Messages in this thread Patch in this message | | | Date | Tue, 19 May 2020 00:14:43 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH 2/4] arm64: Extract kprobes_save_local_irqflag() and kprobes_restore_local_irqflag() |
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On Sat, 16 May 2020 09:17:21 -0700 Doug Anderson <dianders@chromium.org> wrote:
> Hi, > > On Sat, May 16, 2020 at 1:47 AM liwei (GF) <liwei391@huawei.com> wrote: > > > > >> - kprobes_save_local_irqflag(kcb, regs); > > >> + kernel_prepare_single_step(&kcb->saved_irqflag, regs); > > > > > > Is there some reason to have two functions? It seems like every time > > > you call kernel_enable_single_step() you'd want to call > > > kernel_prepare_single_step(). ...and every time you call > > > kernel_disable_single_step() you'd want to call > > > kernel_cleanup_single_step(). > > > > > > Maybe you can just add the flags parameter to > > > kernel_enable_single_step() / kernel_disable_single_step() and put the > > > code in there? > > > > > > > As kernel_enable_single_step() / kernel_disable_single_step() are also called in > > breakpoint_handler() and watchpoint_handler(), i am not sure it's a right thing > > to put the daif flag prepare/cleanup into them, especially we don't have a context > > to save the flags. > > I think you misunderstood what I was suggesting. Maybe better with > examples? I was suggesting doing this: > > kcb->saved_irqflag = kernel_enable_single_step(regs); > ... > kernel_disable_single_step(kcb->saved_irqflag, regs); > > To me that seems better than what you have now: > > kcb->saved_irqflag = kernel_prepare_single_step(regs); > kernel_enable_single_step(regs); > ... > kernel_cleanup_single_step(kcb->saved_irqflag, regs); > kernel_disable_single_step(); > > ...or am I confused?
+1, this sounds good to me. Currently arch/arm64/kernel/probes/kprobes.c has a code which sololy use kernel_disable_single_step() without regs restoring, but it looks like a bug there. So maybe you need following patch.
Thank you,
----- From: Masami Hiramatsu <mhiramat@kernel.org> Date: Mon, 18 May 2020 23:08:28 +0900 Subject: [PATCH] arm64: kprobes: Restore saved interrupt flag before disabling single step
Restore the saved interrupt flag in kprobe_ctlblk to regs->pstate when a page fault happens on single-stepping instruction. Without this fix, we will lose the flag if it happens because kcb->saved_irqflag only knows the previous flag.
Fixes: 2dd0e8d2d2a1 ("arm64: Kprobes with single stepping support") Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Cc: stable@vger.kernel.org --- arch/arm64/kernel/probes/kprobes.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c index d1c95dcf1d78..73fb99770f69 100644 --- a/arch/arm64/kernel/probes/kprobes.c +++ b/arch/arm64/kernel/probes/kprobes.c @@ -308,6 +308,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr) if (!instruction_pointer(regs)) BUG(); + kprobes_restore_local_irqflag(kcb, regs); kernel_disable_single_step(); if (kcb->kprobe_status == KPROBE_REENTER) -- 2.25.1
-- Masami Hiramatsu <mhiramat@kernel.org>
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