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From: Leo Yan <leo.yan@linaro.org>
To: Arnaldo Carvalho de Melo <acme@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Ingo Molnar <mingo@redhat.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Will Deacon <will@kernel.org>,
	Russell King <linux@armlinux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Mathieu Poirier <mathieu.poirier@linaro.org>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Mike Leach <mike.leach@linaro.org>,
	John Garry <john.garry@huawei.com>,
	Andi Kleen <ak@linux.intel.com>,
	Riccardo Mancini <rickyman7@gmail.com>,
	Jin Yao <yao.jin@linux.intel.com>,
	Li Huafei <lihuafei1@huawei.com>,
	coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org,
	linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Leo Yan <leo.yan@linaro.org>
Subject: [PATCH v1 3/3] perf auxtrace arm: Support compat_auxtrace_mmap__{read_head|write_tail}
Date: Mon,  9 Aug 2021 19:27:27 +0800	[thread overview]
Message-ID: <20210809112727.596876-4-leo.yan@linaro.org> (raw)
In-Reply-To: <20210809112727.596876-1-leo.yan@linaro.org>

When the tool runs with compat mode on Arm platform, the kernel is in
64-bit mode and user space is in 32-bit mode; the user space can use
instructions "ldrd" and "strd" for 64-bit value atomicity.

This patch adds compat_auxtrace_mmap__{read_head|write_tail} for arm
building, it uses "ldrd" and "strd" instructions to ensure accessing
atomicity for aux head and tail.  The file arch/arm/util/auxtrace.c is
built for arm and arm64 building, these two functions are not needed for
arm64, so check the compiler macro "__arm__" to only include them for
arm building.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
 tools/perf/arch/arm/util/auxtrace.c | 32 +++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/tools/perf/arch/arm/util/auxtrace.c b/tools/perf/arch/arm/util/auxtrace.c
index b187bddbd01a..c7c7ec0812d5 100644
--- a/tools/perf/arch/arm/util/auxtrace.c
+++ b/tools/perf/arch/arm/util/auxtrace.c
@@ -107,3 +107,35 @@ struct auxtrace_record
 	*err = 0;
 	return NULL;
 }
+
+#if defined(__arm__)
+u64 compat_auxtrace_mmap__read_head(struct auxtrace_mmap *mm)
+{
+	struct perf_event_mmap_page *pc = mm->userpg;
+	u64 result;
+
+	__asm__ __volatile__(
+"	ldrd    %0, %H0, [%1]"
+	: "=&r" (result)
+	: "r" (&pc->aux_head), "Qo" (pc->aux_head)
+	);
+
+	return result;
+}
+
+int compat_auxtrace_mmap__write_tail(struct auxtrace_mmap *mm, u64 tail)
+{
+	struct perf_event_mmap_page *pc = mm->userpg;
+
+	/* Ensure all reads are done before we write the tail out */
+	smp_mb();
+
+	__asm__ __volatile__(
+"	strd    %2, %H2, [%1]"
+	: "=Qo" (pc->aux_tail)
+	: "r" (&pc->aux_tail), "r" (tail)
+	);
+
+	return 0;
+}
+#endif
-- 
2.25.1


  parent reply	other threads:[~2021-08-09 11:27 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-09 11:27 [PATCH v1 0/3] perf: Support compat mode for AUX ring buffer Leo Yan
2021-08-09 11:27 ` [PATCH v1 1/3] perf env: Track kernel 64-bit mode in environment Leo Yan
2021-08-09 20:11   ` Arnaldo Carvalho de Melo
2021-08-09 11:27 ` [PATCH v1 2/3] perf auxtrace: Add compat_auxtrace_mmap__{read_head|write_tail} Leo Yan
2021-08-09 20:12   ` Arnaldo Carvalho de Melo
2021-08-12  9:23   ` Adrian Hunter
2021-08-13 16:22   ` James Clark
2021-08-23  9:51     ` Leo Yan
2021-08-23 10:57       ` James Clark
2021-08-23 12:13         ` Leo Yan
2021-08-23 16:00           ` James Clark
2021-08-24  2:13             ` Leo Yan
2021-08-09 11:27 ` Leo Yan [this message]
2021-08-23 12:23   ` [PATCH v1 3/3] perf auxtrace arm: Support compat_auxtrace_mmap__{read_head|write_tail} James Clark
2021-08-23 13:30     ` Leo Yan
2021-08-23 13:39       ` Russell King (Oracle)
2021-08-23 14:54         ` Leo Yan

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