csky/kprobe: reclaim insn_slot on kprobe unregistration

On kprobe registration kernel allocate one insn_slot for new kprobe,
but it forget to reclaim the insn_slot on unregistration, leading to a
potential leakage.

Reported-by: Chen Guokai <chenguokai17@mails.ucas.ac.cn>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Liao Chang <liaochang1@huawei.com>
Signed-off-by: Guo Ren <guoren@kernel.org>

csky: patch_text: Fixup last cpu should be master

These patch_text implementations are using stop_machine_cpuslocked
infrastructure with atomic cpu_count. The original idea: When the
master CPU patch_text, the others should wait for it. But current
implementation is using the first CPU as master, which couldn't
guarantee the remaining CPUs are waiting. This patch changes the
last CPU as the master to solve the potential risk.

Fixes: 33e53ae1ce41 ("csky: Add kprobes supported")
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: <stable@vger.kernel.org>

kprobes: treewide: Make it harder to refer kretprobe_trampoline directly

Since now there is kretprobe_trampoline_addr() for referring the
address of kretprobe trampoline code, we don't need to access
kretprobe_trampoline directly.

Make it harder to refer by renaming it to __kretprobe_trampoline().

Link: https://lkml.kernel.org/r/163163045446.489837.14510577516938803097.stgit@devnote2

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler()

The __kretprobe_trampoline_handler() callback, called from low level
arch kprobes methods, has the 'trampoline_address' parameter, which is
entirely superfluous as it basically just replicates:

dereference_kernel_function_descriptor(kretprobe_trampoline)

In fact we had bugs in arch code where it wasn't replicated correctly.

So remove this superfluous parameter and use kretprobe_trampoline_addr()
instead.

Link: https://lkml.kernel.org/r/163163044546.489837.13505751885476015002.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kprobes: treewide: Cleanup the error messages for kprobes

This clean up the error/notification messages in kprobes related code.
Basically this defines 'pr_fmt()' macros for each files and update
the messages which describes

- what happened,
- what is the kernel going to do or not do,
- is the kernel fine,
- what can the user do about it.

Also, if the message is not needed (e.g. the function returns unique
error code, or other error message is already shown.) remove it,
and replace the message with WARN_*() macros if suitable.

Link: https://lkml.kernel.org/r/163163036568.489837.14085396178727185469.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

arch/csky/kernel/probes/kprobes.c: fix bugon.cocci warnings

Use BUG_ON instead of a if condition followed by BUG.

Generated by: scripts/coccinelle/misc/bugon.cocci

Link: https://lkml.kernel.org/r/alpine.DEB.2.22.394.2107061049150.7197@hadrien
Fixes: 7d37cb2c912d ("lib: fix kconfig dependency on ARCH_WANT_FRAME_POINTERS")
Signed-off-by: kernel test robot <lkp@intel.com>
Signed-off-by: Julia Lawall <julia.lawall@inria.fr>
Reported-by: kernel test robot <lkp@intel.com>
Cc: Julian Braha <julianbraha@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kprobes: Do not increment probe miss count in the fault handler

Kprobes has a counter 'nmissed', that is used to count the number of
times a probe handler was not called. This generally happens when we hit
a kprobe while handling another kprobe.

However, if one of the probe handlers causes a fault, we are currently
incrementing 'nmissed'. The comment in fault handler indicates that this
can be used to account faults taken by the probe handlers. But, this has
never been the intention as is evident from the comment above 'nmissed'
in 'struct kprobe':

/*count the number of times this probe was temporarily disarmed */
unsigned long nmissed;

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lkml.kernel.org/r/20210601120150.672652-1-naveen.n.rao@linux.vnet.ibm.com

kprobes: Remove kprobe::fault_handler

The reason for kprobe::fault_handler(), as given by their comment:

* We come here because instructions in the pre/post
* handler caused the page_fault, this could happen
* if handler tries to access user space by
* copy_from_user(), get_user() etc. Let the
* user-specified handler try to fix it first.

Is just plain bad. Those other handlers are ran from non-preemptible
context and had better use _nofault() functions. Also, there is no
upstream usage of this.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20210525073213.561116662@infradead.org

csky: kprobes: Use generic kretprobe trampoline handler

Use the generic kretprobe trampoline handler. Don't use
framepointer verification.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Guo Ren <guoren@kernel.org>
Link: https://lore.kernel.org/r/159870605775.1229682.2627276871589951304.stgit@devnote2

csky: Add kprobes supported

This patch enable kprobes, kretprobes, ftrace interface. It utilized
software breakpoint and single step debug exceptions, instructions
simulation on csky.

We use USR_BKPT replace origin instruction, and the kprobe handler
prepares an excutable memory slot for out-of-line execution with a
copy of the original instruction being probed. Most of instructions
could be executed by single-step, but some instructions need origin
pc value to execute and we need software simulate these instructions.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>