Re: [PATCH 1/1 next] perf libunwind: Fixup conversion perf_sample->user_regs to a pointer

[Namhyung Kim <namhyung@kernel.org>]

On Fri, Mar 07, 2025 at 12:34:48PM -0300, Arnaldo Carvalho de Melo wrote:
> From: Arnaldo Carvalho de Melo <acme@redhat.com>
> 
> The dc6d2bc2d893a878 ("perf sample: Make user_regs and intr_regs optional") misses
> the changes to a file, resulting in this problem:
> 
>   $ make LIBUNWIND=1 -C tools/perf O=/tmp/build/perf-tools-next install-bin
>   <SNIP>
>     CC      /tmp/build/perf-tools-next/util/unwind-libunwind-local.o
>     CC      /tmp/build/perf-tools-next/util/unwind-libunwind.o
>   <SNIP>
>   util/unwind-libunwind-local.c: In function ‘access_mem’:
>   util/unwind-libunwind-local.c:582:56: error: ‘ui->sample->user_regs’ is a pointer; did you mean to use ‘->’?
>     582 |         if (__write || !stack || !ui->sample->user_regs.regs) {
>         |                                                        ^
>         |                                                        ->
>   util/unwind-libunwind-local.c:587:38: error: passing argument 2 of ‘perf_reg_value’ from incompatible pointer type [-Wincompatible-pointer-types]
>     587 |         ret = perf_reg_value(&start, &ui->sample->user_regs,
>         |                                      ^~~~~~~~~~~~~~~~~~~~~~
>         |                                      |
>         |                                      struct regs_dump **
> <SNIP>
>   ⬢ [acme@toolbox perf-tools-next]$ git bisect bad
>   dc6d2bc2d893a878e7b58578ff01b4738708deb4 is the first bad commit
>   commit dc6d2bc2d893a878e7b58578ff01b4738708deb4 (HEAD)
>   Author: Ian Rogers <irogers@google.com>
>   Date:   Mon Jan 13 11:43:45 2025 -0800
> 
>       perf sample: Make user_regs and intr_regs optional
> 
> Detected using:
> 
>   make -C tools/perf build-test
> 
> Fixes: dc6d2bc2d893a878 ("perf sample: Make user_regs and intr_regs optional")
> Cc: Adrian Hunter <adrian.hunter@intel.com>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Andi Kleen <ak@linux.intel.com>
> Cc: Charlie Jenkins <charlie@rivosinc.com>
> Cc: Ian Rogers <irogers@google.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: James Clark <james.clark@linaro.org>
> Cc: John Garry <john.g.garry@oracle.com>
> Cc: Kan Liang <kan.liang@linux.intel.com>
> Cc: Leo Yan <leo.yan@linux.dev>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Michael Petlan <mpetlan@redhat.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Tavian Barnes <tavianator@tavianator.com>
> Cc: Veronika Molnarova <vmolnaro@redhat.com>
> Cc: coresight@lists.linaro.org
> Cc: linux-arm-kernel@lists.infradead.org
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> ---
>  tools/perf/util/unwind-libunwind-local.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/perf/util/unwind-libunwind-local.c b/tools/perf/util/unwind-libunwind-local.c
> index 16c2b03831f39afc..cc0e41f2c2f2ef10 100644
> --- a/tools/perf/util/unwind-libunwind-local.c
> +++ b/tools/perf/util/unwind-libunwind-local.c
> @@ -579,12 +579,12 @@ static int access_mem(unw_addr_space_t __maybe_unused as,
>  	int ret;
>  
>  	/* Don't support write, probably not needed. */
> -	if (__write || !stack || !ui->sample->user_regs.regs) {
> +	if (__write || !stack || !ui->sample->user_regs->regs) {

The sample->user_regs can be NULL and I guess it's only allocated when
it has some regs.  Then probably it should be like:

	if (__write || !stack || !ui->sample->user_regs) {


>  		*valp = 0;
>  		return 0;
>  	}
>  
> -	ret = perf_reg_value(&start, &ui->sample->user_regs,
> +	ret = perf_reg_value(&start, perf_sample__user_regs(ui->sample),
>  			     perf_arch_reg_sp(arch));
>  	if (ret)
>  		return ret;
> @@ -628,7 +628,7 @@ static int access_reg(unw_addr_space_t __maybe_unused as,
>  		return 0;
>  	}
>  
> -	if (!ui->sample->user_regs.regs) {
> +	if (!ui->sample->user_regs->regs) {

Ditto.


>  		*valp = 0;
>  		return 0;
>  	}
> @@ -637,7 +637,7 @@ static int access_reg(unw_addr_space_t __maybe_unused as,
>  	if (id < 0)
>  		return -EINVAL;
>  
> -	ret = perf_reg_value(&val, &ui->sample->user_regs, id);
> +	ret = perf_reg_value(&val, perf_sample__user_regs(ui->sample), id);
>  	if (ret) {
>  		if (!ui->best_effort)
>  			pr_err("unwind: can't read reg %d\n", regnum);
> @@ -741,7 +741,7 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
>  	unw_cursor_t c;
>  	int ret, i = 0;
>  
> -	ret = perf_reg_value(&val, &ui->sample->user_regs,
> +	ret = perf_reg_value(&val, perf_sample__user_regs(ui->sample),
>  			     perf_arch_reg_ip(arch));
>  	if (ret)
>  		return ret;
> @@ -808,7 +808,7 @@ static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg,
>  		.best_effort  = best_effort
>  	};
>  
> -	if (!data->user_regs.regs)
> +	if (!data->user_regs->regs)

Ditto.

Thanks,
Namhyung


>  		return -EINVAL;
>  
>  	if (max_stack <= 0)
> -- 
> 2.47.0
>