Re: [PATCH v3 17/21] perf annotate-arm64: Support 'mov' instruction tracking

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Type state corruption due to DWARF register overloading for the stack pointer (`sp`) and zero registers (`xzr`/`wzr`).
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commit 8b77f0fe5f1ec7e9d14eee63f44f48d6c55f7234
Author: Tengda Wu <wutengda@huaweicloud.com>

perf annotate-arm64: Support 'mov' instruction tracking

This commit extends update_insn_state() for arm64 to track register-to-register
and immediate-to-register 'mov' instructions. It propagates data type
information or immediate values to the destination register to improve type
inference.

> diff --git a/tools/perf/util/annotate-arch/annotate-arm64.c b/tools/perf/util/annotate-arch/annotate-arm64.c
> --- a/tools/perf/util/annotate-arch/annotate-arm64.c
> +++ b/tools/perf/util/annotate-arch/annotate-arm64.c

[ ... ]

> +static void update_mov_insn_state(struct type_state *state,
> +				  struct disasm_line *dl,
> +				  struct annotated_op_loc *src,
> +				  struct annotated_op_loc *dst)
> +{

[ ... ]

> +	if (!has_reg_type(state, sreg) || !state->regs[sreg].ok) {
> +		invalidate_reg_state(tsr);
> +		return;
> +	}
> +
> +	tsr->type = state->regs[sreg].type;

[Severity: Medium]
Will this code corrupt the stack pointer's type state if the zero register
(xzr or wzr) is used in a mov instruction?

Looking at tools/perf/util/dwarf-regs-arch/dwarf-regs-arm64.c, the function
__get_dwarf_regnum_arm64() maps sp, wzr, and xzr all to DWARF register 31:

    if (!strcmp(name, "sp") || !strcmp(name, "wzr") || !strcmp(name, "xzr"))
        return 31;

If a zero register is used as a destination (e.g., mov xzr, x0), does its
tracked state overwrite the tracked state of the stack pointer?

Conversely, if a zero register is used as a source (e.g., mov x0, xzr),
does the destination register incorrectly inherit the type of the stack
pointer instead of being treated as a constant 0?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260701035355.752944-1-wutengda@huaweicloud.com?part=17