Re: [PATCH v5 08/26] perf annotate: Adapt arch__dwarf_regnum() for arm64

[Namhyung Kim <namhyung@kernel.org>]

On Tue, Sep 08, 2026 at 01:05:11PM +0000, Tengda Wu wrote:
> Currently, arch__dwarf_regnum() assumes that all architectures use a
> register prefix character (e.g., '%' for x86) defined by
> arch->objdump.register_char, and uses it to match register names in
> objdump output. However, this assumption does not hold for arm64,
> where assembly syntax uses bare register names like 'x0', 'w1'
> without any prefix.
> 
> As a result, arm64 builds may fail to correctly recognize register
> names from objdump disassembly, leading to incomplete or incorrect
> annotation output.
> 
> To address this:
> 
> - Make the register prefix check optional, allowing architectures
>   without a prefix character to be parsed correctly.
> 
> - Extend the delimiter set in strpbrk() to include the closing square
>   bracket ']'. In arm64 assembly, memory operands often use bracketed
>   syntax such as '[x1, #16]' or '[x2]'. Adding ']' ensures clean
>   extraction of register names like 'x2' without trailing characters.
> 
> Signed-off-by: Tengda Wu <wutengda@huaweicloud.com>

Reviewed-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung

> ---
>  tools/perf/util/annotate.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
> index a3d48cf88dad..710a67980cea 100644
> --- a/tools/perf/util/annotate.c
> +++ b/tools/perf/util/annotate.c
> @@ -2474,19 +2474,21 @@ int annotate_check_args(void)
>  
>  int arch__dwarf_regnum(const struct arch *arch, const char *str)
>  {
> -	const char *p;
> +	const char *p = str;
>  	char *regname, *q;
>  	int reg;
>  
> -	p = strchr(str, arch->objdump.register_char);
> -	if (p == NULL)
> -		return -1;
> +	if (arch->objdump.register_char) {
> +		p = strchr(str, arch->objdump.register_char);
> +		if (p == NULL)
> +			return -1;
> +	}
>  
>  	regname = strdup(p);
>  	if (regname == NULL)
>  		return -1;
>  
> -	q = strpbrk(regname, ",) ");
> +	q = strpbrk(regname, ",)] ");
>  	if (q)
>  		*q = '\0';
>  
> -- 
> 2.34.1
>