linux-kernel - Re: [PATCH 19/19] perf: Make perf_pmu

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Message-ID: <4cea6430-efb7-43fa-9514-404c25f36595@amd.com>
Date: Mon, 20 Jan 2025 16:45:16 +0530
From: Ravi Bangoria <ravi.bangoria@....com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: "mingo@...nel.org" <mingo@...nel.org>,
 "lucas.demarchi@...el.com" <lucas.demarchi@...el.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "willy@...radead.org" <willy@...radead.org>,
 "acme@...nel.org" <acme@...nel.org>,
 "namhyung@...nel.org" <namhyung@...nel.org>,
 "mark.rutland@....com" <mark.rutland@....com>,
 "alexander.shishkin@...ux.intel.com" <alexander.shishkin@...ux.intel.com>,
 "jolsa@...nel.org" <jolsa@...nel.org>,
 "irogers@...gle.com" <irogers@...gle.com>,
 "adrian.hunter@...el.com" <adrian.hunter@...el.com>,
 "kan.liang@...ux.intel.com" <kan.liang@...ux.intel.com>,
 Ravi Bangoria <ravi.bangoria@....com>
Subject: Re: [PATCH 19/19] perf: Make perf_pmu_unregister() useable

Hi Peter,

On 18-Jan-25 2:34 AM, Peter Zijlstra wrote:
> On Fri, Jan 17, 2025 at 02:04:23PM +0100, Peter Zijlstra wrote:
> 
>> Anyway, let me go break this up into individual patches and go test
>> this -- after lunch!
> 
> OK, so aside from a few dumb mistakes, the result seems to hold up with
> your tinypmu testcase. I left it running for about 30 minutes.
> 
> I pushed out the latest patches to queue/perf/pmu-unregister

I'll spend some time to go through the changes.

I ran fuzzer over the weekend with latest queue/perf/pmu-unregister
and I saw this kernel crash:

  BUG: kernel NULL pointer dereference, address: 00000000000000d0
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD 12a922067 P4D 0
  Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI
  CPU: 8 UID: 1002 PID: 8505 Comm: perf_fuzzer Kdump: loaded Tainted: G        W  O       6.13.0-rc1-pmu-unregister+ #171
  Tainted: [W]=WARN, [O]=OOT_MODULE
  Hardware name: AMD Corporation RUBY/RUBY, BIOS RRR1009C 07/21/2023
  RIP: 0010:perf_mmap_to_page+0x6/0xc0
  Code: ...
  RSP: 0018:ffa0000003aff910 EFLAGS: 00010206
  RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000008
  RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
  RBP: ffa0000003aff980 R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
  R13: 00007b2b02ca8000 R14: ff1100014f9cc5c0 R15: 0000000000000009
  FS:  00007b2b02e03740(0000) GS:ff11001009000000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00000000000000d0 CR3: 000000014f99c001 CR4: 0000000000f71ef0
  PKRU: 55555554
  Call Trace:
   <TASK>
   ? show_regs+0x6c/0x80
   ? __die+0x24/0x80
   ? page_fault_oops+0x155/0x570
   ? do_user_addr_fault+0x4b2/0x870
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? get_page_from_freelist+0x3c7/0x1680
   ? exc_page_fault+0x82/0x1b0
   ? asm_exc_page_fault+0x27/0x30
   ? perf_mmap_to_page+0x6/0xc0
   ? perf_mmap+0x237/0x710
   __mmap_region+0x6d5/0xb90
   mmap_region+0x8d/0xc0
   do_mmap+0x349/0x630
   vm_mmap_pgoff+0xf4/0x1c0
   ksys_mmap_pgoff+0x177/0x240
   __x64_sys_mmap+0x33/0x70
   x64_sys_call+0x24b9/0x2650
   do_syscall_64+0x7e/0x170
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? sched_tick+0x119/0x320
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? sysvec_irq_work+0x4f/0xc0
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? rcu_report_qs_rnp+0xd1/0x140
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? rcu_core+0x1c2/0x380
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? rcu_core_si+0xe/0x20
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? handle_softirqs+0xe7/0x330
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? irqentry_exit_to_user_mode+0x43/0x250
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? irqentry_exit+0x43/0x50
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? sysvec_apic_timer_interrupt+0x4f/0xc0
   entry_SYSCALL_64_after_hwframe+0x76/0x7e
  RIP: 0033:0x7b2b02b2531c
  Code: ...
  RSP: 002b:00007ffc3b177880 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
  RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007b2b02b2531c
  RDX: 0000000000000003 RSI: 0000000000009000 RDI: 0000000000000000
  RBP: 00007ffc3b177890 R08: 0000000000000003 R09: 0000000000000000
  R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000001
  R13: 0000000000000000 R14: 0000636a69c7bb60 R15: 00007b2b02e55000
   </TASK>
  Modules linked in: ...
  CR2: 00000000000000d0
  ---[ end trace 0000000000000000 ]---

Thanks,
Ravi