Re: [PATCH v1] perf record: Refactor ARM64 leaf caller setup out of arch

[James Clark <james.clark@linaro.org>]

On 07/05/2026 6:06 pm, Ian Rogers wrote:
> Code in tools/perf/arch causes portability issues/opaqueness and LTO
> issues due to the use of weak symbols. Move the adding of LR to the
> sample_user_regs into arm64-frame-pointer-unwind-support.c conditional
> on EM_HOST == EM_AARCH64 (false on all non-ARM64 builds). This also
> better encapsulates the use of the sampled registers by
> get_leaf_frame_caller_aarch64 and the set up by the new
> add_leaf_frame_caller_opts_aarch64, exposing opportunities for
> possibly sampling PC and SP to help the unwinder.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>   tools/perf/arch/arm64/util/Build                     |  1 -
>   tools/perf/arch/arm64/util/machine.c                 | 12 ------------
>   tools/perf/builtin-record.c                          | 11 +++++------
>   tools/perf/util/arm64-frame-pointer-unwind-support.c |  6 ++++++
>   tools/perf/util/arm64-frame-pointer-unwind-support.h |  2 ++
>   5 files changed, 13 insertions(+), 19 deletions(-)
>   delete mode 100644 tools/perf/arch/arm64/util/machine.c
> 
> diff --git a/tools/perf/arch/arm64/util/Build b/tools/perf/arch/arm64/util/Build
> index 4e06a08d281a..638aa6948ab5 100644
> --- a/tools/perf/arch/arm64/util/Build
> +++ b/tools/perf/arch/arm64/util/Build
> @@ -5,7 +5,6 @@ perf-util-y += ../../arm/util/pmu.o
>   perf-util-y += arm-spe.o
>   perf-util-y += header.o
>   perf-util-y += hisi-ptt.o
> -perf-util-y += machine.o
>   perf-util-y += mem-events.o
>   perf-util-y += pmu.o
>   perf-util-y += tsc.o
> diff --git a/tools/perf/arch/arm64/util/machine.c b/tools/perf/arch/arm64/util/machine.c
> deleted file mode 100644
> index 80fb13c958d9..000000000000
> --- a/tools/perf/arch/arm64/util/machine.c
> +++ /dev/null
> @@ -1,12 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0
> -
> -#include "callchain.h" // prototype of arch__add_leaf_frame_record_opts
> -#include "perf_regs.h"
> -#include "record.h"
> -
> -#define SMPL_REG_MASK(b) (1ULL << (b))
> -
> -void arch__add_leaf_frame_record_opts(struct record_opts *opts)
> -{
> -	opts->sample_user_regs |= SMPL_REG_MASK(PERF_REG_ARM64_LR);
> -}
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 4a5eba498c02..272bba7f4b9e 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -14,6 +14,7 @@
>   #include "util/parse-events.h"
>   #include "util/config.h"
>   
> +#include "util/arm64-frame-pointer-unwind-support.h"
>   #include "util/callchain.h"
>   #include "util/cgroup.h"
>   #include "util/header.h"
> @@ -3230,10 +3231,6 @@ static int record__parse_off_cpu_thresh(const struct option *opt,
>   	return 0;
>   }
>   
> -void __weak arch__add_leaf_frame_record_opts(struct record_opts *opts __maybe_unused)
> -{
> -}
> -
>   static int parse_control_option(const struct option *opt,
>   				const char *str,
>   				int unset __maybe_unused)
> @@ -4319,8 +4316,10 @@ int cmd_record(int argc, const char **argv)
>   
>   	evlist__warn_user_requested_cpus(rec->evlist, rec->opts.target.cpu_list);
>   
> -	if (callchain_param.enabled && callchain_param.record_mode == CALLCHAIN_FP)
> -		arch__add_leaf_frame_record_opts(&rec->opts);
> +	if (callchain_param.enabled && callchain_param.record_mode == CALLCHAIN_FP) {
> +		if (EM_HOST == EM_AARCH64)
> +			add_leaf_frame_caller_opts_aarch64(&rec->opts);
> +	}
>   
>   	err = -ENOMEM;
>   	if (evlist__create_maps(rec->evlist, &rec->opts.target) < 0) {
> diff --git a/tools/perf/util/arm64-frame-pointer-unwind-support.c b/tools/perf/util/arm64-frame-pointer-unwind-support.c
> index 858ce2b01812..3af8c7a466e0 100644
> --- a/tools/perf/util/arm64-frame-pointer-unwind-support.c
> +++ b/tools/perf/util/arm64-frame-pointer-unwind-support.c
> @@ -2,6 +2,7 @@
>   #include "arm64-frame-pointer-unwind-support.h"
>   #include "callchain.h"
>   #include "event.h"
> +#include "record.h"
>   #include "unwind.h"
>   #include <string.h>
>   
> @@ -16,6 +17,11 @@ struct entries {
>   
>   #define SMPL_REG_MASK(b) (1ULL << (b))
>   
> +void add_leaf_frame_caller_opts_aarch64(struct record_opts *opts)
> +{
> +	opts->sample_user_regs |= SMPL_REG_MASK(PERF_REG_ARM64_LR);
> +}
> +
>   static bool get_leaf_frame_caller_enabled(struct perf_sample *sample)
>   {
>   	struct regs_dump *regs;
> diff --git a/tools/perf/util/arm64-frame-pointer-unwind-support.h b/tools/perf/util/arm64-frame-pointer-unwind-support.h
> index 42d3a45490f5..ba35b295bfcd 100644
> --- a/tools/perf/util/arm64-frame-pointer-unwind-support.h
> +++ b/tools/perf/util/arm64-frame-pointer-unwind-support.h
> @@ -5,8 +5,10 @@
>   #include <linux/types.h>
>   
>   struct perf_sample;
> +struct record_opts;
>   struct thread;
>   
> +void add_leaf_frame_caller_opts_aarch64(struct record_opts *opts);
>   u64 get_leaf_frame_caller_aarch64(struct perf_sample *sample, struct thread *thread, int user_idx);
>   
>   #endif /* __PERF_ARM_FRAME_POINTER_UNWIND_SUPPORT_H */

Reviewed-by: James Clark <james.clark@linaro.org>