Re: [PATCH v2 12/16] perf annotate-arm64: Support 'mov' instruction tracking

[Namhyung Kim]

On Fri, Apr 03, 2026 at 09:47:56AM +0000, Tengda Wu wrote:
> Extend update_insn_state() for arm64 to handle register-to-register
> 'mov' instructions.
> 
> When a 'mov' instruction occurs between two registers, the data type
> information (DWARF type, kind, and offset) needs to be propagated from
> the source register to the destination register. This ensures that if
> a pointer or a structure was previously identified in one register,
> the tracker continues to recognize it after it is moved.
> 
> A real-world example is shown below:
> 
>   ffff8000803eebf8 <get_vma_policy>:
>   ffff8000803eec20:  mov  x21, x0  // x0 (struct vm_area_struct*) -> x21
>   ffff8000803eec28:  ldr  x2, [x0, #112]
>   ffff8000803eec2c:  cbz  x2, ffff8000803eec94 <get_vma_policy+0x9c>
>   ffff8000803eec94:  ldr  x0, [x21, #152]  // PMU sample
> 
> Before this commit, the type of x21 was unknown, causing the subsequent
> inference to fail:
> 
>   var [0] reg0 offset 0 type='struct vm_area_struct*' size=0x8
>   chk [9c] reg21 offset=0x98 ok=0 kind=0 cfa : no type information
>   final result: no type information
> 
> After this commit, the type of x21 is correctly inferred as 'vm_area_struct':
> 
>   var [0] reg0 offset 0 type='struct vm_area_struct*' size=0x8
>   mov [28] reg0 -> reg21 type='struct vm_area_struct*' size=0x8
>   chk [9c] reg21 offset=0x98 ok=1 kind=1 (struct vm_area_struct*) : Good!
>   found by insn track: 0x98(reg21) type-offset=0x98
>   final result:  type='struct vm_area_struct' size=0xb0
> 
> Signed-off-by: Tengda Wu <wutengda@xxxxxxxxxxxxxxx>
> ---
>  .../perf/util/annotate-arch/annotate-arm64.c  | 28 +++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/tools/perf/util/annotate-arch/annotate-arm64.c b/tools/perf/util/annotate-arch/annotate-arm64.c
> index f9100230c2f6..013b673f4861 100644
> --- a/tools/perf/util/annotate-arch/annotate-arm64.c
> +++ b/tools/perf/util/annotate-arch/annotate-arm64.c
> @@ -308,6 +308,34 @@ static void update_insn_state_arm64(struct type_state *state,
>  	sreg = src->reg1;
>  	dreg = dst->reg1;
>  
> +	/* Register to register transfers */
> +	if (!strcmp(dl->ins.name, "mov")) {
> +		if (!has_reg_type(state, sreg))
> +			return;
> +
> +		tsr = &state->regs[sreg];
> +		tsr->copied_from = -1;
> +
> +		if (!has_reg_type(state, dreg) ||
> +		    !state->regs[dreg].ok) {
> +			tsr->ok = false;
> +			return;
> +		}

Does this handle an immediate value?

> +
> +		tsr->type = state->regs[dreg].type;
> +		tsr->kind = state->regs[dreg].kind;
> +		tsr->offset = state->regs[dreg].offset;
> +		tsr->ok = true;

Probably safe to use 'state->regs[dreg].ok'.

Anyway, the same concern.  The src and dst are reversed.

Thanks,
Namhyung

> +
> +		if (tsr->kind == TSR_KIND_TYPE || tsr->kind == TSR_KIND_POINTER)
> +			tsr->copied_from = dreg;
> +
> +		pr_debug_dtp("mov [%x] reg%d -> reg%d",
> +			     insn_offset, dreg, sreg);
> +		pr_debug_type_name(&tsr->type, tsr->kind);
> +		return;
> +	}
> +
>  	if (dloc->fb_cfa) {
>  		u64 ip = dloc->ms->sym->start + dl->al.offset;
>  		u64 pc = map__rip_2objdump(dloc->ms->map, ip);
> -- 
> 2.34.1
>