linux-kernel - [PATCH] drivers: perf: ctr_get_width function for legacy is not defined

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Message-ID: <20231127095403.272424-1-vadim.shakirov@syntacore.com>
Date:   Mon, 27 Nov 2023 12:54:03 +0300
From:   Vadim Shakirov <vadim.shakirov@...tacore.com>
To:     Atish Patra <atishp@...shpatra.org>
CC:     Vadim Shakirov <vadim.shakirov@...tacore.com>,
        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>,
        "Alexandre Ghiti" <alexghiti@...osinc.com>,
        Andrew Jones <ajones@...tanamicro.com>,
        <linux-riscv@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] drivers: perf: ctr_get_width function for legacy is not defined

With parameters CONFIG_RISCV_PMU_LEGACY=y and CONFIG_RISCV_PMU_SBI=n
linux kernel crashes when you try perf record:

$ perf record ls
[   46.749286] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[   46.750199] Oops [#1]
[   46.750342] Modules linked in:
[   46.750608] CPU: 0 PID: 107 Comm: perf-exec Not tainted 6.6.0 #2
[   46.750906] Hardware name: riscv-virtio,qemu (DT)
[   46.751184] epc : 0x0
[   46.751430]  ra : arch_perf_update_userpage+0x54/0x13e
[   46.751680] epc : 0000000000000000 ra : ffffffff8072ee52 sp : ff2000000022b8f0
[   46.751958]  gp : ffffffff81505988 tp : ff6000000290d400 t0 : ff2000000022b9c0
[   46.752229]  t1 : 0000000000000001 t2 : 0000000000000003 s0 : ff2000000022b930
[   46.752451]  s1 : ff600000028fb000 a0 : 0000000000000000 a1 : ff600000028fb000
[   46.752673]  a2 : 0000000ae2751268 a3 : 00000000004fb708 a4 : 0000000000000004
[   46.752895]  a5 : 0000000000000000 a6 : 000000000017ffe3 a7 : 00000000000000d2
[   46.753117]  s2 : ff600000028fb000 s3 : 0000000ae2751268 s4 : 0000000000000000
[   46.753338]  s5 : ffffffff8153e290 s6 : ff600000863b9000 s7 : ff60000002961078
[   46.753562]  s8 : ff60000002961048 s9 : ff60000002961058 s10: 0000000000000001
[   46.753783]  s11: 0000000000000018 t3 : ffffffffffffffff t4 : ffffffffffffffff
[   46.754005]  t5 : ff6000000292270c t6 : ff2000000022bb30
[   46.754179] status: 0000000200000100 badaddr: 0000000000000000 cause: 000000000000000c
[   46.754653] Code: Unable to access instruction at 0xffffffffffffffec.
[   46.754939] ---[ end trace 0000000000000000 ]---
[   46.755131] note: perf-exec[107] exited with irqs disabled
[   46.755546] note: perf-exec[107] exited with preempt_count 4

This happens because in the legacy case the ctr_get_width function was not
defined, but it is used in arch_perf_update_userpage.

Fixes: cc4c07c89aad ("drivers: perf: Implement perf event mmap support in the SBI backend")
Signed-off-by: Vadim Shakirov <vadim.shakirov@...tacore.com>
---
 drivers/perf/riscv_pmu_legacy.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/perf/riscv_pmu_legacy.c b/drivers/perf/riscv_pmu_legacy.c
index 79fdd667922e..a179ed6ac980 100644
--- a/drivers/perf/riscv_pmu_legacy.c
+++ b/drivers/perf/riscv_pmu_legacy.c
@@ -37,6 +37,12 @@ static int pmu_legacy_event_map(struct perf_event *event, u64 *config)
 	return pmu_legacy_ctr_get_idx(event);
 }
 
+/* cycle & instret are always 64 bit, one bit less according to SBI spec */
+static int pmu_legacy_ctr_get_width(int idx)
+{
+	return 63;
+}
+
 static u64 pmu_legacy_read_ctr(struct perf_event *event)
 {
 	struct hw_perf_event *hwc = &event->hw;
@@ -111,7 +117,7 @@ static void pmu_legacy_init(struct riscv_pmu *pmu)
 	pmu->ctr_stop = NULL;
 	pmu->event_map = pmu_legacy_event_map;
 	pmu->ctr_get_idx = pmu_legacy_ctr_get_idx;
-	pmu->ctr_get_width = NULL;
+	pmu->ctr_get_width = pmu_legacy_ctr_get_width;
 	pmu->ctr_clear_idx = NULL;
 	pmu->ctr_read = pmu_legacy_read_ctr;
 	pmu->event_mapped = pmu_legacy_event_mapped;
-- 
2.34.1