[PATCH v2 01/14] perf sample: Allow decoders to supply branch return addresses
Adrian Hunter
adrian.hunter at intel.com
Thu Sep 24 06:00:39 PDT 2026
On 23/09/2026 18:21, Leo Yan wrote:
> The thread stack derives return addresses from IP + insn_len. For an
> interrupt or fault, the return address can instead be the sample IP even
> when instruction bytes at that address are available.
>
> Add ret_addr to perf_sample and prefer it in thread_stack__trace_end()
> and thread_stack__process() when supplied. Initialize it to zero so other
> samples retain the IP + insn_len calculation.
>
> Add a regression test for explicit exception return addresses and the
> ordinary call fallback when the return address is zero.
>
> Assisted-by: Codex:gpt-6
> Signed-off-by: Leo Yan <leo.yan at arm.com>
Reviewed-by: Adrian Hunter <adrian.hunter at intel.com>
> ---
> tools/perf/tests/Build | 1 +
> tools/perf/tests/builtin-test.c | 1 +
> tools/perf/tests/tests.h | 1 +
> tools/perf/tests/thread-stack.c | 106 ++++++++++++++++++++++++++++++++++++++++
> tools/perf/util/sample.c | 1 +
> tools/perf/util/sample.h | 5 ++
> tools/perf/util/thread-stack.c | 5 +-
> 7 files changed, 118 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/tests/Build b/tools/perf/tests/Build
> index 81c311b131b72715f11b6501511a18dce2af07df..d03ae938dd0ad92f78f8de6900ce7161f39fc3bc 100644
> --- a/tools/perf/tests/Build
> +++ b/tools/perf/tests/Build
> @@ -29,6 +29,7 @@ perf-test-y += task-exit.o
> perf-test-y += sw-clock.o
> perf-test-y += mmap-thread-lookup.o
> perf-test-y += thread-maps-share.o
> +perf-test-y += thread-stack.o
> perf-test-$(CONFIG_LIBTRACEEVENT) += switch-tracking.o
> perf-test-y += keep-tracking.o
> perf-test-y += code-reading.o
> diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
> index d2f594921e25bda9fc662e7ba82464bfef1b752b..6259ed805c5f75799d52ac742b77cf278f98bd9d 100644
> --- a/tools/perf/tests/builtin-test.c
> +++ b/tools/perf/tests/builtin-test.c
> @@ -112,6 +112,7 @@ static struct test_suite *generic_tests[] = {
> &suite__hists_filter,
> &suite__mmap_thread_lookup,
> &suite__thread_maps_share,
> + &suite__thread_stack,
> &suite__hists_output,
> &suite__hists_cumulate,
> #ifdef HAVE_LIBTRACEEVENT
> diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h
> index 9c96f33483d1435644da6068c3802f7a914a9de0..b2520a564417b61718f1dcb23da1f8cc0f601906 100644
> --- a/tools/perf/tests/tests.h
> +++ b/tools/perf/tests/tests.h
> @@ -138,6 +138,7 @@ DECLARE_SUITE(expr);
> DECLARE_SUITE(hists_filter);
> DECLARE_SUITE(mmap_thread_lookup);
> DECLARE_SUITE(thread_maps_share);
> +DECLARE_SUITE(thread_stack);
> DECLARE_SUITE(hists_output);
> DECLARE_SUITE(hists_cumulate);
> DECLARE_SUITE(switch_tracking);
> diff --git a/tools/perf/tests/thread-stack.c b/tools/perf/tests/thread-stack.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..0239e3bee34faf8fd4ddc7b723cf479609760064
> --- /dev/null
> +++ b/tools/perf/tests/thread-stack.c
> @@ -0,0 +1,106 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/kernel.h>
> +#include <unistd.h>
> +#include "tests.h"
> +#include "util/addr_location.h"
> +#include "util/event.h"
> +#include "util/sample.h"
> +#include "util/thread.h"
> +#include "util/thread-stack.h"
> +
> +#define CALL_REF 1234UL
> +#define RET_REF 5678UL
> +
> +struct return_check {
> + unsigned int matched;
> + unsigned int unmatched;
> +};
> +
> +static int check_call_return(struct call_return *cr,
> + u64 *parent_db_id __maybe_unused, void *data)
> +{
> + struct return_check *check = data;
> +
> + if (cr->call_ref == CALL_REF && cr->return_ref == RET_REF && !cr->flags)
> + check->matched++;
> + else
> + check->unmatched++;
> +
> + return 0;
> +}
> +
> +/* A zero expected_ret_addr asks the stack to use ip + insn_len. */
> +static int check_return_address(u64 expected_ret_addr, u64 actual_ret_addr,
> + u32 flags)
> +{
> + struct call_return_processor *crp;
> + struct return_check check = { };
> + struct thread *thread;
> + struct addr_location from = { }, to = { };
> + struct perf_sample sample = { };
> + int ret = TEST_FAIL;
> +
> + thread = thread__new(getpid(), getpid());
> + if (!thread)
> + return TEST_FAIL;
> +
> + crp = call_return_processor__new(check_call_return, &check);
> + if (!crp)
> + goto out;
> +
> + sample.ip = 0x1000; /* Call or exception source addr */
> + sample.addr = 0x2000; /* Callee or exception handler addr */
> + sample.ret_addr = expected_ret_addr;
> + sample.flags = PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_CALL | flags;
> + sample.time = 1;
> + /* Model the opcode length after an instruction fetch. */
> + sample.insn_len = 4;
> + if (thread_stack__process(thread, thread__comm(thread), &sample,
> + &from, &to, CALL_REF, crp))
> + goto out;
> +
> + sample.ip = 0x2000; /* Return instruction addr */
> + sample.addr = actual_ret_addr; /* Return branch target addr */
> + sample.ret_addr = 0;
> + sample.flags = PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_RETURN |
> + (flags & (PERF_IP_FLAG_INTERRUPT | PERF_IP_FLAG_SYSCALLRET));
> + sample.time = 2;
> + if (thread_stack__process(thread, thread__comm(thread), &sample,
> + &to, &from, RET_REF, crp))
> + goto out;
> +
> + if (check.matched == 1 && !check.unmatched)
> + ret = TEST_OK;
> +
> +out:
> + thread__put(thread);
> + call_return_processor__free(crp);
> + return ret;
> +}
> +
> +static int test__thread_stack(struct test_suite *test __maybe_unused,
> + int subtest __maybe_unused)
> +{
> + static const struct {
> + const char *name;
> + u64 expected_ret_addr;
> + u64 actual_ret_addr;
> + u32 flags;
> + } cases[] = {
> + { "ordinary call", 0, 0x1004, 0 },
> + { "interrupt", 0x1000, 0x1000, PERF_IP_FLAG_ASYNC | PERF_IP_FLAG_INTERRUPT },
> + { "fault or trap", 0x1000, 0x1000, PERF_IP_FLAG_INTERRUPT },
> + { "SVC", 0x1004, 0x1004, PERF_IP_FLAG_SYSCALLRET },
> + };
> +
> + for (size_t i = 0; i < ARRAY_SIZE(cases); i++) {
> + if (check_return_address(cases[i].expected_ret_addr,
> + cases[i].actual_ret_addr, cases[i].flags)) {
> + pr_debug("Incorrect return address for %s\n", cases[i].name);
> + return TEST_FAIL;
> + }
> + }
> + return TEST_OK;
> +}
> +
> +DEFINE_SUITE("Thread stack return addresses after instruction fetching", thread_stack);
> diff --git a/tools/perf/util/sample.c b/tools/perf/util/sample.c
> index bccc19e2aaf25118a8ecde88473aa6cb16fa561a..4abb689132bc27d0f2318eeafca20f7e57621837 100644
> --- a/tools/perf/util/sample.c
> +++ b/tools/perf/util/sample.c
> @@ -29,6 +29,7 @@ void perf_sample__init(struct perf_sample *sample, bool all)
> sample->intr_regs = NULL;
> sample->merged_callchain = false;
> sample->callchain = NULL;
> + sample->ret_addr = 0;
> }
> }
>
> diff --git a/tools/perf/util/sample.h b/tools/perf/util/sample.h
> index cb4b16654876e9a5c3bfd66be3e0235ac15795e0..865ed18200f1339f5949ef3f185ed57a34aace72 100644
> --- a/tools/perf/util/sample.h
> +++ b/tools/perf/util/sample.h
> @@ -131,6 +131,11 @@ struct perf_sample {
> u64 time;
> /** @addr: The sample event PERF_SAMPLE_ADDR value. */
> u64 addr;
> + /**
> + * @ret_addr: Return address supplied by the decoder for a branch sample.
> + * Zero means use ip + insn_len.
> + */
> + u64 ret_addr;
> /** @id: The sample event PERF_SAMPLE_ID or PERF_SAMPLE_IDENTIFIER value. */
> u64 id;
> /** @stream_id: The sample event PERF_SAMPLE_STREAM_ID value. */
> diff --git a/tools/perf/util/thread-stack.c b/tools/perf/util/thread-stack.c
> index 1360f44421ef8bb80fe5cfdba59be7e6029b0240..d452d1a7eabb16f040ca3dada23e6fdec8fb1088 100644
> --- a/tools/perf/util/thread-stack.c
> +++ b/tools/perf/util/thread-stack.c
> @@ -1030,7 +1030,7 @@ static int thread_stack__trace_end(struct thread_stack *ts,
> cp = call_path__findnew(cpr, ts->stack[ts->cnt - 1].cp, NULL, 0,
> ts->kernel_start);
>
> - ret_addr = sample->ip + sample->insn_len;
> + ret_addr = sample->ret_addr ? sample->ret_addr : sample->ip + sample->insn_len;
>
> return thread_stack__push_cp(ts, ret_addr, sample->time, ref, cp,
> false, true);
> @@ -1154,7 +1154,8 @@ int thread_stack__process(struct thread *thread, struct comm *comm,
> if (!sample->ip || !sample->addr)
> return 0;
>
> - ret_addr = sample->ip + sample->insn_len;
> + /* Opcode fetching must not change a decoder-supplied return address. */
> + ret_addr = sample->ret_addr ? sample->ret_addr : sample->ip + sample->insn_len;
> if (ret_addr == sample->addr)
> return 0; /* Zero-length calls are excluded */
>
>
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