Re: [PATCH v7] arm64: kprobe: Enable OPTPROBE for arm64

[Qinxin Xia]

在 2025/4/4 7:34, Masami Hiramatsu (Google) 写道:
> On Sun, 16 Feb 2025 15:00:44 +0800
> Qinxin Xia <xiaqinxin@xxxxxxxxxx> 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.