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From: Peter Zijlstra <peterz@infradead.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@kernel.org>,
	Oleg Nesterov <oleg@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
	"David S . Miller" <davem@davemloft.net>, X86 ML <x86@kernel.org>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [RFC PATCH 1/1] x86/kprobes: Use int3 instead of debug trap for single-step
Date: Tue, 2 Mar 2021 09:06:47 +0100	[thread overview]
Message-ID: <YD3yF2DnZgzmLlY1@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <161460769556.430263.12936080446789384938.stgit@devnote2>

On Mon, Mar 01, 2021 at 11:08:15PM +0900, Masami Hiramatsu wrote:

> +static void kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs)
> +{
> +	unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
> +
> +	ip += p->ainsn.rel32;
> +	int3_emulate_jmp(regs, ip);
> +}
> +NOKPROBE_SYMBOL(kprobe_emulate_jmp);

Would it make sense to have this be something like:

static void kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs, bool cond)
{
	unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;

	if (cond)
		ip += p->ainsn.rel32;
	int3_emulate_jmp(regs, ip);
}

> +static void kprobe_emulate_jcc(struct kprobe *p, struct pt_regs *regs)
> +{
> +	bool invert = p->ainsn.jcc.type & 1;
> +	bool match;
> +
> +	if (p->ainsn.jcc.type < 0xc) {
> +		match = regs->flags & jcc_mask[p->ainsn.jcc.type >> 1];
> +	} else {
> +		match = ((regs->flags & X86_EFLAGS_SF) >> X86_EFLAGS_SF_BIT) ^
> +			((regs->flags & X86_EFLAGS_OF) >> X86_EFLAGS_OF_BIT);
> +		if (p->ainsn.jcc.type >= 0xe)
> +			match = match && (regs->flags & X86_EFLAGS_ZF);
> +	}
> +	if ((match && !invert) || (!match && invert))
> +		kprobe_emulate_jmp(p, regs);
> +	else
> +		regs->ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;

Then you can do:

	kprobe_emulate_jmp(p, regs, match);

> +}
> +NOKPROBE_SYMBOL(kprobe_emulate_jcc);
> +
> +static void kprobe_emulate_loop(struct kprobe *p, struct pt_regs *regs)
> +{
> +	bool match;
> +
> +	if (p->ainsn.loop.type != 3) {	/* LOOP* */
> +		if (p->ainsn.loop.asize == 32)
> +			match = ((*(u32 *)&regs->cx)--) != 0;
> +#ifdef CONFIG_X86_64
> +		else if (p->ainsn.loop.asize == 64)
> +			match = ((*(u64 *)&regs->cx)--) != 0;
> +#endif
> +		else
> +			match = ((*(u16 *)&regs->cx)--) != 0;
> +	} else {			/* JCXZ */
> +		if (p->ainsn.loop.asize == 32)
> +			match = *(u32 *)(&regs->cx) == 0;
> +#ifdef CONFIG_X86_64
> +		else if (p->ainsn.loop.asize == 64)
> +			match = *(u64 *)(&regs->cx) == 0;
> +#endif
> +		else
> +			match = *(u16 *)(&regs->cx) == 0;
> +	}
> +
> +	if (p->ainsn.loop.type == 0)	/* LOOPNE */
> +		match = match && !(regs->flags & X86_EFLAGS_ZF);
> +	else if (p->ainsn.loop.type == 1)	/* LOOPE */
> +		match = match && (regs->flags & X86_EFLAGS_ZF);
> +
> +	if (match)
> +		kprobe_emulate_jmp(p, regs);
> +	else
> +		regs->ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;

and here.

> +}
> +NOKPROBE_SYMBOL(kprobe_emulate_loop);

  reply	other threads:[~2021-03-02  8:40 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-23 23:24 Why do kprobes and uprobes singlestep? Andy Lutomirski
2021-02-24  1:17 ` Masami Hiramatsu
2021-02-24 19:45   ` Andy Lutomirski
2021-02-25  2:22     ` Masami Hiramatsu
2021-02-25  6:03       ` Andy Lutomirski
2021-02-25  9:11         ` Masami Hiramatsu
2021-03-01 14:08       ` [RFC PATCH 0/1] x86/kprobes: Remoev single-step trap from x86 kprobes Masami Hiramatsu
2021-03-01 14:08         ` [RFC PATCH 1/1] x86/kprobes: Use int3 instead of debug trap for single-step Masami Hiramatsu
2021-03-02  8:06           ` Peter Zijlstra [this message]
2021-03-02  8:38           ` Peter Zijlstra
2021-03-02  8:41           ` Peter Zijlstra
2021-03-02  8:54             ` Peter Zijlstra
2021-03-02 12:51               ` Masami Hiramatsu
2021-03-02 13:58               ` Peter Zijlstra
2021-03-02 15:25       ` [PATCH -tip 0/3] x86/kprobes: Remoev single-step trap from x86 kprobes Masami Hiramatsu
2021-03-02 15:25         ` [PATCH -tip 1/3] x86/kprobes: Retrieve correct opcode for group instruction Masami Hiramatsu
2021-03-23 15:15           ` [tip: x86/core] " tip-bot2 for Masami Hiramatsu
2021-03-02 15:25         ` [PATCH -tip 2/3] x86/kprobes: Identify far indirect JMP correctly Masami Hiramatsu
2021-03-23 15:15           ` [tip: x86/core] " tip-bot2 for Masami Hiramatsu
2021-03-02 15:25         ` [PATCH -tip 3/3] x86/kprobes: Use int3 instead of debug trap for single-step Masami Hiramatsu
2021-03-23 15:15           ` [tip: x86/core] " tip-bot2 for Masami Hiramatsu
2021-03-17 14:55         ` [PATCH -tip 0/3] x86/kprobes: Remoev single-step trap from x86 kprobes Masami Hiramatsu
2021-03-17 16:26           ` Peter Zijlstra
2021-03-17 17:45             ` Andy Lutomirski
2021-02-25  9:59     ` Why do kprobes and uprobes singlestep? Peter Zijlstra
2021-03-01 16:51 ` Oleg Nesterov
2021-03-02  1:36   ` Andy Lutomirski
2021-03-02 20:24     ` Alexei Starovoitov
2021-03-02 21:02       ` Andy Lutomirski
2021-03-03  1:22         ` Alexei Starovoitov
2021-03-03  1:46           ` Andy Lutomirski
2021-03-03  2:18             ` Alexei Starovoitov
2021-03-03 13:27               ` Oleg Nesterov
2021-03-03 18:11               ` Daniel Xu
2021-03-03 19:14                 ` Andy Lutomirski
2021-03-02 20:25     ` Oleg Nesterov
2021-03-02 20:35       ` Andy Lutomirski
2021-03-02 20:28     ` Oleg Nesterov
2021-03-02  2:22   ` Masami Hiramatsu
2021-03-02  2:48     ` Andy Lutomirski
2021-03-02 20:31     ` Oleg Nesterov

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