linux-kernel - Re: [PATCH v7] arm64: kprobe: Enable OPTPROBE for arm64

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Message-ID: <eea41388-cdee-492c-b636-3aa3341bf0a7@huawei.com>
Date: Thu, 10 Apr 2025 11:54:51 +0800
From: Qinxin Xia <xiaqinxin@...wei.com>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>, Mark Rutland
	<mark.rutland@....com>
CC: <yangyicong@...wei.com>, <catalin.marinas@....com>, <will@...nel.org>,
	<naveen.n.rao@...ux.ibm.com>, <anil.s.keshavamurthy@...el.com>,
	<davem@...emloft.net>, <linuxarm@...wei.com>, <linux-kernel@...r.kernel.org>,
	<fanghao11@...wei.com>, <prime.zeng@...ilicon.com>, <xuwei5@...wei.com>,
	<jonathan.cameron@...wei.com>
Subject: Re: [PATCH v7] arm64: kprobe: Enable OPTPROBE for arm64


在 2025/4/4 7:34, Masami Hiramatsu (Google) 写道:
> On Sun, 16 Feb 2025 15:00:44 +0800
> Qinxin Xia <xiaqinxin@...wei.com> wrote:
>
>> +#define        OPT_SLOT_SIZE   65536
>> +
>> +	.global optinsn_slot
>> +optinsn_slot:
>> +	.space  OPT_SLOT_SIZE
>> +
>> +SYM_CODE_START(optprobe_common)
>> +	stp x2, x3, [sp, #S_X2]
>> +	stp x4, x5, [sp, #S_X4]
>> +	stp x6, x7, [sp, #S_X6]
>> +	stp x8, x9, [sp, #S_X8]
>> +	stp x10, x11, [sp, #S_X10]
>> +	stp x12, x13, [sp, #S_X12]
>> +	stp x14, x15, [sp, #S_X14]
>> +	stp x16, x17, [sp, #S_X16]
>> +	stp x18, x19, [sp, #S_X18]
>> +	stp x20, x21, [sp, #S_X20]
>> +	stp x22, x23, [sp, #S_X22]
>> +	stp x24, x25, [sp, #S_X24]
>> +	stp x26, x27, [sp, #S_X26]
>> +	stp x28, x29, [sp, #S_X28]
>> +	add x2, sp, #PT_REGS_SIZE
>> +	str x2, [sp, #S_SP]
>> +	/* Construct a useful saved PSTATE */
>> +	mrs x2, nzcv
>> +	mrs x3, daif
>> +	orr x2, x2, x3
>> +	mrs x3, CurrentEL
>> +	orr x2, x2, x3
>> +	mrs x3, SPSel
>> +	orr x2, x2, x3
>> +	adr x1, 2f
>> +	stp x1, x2, [sp, #S_PC]
>> +
>> +	/* set the pt_regs address to x1 */
>> +	mov x1, sp
>> +	/* store lr of optprobe_common temporary */
>> +	stp x29, x30, [sp, #-16]!
>> +	mov x29, sp
>> +
>> +	bl optprobe_optimized_callback
>> +
>> +	ldp x29, x30, [sp], #16
>> +
>> +	ldr x0, [sp, #S_PSTATE]
>> +	and x0, x0, #(PSR_N_BIT | PSR_Z_BIT | PSR_C_BIT | PSR_V_BIT)
>> +	msr nzcv, x0
> BTW, can this code save all registers including flags?
> Previously I talked with Mark and he mentioned there is no way to
> save pstate register correctly. That is why we could not implement
> this feature.
>
>
> Thank you,
>
Hello,

Same way to save regs with kprobe trampoline,

you can see in arch/arm64/kernel/probes/kprobes_trampoline.S

Thank you.