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Message-ID: <CAEr6+EC2wPAtK8zb3=e1mUiya3gv0UhqF9J_ySYx9p_96pB+tg@mail.gmail.com>
Date: Sat, 10 Dec 2022 21:54:34 +0800
From: Jeff Xie <xiehuan09@...il.com>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: Tiezhu Yang <yangtiezhu@...ngson.cn>,
WANG Xuerui <kernel@...0n.name>,
Masami Hiramatsu <mhiramat@...nel.org>,
loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 0/4] Add kprobe and kretprobe support for LoongArch
On Fri, Dec 9, 2022 at 6:01 PM Huacai Chen <chenhuacai@...nel.org> wrote:
>
> Hi, Masami,
>
> This series looks good to me now, but I'm not familiar with kprobes.
> So, if you have any comments, please let me know.
>
> And Jeff,
>
> As we all know, you are an expert in this domain, so could you please
> help me to test this series?
>
> If there are no objections, I plan to merge this series in a few days.
> But since the next merge window will be open soon, if there are any
> problems, I will revert the patches to wait for the next cycle.
I can't use the kprobe function normally now, tested the function from
the branch: https://github.com/loongson/linux/commits/loongarch-next
steps:
1. Try to probe __memset_fast()
[root@...ngarch ]# cat /proc/kallsyms | grep __memset_fast
90000000012c75f0 T __memset_fast
./samples/kprobes/kprobe_example.c
static char symbol[KSYM_NAME_LEN] = "__memset_fast";
2. Loading the kprobe_example.ko
[root@...ngarch mnt]# insmod ./kprobe_example.ko
*** The system will keep hanging ***
dmesg-messages:
gef➤ lx-dmesg
[ 12.348047] handler_pre: <__memset_fast> p->addr =
0x(____ptrval____), era = 0x90000000012c75f0, estat = 0xc0000
[ 12.348512] handler_post: <__memset_fast> p->addr =
0x(____ptrval____), estat = 0xc0000
[ 12.348525] handler_post: <__memset_fast> p->addr =
0x(____ptrval____), estat = 0xc0000
[ 12.349248] handler_pre: <__memset_fast> p->addr =
0x(____ptrval____), era = 0x90000000012c75f0, estat = 0xc0000
[ 12.349259] handler_post: <__memset_fast> p->addr =
0x(____ptrval____), estat = 0xc0000
call trace:
gef➤ bt
#0 0x90000000012f45f8 in queued_spin_lock_slowpath
(lock=0x9000000001cc0018 <die_lock>, val=0x1) at
kernel/locking/qspinlock.c:383
#1 0x9000000000223b2c in die (str=str@...ry=0x90000000017e3488 "Break
instruction in kernel code", regs=regs@...ry=0x900000010fd735f0) at
arch/loongarch/kernel/traps.c:240
#2 0x90000000012e3968 in die_if_kernel (regs=<optimized out>,
str=<optimized out>) at ./arch/loongarch/include/asm/ptrace.h:131
#3 do_bp (regs=0x900000010fd735f0) at arch/loongarch/kernel/traps.c:485
#4 0x9000000001cb1924 in exception_handlers ()
Backtrace stopped: frame did not save the PC
> Thanks,
> Huacai
>
> On Fri, Dec 9, 2022 at 4:53 PM Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:
> >
> > v10:
> > -- Remove sign_extend() based on the latest code
> > -- Rename insns_are_not_supported() to insns_not_supported()
> > -- Rename insns_are_not_simulated() to insns_not_simulated()
> > -- Set KPROBE_HIT_SSDONE if cur->post_handler is not NULL
> > -- Enable preemption for KPROBE_REENTER in kprobe_fault_handler()
> >
> > v9:
> > -- Rename sign_extended() to sign_extend()
> > -- Modify kprobe_fault_handler() to handle all of kprobe_status
> >
> > v8:
> > -- Put "regs->csr_prmd &= ~CSR_PRMD_PIE;" ahead to save one line
> > -- Add code comment of preempt_disable()
> > -- Put kprobe_page_fault() in __do_page_fault()
> > -- Modify the check condition of break insn in kprobe_breakpoint_handler()
> >
> > v7:
> > -- Remove stop_machine_cpuslocked() related code
> >
> > v6:
> > -- Add a new patch to redefine larch_insn_patch_text() with
> > stop_machine_cpuslocked()
> > -- Modify kprobe_breakpoint_handler() to consider the original
> > insn is break and return the correct value
> > -- Modify do_bp() to refresh bcode when original insn is break
> >
> > v5:
> > -- Rebase on the latest code
> > -- Use stop_machine_cpuslocked() to modify insn to avoid CPU race
> >
> > v4:
> > -- Remove kprobe_exceptions_notify() in kprobes.c
> > -- Call kprobe_breakpoint_handler() and kprobe_singlestep_handler()
> > in do_bp()
> >
> > v3:
> > -- Rebase on the latest code
> > -- Check the alignment of PC in simu_branch() and simu_pc()
> > -- Add ibar in flush_insn_slot()
> > -- Rename kprobe_{pre,post}_handler() to {post_}kprobe_handler
> > -- Add preempt_disable() and preempt_enable_no_resched()
> > -- Remove r0 save/restore and do some minor changes
> > in kprobes_trampoline.S
> > -- Do not enable CONFIG_KPROBES by default
> >
> > v2:
> > -- Split simu_branch() and simu_pc() into a single patch
> > -- Call kprobe_page_fault() in do_page_fault()
> > -- Add kprobes_trampoline.S for kretprobe
> >
> > Tiezhu Yang (4):
> > LoongArch: Simulate branch and PC instructions
> > LoongArch: Add kprobe support
> > LoongArch: Add kretprobe support
> > samples/kprobes: Add LoongArch support
> >
> > arch/loongarch/Kconfig | 2 +
> > arch/loongarch/include/asm/inst.h | 20 ++
> > arch/loongarch/include/asm/kprobes.h | 59 +++++
> > arch/loongarch/include/asm/ptrace.h | 1 +
> > arch/loongarch/kernel/Makefile | 2 +
> > arch/loongarch/kernel/inst.c | 123 ++++++++++
> > arch/loongarch/kernel/kprobes.c | 364 +++++++++++++++++++++++++++++
> > arch/loongarch/kernel/kprobes_trampoline.S | 96 ++++++++
> > arch/loongarch/kernel/traps.c | 13 +-
> > arch/loongarch/mm/fault.c | 3 +
> > samples/kprobes/kprobe_example.c | 8 +
> > 11 files changed, 687 insertions(+), 4 deletions(-)
> > create mode 100644 arch/loongarch/include/asm/kprobes.h
> > create mode 100644 arch/loongarch/kernel/kprobes.c
> > create mode 100644 arch/loongarch/kernel/kprobes_trampoline.S
> >
> > --
> > 2.1.0
> >
--
Thanks,
JeffXie
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