linux-kernel - [PATCH v3 1/1] perf: RISC-V: Limit the number of counters returned from SBI

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Date:   Fri, 5 May 2023 07:20:57 +0000
From:   Viacheslav Mitrofanov <v.v.mitrofanov@...ro.com>
To:     unlisted-recipients:; (no To-header on input)
CC:     <linux@...ro.com>,
        Viacheslav Mitrofanov <v.v.mitrofanov@...ro.com>,
        Andrew Jones <ajones@...tanamicro.com>,
        Atish Patra <atishp@...osinc.com>,
        Atish Patra <atishp@...shpatra.org>,
        Anup Patel <anup@...infault.org>,
        "Will Deacon" <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        <linux-riscv@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH v3 1/1] perf: RISC-V: Limit the number of counters returned from SBI

Perf gets the number of supported counters from SBI. If it happens that
the number of returned counters more than RISCV_MAX_COUNTERS the code
trusts it. It does not lead to an immediate problem but can potentially
lead to it. Prevent getting more than RISCV_MAX_COUNTERS from SBI.

Signed-off-by: Viacheslav Mitrofanov <v.v.mitrofanov@...ro.com>
Reviewed-by: Andrew Jones <ajones@...tanamicro.com>
Reviewed-by: Atish Patra <atishp@...osinc.com>
---
Chnages in v3:
- Detail the output

Changes in v2:
- Add new line
- Substitute pr_warn for pr_info

 drivers/perf/riscv_pmu_sbi.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
index 70cb50fd41c2..7bf494930e92 100644
--- a/drivers/perf/riscv_pmu_sbi.c
+++ b/drivers/perf/riscv_pmu_sbi.c
@@ -868,6 +868,12 @@ static int pmu_sbi_device_probe(struct platform_device *pdev)
 		goto out_free;
 	}
 
+	/* It is possible to get from SBI more than max number of counters */
+	if (num_counters > RISCV_MAX_COUNTERS) {
+		num_counters = RISCV_MAX_COUNTERS;
+		pr_info("SBI returned more than maximum number of counters. Limiting the number of counters to %d\n", num_counters);
+	}
+
 	/* cache all the information about counters now */
 	if (pmu_sbi_get_ctrinfo(num_counters, &cmask))
 		goto out_free;
-- 
2.37.2