linux-kernel - [PATCH 6/8] perf libunwind: arm64 pointer authentication

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Message-Id: <20220704145333.22557-7-andrew.kilroy@arm.com>
Date:   Mon,  4 Jul 2022 15:53:30 +0100
From:   Andrew Kilroy <andrew.kilroy@....com>
To:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        acme@...nel.org
Cc:     Andrew Kilroy <andrew.kilroy@....com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Tom Rix <trix@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, llvm@...ts.linux.dev
Subject: [PATCH 6/8] perf libunwind: arm64 pointer authentication

Make use of new changes in libunwind to decode a pointer which has a
pointer authentication code (PAC) in it.

Before this patch, perf is not able to produce stack traces where the
instruction addresses had PACs in them.

This commit has a dependency on a libunwind pull request:

  https://github.com/libunwind/libunwind/pull/360

Signed-off-by: Andrew Kilroy <andrew.kilroy@....com>
---
 tools/perf/util/unwind-libunwind-local.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tools/perf/util/unwind-libunwind-local.c b/tools/perf/util/unwind-libunwind-local.c
index 6e5b8cce47bf..6983a3e76a71 100644
--- a/tools/perf/util/unwind-libunwind-local.c
+++ b/tools/perf/util/unwind-libunwind-local.c
@@ -652,6 +652,15 @@ static void display_error(int err)
 	}
 }
 
+#ifndef NO_LIBUNWIND_ARM64_PTRAUTH
+static unw_word_t get_insn_mask(unw_addr_space_t addr_space __maybe_unused, void *unwind_info_ptr)
+{
+	struct unwind_info *ui = unwind_info_ptr;
+	unw_word_t mask = ui->sample->ptrauth.insn_mask;
+	return mask;
+}
+#endif
+
 static unw_accessors_t accessors = {
 	.find_proc_info		= find_proc_info,
 	.put_unwind_info	= put_unwind_info,
@@ -661,6 +670,9 @@ static unw_accessors_t accessors = {
 	.access_fpreg		= access_fpreg,
 	.resume			= resume,
 	.get_proc_name		= get_proc_name,
+#ifndef NO_LIBUNWIND_ARM64_PTRAUTH
+	.ptrauth_insn_mask	= get_insn_mask,
+#endif
 };
 
 static int _unwind__prepare_access(struct maps *maps)
-- 
2.17.1