Re: [PATCH v2 2/4] perf tools: Use dynamic register set for Dwarf unwind

On 17/05/2022 12:03, Leo Yan wrote:

On Tue, May 17, 2022 at 11:20:03AM +0100, James Clark wrote:

quoted

Architectures can detect availability of extra registers at
runtime so use this more complete set for unwinding. This
will include the VG register on arm64 in a later commit.

If the function isn't implemented then PERF_REGS_MASK is
returned and there is no change.

Signed-off-by: James Clark <redacted>

This patch looks good to me:
Reviewed-by: Leo Yan <redacted>

Just curious, do you think should update the test (e.g.
arch/arm64/tests/dwarf-unwind.c) to use arch__user_reg_mask()?

I don't think so because the normal set of registers is manually
loaded in tools/perf/arch/arm64/tests/regs_load.S so it wouldn't
include this pseudo register. Also there is no SVE in the call
chain of the test so it would never have an effect.

I could add a new test for SVE, but it depends on getting the
libunwind changes through first so will have to come later.

Thanks,
James

Thanks,
Leo

quoted

---
 tools/perf/util/evsel.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 5fd7924f8eb3..787bbcbcd2ae 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c

@@ -896,7 +896,7 @@ static void __evsel__config_callchain(struct evsel *evsel, struct record_opts *o
 					   "specifying a subset with --user-regs may render DWARF unwinding unreliable, "
 					   "so the minimal registers set (IP, SP) is explicitly forced.\n");
 			} else {
-				attr->sample_regs_user |= PERF_REGS_MASK;
+				attr->sample_regs_user |= arch__user_reg_mask();
 			}
 			attr->sample_stack_user = param->dump_size;
 			attr->exclude_callchain_user = 1;

-- 
2.28.0

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