This makes the total used length
shorter.
- Fix to update dynamic used data size counter only if fetcharg uses
the dynamic size data. This may mis-count the used dynamic data
size and corrupt data.
- Revert "tracing: Add "(fault)" name injection to kernel probes"
because that did not work correctly with a bug, and we agreed the
current '(fault)' output (instead of '"(fault)"' like a string)
explains what happened more clearly.
- Fix to record 0-length (means fault access) data_loc data in fetch
function itself, instead of store_trace_args(). If we record an
array of string, this will fix to save fault access data on each
entry of the array correctly.
* tag 'probes-fixes-v6.5-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
tracing/probes: Fix to record 0-length data_loc in fetch_store_string*() if fails
Revert "tracing: Add "(fault)" name injection to kernel probes"
tracing/probes: Fix to update dynamic data counter if fetcharg uses it
tracing/probes: Fix not to count error code to total length
tracing/probes: Fix to avoid double count of the string length on the array
fprobes: Add a comment why fprobe_kprobe_handler exits if kprobe is running
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Add a comment the reason why fprobe_kprobe_handler() exits if any other
kprobe is running.
Link: https://lore.kernel.org/all/168874788299.159442.2485957441413653858.stgit@devnote2/
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Link: https://lore.kernel.org/all/20230706120916.3c6abf15@gandalf.local.home/
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull probes fixes from Masami Hiramatsu:
- Fix fprobe's rethook release issues:
- Release rethook after ftrace_ops is unregistered so that the
rethook is not accessed after free.
- Stop rethook before ftrace_ops is unregistered so that the
rethook is NOT used after exiting unregister_fprobe()
- Fix eprobe cleanup logic. If it attaches to multiple events and
failes to enable one of them, rollback all enabled events correctly.
- Fix fprobe to unlock ftrace recursion lock correctly when it missed
by another running kprobe.
- Cleanup kprobe to remove unnecessary NULL.
- Cleanup kprobe to remove unnecessary 0 initializations.
* tag 'probes-fixes-v6.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
fprobe: Ensure running fprobe_exit_handler() finished before calling rethook_free()
kernel: kprobes: Remove unnecessary ‘0’ values
kprobes: Remove unnecessary ‘NULL’ values from correct_ret_addr
fprobe: add unlock to match a succeeded ftrace_test_recursion_trylock
kernel/trace: Fix cleanup logic of enable_trace_eprobe
fprobe: Release rethook after the ftrace_ops is unregistered
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rethook_free()
Ensure running fprobe_exit_handler() has finished before
calling rethook_free() in the unregister_fprobe() so that caller can free
the fprobe right after unregister_fprobe().
unregister_fprobe() ensured that all running fprobe_entry/exit_handler()
have finished by calling unregister_ftrace_function() which synchronizes
RCU. But commit 5f81018753df ("fprobe: Release rethook after the ftrace_ops
is unregistered") changed to call rethook_free() after
unregister_ftrace_function(). So call rethook_stop() to make rethook
disabled before unregister_ftrace_function() and ensure it again.
Here is the possible code flow that can call the exit handler after
unregister_fprobe().
------
CPU1 CPU2
call unregister_fprobe(fp)
...
__fprobe_handler()
rethook_hook() on probed function
unregister_ftrace_function()
return from probed function
rethook hooks
find rh->handler == fprobe_exit_handler
call fprobe_exit_handler()
rethook_free():
set rh->handler = NULL;
return from unreigster_fprobe;
call fp->exit_handler() <- (*)
------
(*) At this point, the exit handler is called after returning from
unregister_fprobe().
This fixes it as following;
------
CPU1 CPU2
call unregister_fprobe()
...
rethook_stop():
set rh->handler = NULL;
__fprobe_handler()
rethook_hook() on probed function
unregister_ftrace_function()
return from probed function
rethook hooks
find rh->handler == NULL
return from rethook
rethook_free()
return from unreigster_fprobe;
------
Link: https://lore.kernel.org/all/168873859949.156157.13039240432299335849.stgit@devnote2/
Fixes: 5f81018753df ("fprobe: Release rethook after the ftrace_ops is unregistered")
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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Unlock ftrace recursion lock when fprobe_kprobe_handler() is failed
because of some running kprobe.
Link: https://lore.kernel.org/all/20230703092336.268371-1-zegao@tencent.com/
Fixes: 3cc4e2c5fbae ("fprobe: make fprobe_kprobe_handler recursion free")
Reported-by: Yafang <laoar.shao@gmail.com>
Closes: https://lore.kernel.org/linux-trace-kernel/CALOAHbC6UpfFOOibdDiC7xFc5YFUgZnk3MZ=3Ny6we=AcrNbew@mail.gmail.com/
Signed-off-by: Ze Gao <zegao@tencent.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
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While running bpf selftests it's possible to get following fault:
general protection fault, probably for non-canonical address \
0x6b6b6b6b6b6b6b6b: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC NOPTI
...
Call Trace:
<TASK>
fprobe_handler+0xc1/0x270
? __pfx_bpf_testmod_init+0x10/0x10
? __pfx_bpf_testmod_init+0x10/0x10
? bpf_fentry_test1+0x5/0x10
? bpf_fentry_test1+0x5/0x10
? bpf_testmod_init+0x22/0x80
? do_one_initcall+0x63/0x2e0
? rcu_is_watching+0xd/0x40
? kmalloc_trace+0xaf/0xc0
? do_init_module+0x60/0x250
? __do_sys_finit_module+0xac/0x120
? do_syscall_64+0x37/0x90
? entry_SYSCALL_64_after_hwframe+0x72/0xdc
</TASK>
In unregister_fprobe function we can't release fp->rethook while it's
possible there are some of its users still running on another cpu.
Moving rethook_free call after fp->ops is unregistered with
unregister_ftrace_function call.
Link: https://lore.kernel.org/all/20230615115236.3476617-1-jolsa@kernel.org/
Fixes: 5b0ab78998e3 ("fprobe: Add exit_handler support")
Cc: stable@vger.kernel.org
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
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Add fprobe events for tracing function entry and exit instead of kprobe
events. With this change, we can continue to trace function entry/exit
even if the CONFIG_KPROBES_ON_FTRACE is not available. Since
CONFIG_KPROBES_ON_FTRACE requires the CONFIG_DYNAMIC_FTRACE_WITH_REGS,
it is not available if the architecture only supports
CONFIG_DYNAMIC_FTRACE_WITH_ARGS. And that means kprobe events can not
probe function entry/exit effectively on such architecture.
But this can be solved if the dynamic events supports fprobe events.
The fprobe event is a new dynamic events which is only for the function
(symbol) entry and exit. This event accepts non register fetch arguments
so that user can trace the function arguments and return values.
The fprobe events syntax is here;
f[:[GRP/][EVENT]] FUNCTION [FETCHARGS]
f[MAXACTIVE][:[GRP/][EVENT]] FUNCTION%return [FETCHARGS]
E.g.
# echo 'f vfs_read $arg1' >> dynamic_events
# echo 'f vfs_read%return $retval' >> dynamic_events
# cat dynamic_events
f:fprobes/vfs_read__entry vfs_read arg1=$arg1
f:fprobes/vfs_read__exit vfs_read%return arg1=$retval
# echo 1 > events/fprobes/enable
# head -n 20 trace | tail
# TASK-PID CPU# ||||| TIMESTAMP FUNCTION
# | | | ||||| | |
sh-142 [005] ...1. 448.386420: vfs_read__entry: (vfs_read+0x4/0x340) arg1=0xffff888007f7c540
sh-142 [005] ..... 448.386436: vfs_read__exit: (ksys_read+0x75/0x100 <- vfs_read) arg1=0x1
sh-142 [005] ...1. 448.386451: vfs_read__entry: (vfs_read+0x4/0x340) arg1=0xffff888007f7c540
sh-142 [005] ..... 448.386458: vfs_read__exit: (ksys_read+0x75/0x100 <- vfs_read) arg1=0x1
sh-142 [005] ...1. 448.386469: vfs_read__entry: (vfs_read+0x4/0x340) arg1=0xffff888007f7c540
sh-142 [005] ..... 448.386476: vfs_read__exit: (ksys_read+0x75/0x100 <- vfs_read) arg1=0x1
sh-142 [005] ...1. 448.602073: vfs_read__entry: (vfs_read+0x4/0x340) arg1=0xffff888007f7c540
sh-142 [005] ..... 448.602089: vfs_read__exit: (ksys_read+0x75/0x100 <- vfs_read) arg1=0x1
Link: https://lore.kernel.org/all/168507469754.913472.6112857614708350210.stgit@mhiramat.roam.corp.google.com/
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/all/202302011530.7vm4O8Ro-lkp@intel.com/
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
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Pass return address as 'ret_ip' to the fprobe entry and return handlers
so that the fprobe user handler can get the reutrn address without
analyzing arch-dependent pt_regs.
Link: https://lore.kernel.org/all/168507467664.913472.11642316698862778600.stgit@mhiramat.roam.corp.google.com/
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
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fprobe_hander and fprobe_kprobe_handler has guarded ftrace recursion
detection but fprobe_exit_handler has not, which possibly introduce
recursive calls if the fprobe exit callback calls any traceable
functions. Checking in fprobe_hander or fprobe_kprobe_handler
is not enough and misses this case.
So add recursion free guard the same way as fprobe_hander. Since
ftrace recursion check does not employ ip(s), so here use entry_ip and
entry_parent_ip the same as fprobe_handler.
Link: https://lore.kernel.org/all/20230517034510.15639-4-zegao@tencent.com/
Fixes: 5b0ab78998e3 ("fprobe: Add exit_handler support")
Signed-off-by: Ze Gao <zegao@tencent.com>
Cc: stable@vger.kernel.org
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
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Current implementation calls kprobe related functions before doing
ftrace recursion check in fprobe_kprobe_handler, which opens door
to kernel crash due to stack recursion if preempt_count_{add, sub}
is traceable in kprobe_busy_{begin, end}.
Things goes like this without this patch quoted from Steven:
"
fprobe_kprobe_handler() {
kprobe_busy_begin() {
preempt_disable() {
preempt_count_add() { <-- trace
fprobe_kprobe_handler() {
[ wash, rinse, repeat, CRASH!!! ]
"
By refactoring the common part out of fprobe_kprobe_handler and
fprobe_handler and call ftrace recursion detection at the very beginning,
the whole fprobe_kprobe_handler is free from recursion.
[ Fix the indentation of __fprobe_handler() parameters. ]
Link: https://lore.kernel.org/all/20230517034510.15639-3-zegao@tencent.com/
Fixes: ab51e15d535e ("fprobe: Introduce FPROBE_FL_KPROBE_SHARED flag for fprobe")
Signed-off-by: Ze Gao <zegao@tencent.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
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The commit 39d954200bf6 ("fprobe: Skip exit_handler if entry_handler returns
!0") introduced a hidden dependency of 'ret' local variable in the
fprobe_handler(), Smatch warns the `ret` can be accessed without
initialization.
kernel/trace/fprobe.c:59 fprobe_handler()
error: uninitialized symbol 'ret'.
kernel/trace/fprobe.c
49 fpr->entry_ip = ip;
50 if (fp->entry_data_size)
51 entry_data = fpr->data;
52 }
53
54 if (fp->entry_handler)
55 ret = fp->entry_handler(fp, ip, ftrace_get_regs(fregs), entry_data);
ret is only initialized if there is an ->entry_handler
56
57 /* If entry_handler returns !0, nmissed is not counted. */
58 if (rh) {
rh is only true if there is an ->exit_handler. Presumably if you have
and ->exit_handler that means you also have a ->entry_handler but Smatch
is not smart enough to figure it out.
--> 59 if (ret)
^^^
Warning here.
60 rethook_recycle(rh);
61 else
62 rethook_hook(rh, ftrace_get_regs(fregs), true);
63 }
64 out:
65 ftrace_test_recursion_unlock(bit);
66 }
Link: https://lore.kernel.org/all/168100731160.79534.374827110083836722.stgit@devnote2/
Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://lore.kernel.org/all/85429a5c-a4b9-499e-b6c0-cbd313291c49@kili.mountain
Fixes: 39d954200bf6 ("fprobe: Skip exit_handler if entry_handler returns !0")
Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
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Skip hooking function return and calling exit_handler if the
entry_handler() returns !0.
Link: https://lkml.kernel.org/r/167526699798.433354.10998365726830117303.stgit@mhiramat.roam.corp.google.com
Cc: Florent Revest <revest@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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Add nr_maxactive to specify rethook_node pool size. This means
the maximum number of actively running target functions concurrently
for probing by exit_handler. Note that if the running function is
preempted or sleep, it is still counted as 'active'.
Link: https://lkml.kernel.org/r/167526697917.433354.17779774988245113106.stgit@mhiramat.roam.corp.google.com
Cc: Florent Revest <revest@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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Pass the private entry_data to the entry and exit handlers so that
they can share the context data, something like saved function
arguments etc.
User must specify the private entry_data size by @entry_data_size
field before registering the fprobe.
Link: https://lkml.kernel.org/r/167526696173.433354.17408372048319432574.stgit@mhiramat.roam.corp.google.com
Cc: Florent Revest <revest@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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Since commit ab51e15d535e ("fprobe: Introduce FPROBE_FL_KPROBE_SHARED flag
for fprobe") introduced fprobe_kprobe_handler() for fprobe::ops::func,
unregister_fprobe() fails to unregister the registered if user specifies
FPROBE_FL_KPROBE_SHARED flag.
Moreover, __register_ftrace_function() is possible to change the
ftrace_ops::func, thus we have to check fprobe::ops::saved_func instead.
To check it correctly, it should confirm the fprobe::ops::saved_func is
either fprobe_handler() or fprobe_kprobe_handler().
Link: https://lore.kernel.org/all/166677683946.1459107.15997653945538644683.stgit@devnote3/
Fixes: cad9931f64dc ("fprobe: Add ftrace based probe APIs")
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
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Check if fp->rethook succeeded to be allocated. Otherwise, if
rethook_alloc() fails, then we end up dereferencing a NULL pointer in
rethook_add_node().
Link: https://lore.kernel.org/all/20221025031209.954836-1-rafaelmendsr@gmail.com/
Fixes: 5b0ab78998e3 ("fprobe: Add exit_handler support")
Cc: stable@vger.kernel.org
Signed-off-by: Rafael Mendonca <rafaelmendsr@gmail.com>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
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Using ftrace_lookup_symbols to speed up symbols lookup
in register_fprobe_syms API.
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20220510122616.2652285-4-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Since ftrace_ops::local_hash::filter_hash field is an __rcu pointer,
we have to use rcu_access_pointer() to access it.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/164802093635.1732982.4938094876018890866.stgit@devnote2
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Fix the type mismatching warning of 'rethook_node vs fprobe_rethook_node'
found by Smatch.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/164802092611.1732982.12268174743437084619.stgit@devnote2
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Introduce FPROBE_FL_KPROBE_SHARED flag for sharing fprobe callback with
kprobes safely from the viewpoint of recursion.
Since the recursion safety of the fprobe (and ftrace) is a bit different
from the kprobes, this may cause an issue if user wants to run the same
code from the fprobe and the kprobes.
The kprobes has per-cpu 'current_kprobe' variable which protects the
kprobe handler from recursion in any case. On the other hand, the fprobe
uses only ftrace_test_recursion_trylock(), which will allow interrupt
context calls another (or same) fprobe during the fprobe user handler is
running.
This is not a matter in cases if the common callback shared among the
kprobes and the fprobe has its own recursion detection, or it can handle
the recursion in the different contexts (normal/interrupt/NMI.)
But if it relies on the 'current_kprobe' recursion lock, it has to check
kprobe_running() and use kprobe_busy_*() APIs.
Fprobe has FPROBE_FL_KPROBE_SHARED flag to do this. If your common callback
code will be shared with kprobes, please set FPROBE_FL_KPROBE_SHARED
*before* registering the fprobe, like;
fprobe.flags = FPROBE_FL_KPROBE_SHARED;
register_fprobe(&fprobe, "func*", NULL);
This will protect your common callback from the nested call.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Tested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/164735293127.1084943.15687374237275817599.stgit@devnote2
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Add exit_handler to fprobe. fprobe + rethook allows us to hook the kernel
function return. The rethook will be enabled only if the
fprobe::exit_handler is set.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Tested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/164735290790.1084943.10601965782208052202.stgit@devnote2
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The fprobe is a wrapper API for ftrace function tracer.
Unlike kprobes, this probes only supports the function entry, but this
can probe multiple functions by one fprobe. The usage is similar, user
will set their callback to fprobe::entry_handler and call
register_fprobe*() with probed functions.
There are 3 registration interfaces,
- register_fprobe() takes filtering patterns of the functin names.
- register_fprobe_ips() takes an array of ftrace-location addresses.
- register_fprobe_syms() takes an array of function names.
The registered fprobes can be unregistered with unregister_fprobe().
e.g.
struct fprobe fp = { .entry_handler = user_handler };
const char *targets[] = { "func1", "func2", "func3"};
...
ret = register_fprobe_syms(&fp, targets, ARRAY_SIZE(targets));
...
unregister_fprobe(&fp);
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Tested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/164735283857.1084943.1154436951479395551.stgit@devnote2
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